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Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
Clinical factors affecting adhesion/ cosmetic dentistry training
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Clinical factors affecting adhesion/ cosmetic dentistry training

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  • 1. Dentin Bonding AgentsDentin Bonding Agents INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
  • 2. CONTENTSCONTENTS  INTRODUCTIONINTRODUCTION  HISTORICAL BACK GROUNDHISTORICAL BACK GROUND  PRINCIPLES OF ADHESIONPRINCIPLES OF ADHESION  REQUIREMENTS FOR ADHESIONREQUIREMENTS FOR ADHESION  MECHANISMS OF ADHESIONMECHANISMS OF ADHESION  COMPOSITION AND MICROMORPHOLOGYCOMPOSITION AND MICROMORPHOLOGY OF ENAMELOF ENAMEL  ENAMEL ADHESIONENAMEL ADHESION  ENAMEL BONDING AGENTSENAMEL BONDING AGENTS  COMPOSITION AND MICROMORPHOLOGYCOMPOSITION AND MICROMORPHOLOGY OF DENTINOF DENTIN  DENTIN ADHESIONDENTIN ADHESION www.indiandentalacademy.comwww.indiandentalacademy.com
  • 3.  FACTORS AFFECTING ADHESIONFACTORS AFFECTING ADHESION  DENTIN SMEAR LAYERDENTIN SMEAR LAYER  DENTIN CONDITIONERSDENTIN CONDITIONERS  PRIMERSPRIMERS  ROLE OF HYBRID LAYERROLE OF HYBRID LAYER  REQUIREMENTS OF BONDING AGENTSREQUIREMENTS OF BONDING AGENTS  CLASSIFICATION OF BONDING AGENTSCLASSIFICATION OF BONDING AGENTS  MODREN CLASSIFICATION OF ADHESIVESMODREN CLASSIFICATION OF ADHESIVES  MOIST VERSUS DRY DENTIN BONDINGMOIST VERSUS DRY DENTIN BONDING  ROLE OF PROTIENS IN DENTIN BONDINGROLE OF PROTIENS IN DENTIN BONDING  MICROLEAKAGEMICROLEAKAGE  BIOCOMPATIBILITYBIOCOMPATIBILITY  CONCLUSIONCONCLUSION  BIBLOGRAPHYBIBLOGRAPHY www.indiandentalacademy.comwww.indiandentalacademy.com
  • 4. CLINICAL FACTORS AFFECTINGCLINICAL FACTORS AFFECTING ADHESION:ADHESION: 1.1. Salivary and / or blood contaminationSalivary and / or blood contamination: -: - Difficulty in controlling saliva or blood whileDifficulty in controlling saliva or blood while accomplishing restorative therapy is aaccomplishing restorative therapy is a significant challenge, these contaminants cansignificant challenge, these contaminants can influence some adhesion concepts in ainfluence some adhesion concepts in a negative manner. Although dentin is wetnegative manner. Although dentin is wet substance, the constituents of saliva and bloodsubstance, the constituents of saliva and blood create an environment that can destroy dentincreate an environment that can destroy dentin bonding.bonding. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 5. Thus for years both textbooks ofThus for years both textbooks of operative dentistry and many adhesiveoperative dentistry and many adhesive manufacturers have recommended themanufacturers have recommended the use of rubber dam for proper isolationuse of rubber dam for proper isolation and prevention of cavity contamination.and prevention of cavity contamination. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 6.  Fritz et alFritz et al studied the effect of salivarystudied the effect of salivary contamination during bonding procedures,contamination during bonding procedures, on the bond strength. They stated thaton the bond strength. They stated that any kind of contamination of the bondingany kind of contamination of the bonding area should be avoided which is still bestarea should be avoided which is still best accomplished with rubber dam. Oneaccomplished with rubber dam. One bottle bonding agents have the advantagebottle bonding agents have the advantage that in contrast to previous generationthat in contrast to previous generation adhesives; they are less sensitive toadhesives; they are less sensitive to salivary contamination of etched enamelsalivary contamination of etched enamel and dentin.and dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 7. They concluded that:They concluded that:  Air-drying of the contaminated area mustAir-drying of the contaminated area must strictly be avoided.strictly be avoided.  Contamination of the uncured adhesive isContamination of the uncured adhesive is not critical because saliva and adhesive arenot critical because saliva and adhesive are simply cleaned and the adhesive is reapplied.simply cleaned and the adhesive is reapplied.  Any contamination of already cured adhesiveAny contamination of already cured adhesive layer seriously compromises the bond, nolayer seriously compromises the bond, no matter how carefully the contaminant ismatter how carefully the contaminant is rinsed; this situation calls for resurfacing ofrinsed; this situation calls for resurfacing of the cavity and repetition of the entirethe cavity and repetition of the entire bonding procedure.bonding procedure. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 8.  T Kaneshima et al, in 2001, conducted aT Kaneshima et al, in 2001, conducted a study to evaluate the influence of bloodstudy to evaluate the influence of blood contamination on bond strengths. Thecontamination on bond strengths. The results obtained may be summarized asresults obtained may be summarized as follows:follows: If blood contamination occurred beforeIf blood contamination occurred before collagen fibers were exposed by eithercollagen fibers were exposed by either phosphoric acid etching or self-etchingphosphoric acid etching or self-etching primer application, the contaminationprimer application, the contamination had almost no influence on bondhad almost no influence on bond strength.strength. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 9.  Blood contamination of the dentin surfaceBlood contamination of the dentin surface where collagen fibers had been exposedwhere collagen fibers had been exposed decreased the bond strength even if thedecreased the bond strength even if the blood was washed away with a stream ofblood was washed away with a stream of water and air dried. However, when thewater and air dried. However, when the contaminated collagen fibers werecontaminated collagen fibers were dissolved or when blood contaminationdissolved or when blood contamination occurred after the exposed collagen fibersoccurred after the exposed collagen fibers were dissolved, the bond strength couldwere dissolved, the bond strength could be maintained by rinsing the blood awaybe maintained by rinsing the blood away and applying the self-etching dentinand applying the self-etching dentin primer.primer. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 10. The bond strength markedly decreasedThe bond strength markedly decreased when blood contamination occurred afterwhen blood contamination occurred after the self-etching primer application, butthe self-etching primer application, but was restored by reapplying the primer.was restored by reapplying the primer.  Based on these results, it is suggestedBased on these results, it is suggested that if the contamination occurred on thethat if the contamination occurred on the dentin where the self-etching dentin primerdentin where the self-etching dentin primer had already been applied, thehad already been applied, the contaminated surface should be rinsedcontaminated surface should be rinsed with water, air dried, and recoated with thewith water, air dried, and recoated with the dentin primer to restore the bond strengthdentin primer to restore the bond strength potential.potential. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 11. Moisture Contamination from AirMoisture Contamination from Air syringessyringes::  An unrecognized problem in most dentalAn unrecognized problem in most dental offices is water leakage from air wateroffices is water leakage from air water syringes. The source of leakage can besyringes. The source of leakage can be lack of drying devices on airlines leadinglack of drying devices on airlines leading from compressor, allowing wet air hasfrom compressor, allowing wet air has carried to the syringe.carried to the syringe. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 12. Oil contamination of hand piece or AirOil contamination of hand piece or Air water syringewater syringe: -: -  Adhesives combined with oilAdhesives combined with oil contamination provided an unpredictablecontamination provided an unpredictable clinical result and potential clinical failure.clinical result and potential clinical failure. Observation of oil present in the airlines isObservation of oil present in the airlines is not difficult.not difficult. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 13.  A simple test may be conducted byA simple test may be conducted by blowing air from air syringe or hand pieceblowing air from air syringe or hand piece on to a dry impermeable surface such ason to a dry impermeable surface such as glass slab or dry rubber glove andglass slab or dry rubber glove and observing any residue that is present. Oilobserving any residue that is present. Oil appears similar to water on dry surface butappears similar to water on dry surface but will not evaporate. Water will evaporatewill not evaporate. Water will evaporate from the test surface. Removing all oilfrom the test surface. Removing all oil from dental airlines should be thefrom dental airlines should be the immediate objective. Oil filters should beimmediate objective. Oil filters should be placed after the air compressor and beforeplaced after the air compressor and before the air syringe or hand piece.the air syringe or hand piece. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 14.  However, Bruno T. Rosa et al conducted aHowever, Bruno T. Rosa et al conducted a study to evaluate resin bond strength tostudy to evaluate resin bond strength to enamel contaminated with handpiece oil.enamel contaminated with handpiece oil. The result of this study showed that- allThe result of this study showed that- all bonding systems tested in this study havebonding systems tested in this study have a mean shear bond strength of at least 20a mean shear bond strength of at least 20 Mpa to dry, uncontaminated etchedMpa to dry, uncontaminated etched enamel. In both situations ofenamel. In both situations of contamination with oil, before or aftercontamination with oil, before or after etching, the mean shear bond strengthetching, the mean shear bond strength was atleast 18 MPa for all adhesives,was atleast 18 MPa for all adhesives, which indicates that oil contamination hadwhich indicates that oil contamination had little effect on bondinglittle effect on bonding www.indiandentalacademy.comwww.indiandentalacademy.com
  • 15. Surface roughness of tooth surfaceSurface roughness of tooth surface:: --  Use of diamonds for tooth preparation isUse of diamonds for tooth preparation is most common in clinical dentistry.most common in clinical dentistry. Diamonds create irregularities in toothDiamonds create irregularities in tooth structure that is related directly to the size ofstructure that is related directly to the size of the diamond particles used on the diamondthe diamond particles used on the diamond abrasive instrument. Increased surface areaabrasive instrument. Increased surface area created by surface roughness explains thecreated by surface roughness explains the slight better bonds. It is possible thatslight better bonds. It is possible that mechanical retention may be increasedmechanical retention may be increased slightly by the microscopic roughnessslightly by the microscopic roughness produced on dentin or enamel by cuttingproduced on dentin or enamel by cutting instruments .instruments . www.indiandentalacademy.comwww.indiandentalacademy.com
  • 16. Mechanical under cuts in toothMechanical under cuts in tooth preparationpreparation: -: -  Since, the beginning of dentistry, mechanicalSince, the beginning of dentistry, mechanical under cuts has been placed in toothunder cuts has been placed in tooth preparation to provide retention forpreparation to provide retention for subsequently used restorative materials. Ifsubsequently used restorative materials. If undercuts are present in tooth structure, theyundercuts are present in tooth structure, they hold restorative materials from bodilyhold restorative materials from bodily dislodgment from the preparations, and theydislodgment from the preparations, and they may also resist some microscopic movementmay also resist some microscopic movement of the restorative material caused by thermalof the restorative material caused by thermal or polymerization influences.or polymerization influences. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 17.  Therefore, restorations with traditional dentinTherefore, restorations with traditional dentin undercuts as well as chemical bonding, mayundercuts as well as chemical bonding, may produce better results, such as less leakageproduce better results, such as less leakage than those depending on adhesive alone.than those depending on adhesive alone. (Clim 1990). Whereas in a recent review of(Clim 1990). Whereas in a recent review of literature, Gordon J. Christensen hasliterature, Gordon J. Christensen has suggested “It seems logical to bondsuggested “It seems logical to bond restorative materials to tooth structures,restorative materials to tooth structures, reducing or eliminating the need to cut awayreducing or eliminating the need to cut away enamel or dentin to produce retentiveenamel or dentin to produce retentive grooves and undercuts, and reducinggrooves and undercuts, and reducing leakage around restorations.”leakage around restorations.” www.indiandentalacademy.comwww.indiandentalacademy.com
  • 18. 6.6. Presence of plaque, calculus, andPresence of plaque, calculus, and extrinsic stains / debrisextrinsic stains / debris:: --  Any enamel / dentin surface that requiresAny enamel / dentin surface that requires bonding must be cleaned thoroughly beforebonding must be cleaned thoroughly before the bonding procedure begins. Plaquethe bonding procedure begins. Plaque present on the tooth surface preventspresent on the tooth surface prevents etching with 37% phosphoric acid. Toothetching with 37% phosphoric acid. Tooth surface stains and dental calculus if notsurface stains and dental calculus if not removed will not permit bonding. The toothremoved will not permit bonding. The tooth surface should be cleaned thoroughly beforesurface should be cleaned thoroughly before bonding either by use of scalers, abrasivebonding either by use of scalers, abrasive prophylactic pastes, rubber cups or evenprophylactic pastes, rubber cups or even abrasive rotary instruments.abrasive rotary instruments. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 19. TOOTH RELATED FACTORS AFFECTINGTOOTH RELATED FACTORS AFFECTING ADHESIONADHESION  1.1. Physico chemical properties of dentin thatPhysico chemical properties of dentin that complicate dentinal adhesioncomplicate dentinal adhesion: -: - www.indiandentalacademy.comwww.indiandentalacademy.com
  • 20.  Mineralized dentin is relatively stiff whichMineralized dentin is relatively stiff which varies with dentinal depth. Following acidvaries with dentinal depth. Following acid etching the de-mineralized dentin matrixetching the de-mineralized dentin matrix becomes very soft and elastic. Infact, thebecomes very soft and elastic. Infact, the modulus of elasticity of demineralizedmodulus of elasticity of demineralized dentinal matrix is only about 5Mpadentinal matrix is only about 5Mpa (Macid(Macid et al 1996et al 1996), which is 100 times lower than), which is 100 times lower than that of mineralized dentin. The clinicalthat of mineralized dentin. The clinical implication of this low stiffness is that theimplication of this low stiffness is that the fibril network can easily collapse when air-fibril network can easily collapse when air- dried, there by interfering with the up takedried, there by interfering with the up take of adhesive monomers.of adhesive monomers. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 21.  Further the permeability of bondingFurther the permeability of bonding substrates to monomers and monomersubstrates to monomers and monomer diffusability in to the substrates are essentialdiffusability in to the substrates are essential factors for the hybridization of resins infactors for the hybridization of resins in dental substrates. Mineralized dentinaldental substrates. Mineralized dentinal matrix is relatively impermeable.matrix is relatively impermeable. Permeability refers the ability of substance toPermeability refers the ability of substance to move across diffusion Barrier (i.e. amove across diffusion Barrier (i.e. a substrate). Two types of dentinalsubstrate). Two types of dentinal permeability must be considered. Thepermeability must be considered. The diffusion of substances through tubulesdiffusion of substances through tubules filled with dentinal fluid to reach the pulp isfilled with dentinal fluid to reach the pulp is intratubular dentinal permeability (Hansen etintratubular dentinal permeability (Hansen et al. 1992; Hanks et al. 1994).al. 1992; Hanks et al. 1994). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 22.  The second important type of dentinalThe second important type of dentinal permeability is the diffusion of monomer intopermeability is the diffusion of monomer into demineralized intertubular dentin, the dentindemineralized intertubular dentin, the dentin between the tubules. This is referred to asbetween the tubules. This is referred to as intertubular dentinal permeability. After theintertubular dentinal permeability. After the surface is acid etched and rinsed with water,surface is acid etched and rinsed with water, these spaces are filled with water. It isthese spaces are filled with water. It is through these spaces that adhesivethrough these spaces that adhesive monomer must diffuse if it has to infiltratemonomer must diffuse if it has to infiltrate the demineralized dentinal matrix. Boththe demineralized dentinal matrix. Both intratubular and intertubular dentinalintratubular and intertubular dentinal permeability are important in dentin bonding.permeability are important in dentin bonding. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 23.  Along with this dentinal permeability andAlong with this dentinal permeability and consequent internal dentinal wetness,consequent internal dentinal wetness, these depend on several factors like thethese depend on several factors like the diameter and the length of the tubule, thediameter and the length of the tubule, the viscosity of the dentinal fluid,the surfaceviscosity of the dentinal fluid,the surface area available for diffusion, the patency ofarea available for diffusion, the patency of the tubules and rate of removal ofthe tubules and rate of removal of substances. The variability in dentinalsubstances. The variability in dentinal permeability makes it a more difficultpermeability makes it a more difficult substrate for bonding.substrate for bonding. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 24.  Dentinal tubules permit adhesiveDentinal tubules permit adhesive monomer to go down to the tubules formonomer to go down to the tubules for varying distances. Most tubules containvarying distances. Most tubules contain multiple lateral branches that radiate 2 to 6multiple lateral branches that radiate 2 to 6 um from the lumen and they provideum from the lumen and they provide another route for monomer infiltration ofanother route for monomer infiltration of hybrid layerhybrid layer (Mjor and Nardaul .1996.)(Mjor and Nardaul .1996.) www.indiandentalacademy.comwww.indiandentalacademy.com
  • 25.  The resin monomers penetrate acid etchedThe resin monomers penetrate acid etched collagen fibrils through the spaces that cancollagen fibrils through the spaces that can swell or shrink depending on the bondingswell or shrink depending on the bonding conditions. Under some conditions (highconditions. Under some conditions (high water concentration, acidic pH) the collagenwater concentration, acidic pH) the collagen fibrils might swell slightly and reduce thefibrils might swell slightly and reduce the width of the peri fibrillar spaces making itwidth of the peri fibrillar spaces making it more difficult for primer monomers tomore difficult for primer monomers to infiltrate the collagen network. Under otherinfiltrate the collagen network. Under other conditions (air drying, dehydration by waterconditions (air drying, dehydration by water miscible organic solvents) the collagenmiscible organic solvents) the collagen fibrils may shrink (decreasing their diameter)fibrils may shrink (decreasing their diameter) there by bringing the adjacent fibrils in to anthere by bringing the adjacent fibrils in to an intimate contact with each other.intimate contact with each other. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 26.  As a result the collagen peptides mayAs a result the collagen peptides may form inter molecular hydrogen bonds withform inter molecular hydrogen bonds with the nearest neighboring collagen peptides,the nearest neighboring collagen peptides, which may contribute to further collapse ofwhich may contribute to further collapse of the network by causing shortening of thethe network by causing shortening of the fibrils and an increase in stiffnessfibrils and an increase in stiffness (Maciel(Maciel et at 1996et at 1996). So over drying of collagen). So over drying of collagen fibrils should be avoided.fibrils should be avoided. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 27. 2.2. Fluoride content of teethFluoride content of teeth  Increased fluoride content of enamel hasIncreased fluoride content of enamel has been shown to resist acid etching. Thisbeen shown to resist acid etching. This reduction is not significant clinically if thereduction is not significant clinically if the etching time is increased to allow moreetching time is increased to allow more time for the acid to etch the enameltime for the acid to etch the enamel surface and produce more roughness.surface and produce more roughness. Clinicians are now etching apparentlyClinicians are now etching apparently normal enamel for 15 sec and enamel thatnormal enamel for 15 sec and enamel that shows signs of fluoridation for double thatshows signs of fluoridation for double that time or more.time or more. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 28. 3.3. Dentinal canal characteristics: -Dentinal canal characteristics: -  Dentinal canals at the external surface ofDentinal canals at the external surface of roots or near the dentino enamel junctionroots or near the dentino enamel junction have small diameters. Whereas dentinalhave small diameters. Whereas dentinal canals close to the pulp are larger incanals close to the pulp are larger in diameter. Old dentin has smaller dentinaldiameter. Old dentin has smaller dentinal canals, while new dentin has largercanals, while new dentin has larger dentinal canalsdentinal canals (pashley 1990).(pashley 1990). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 29. 4.4. Transformed dentin surface due toTransformed dentin surface due to physiological and pathologicalphysiological and pathological process: -process: -  Structural changes can occur in theStructural changes can occur in the dentinal tubule due to carious, erosive anddentinal tubule due to carious, erosive and abrasive processes and physiologicalabrasive processes and physiological aging. In carious instances the lumen ofaging. In carious instances the lumen of the dentinal tubules are very narrow orthe dentinal tubules are very narrow or may even be obliterated by deposition ofmay even be obliterated by deposition of intratubular crystals and apposition ofintratubular crystals and apposition of irregular sclerotic dentin. Even repairativeirregular sclerotic dentin. Even repairative dentin forms at the pulpal aspect of thedentin forms at the pulpal aspect of the lesion.lesion. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 30.  In the normal dentin the odontoblasticIn the normal dentin the odontoblastic process extend through out the entireprocess extend through out the entire thickness of dentin but in the case ofthickness of dentin but in the case of carious dentin, they disappear at thecarious dentin, they disappear at the bottom of the carious lesions, collapsingbottom of the carious lesions, collapsing with fringe like ends.with fringe like ends.  This results in reduction of dentinThis results in reduction of dentin permeability. Further permeability ispermeability. Further permeability is reduced in aged sound dentin due toreduced in aged sound dentin due to progressive deposition of peritubularprogressive deposition of peritubular dentin and crystal formation in the tubules.dentin and crystal formation in the tubules. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 31.  AR Yazici et al conducted a study in 2004AR Yazici et al conducted a study in 2004 to evaluate the bond strengths of soundto evaluate the bond strengths of sound versus caries-effected dentin using a self-versus caries-effected dentin using a self- etching adhesive system, Clearfil SEetching adhesive system, Clearfil SE Bond. The results of this in vitro studyBond. The results of this in vitro study indicated that the bond strength of theindicated that the bond strength of the self-etching adhesive system, Clearfil SEself-etching adhesive system, Clearfil SE Bond to sound dentin was greater than toBond to sound dentin was greater than to caries affected dentin.caries affected dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 32.  Whereas a recent study by A. Sengun etWhereas a recent study by A. Sengun et al has shown that the bond strengths ofal has shown that the bond strengths of Clearfil SE was similar to both cariesClearfil SE was similar to both caries affected and normal dentinaffected and normal dentin  S. M. Kwong et al conducted a study toS. M. Kwong et al conducted a study to evaluate the bond strengths to scleroticevaluate the bond strengths to sclerotic dentin using a self-etching and a total-dentin using a self-etching and a total- etching technique and they concluded thatetching technique and they concluded that removal of the surface layers of scleroticremoval of the surface layers of sclerotic dentin and/or conditioning with strongerdentin and/or conditioning with stronger acids may be beneficial to obtain strongeracids may be beneficial to obtain stronger bonding to sclerotic dentin.bonding to sclerotic dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 33. The dentin smear layer and permeability:The dentin smear layer and permeability:  When the tooth surface is instrumentedWhen the tooth surface is instrumented with rotary and manual instruments duringwith rotary and manual instruments during cavity preparation, cutting debris iscavity preparation, cutting debris is smeared over the enamel and dentinalsmeared over the enamel and dentinal surfaces what is termed the smear layer.surfaces what is termed the smear layer. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 34.  The burnishing action of cuttingThe burnishing action of cutting instruments generate a considerableinstruments generate a considerable amount of frictional heat locally, so thatamount of frictional heat locally, so that the smear layer gets attached to thethe smear layer gets attached to the underlying surface in a manner thatunderlying surface in a manner that prevents it from being rinsed off orprevents it from being rinsed off or scrubbed away. This smear debrisscrubbed away. This smear debris occludes the dentinal tubules with theoccludes the dentinal tubules with the formation of smear plugs which affect theformation of smear plugs which affect the bonding negatively.bonding negatively. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 35. DENTIN SMEAR LAYERDENTIN SMEAR LAYER  Smear layerSmear layer - It is tenacious deposit of- It is tenacious deposit of microscopic debris that covers enamelmicroscopic debris that covers enamel and dentin surfaces and that have beenand dentin surfaces and that have been created during the preparation of enamelcreated during the preparation of enamel and dentin and its presence complicatesand dentin and its presence complicates resin bonding.resin bonding. Eick and othersEick and others (1970)(1970) first described this smear layer.first described this smear layer. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 36.  When viewed under scanning electronWhen viewed under scanning electron microscope the smear layer has anmicroscope the smear layer has an amorphous, irregular and granularamorphous, irregular and granular appearance that represents dentinalappearance that represents dentinal shavings, hydroxy apatite, tissue debris,shavings, hydroxy apatite, tissue debris, odontoblastic processes, obliteratedodontoblastic processes, obliterated tubule orifices, bacteria, denaturedtubule orifices, bacteria, denatured collagen etc.collagen etc. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 37. Composition:Composition:  The composition of smear layer reflects theThe composition of smear layer reflects the composition of the dentin from which it iscomposition of the dentin from which it is formed (Eick et al 1970). Thus the smearformed (Eick et al 1970). Thus the smear layer in superficial normal dentin may have alayer in superficial normal dentin may have a composition close to that of intertubularcomposition close to that of intertubular dentin where as the composition of smeardentin where as the composition of smear layer in deep dentin would reflect its degreelayer in deep dentin would reflect its degree of mineralization. However smear layer foundof mineralization. However smear layer found on deep dentin contains more organicon deep dentin contains more organic component than those found on thecomponent than those found on the superficial dentin.superficial dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 38.  Scanning electron microscopicScanning electron microscopic examination has disclosed that itsexamination has disclosed that its composition is both organic and inorganic.composition is both organic and inorganic. The inorganic material in the smear layerThe inorganic material in the smear layer is made up of tooth structures and someis made up of tooth structures and some non specific inorganic contaminants. Thenon specific inorganic contaminants. The organic components may consists oforganic components may consists of heated coagulated proteins, odontoblastsheated coagulated proteins, odontoblasts plus saliva, blood cells andplus saliva, blood cells and microorganism.microorganism. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 39. Morphology:Morphology:  The smear layer consists of two separateThe smear layer consists of two separate layers, a superficial layer, and a layerlayers, a superficial layer, and a layer loosely attached to the underlying dentin.loosely attached to the underlying dentin.  Dentin debris enters the orifice of theDentin debris enters the orifice of the dentinal tubules and acts as smear plugs,dentinal tubules and acts as smear plugs, which can decrease the dentinwhich can decrease the dentin permeability by up to 86% (Meryon et al,permeability by up to 86% (Meryon et al, 1987).1987). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 40. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 41.  The smear layer is neither always firmlyThe smear layer is neither always firmly attached nor it is continuous over theattached nor it is continuous over the substrate. Clinically produced smear layersubstrate. Clinically produced smear layer have an average depth of 1-5 µmhave an average depth of 1-5 µm (Goldman et at 1981, Madder et at 1984).(Goldman et at 1981, Madder et at 1984). The depth entering the dentinal tubuleThe depth entering the dentinal tubule may vary from a few um up to 40 µm.may vary from a few um up to 40 µm. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 42.  Cengiz et at 1970 proposed that theCengiz et at 1970 proposed that the penetration of smear layer into dentinalpenetration of smear layer into dentinal tubules could be caused by capillarytubules could be caused by capillary action as a result of adhesive forcesaction as a result of adhesive forces between the dentinal tubules and thebetween the dentinal tubules and the smear material. One can conclude that asmear material. One can conclude that a smear layer is present on all tooth that aresmear layer is present on all tooth that are prepared for restorative purpose unlessprepared for restorative purpose unless the dentin surface was treated with anthe dentin surface was treated with an acid or a chelating agent.acid or a chelating agent. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 43. Several factors may cause the depth ofSeveral factors may cause the depth of smear layer to varysmear layer to vary::  dry or wet cutting of dentindry or wet cutting of dentin  type of instrument usedtype of instrument used  area and composition of dentinarea and composition of dentin www.indiandentalacademy.comwww.indiandentalacademy.com
  • 44.  Cutting the tooth without a water spray willCutting the tooth without a water spray will produce a thicker layer of dentin debrisproduce a thicker layer of dentin debris and the use of coarse diamond bursand the use of coarse diamond burs produce a thicker smear layer than theproduce a thicker smear layer than the use of carbide burs.use of carbide burs.  Both steel and tungsten carbide burs showBoth steel and tungsten carbide burs show a rapid detoriation of the cutting edges,a rapid detoriation of the cutting edges, which significantly diminishes the cuttingwhich significantly diminishes the cutting efficiency of the bur, probably increasesefficiency of the bur, probably increases frictional heat and causes smearing.frictional heat and causes smearing. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 45.  A significant difference exits when theA significant difference exits when the burs are used with or without a coolant ofburs are used with or without a coolant of water spray. In the absence of coolantwater spray. In the absence of coolant smeared debris can be found commonlysmeared debris can be found commonly on the surface. The smeared debris doeson the surface. The smeared debris does not form a continuous layer but exists asnot form a continuous layer but exists as localized islands with discontinuitieslocalized islands with discontinuities exposing the underlying dentin. Coolant ofexposing the underlying dentin. Coolant of water spray does not prevent smearingwater spray does not prevent smearing but appears to significantly reduce thebut appears to significantly reduce the amount and distribution of it.amount and distribution of it. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 46.  In addition, its composition is influencedIn addition, its composition is influenced by the area of dentin where it isby the area of dentin where it is generated, because of varying organic togenerated, because of varying organic to inorganic component ratios andinorganic component ratios and percentage of dentinal tubules. All ofpercentage of dentinal tubules. All of these variables can affect the integrity,these variables can affect the integrity, morphology and composition of the smearmorphology and composition of the smear layer and perhaps its potential to bondlayer and perhaps its potential to bond with a dentin bonding agent.with a dentin bonding agent. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 47. REMOVAL OF SMEAR LAYERREMOVAL OF SMEAR LAYER  There are two divergent opinions aboutThere are two divergent opinions about smear layer treatment. Some believe thatsmear layer treatment. Some believe that the smear layer acts as an effectivethe smear layer acts as an effective natural cavity liner that seals the dentinalnatural cavity liner that seals the dentinal tubules and reduces permeability, makingtubules and reduces permeability, making the smear a clinical asset. Other arguesthe smear a clinical asset. Other argues that the smear layer interferes withthat the smear layer interferes with adhesion of restorative materials, servingadhesion of restorative materials, serving as focus of bacteria, and therefore itas focus of bacteria, and therefore it should be removed.should be removed. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 48.  Brannstrom et al reported that the smearBrannstrom et al reported that the smear layer, which was firmly attached to thelayer, which was firmly attached to the dentin initially, became loose and wasdentin initially, became loose and was largely replaced by bacteria and fluid withlargely replaced by bacteria and fluid with in a few weeks.in a few weeks. PashleyPashley and othersand others found that smear layer was effective infound that smear layer was effective in restricting dentin permeability. In addition,restricting dentin permeability. In addition, they found that shear bond strength tothey found that shear bond strength to dentin with smear layer intact were higherdentin with smear layer intact were higher than to dentin with smear layer removed.than to dentin with smear layer removed. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 49.  The removal of smear layer andThe removal of smear layer and demineralization of the dentin matrixdemineralization of the dentin matrix may facilitate bonding through amay facilitate bonding through a number of mechanisms.number of mechanisms. 1.1. The exposed collagen may provideThe exposed collagen may provide reactive groups that can chemicallyreactive groups that can chemically interact with bonding primers.interact with bonding primers. 2.2. Exposure of collagen fibrils and theirExposure of collagen fibrils and their epsilon-amino groups, which mayepsilon-amino groups, which may catalyze HEMA polymerization.catalyze HEMA polymerization. 3.3. Exposure of intact collagen thatExposure of intact collagen that serves as a scaffold for the creationserves as a scaffold for the creation of resin collagen hybrid layer.of resin collagen hybrid layer. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 50.  The retention of smear layer not onlyThe retention of smear layer not only lowers dentin permeability but also maylowers dentin permeability but also may prevent the decrease in bond strengthprevent the decrease in bond strength seen with some bonding systems, asseen with some bonding systems, as deeper dentin is prepared. It also greatlydeeper dentin is prepared. It also greatly lowers the effects of pulpal pressure onlowers the effects of pulpal pressure on bond strengths.bond strengths. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 51.  Another approach to avoiding the intrinsicAnother approach to avoiding the intrinsic weakness of the smear layer is to removeweakness of the smear layer is to remove it, but use some of the mineral in theit, but use some of the mineral in the smear layer to react with ions in thesmear layer to react with ions in the etching to form insoluble precipitates thatetching to form insoluble precipitates that adhere to each other and to underlyingadhere to each other and to underlying dentin matrix more firmly than did thedentin matrix more firmly than did the original smear layer particles.original smear layer particles. Bowen et alBowen et al used ferric oxalate in 2.5% nitric acid forused ferric oxalate in 2.5% nitric acid for this purpose.this purpose. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 52.  In order to chemically attach a restorativeIn order to chemically attach a restorative system to tooth structure, one of thesystem to tooth structure, one of the several options must be considered for theseveral options must be considered for the smear layer. For the currently availablesmear layer. For the currently available dentin bonding agents, the smear layer isdentin bonding agents, the smear layer is managed in one of the five ways:managed in one of the five ways: www.indiandentalacademy.comwww.indiandentalacademy.com
  • 53. 1.1. No treatment at allNo treatment at all: The smear layer is left: The smear layer is left in places with out modification, and thein places with out modification, and the dentin bonding agent applied directly to it.dentin bonding agent applied directly to it. 2.2. Dissolution of smear layerDissolution of smear layer: The dissolved: The dissolved smear layer plays a part in chemicalsmear layer plays a part in chemical attachment of dentin bonding agent toattachment of dentin bonding agent to dentin.dentin. 3.3. The smear layer is removedThe smear layer is removed: The dentin: The dentin bonding agent develops chemicalbonding agent develops chemical attachment directly to intact dentin.attachment directly to intact dentin. 4.4. The modification of the smear layerThe modification of the smear layer: This: This process theoretically improves theprocess theoretically improves the attachment of smear layer to dentin.attachment of smear layer to dentin. 5.5. Smear layer removal and its replacementSmear layer removal and its replacement byby another mediating agent.another mediating agent. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 54. System that work by removing the smearSystem that work by removing the smear layer:layer:  All bond all etch technique.All bond all etch technique.  Gluma bond system.Gluma bond system.  Denthesive.Denthesive.  Clear fill liner bond system.Clear fill liner bond system.  Scotch bond 2.Scotch bond 2.  Syntac.Syntac.  Tenure.Tenure.  X-R bond.X-R bond. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 55.  Systems that work by preserve the smearSystems that work by preserve the smear layerlayer  All bond 2All bond 2  Prisma universal Bond 3Prisma universal Bond 3  Tripton,Tripton,  Tokuso light bond.Tokuso light bond.  Systems that work by dissolve the smearSystems that work by dissolve the smear layerlayer  XR – BondXR – Bond  Imperva BondImperva Bond  Systems that work by modification of theSystems that work by modification of the smear layersmear layer  All bondAll bond  Prisma universal Bond - 2.Prisma universal Bond - 2. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 56. Methods of Removal of Smear LayerMethods of Removal of Smear Layer  Brannstrom’s group has publishedBrannstrom’s group has published several articles describing the use ofseveral articles describing the use of water, hydrogen peroxide,water, hydrogen peroxide, benzalkonuim chloride, EDTA(Ethylenebenzalkonuim chloride, EDTA(Ethylene Diamine TetraAcetic Acid) and otherDiamine TetraAcetic Acid) and other agents to remove the smear layer.agents to remove the smear layer. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 57.  He has formulated severalHe has formulated several commercially available products likecommercially available products like Tublicid, that are designed to removeTublicid, that are designed to remove most smear layer without removingmost smear layer without removing smear debris that has fallen intosmear debris that has fallen into orifices of the tubules of the dentin.orifices of the tubules of the dentin. Though this concept is ideal, it isThough this concept is ideal, it is difficult to achieve clinically because ofdifficult to achieve clinically because of complex geometry of many cavitiescomplex geometry of many cavities and difficulty in obtaining adequateand difficulty in obtaining adequate access.access. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 58. 1.1. Remove the smear layer by etchingRemove the smear layer by etching with acid.with acid.  Etching dentin with 6% citric acid forEtching dentin with 6% citric acid for 60 sec removes the entire smear layer60 sec removes the entire smear layer as does 15 sec of etching with 37%as does 15 sec of etching with 37% phosphoric acid.phosphoric acid. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 59.  The advantages are:The advantages are:  The smear layer is essentially removedThe smear layer is essentially removed  The tubules are open and available forThe tubules are open and available for retentionretention  The surface collagen is exposed for possibleThe surface collagen is exposed for possible covalent linkages with new experimentalcovalent linkages with new experimental primers.primers.  When smear layer is removed, one does notWhen smear layer is removed, one does not have to worry about its slow dissolutionhave to worry about its slow dissolution under a restoration leaving a void betweenunder a restoration leaving a void between the cavity wall and the restoration, whichthe cavity wall and the restoration, which might permit bacterial colonization.might permit bacterial colonization. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 60.  The disadvantage is:The disadvantage is:  In the absence of smear layer there isIn the absence of smear layer there is no physical barrier to bacterialno physical barrier to bacterial penetration of dentinal tubules.penetration of dentinal tubules. 2. Another entirely different approach2. Another entirely different approach would lie to use a resin that wouldwould lie to use a resin that would infiltrate through the entire thicknessinfiltrate through the entire thickness of smear layer and either bond toof smear layer and either bond to underlying matrix or penetrate intounderlying matrix or penetrate into the tubules.the tubules. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 61. 3.To try to fix the smear layer by3.To try to fix the smear layer by gluteraldehyde or tanning agents such asgluteraldehyde or tanning agents such as tannic acids or ferric chloride.tannic acids or ferric chloride. The idea is toThe idea is to increase the cross linking of exposedincrease the cross linking of exposed collagen within the smear layer and betweencollagen within the smear layer and between it and the matrix of the underlying dentin toit and the matrix of the underlying dentin to improve its cohesion.improve its cohesion. 4.A fourth and most recent approach4.A fourth and most recent approach to theto the problem is to remove the smear layer byproblem is to remove the smear layer by etching with acid and replace it with anetching with acid and replace it with an artificial smear layer composed by aartificial smear layer composed by a crystaline precipitate.crystaline precipitate.  Bowen has used this approach by treatingBowen has used this approach by treating dentin with 5% ferric oxalate which replaceddentin with 5% ferric oxalate which replaced the original smear layers.the original smear layers. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 62. DENTIN CONDITIONERS: -DENTIN CONDITIONERS: -  There is confusion regarding two terms –There is confusion regarding two terms – etchants and conditioners. Acids such asetchants and conditioners. Acids such as phosphoric, maleic, nitric, or citric are usedphosphoric, maleic, nitric, or citric are used for partial or total removal of the smear layerfor partial or total removal of the smear layer and superficial demineralization of theand superficial demineralization of the underlying dentin. Such liquids or gels areunderlying dentin. Such liquids or gels are termed etchants and may also be calledtermed etchants and may also be called conditioners by some dental manufacturers.conditioners by some dental manufacturers. Etching implies the dissolution of theEtching implies the dissolution of the substrate, whereas conditioning involvessubstrate, whereas conditioning involves cleaning structural alteration, and increasingcleaning structural alteration, and increasing the adhesiveness of the substratethe adhesiveness of the substrate ( Jendresen and Glantz, 1981).( Jendresen and Glantz, 1981).www.indiandentalacademy.comwww.indiandentalacademy.com
  • 63.  Conditioning of the dentin will be definedConditioning of the dentin will be defined as any alteration of dentin done after theas any alteration of dentin done after the creation of dentin cutting debris, termedcreation of dentin cutting debris, termed the smear layer. The objective of dentinthe smear layer. The objective of dentin conditioning is to create a surface capableconditioning is to create a surface capable of micro mechanical and possibleof micro mechanical and possible chemical bonding to a dentin bondingchemical bonding to a dentin bonding agent. The principal effects ofagent. The principal effects of conditioning of dentin may be classifiedconditioning of dentin may be classified as:as:  Physical changes.Physical changes.  Chemical changes.Chemical changes. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 64.  Physical changesPhysical changes:: 1. Increase or decrease in the thickness and1. Increase or decrease in the thickness and morphology of the smear layer.morphology of the smear layer. 2. Changes in the shape of the dentinal2. Changes in the shape of the dentinal tubules.tubules.  Chemical changesChemical changes:: 1. Modifications of organic matter.1. Modifications of organic matter. 2. Decalcification of the inorganic matter.2. Decalcification of the inorganic matter. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 65.  Conditioning of dentin may be done inConditioning of dentin may be done in several means.several means.  1) Chemical:1) Chemical: a) Acidsa) Acids  2) Thermal:2) Thermal: a) Lasersa) Lasers  3) Mechanical:3) Mechanical: a) Abrasiona) Abrasion www.indiandentalacademy.comwww.indiandentalacademy.com
  • 66. CHEMICALCHEMICAL  Acid conditionersAcid conditioners:: These acidic conditioners demineralizeThese acidic conditioners demineralize dentin to a depth of at least 2-5dentin to a depth of at least 2-5 µµm. Them. The factors that limit the depth offactors that limit the depth of demineralization are:demineralization are:  Type of acidType of acid  Etching timeEtching time  Strengthening of acidStrengthening of acid  Buffering capacity of the dentin.Buffering capacity of the dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 67.  Historically several acids have beenHistorically several acids have been researched as dentin conditioners. Theseresearched as dentin conditioners. These include hydrochloric acid, oxalic acid,include hydrochloric acid, oxalic acid, pyruvic acid, maleic acid, phosphoric acid,pyruvic acid, maleic acid, phosphoric acid, 10% citric acid, and 10% citric acid with10% citric acid, and 10% citric acid with 3% ferric chloride, 10% citric acid with3% ferric chloride, 10% citric acid with 20% calcium chloride, 2.5% nitric acid and20% calcium chloride, 2.5% nitric acid and chelators like EDTA.chelators like EDTA. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 68. Phosphoric acid: -Phosphoric acid: -  It was the first dentin conditioner that wasIt was the first dentin conditioner that was successfully used to remove the smearsuccessfully used to remove the smear layer, etch the dentin and restore it withlayer, etch the dentin and restore it with adhesive composite resin (adhesive composite resin (Fusayama andFusayama and other, 1979other, 1979)) www.indiandentalacademy.comwww.indiandentalacademy.com
  • 69. Scanning electron micrograph of etched dentin showing exposed collagen fibers. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 70.  This helps by removing the surface dentin,This helps by removing the surface dentin, leaving a clean, well-defined etchingleaving a clean, well-defined etching pattern where the tubules are enlargedpattern where the tubules are enlarged into funnel shape. Phosphoric acid is theinto funnel shape. Phosphoric acid is the acid of choice currently for the etchingacid of choice currently for the etching purpose.purpose.  However, controversy remains about theHowever, controversy remains about the optimal concentration of H3PO4. Theoptimal concentration of H3PO4. The most widely used concentrations used inmost widely used concentrations used in clinical practice exceed 30% phosphoricclinical practice exceed 30% phosphoric acid.acid. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 71. Total etch/all etch technique:Total etch/all etch technique:  FusayamaFusayama pioneered the research of totalpioneered the research of total etching establishing the protocol foretching establishing the protocol for simultaneous etching of dentin andsimultaneous etching of dentin and enamel with phosphoric acid in 1979.enamel with phosphoric acid in 1979.  Kuraray’s original clearfil new bondKuraray’s original clearfil new bond system accomplishes the total etch usingsystem accomplishes the total etch using 37% phosphoric acid for 60 seconds.37% phosphoric acid for 60 seconds. Bisco system uses 10% phosphoric acidBisco system uses 10% phosphoric acid for 15sec in all etch technique.for 15sec in all etch technique. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 72. THERMAL MODIFICATIONSTHERMAL MODIFICATIONS  Lasers: -Lasers: -  Hard tissue lasers in dentistry are anHard tissue lasers in dentistry are an emerging technology. A pulsed Nd-YAGemerging technology. A pulsed Nd-YAG laser will not disturb the pulp, even whenlaser will not disturb the pulp, even when the approach is as close as 1the approach is as close as 1µµm. Most ofm. Most of the research has been conducted on drythe research has been conducted on dry dentin, but laser will operate on dentindentin, but laser will operate on dentin immersed in saliva/water.immersed in saliva/water. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 73.  The mechanism of dentin removal is throughThe mechanism of dentin removal is through microscopic explosions caused by themicroscopic explosions caused by the thermal transients. The carbonized, blackthermal transients. The carbonized, black soot that results is easily washed off withsoot that results is easily washed off with water. The laser treatment results inwater. The laser treatment results in desensitized dentin, presumably bydesensitized dentin, presumably by occlusion of the open and permeableocclusion of the open and permeable dentinal tubules. Microorganisms anddentinal tubules. Microorganisms and organic debris are eliminated from the lasedorganic debris are eliminated from the lased surfaces. The laser decreases the organicsurfaces. The laser decreases the organic fraction and increases the inorganic fractionfraction and increases the inorganic fraction of the dentin surface.of the dentin surface.  The bond strength increased by 60% whenThe bond strength increased by 60% when this was done presumably by increasing thethis was done presumably by increasing the bondable inorganic fraction of the dentinbondable inorganic fraction of the dentin surface. The laser may create microsurface. The laser may create micro mechanical retention (white and othersmechanical retention (white and otherswww.indiandentalacademy.comwww.indiandentalacademy.com
  • 74. MECHANICAL MODIFICATIONSMECHANICAL MODIFICATIONS  Micro-abrasionsMicro-abrasions It is a mechanical means of modification ofIt is a mechanical means of modification of dentin. Aluminum oxide is used for the purposedentin. Aluminum oxide is used for the purpose of micro abrasion. It removes healthy as well asof micro abrasion. It removes healthy as well as diseased dentin and results in a smear layer. Itsdiseased dentin and results in a smear layer. Its abrasion action depends on the particle size asabrasion action depends on the particle size as well as the velocity. The 0.5-micron or largerwell as the velocity. The 0.5-micron or larger particles create a smear on the dentin andparticles create a smear on the dentin and increase the surface area (Blake 1991). Theincrease the surface area (Blake 1991). The smear layer formed might be used to enhancesmear layer formed might be used to enhance the bond strengths of smear-mediated dentinthe bond strengths of smear-mediated dentin bonding agents.bonding agents. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 75.  An in vitro investigation of a comparison ofAn in vitro investigation of a comparison of bond strengths of composite to etchedbond strengths of composite to etched and air abraded human enamel surfacesand air abraded human enamel surfaces was done by G.B. Gray et al in 2006. Theywas done by G.B. Gray et al in 2006. They concluded composite resin applied toconcluded composite resin applied to enamel surfaces prepared using an acidenamel surfaces prepared using an acid etch procedure exhibited higher bondetch procedure exhibited higher bond strengths than those prepared with airstrengths than those prepared with air abrasion technology.abrasion technology. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 76. PRIMERS:PRIMERS:  Primer is a hydrophilic, low-viscocityPrimer is a hydrophilic, low-viscocity monomer dissolved in solvents such asmonomer dissolved in solvents such as water, acetone, or alcohol – are applied towater, acetone, or alcohol – are applied to the etched or conditioned dentin substratethe etched or conditioned dentin substrate but are not rinsed off.but are not rinsed off. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 77.  Nowadays major advances have beenNowadays major advances have been achieved in adhesion by the introduction ofachieved in adhesion by the introduction of primers, which promote wetting of the dentinprimers, which promote wetting of the dentin with the bonding agent, and penetration ofwith the bonding agent, and penetration of the bonding agent into the dentin. Primerthe bonding agent into the dentin. Primer monomers are amphiphilic i.e. they containmonomers are amphiphilic i.e. they contain hydrophilic groups. E.g.: -OH, -COOH forhydrophilic groups. E.g.: -OH, -COOH for better compatibility of the resin monomersbetter compatibility of the resin monomers with the moist dentin, and hydrophobicwith the moist dentin, and hydrophobic methacrylate groups for the co-methacrylate groups for the co- polymerization with the bonding resin. Thepolymerization with the bonding resin. The objective of this step is to transform theobjective of this step is to transform the hydrophilic dentin surface in to ahydrophilic dentin surface in to a hydrophobic and spongy state. Nakabayashihydrophobic and spongy state. Nakabayashi and Pashley summarized the function ofand Pashley summarized the function of dentin primer as “to maintain or recover thedentin primer as “to maintain or recover the porosity of the demineralized dentin”.porosity of the demineralized dentin”. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 78.  Primers are monomers dissolved inPrimers are monomers dissolved in solvents . Organic solvents aid insolvents . Organic solvents aid in displacing water, expanding or re-displacing water, expanding or re- expanding the collagen fiber network andexpanding the collagen fiber network and thus promoting the infiltration of thethus promoting the infiltration of the monomer into the sub-micron ormonomer into the sub-micron or nanometer sized spaces within thenanometer sized spaces within the collagen fiber network.collagen fiber network.  Besides HEMA, most of the primersBesides HEMA, most of the primers contain other monomers such as NPG-contain other monomers such as NPG- GMA, PMDM, BPDM and PENTA. MoreGMA, PMDM, BPDM and PENTA. More recent primers also include a chemical /recent primers also include a chemical / photo polymerization initiator so that theirphoto polymerization initiator so that their monomers can be polymerized inside.monomers can be polymerized inside.www.indiandentalacademy.comwww.indiandentalacademy.com
  • 79. WET VERSUS DRY BONDING:WET VERSUS DRY BONDING:  The concept of ‘Moist’ or ‘Wet’ bondingThe concept of ‘Moist’ or ‘Wet’ bonding technique was proposed by Dr. Johntechnique was proposed by Dr. John Kanka (1990). Vital dentin is inherentlyKanka (1990). Vital dentin is inherently wet; therefore complete drying of dentin iswet; therefore complete drying of dentin is difficult to achieve clinically. Water hasdifficult to achieve clinically. Water has been considered an obstacle for attainingbeen considered an obstacle for attaining an effective adhesion of resins to dentin.an effective adhesion of resins to dentin. With that in mind, research has shiftedWith that in mind, research has shifted towards development of dentin adhesivestowards development of dentin adhesives compatible with humid environments.compatible with humid environments. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 80.  Most newer adhesives combineMost newer adhesives combine hydrophilic and hydrophobic monomers inhydrophilic and hydrophobic monomers in the same bottle, dissolved in an organicthe same bottle, dissolved in an organic solvent such as ethanol or acetone. Thesolvent such as ethanol or acetone. The “wet – bonding” technique prevents the“wet – bonding” technique prevents the spatial alternations (i.e. collagen collapse)spatial alternations (i.e. collagen collapse) that occur upon drying demineralizedthat occur upon drying demineralized dentin, such alterations may prevent thedentin, such alterations may prevent the monomers from penetrating labyrinth ofmonomers from penetrating labyrinth of nano channels formed by dissolution ofnano channels formed by dissolution of hydroxyapatite crystals between collagenhydroxyapatite crystals between collagen fibers (Maciel KT et al 1996).fibers (Maciel KT et al 1996). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 81. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 82. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 83.  The use of adhesive systems on moist dentin isThe use of adhesive systems on moist dentin is made possible by incorporation of the organicmade possible by incorporation of the organic solvents acetone or ethanol in primers orsolvents acetone or ethanol in primers or adhesives. Because the solvent can displaceadhesives. Because the solvent can displace water from both the dentin surface and the moistwater from both the dentin surface and the moist collagen network, it promotes the infiltration ofcollagen network, it promotes the infiltration of resin monomers throughout the nano spaces ofresin monomers throughout the nano spaces of the dense collagen web. The “Wet bonding”the dense collagen web. The “Wet bonding” technique has been shown repeatedly totechnique has been shown repeatedly to enhance bond strengths because waterenhance bond strengths because water preserves the porosity of collagen networkpreserves the porosity of collagen network available for monomer inter diffusion (Kanca Javailable for monomer inter diffusion (Kanca J 1992).1992). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 84.  If the dentin surface is dried with air, theIf the dentin surface is dried with air, the collagen undergoes immediate collapsecollagen undergoes immediate collapse and prevents resin monomers fromand prevents resin monomers from penetrating (Carvalho RM et al 1996).penetrating (Carvalho RM et al 1996). Kanca and Gwinnett (1992) recommendedKanca and Gwinnett (1992) recommended that etched dentin should not be driedthat etched dentin should not be dried before application of the bonding primer.before application of the bonding primer. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 85.  The clinician must be aware that pooledThe clinician must be aware that pooled moisture should not remain on the tooth,moisture should not remain on the tooth, because excess water can dilute thebecause excess water can dilute the primer and render it less effective. (Tay etprimer and render it less effective. (Tay et al 1996). A glistening hydrated surface isal 1996). A glistening hydrated surface is preferred. Many clinicians, however, stillpreferred. Many clinicians, however, still dry the tooth preparation after rinsingdry the tooth preparation after rinsing away the etching gel to check for theaway the etching gel to check for the classic etched enamel appearance.classic etched enamel appearance. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 86.  Because it is clinically impossible to dry enamelBecause it is clinically impossible to dry enamel without simultaneously drying dentin, the dentinwithout simultaneously drying dentin, the dentin collagen collapses easily upon air dryingcollagen collapses easily upon air drying resulting in the closing of the micropores in theresulting in the closing of the micropores in the exposed intertubular collagen (Tay FR andexposed intertubular collagen (Tay FR and Gwinett AJ 1996) For acetone based water –Gwinett AJ 1996) For acetone based water – free dentin bonding systems, the etched dentinfree dentin bonding systems, the etched dentin surface must be rewetted before applying thesurface must be rewetted before applying the adhesives. Rewetting the dried etched dentinadhesives. Rewetting the dried etched dentin with water or with aqueous rewetting agents haswith water or with aqueous rewetting agents has been demonstrated to restore bond strengthbeen demonstrated to restore bond strength values and to raise the collapsed collagenvalues and to raise the collapsed collagen network to a level similar to a “wet bondingnetwork to a level similar to a “wet bonding technique” (Gwinett AJ 1994).technique” (Gwinett AJ 1994). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 87.  Some authors have suggested that theSome authors have suggested that the inclusion of water in the composition ofinclusion of water in the composition of some adhesives may result in rewettingsome adhesives may result in rewetting the collagen fibers in areas that are notthe collagen fibers in areas that are not fully moist, thus opening the interfibrillarfully moist, thus opening the interfibrillar spaces to the infiltration of the primingspaces to the infiltration of the priming resin. Therefore the simultaneousresin. Therefore the simultaneous inclusion of both an organic solvent andinclusion of both an organic solvent and water may be fundamental for the bestwater may be fundamental for the best infiltration of some adhesives intoinfiltration of some adhesives into demineralized dentin. This could result indemineralized dentin. This could result in a less technique-sensitive procedure.a less technique-sensitive procedure. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 88.  A review of literature has showed that moistA review of literature has showed that moist bonding is only essential for particular bondingbonding is only essential for particular bonding systems with low water content of primer suchsystems with low water content of primer such as all bond 2. The primer of all bond 2 containsas all bond 2. The primer of all bond 2 contains acetone as solvent with only 5% of water. Inacetone as solvent with only 5% of water. In contrast with water content of 20% or more (e.g.contrast with water content of 20% or more (e.g. opti -bond FL, scotch bond multipurpose) areopti -bond FL, scotch bond multipurpose) are able to re-expand the collapsed collagen due toable to re-expand the collapsed collagen due to their intrinsic rewetting capacity. Acetone basedtheir intrinsic rewetting capacity. Acetone based primers adhesive (e.g. prime and bond 2.1, one-primers adhesive (e.g. prime and bond 2.1, one- step) have shown higher bond strengths andstep) have shown higher bond strengths and reduced micro-leakage when a moist bondingreduced micro-leakage when a moist bonding protocol is followed.protocol is followed. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 89.  So, moist bonding is only mandatory inSo, moist bonding is only mandatory in bonding system with minimal waterbonding system with minimal water content of the primer / primer adhesives,content of the primer / primer adhesives, while water based primers / primerwhile water based primers / primer adhesives have shown to be less sensitiveadhesives have shown to be less sensitive to variations in the moisture of the etchedto variations in the moisture of the etched dentin surface.dentin surface.  When etched dentin is dried using an airWhen etched dentin is dried using an air syringe bond strength decreasesyringe bond strength decrease substantially, especially for acetone andsubstantially, especially for acetone and ethanol – based dentin adhesive systemsethanol – based dentin adhesive systems (Kanca J 1992).(Kanca J 1992). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 90.  When water is removed the elasticWhen water is removed the elastic characteristics of collagen may be lost. Thecharacteristics of collagen may be lost. The collapse of the collagen fibers upon drying maycollapse of the collagen fibers upon drying may therefore be a result of the changes in thetherefore be a result of the changes in the molecular arrangement. While in a wet state,molecular arrangement. While in a wet state, wide gaps separate the collagen molecules fromwide gaps separate the collagen molecules from each other, in a dry state, the molecules areeach other, in a dry state, the molecules are arranged more compactly like a heap of cookedarranged more compactly like a heap of cooked noodles. This is because extrafibrillar space innoodles. This is because extrafibrillar space in hydrated Type I collagen are filled with water,hydrated Type I collagen are filled with water, while dried collagen has fewer extrafibrillarwhile dried collagen has fewer extrafibrillar spaces open for the penetration of thespaces open for the penetration of the monomers included in the adhesive systems.monomers included in the adhesive systems. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 91.  Water removal also may permit additionalWater removal also may permit additional hydrogen bonds to form between collagenhydrogen bonds to form between collagen molecules that were previously bonded to watermolecules that were previously bonded to water molecules, leaving no interfibrillar space. Duringmolecules, leaving no interfibrillar space. During air drying, water that occupies the interfibrillarair drying, water that occupies the interfibrillar spaces previously filled with hydroxyapatitespaces previously filled with hydroxyapatite crystals is lost by evaporation, resulting in acrystals is lost by evaporation, resulting in a decrease of the volume of a collagen network todecrease of the volume of a collagen network to approximately one third of its original volume.approximately one third of its original volume. When air -dried demineralized dentin is rewetWhen air -dried demineralized dentin is rewet with water, the collagen matrix may re – expandwith water, the collagen matrix may re – expand and recover its primary dimensions to the levelsand recover its primary dimensions to the levels of the original hydrated state (Maciel et al 1996).of the original hydrated state (Maciel et al 1996). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 92.  This spatial re – expansion occurs because theThis spatial re – expansion occurs because the spaces between fibers are refilled with water andspaces between fibers are refilled with water and because Type I collagen itself is capable tobecause Type I collagen itself is capable to undergoing expansion upon rehydration. Theundergoing expansion upon rehydration. The stiffness of decalcified dentin increases whenstiffness of decalcified dentin increases when the tissue is dehydrated either chemically inthe tissue is dehydrated either chemically in water – miscible solvents or physically in air. Thewater – miscible solvents or physically in air. The increase in stiffness is reversed whenincrease in stiffness is reversed when specimens are rehydrated in water. Thereforespecimens are rehydrated in water. Therefore rewetting dentin after air – drying to check forrewetting dentin after air – drying to check for the enamel frosty aspect may be an acceptablethe enamel frosty aspect may be an acceptable clinical procedure.clinical procedure. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 93.  Clinically, it is very difficult to either assess orClinically, it is very difficult to either assess or standardize the ideal amount of moisture thatstandardize the ideal amount of moisture that should be left on the dentin surface before theshould be left on the dentin surface before the application of the adhesive system. The idealapplication of the adhesive system. The ideal dentin surface for moist bonding is visibly moistdentin surface for moist bonding is visibly moist but without an excess of water leading to abut without an excess of water leading to a meniscus on the surface. Ideally, water shouldmeniscus on the surface. Ideally, water should form a uniform layer with out pooling (over wet)form a uniform layer with out pooling (over wet) and with our dry areas (over dried). Therefore airand with our dry areas (over dried). Therefore air drying with an air – water syringe after rinsing offdrying with an air – water syringe after rinsing off the etching gel is not recommended because itthe etching gel is not recommended because it cannot produce a uniform layer of water on thecannot produce a uniform layer of water on the surface.surface. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 94.  A recent study demonstrated that the excessA recent study demonstrated that the excess water after rinsing the etching gel can bewater after rinsing the etching gel can be removed with a damp cotton pellet, a disposableremoved with a damp cotton pellet, a disposable brush, or a tissue paper without adverselybrush, or a tissue paper without adversely affecting bond strengths.affecting bond strengths.  Research has demonstrated that moist bondingResearch has demonstrated that moist bonding increases the bond strengths of many bondingincreases the bond strengths of many bonding systems. However the water present in betweensystems. However the water present in between the fibrils should be displaced completely and ifthe fibrils should be displaced completely and if too much water is present, the resin monomerstoo much water is present, the resin monomers may not be able to successfully compete for themay not be able to successfully compete for the collages fibril surface there by leaving a void.collages fibril surface there by leaving a void. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 95.  Jorge Perdigao et al conducted a study toJorge Perdigao et al conducted a study to determine the effect of solvent anddetermine the effect of solvent and rewetting time on dentin adhesion. Theyrewetting time on dentin adhesion. They concluded that:concluded that: www.indiandentalacademy.comwww.indiandentalacademy.com
  • 96.  When dentin is left moist, all DBSs resultWhen dentin is left moist, all DBSs result in similar bond strengths regardless ofin similar bond strengths regardless of their solvent.their solvent.  water-based adhesives are less sensitivewater-based adhesives are less sensitive to variations in surface moisture thanto variations in surface moisture than ethanol or acetone-based DBSs.ethanol or acetone-based DBSs.  Rewetting dentin after air drying restoresRewetting dentin after air drying restores the bond strengths to the level obtainedthe bond strengths to the level obtained on moist dentin, if rewetting is performedon moist dentin, if rewetting is performed for twice as long as the air drying.for twice as long as the air drying. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 97.  L Hitme et al, in 2002, conducted a study toL Hitme et al, in 2002, conducted a study to evaluate the influence of drying and HEMAevaluate the influence of drying and HEMA treatment on dentin wettability. They havetreatment on dentin wettability. They have concluded that air-drying acid-etched dentinconcluded that air-drying acid-etched dentin significantly decreased the spreading/infiltrationsignificantly decreased the spreading/infiltration of water in comparison with blot drying. Re-of water in comparison with blot drying. Re- wetting with water only partly restores thewetting with water only partly restores the spreading/infiltration on etched and air-driedspreading/infiltration on etched and air-dried dentin. However, HEMA primer prevents thedentin. However, HEMA primer prevents the collagen collapse and restores the collapsedcollagen collapse and restores the collapsed collagen network. Although multi-step dentincollagen network. Although multi-step dentin bonding systems can be routinely used inbonding systems can be routinely used in clinical practice because of their primers, the soclinical practice because of their primers, the so called “one bottle” systems must be used onlycalled “one bottle” systems must be used only on blot-dried dentin surfaces.on blot-dried dentin surfaces. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 98. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 99. Application of primerApplication of primer  Bonding can be carried out by applying primer toBonding can be carried out by applying primer to a collapsed matrix followed by application ofa collapsed matrix followed by application of bonding agent or else a primer and bondingbonding agent or else a primer and bonding agent may be directly applied to a non-collapsedagent may be directly applied to a non-collapsed demineralized dentin without the intermediatedemineralized dentin without the intermediate step of primer application. In Prime and bondstep of primer application. In Prime and bond and Bisco one step dental adhesive theyand Bisco one step dental adhesive they combine the priming and bonding step.combine the priming and bonding step.  www.indiandentalacademy.comwww.indiandentalacademy.com
  • 100.  Bonding to the smear layer covered dentinBonding to the smear layer covered dentin was not very successful before 1990 aswas not very successful before 1990 as the resins did not penetrate through thethe resins did not penetrate through the smear layer and the smear layer was verysmear layer and the smear layer was very weakweak (Tao et al 1988).(Tao et al 1988). This led mostThis led most manufactures to use acidic conditioners.manufactures to use acidic conditioners. How ever the resulting soft collagen richHow ever the resulting soft collagen rich surface can collapse and interfere withsurface can collapse and interfere with monomer infiltration.monomer infiltration. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 101.  So in order to prevent this and to simplifySo in order to prevent this and to simplify the number of bonding steps,the number of bonding steps, WatanabeWatanabe (1990(1990) developed a new bonding system) developed a new bonding system which was an aqueous solution of 20%which was an aqueous solution of 20% phenyl-p in 30% HEMA. This self-etchingphenyl-p in 30% HEMA. This self-etching and self-priming system providedand self-priming system provided important new information on smear layerimportant new information on smear layer as bonding substrates. The ideal self-as bonding substrates. The ideal self- etching, self-priming bonding system isetching, self-priming bonding system is one that can penetrate 2.0one that can penetrate 2.0µµm of smearm of smear layer and engage underlying of dentin to alayer and engage underlying of dentin to a depth of 1depth of 1 µµm.m. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 102. Microscopic examination of attachmentsMicroscopic examination of attachments produced by primer has shownproduced by primer has shown deficiencies like:deficiencies like:  Incomplete surface coverageIncomplete surface coverage  Incomplete inter-fibrillar saturation with inIncomplete inter-fibrillar saturation with in the hybrid zone.the hybrid zone.  Incomplete penetration to the full depth ofIncomplete penetration to the full depth of demineralized dentin.demineralized dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 103. Steps for effective priming: -Steps for effective priming: -  One method of improving surfaceOne method of improving surface coverage and diffusion of the primer is bycoverage and diffusion of the primer is by the application of multiple coats. Athe application of multiple coats. A second coat of primer has shown tosecond coat of primer has shown to increase the shear bond strengthincrease the shear bond strength significantly.significantly. JAJA Platt et al conducted a study in 2001, toPlatt et al conducted a study in 2001, to determine the effect of double adhesivedetermine the effect of double adhesive application on the shear bond strength toapplication on the shear bond strength to dentin using three one-bottle adhesivedentin using three one-bottle adhesive systems.systems. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 104. This study showed that:This study showed that:  The dentin shear bond strength of Prime &The dentin shear bond strength of Prime & Bond NT is improved by the use of a secondBond NT is improved by the use of a second application, when following manufacturer’sapplication, when following manufacturer’s instructions.instructions.  The dentin shear bond strength of One StepThe dentin shear bond strength of One Step and Optibond Solo are not improved by theand Optibond Solo are not improved by the use of a second application, when followinguse of a second application, when following manufacturer’s instructions.manufacturer’s instructions.  The surface of dentin should not be over driedThe surface of dentin should not be over dried or over-wet.or over-wet.  The etching time should not exceed the timeThe etching time should not exceed the time recommended by the manufacturers.recommended by the manufacturers. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 105. SOLVENTS:SOLVENTS: --  Three types of solvents are commonlyThree types of solvents are commonly used in dentin adhesives, they include:used in dentin adhesives, they include:  ACETONEACETONE  ETHANOL.ETHANOL.  WATER.WATER. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 106. Basic characteristic of solvents:Basic characteristic of solvents: -- ACETONEACETONE  Highly volatile, evaporates quicklyHighly volatile, evaporates quickly  Excellent water – chaserExcellent water – chaser  Strong drying agentStrong drying agent  Storage and dispensing problems presentStorage and dispensing problems present www.indiandentalacademy.comwww.indiandentalacademy.com
  • 107. ETHANOLETHANOL  Excellent penetration capabilityExcellent penetration capability  Good comprise in respect of evaporationGood comprise in respect of evaporation  Good surface energy for wetting exposedGood surface energy for wetting exposed collagen fiber networkcollagen fiber network WATERWATER  Excellent penetration capabilityExcellent penetration capability  Enables self – etching capability of acidEnables self – etching capability of acid monomersmonomers  Evaporates slowly consequently more difficult toEvaporates slowly consequently more difficult to removeremove  Remaining water may hamper resinRemaining water may hamper resin penetration / polymerizationpenetration / polymerization www.indiandentalacademy.comwww.indiandentalacademy.com
  • 108.  Organic solvents aid in displacing water,Organic solvents aid in displacing water, expanding or re-expanding the collagen network,expanding or re-expanding the collagen network, and thus promoting the infiltration of theand thus promoting the infiltration of the monomer into the submicron or nanometer sizedmonomer into the submicron or nanometer sized spaces within the collagen fiber network.spaces within the collagen fiber network.  AF Reis et al conducted a study to evaluate theAF Reis et al conducted a study to evaluate the effect of organic solvents on one-bottleeffect of organic solvents on one-bottle adhesives’ bond strength to enamel and dentin.adhesives’ bond strength to enamel and dentin. The result of this study demonstrated thatThe result of this study demonstrated that complete solvent elimination did not produce acomplete solvent elimination did not produce a statistical decrease in enamel bond strengths.statistical decrease in enamel bond strengths. However, the high viscocity adhesive solutionHowever, the high viscocity adhesive solution that resulted from solvent evaporationthat resulted from solvent evaporation significantly decreased bond strengths tosignificantly decreased bond strengths to demineralized, moist dentin substrate.demineralized, moist dentin substrate. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 109.  They concluded that this reductionThey concluded that this reduction probably occurred as a function of twoprobably occurred as a function of two factors : incomplete monomer infiltrationfactors : incomplete monomer infiltration and incomplete water displacement. Theand incomplete water displacement. The absence of a water-chaser monomer-absence of a water-chaser monomer- carrier resulted in difficult resin infiltration.carrier resulted in difficult resin infiltration. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 110. HYBRID LAYERHYBRID LAYER  Hybrid layer in dentin was first describedHybrid layer in dentin was first described in detail by Nakabayashi, 1992. A similarin detail by Nakabayashi, 1992. A similar phenomenon was first described in vitrophenomenon was first described in vitro for enamel by Gwinnett and Buonocore infor enamel by Gwinnett and Buonocore in 1965.1965. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 111.  Hybrid layer is an intermediate layer of resin,Hybrid layer is an intermediate layer of resin, collagen, and dentin produced by acid etching ofcollagen, and dentin produced by acid etching of dentin and resin infiltration into the conditioneddentin and resin infiltration into the conditioned dentin.dentin.  Basically it is a transitional zone of resinBasically it is a transitional zone of resin reinforced dentin sandwiched between curedreinforced dentin sandwiched between cured resin and unaltered dentinal substrate and isresin and unaltered dentinal substrate and is generated by monomer impregnation of thegenerated by monomer impregnation of the exposed collagen of demineralized superficialexposed collagen of demineralized superficial dentin, after removal and/or modification of thedentin, after removal and/or modification of the smear layer. The synonyms are “adhesionsmear layer. The synonyms are “adhesion interface”, resin dentin “inter diffusion zone”,interface”, resin dentin “inter diffusion zone”, inter penetration zone”.inter penetration zone”. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 112.  The formation of hybrid zone depends onThe formation of hybrid zone depends on several factorsseveral factors  1) Type of conditioners.1) Type of conditioners.  2) Depth of the cavity, hybrid layer appeared to2) Depth of the cavity, hybrid layer appeared to be thinner at the deeper parts of the dentinbe thinner at the deeper parts of the dentin compared with the middle and superficial parts.compared with the middle and superficial parts. In the superficial dentin most of the hybrid layerIn the superficial dentin most of the hybrid layer is composed of hybridized intertubular dentinis composed of hybridized intertubular dentin with only occasional resin tag penetrating in towith only occasional resin tag penetrating in to the tubules. In deep dentin the tubules are sothe tubules. In deep dentin the tubules are so numerous and so large that there is less amountnumerous and so large that there is less amount of hybridized intertubular dentin and large resinof hybridized intertubular dentin and large resin tags are seen.tags are seen. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 113.  3) Permeability of the dentin surface.3) Permeability of the dentin surface.  4) The conditioning and priming pre4) The conditioning and priming pre treatment procedures.treatment procedures.  5) Diffusability and wettability of monomer5) Diffusability and wettability of monomer resins.resins.  In order to obtain an intimate associationIn order to obtain an intimate association between the resin monomers and collagenbetween the resin monomers and collagen fibrils, the primers and bonding agentsfibrils, the primers and bonding agents must be able to wet the collagen fibrils.must be able to wet the collagen fibrils. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 114. Role of the Hybrid LayerRole of the Hybrid Layer  The role of the hybrid layer in dentinThe role of the hybrid layer in dentin bonding is somewhat controversial.bonding is somewhat controversial. Studies of various adhesive systemsStudies of various adhesive systems report different results. In order to obtainreport different results. In order to obtain proper adhesion, it is essential to create aproper adhesion, it is essential to create a hybrid layer at the resin-dentin interfacehybrid layer at the resin-dentin interface (Nakabayashi, 1985, Sugaizaki, 1991,(Nakabayashi, 1985, Sugaizaki, 1991, Vanmeerbeek and others, 1992, 1993).Vanmeerbeek and others, 1992, 1993). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 115.  A study with Prime & Bond (Dentsply) indicatedA study with Prime & Bond (Dentsply) indicated that the removal of collagen fibers may actuallythat the removal of collagen fibers may actually increase bond strengths of resin to dentin.increase bond strengths of resin to dentin. Studies with One-Step(Bisco) indicated that theStudies with One-Step(Bisco) indicated that the hybrid layer might not play any important role inhybrid layer might not play any important role in the establishment of bond strengths. For athe establishment of bond strengths. For a multibottle adhesive system, All-Bond 2(Bisco),multibottle adhesive system, All-Bond 2(Bisco), one study reported that the presence or absenceone study reported that the presence or absence of the hybrid layer did not affect fractureof the hybrid layer did not affect fracture toughness of resin-dentin interfaces. Thereforetoughness of resin-dentin interfaces. Therefore the presence of the collagen layer wouldthe presence of the collagen layer would presumably allow for the establishment of apresumably allow for the establishment of a stress-relieving layer at the interface.stress-relieving layer at the interface. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 116.  A study using a self-etching primerA study using a self-etching primer demonstrated that dentin bond strengths did notdemonstrated that dentin bond strengths did not vary from 1 day to 6 months to 1 year in teethvary from 1 day to 6 months to 1 year in teeth subjected to occlusal function. It also showedsubjected to occlusal function. It also showed that porosity in the hybrid layer increasedthat porosity in the hybrid layer increased significantly at 1 year, due to loss of resinsignificantly at 1 year, due to loss of resin between the collagen fibers. Since these resultsbetween the collagen fibers. Since these results were obtained with a hybrid layer being createdwere obtained with a hybrid layer being created by a self-etching primer, they cannot beby a self-etching primer, they cannot be generalized to total-etch adhesives. However,generalized to total-etch adhesives. However, they do support the theory that collagen maythey do support the theory that collagen may play an important role in the strength of theplay an important role in the strength of the resin-dentin interface.resin-dentin interface. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 117.  For most dentin adhesives, theFor most dentin adhesives, the ultramorphological characterization of theultramorphological characterization of the transition between the hybrid layer and thetransition between the hybrid layer and the unaffected dentin suggests that there is anunaffected dentin suggests that there is an abrupt shift from hybrid tissue toabrupt shift from hybrid tissue to mineralized tissue, without any emptymineralized tissue, without any empty space or pathway that could result inspace or pathway that could result in leakage. The demarcation line seems toleakage. The demarcation line seems to consist of hydroxyapatite crystalsconsist of hydroxyapatite crystals embedded in the resin from the hybridembedded in the resin from the hybrid layer.layer. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 118.  According to Kanka, acid etched dentin cannotAccording to Kanka, acid etched dentin cannot be dried without shrinking. It is literally floatingbe dried without shrinking. It is literally floating in the rinsing water. If the water is evaporatedin the rinsing water. If the water is evaporated by air-dryng, the collagen fibrillar networkby air-dryng, the collagen fibrillar network collapses into a relatively impermeable organiccollapses into a relatively impermeable organic film that interfares with resin infiltration. Resinfilm that interfares with resin infiltration. Resin tags could still be formed and gave some resintags could still be formed and gave some resin retention, but hybridization of the dentin betweenretention, but hybridization of the dentin between tubules could not occur. This left much nakedtubules could not occur. This left much naked collagen fibrils in the acid etched layer that couldcollagen fibrils in the acid etched layer that could slowly hydrolyze and leads to gap formationslowly hydrolyze and leads to gap formation between resin and dentin.between resin and dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 119.  Kanka discovered that if one left some residualKanka discovered that if one left some residual water in acid etched dentin, bond strength couldwater in acid etched dentin, bond strength could be doubled. Also it creates thicker hybrid layersbe doubled. Also it creates thicker hybrid layers (i.e., more resin uptake in etched surfaces) than(i.e., more resin uptake in etched surfaces) than did dry bonding.did dry bonding.  Most adhesive interface studies by SEMMost adhesive interface studies by SEM (Scanning Electron Microscope) have(Scanning Electron Microscope) have demonstrated creation of hybrid layers. Medinademonstrated creation of hybrid layers. Medina et al, in 2001, in his study had shown that acidet al, in 2001, in his study had shown that acid etching of dentin and the application of Prime &etching of dentin and the application of Prime & Bond are required for the formation of a distinctBond are required for the formation of a distinct hybrid layer and resin tags. However, there washybrid layer and resin tags. However, there was no significant correlation between shear bondno significant correlation between shear bond strength and the thickness of the hybrid layer.strength and the thickness of the hybrid layer. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 120. REQUIREMENTS OF A BONDINGREQUIREMENTS OF A BONDING AGENT:AGENT: A bonding agent is usually an unfilledA bonding agent is usually an unfilled resin that consists of hydrophobicresin that consists of hydrophobic monomers (such as Bis-GMA, TEGDMA,monomers (such as Bis-GMA, TEGDMA, UDMA, and hydrophilic monomers, suchUDMA, and hydrophilic monomers, such as HEMA).as HEMA).  Criteria for an “ideal” dentin bondingCriteria for an “ideal” dentin bonding system were enumerated in 1961 at asystem were enumerated in 1961 at a workshop held at the University of Indianaworkshop held at the University of Indiana Dental School.Dental School. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 121. These criteria were:These criteria were: 1.1. Provide a high bond strength to dentinProvide a high bond strength to dentin that should be present immediately afterthat should be present immediately after placement and that should beplacement and that should be permanent.permanent. 2.2. Provide a bond strength to dentin similarProvide a bond strength to dentin similar to that to enamel.to that to enamel. 3.3. Show good biocompatibility to dentalShow good biocompatibility to dental tissue, including the pulp.tissue, including the pulp. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 122. 4. Minimize microleakage at the margins of4. Minimize microleakage at the margins of restorations.restorations. 5. Prevent recurrent caries and marginal staining.5. Prevent recurrent caries and marginal staining. 6. Be easy to use and minimally technique6. Be easy to use and minimally technique sensitive.sensitive. 7. Possess a good shelf life.7. Possess a good shelf life. 8. Be compatible with a wide range of resins.8. Be compatible with a wide range of resins.  In a current review of literature, J. D. Eick et alIn a current review of literature, J. D. Eick et al had proposed to add the criterion that thehad proposed to add the criterion that the systems should not be toxic or sensitizing tosystems should not be toxic or sensitizing to the operators or patients. And, finally, Bondingthe operators or patients. And, finally, Bonding agents should seal tooth surfaces from oralagents should seal tooth surfaces from oral fluids.fluids. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 123. CLASSIFICATION OF DENTIN BONDINGCLASSIFICATION OF DENTIN BONDING AGENTS:AGENTS:  The BeginningThe Beginning : During the 1950s, the first: During the 1950s, the first attempt to develop an adhesive system forattempt to develop an adhesive system for bonding to dentin was made by Hagger, abonding to dentin was made by Hagger, a Swiss researcher working forSwiss researcher working for Amalgamated Dental Company, London.Amalgamated Dental Company, London. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 124.  The first commercial product was SevritonThe first commercial product was Sevriton Cavity Seal (Amalgamated DentalCavity Seal (Amalgamated Dental Company, London, England); based on .Company, London, England); based on . glycerophosphoric acid dimethacrylateglycerophosphoric acid dimethacrylate (GPDM) chemically activated with sulfinic(GPDM) chemically activated with sulfinic acid was used to bond an auto curingacid was used to bond an auto curing acrylic resin to dentin. But the bondacrylic resin to dentin. But the bond strengths of this primitive adhesionstrengths of this primitive adhesion technique were severely reduced bytechnique were severely reduced by immersion in water.immersion in water. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 125. First Generation Dentin AdhesivesFirst Generation Dentin Adhesives ::  The development of the surface-active co-The development of the surface-active co- monomer NPG-GMA (N-phenylglycinemonomer NPG-GMA (N-phenylglycine glycidyl methacrylate) was the basis forglycidyl methacrylate) was the basis for Cervident (S.S. white, Lake wood, NewCervident (S.S. white, Lake wood, New Jersey), is considered a first generationJersey), is considered a first generation dentin bonding systemdentin bonding system www.indiandentalacademy.comwww.indiandentalacademy.com
  • 126.  NPG- GMA is a bifunctional molecule orNPG- GMA is a bifunctional molecule or coupling agent. This molecule had onecoupling agent. This molecule had one bonding to the dentin while the otherbonding to the dentin while the other bonds to composite resin. Theoretically,bonds to composite resin. Theoretically, this co-monomer could chelate withthis co-monomer could chelate with calcium on the tooth surface to generatecalcium on the tooth surface to generate water-resistant chemical bonds of resin towater-resistant chemical bonds of resin to dentinal calcium. But bond strength of thisdentinal calcium. But bond strength of this first generation bonding adhesive was onlyfirst generation bonding adhesive was only 2 to 3 MPa and clinical results were2 to 3 MPa and clinical results were discouraging.discouraging. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 127. Second Generation Dentin Adhesives :Second Generation Dentin Adhesives :  In 1978, the Clearfil Bond System FIn 1978, the Clearfil Bond System F (Kuraray, Osaka, Japan) was introduced(Kuraray, Osaka, Japan) was introduced in Japan, generally recognized as the firstin Japan, generally recognized as the first product of the second generation dentinproduct of the second generation dentin adhesives. This agent primarily used BIS-adhesives. This agent primarily used BIS- GMA (Bisphenol glycidyl methacrylate)GMA (Bisphenol glycidyl methacrylate) resins containing polymerisableresins containing polymerisable phosphate compounds.phosphate compounds. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 128.  The mechanism by which these secondThe mechanism by which these second generation systems bonded to dentin wasgeneration systems bonded to dentin was postulated to be through an ionic bond topostulated to be through an ionic bond to calcium by chloro phosphate groups.calcium by chloro phosphate groups. These were weak bonds. The smear layerThese were weak bonds. The smear layer was the weakest link in the systemwas the weakest link in the system because of its relatively loose attachmentbecause of its relatively loose attachment to the dentin surface.to the dentin surface. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 129.  In addition to the problems caused by theIn addition to the problems caused by the loosely attached smear layer, these resinsloosely attached smear layer, these resins were devoid of hydrophilic groups, andwere devoid of hydrophilic groups, and therefore had large contact angles ontherefore had large contact angles on intrinsically moist surfaces. They neitherintrinsically moist surfaces. They neither wet dentin well nor penetrate the entirewet dentin well nor penetrate the entire depth of the smear layer, and could notdepth of the smear layer, and could not reach the superficial dentin to establishreach the superficial dentin to establish ionic bonding or resin extensions into theionic bonding or resin extensions into the dentinal tubules. Whatever bonding diddentinal tubules. Whatever bonding did occur was due to interaction with calciumoccur was due to interaction with calcium ions.ions. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 130.  Several other phosphate- ester dentinSeveral other phosphate- ester dentin bonding systems were introduced in thebonding systems were introduced in the early 1980s, including Scotchbond (3Mearly 1980s, including Scotchbond (3M ESPE, St. Paul, Minnesota), Bond liteESPE, St. Paul, Minnesota), Bond lite (Kerr Corporation, Orange, California),(Kerr Corporation, Orange, California), and Prisma Universal Bond (Dentsplyand Prisma Universal Bond (Dentsply Caulk, Milford, Delaware). These second-Caulk, Milford, Delaware). These second- generation dentin bonding systemsgeneration dentin bonding systems typically had in vitro bond strengths of onlytypically had in vitro bond strengths of only 1 to 5 MPa, which was considerably below1 to 5 MPa, which was considerably below the value estimated as the threshold valuethe value estimated as the threshold value for acceptable in vivo retention.for acceptable in vivo retention. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 131. Third Generation Dentin AdhesivesThird Generation Dentin Adhesives ::  The concept of phosphoric acid-etching ofThe concept of phosphoric acid-etching of dentin before application of a phosphatedentin before application of a phosphate ester-type bonding agent was introducedester-type bonding agent was introduced by Fusayama and others in 1979.by Fusayama and others in 1979. However, because of the hydrophobicHowever, because of the hydrophobic nature of the bonding resin, acid-etchingnature of the bonding resin, acid-etching did not produce a significant improvementdid not produce a significant improvement in dentin bond strength, despite the flow ofin dentin bond strength, despite the flow of the resin into the open dentinal tubules.the resin into the open dentinal tubules. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 132.  Furthermore, pulpal inflammatory responsesFurthermore, pulpal inflammatory responses were thought to be triggered by the applicationwere thought to be triggered by the application of acid on dentin surfaces, providing anotherof acid on dentin surfaces, providing another reason for not using acid. Nevertheless,reason for not using acid. Nevertheless, continuing the etched dentin philosophy, Kuraraycontinuing the etched dentin philosophy, Kuraray introduced Clearfil New Bond in 1984. This newintroduced Clearfil New Bond in 1984. This new phosphate- based material contained HEMA andphosphate- based material contained HEMA and a ten- carbon molecule known as 10-MDP (10-a ten- carbon molecule known as 10-MDP (10- Methacryloyloxy decyl dihydrogen phosphate),Methacryloyloxy decyl dihydrogen phosphate), which includes a long hydrophobic and a shortwhich includes a long hydrophobic and a short hydrophilic component.hydrophilic component. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 133.  As further developments ensued, interaction withAs further developments ensued, interaction with the smear layer was appreciated as having athe smear layer was appreciated as having a significant influence on the behaviour ofsignificant influence on the behaviour of adhesive systems. Thus, the third generation ofadhesive systems. Thus, the third generation of adhesive systems used a dentin-conditioningadhesive systems used a dentin-conditioning step as well as an intermediate primer instep as well as an intermediate primer in conjunction with a bonding agent. Theconjunction with a bonding agent. The conditioning agents either modified or removedconditioning agents either modified or removed the smear layer before placement of thethe smear layer before placement of the adhesive resins. These dentin conditionersadhesive resins. These dentin conditioners were designed not to remove the entire smearwere designed not to remove the entire smear layer, but rather to modify it and allowlayer, but rather to modify it and allow penetration of acidic monomers. Despitepenetration of acidic monomers. Despite promising laboratory results, some of thepromising laboratory results, some of the bonding mechanisms developed never resultedbonding mechanisms developed never resulted in satisfactory clinical results.in satisfactory clinical results.www.indiandentalacademy.comwww.indiandentalacademy.com
  • 134.  Tenure (Den-Mat Corp, Santa Maria, CA)Tenure (Den-Mat Corp, Santa Maria, CA) was the first commercial oxylate bondingwas the first commercial oxylate bonding system. Other third-generation productssystem. Other third-generation products include Mirage Bond (Chameleon Dentalinclude Mirage Bond (Chameleon Dental Products, Kansas City, KS), The GlumaProducts, Kansas City, KS), The Gluma bonding system (Miles Dental Products,bonding system (Miles Dental Products, Elkhorn, IN), Scotchbond 2,X R-Primer /Elkhorn, IN), Scotchbond 2,X R-Primer / XR Bond (Sybron / Kerr), Clearfil LinerXR Bond (Sybron / Kerr), Clearfil Liner Bond System (Kuraray Co. Ltd.),Bond System (Kuraray Co. Ltd.), Denthesive (Kulzar Inc.), and PrismaDenthesive (Kulzar Inc.), and Prisma Universal Bond 3 (Dentsply / Caulk).Universal Bond 3 (Dentsply / Caulk). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 135.  The Prisma Universal Bond 3 Primer wasThe Prisma Universal Bond 3 Primer was unique among the third-generationunique among the third-generation systems in that it did not appear to removesystems in that it did not appear to remove the smear layer but penetrated throughthe smear layer but penetrated through and incorporated the smear layer in theand incorporated the smear layer in the adhesive to the underlying dentin. Bondadhesive to the underlying dentin. Bond strengths varied from 9 MPa to 18 MPa.strengths varied from 9 MPa to 18 MPa. The main problem with third generationThe main problem with third generation materials was longevity. Clinical studiesmaterials was longevity. Clinical studies showed that retention began to decreaseshowed that retention began to decrease after three years.after three years. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 136. Fourth Generation Dentin AdhesivesFourth Generation Dentin Adhesives  The complete removal of smear layer isThe complete removal of smear layer is achieved with fourth generation bondingachieved with fourth generation bonding systems. Although the smear layer acts as asystems. Although the smear layer acts as a “diffusion barrier” that decreases the“diffusion barrier” that decreases the permeability of dentin, it can also be consideredpermeability of dentin, it can also be considered an obstacle that must be removed so that resinan obstacle that must be removed so that resin can be bonded to the underlying dentincan be bonded to the underlying dentin substrate. Based on that consideration, fourth-substrate. Based on that consideration, fourth- generation dentin adhesive were introduced forgeneration dentin adhesive were introduced for use on acid etched dentin. Removal of theuse on acid etched dentin. Removal of the smear layer via acid-etching has led tosmear layer via acid-etching has led to significant improvements in the in vitro bondsignificant improvements in the in vitro bond strengths of resins to dentin.strengths of resins to dentin.www.indiandentalacademy.comwww.indiandentalacademy.com
  • 137.  The concept of fourth generation dentinThe concept of fourth generation dentin adhesives was first proposed byadhesives was first proposed by Nakabayashi et al.Nakabayashi et al.  Fourth-generation adhesives, such as All-Fourth-generation adhesives, such as All- Bond 2 (Bisco, Inc., Schaumburg, Illinois),Bond 2 (Bisco, Inc., Schaumburg, Illinois), OptiBond FL (Kerr Corporation, Orange,OptiBond FL (Kerr Corporation, Orange, California), and Scotchbond MultipurposeCalifornia), and Scotchbond Multipurpose (3M ESPE, St. Paul, Minnesota), are(3M ESPE, St. Paul, Minnesota), are basically composed of (1) an acid etchingbasically composed of (1) an acid etching gel that is rinsed off; (2) a solution ofgel that is rinsed off; (2) a solution of primers that are reactive hydrophilicprimers that are reactive hydrophilic monomers in ethanol, acetone, and/ormonomers in ethanol, acetone, and/or water;water; www.indiandentalacademy.comwww.indiandentalacademy.com
  • 138.  and (3) an unfilled or filled fluid bondingand (3) an unfilled or filled fluid bonding agent which generally containsagent which generally contains hydrophobic monomers such as bisphenolhydrophobic monomers such as bisphenol glycidyl methacrylate (Bis-GMA),glycidyl methacrylate (Bis-GMA), frequently combined with hydrophilicfrequently combined with hydrophilic molecules such as HEMA. Other fourth-molecules such as HEMA. Other fourth- generation adhesive systems includegeneration adhesive systems include Imperiva Bond (Shofu Dental Corp., MenloImperiva Bond (Shofu Dental Corp., Menlo Park, CA), Permaquik (Ultradent Products,Park, CA), Permaquik (Ultradent Products, South Jordan, Utah), Opti-BondSouth Jordan, Utah), Opti-Bond (Sybron/Kerr), Solid Bond (Kulzer), Liner(Sybron/Kerr), Solid Bond (Kulzer), Liner Bond 2 (Kuraray).Bond 2 (Kuraray). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 139.  Application of acid to dentin results inApplication of acid to dentin results in partial or total removal of the smear layerpartial or total removal of the smear layer and demineralization of the underlyingand demineralization of the underlying dentin. Besides demineralizingdentin. Besides demineralizing intertubular and peritubular dentin, acidsintertubular and peritubular dentin, acids open the dentin tubules and expose aopen the dentin tubules and expose a dense filigree of collagen fibers, thusdense filigree of collagen fibers, thus increasing the microporosity of theincreasing the microporosity of the intertubular dentin. Dentin isintertubular dentin. Dentin is demineralized upto 7.5demineralized upto 7.5 µµm, depending onm, depending on the type of acid, application time andthe type of acid, application time and concentration.concentration. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 140.  When primer and bonding resins are applied toWhen primer and bonding resins are applied to etched dentin, they penetrate the intertubularetched dentin, they penetrate the intertubular dentin, forming a “hybrid layer”. They alsodentin, forming a “hybrid layer”. They also penetrate and polymerize in the open dentinalpenetrate and polymerize in the open dentinal tubules, forming resin tags. So the adhesivetubules, forming resin tags. So the adhesive systems relying on hybridization as the primarysystems relying on hybridization as the primary mechanism for bonding and sealing can bemechanism for bonding and sealing can be categorized as fourth-generation systemscategorized as fourth-generation systems employing a dentin conditioning step followed byemploying a dentin conditioning step followed by application of a multicomponent resin system.application of a multicomponent resin system.  Mean shear bond strengths of the fourthMean shear bond strengths of the fourth generation systems are reported to range fromgeneration systems are reported to range from 17 MPa to greater than 24 MPa.17 MPa to greater than 24 MPa. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 141. Fifth Generation Dentin AdhesivesFifth Generation Dentin Adhesives ::  Manufacturers have been attempting toManufacturers have been attempting to reduce the number of steps needed andreduce the number of steps needed and the corresponding application time,the corresponding application time, making more user-friendly adhesivemaking more user-friendly adhesive systems. Now, nearly all dental materialssystems. Now, nearly all dental materials manufacturers have a “One-bottle”manufacturers have a “One-bottle” adhesive system available on the market.adhesive system available on the market. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 142.  . Within the last several years, numerous. Within the last several years, numerous simplified bonding systems have beensimplified bonding systems have been introduced : One Step (Bisco, Inc., Illinois);introduced : One Step (Bisco, Inc., Illinois); Prime & Bond 2.1 and Prime & Bond NTPrime & Bond 2.1 and Prime & Bond NT (Dentsply Caulk, Milford, Delaware); Prime &(Dentsply Caulk, Milford, Delaware); Prime & Bond 2.0 (Dentsply De Trey, Germany); SingleBond 2.0 (Dentsply De Trey, Germany); Single Bond (3M ESPE, St. Paul, Minnesota); OptiBondBond (3M ESPE, St. Paul, Minnesota); OptiBond Solo and OptiBond Solo Plus (Kerr Corporation,Solo and OptiBond Solo Plus (Kerr Corporation, California); PQ1 (Ultradent Products, Utah);California); PQ1 (Ultradent Products, Utah); Syntac Single Component, Syntac Sprint andSyntac Single Component, Syntac Sprint and Excite (Ivoclar Vivadent, Schaan, Liechtenstein);Excite (Ivoclar Vivadent, Schaan, Liechtenstein); Bond 1 (Jeneric, Connecticut), One Coat BondBond 1 (Jeneric, Connecticut), One Coat Bond (Colténe, New Jersey); Gluma One Bond(Colténe, New Jersey); Gluma One Bond (Heraeus Kulzer, Indiana), and many others.(Heraeus Kulzer, Indiana), and many others. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 143.  The distinguishing characteristic of the so-calledThe distinguishing characteristic of the so-called fifth-generation system is the combination of thefifth-generation system is the combination of the priming and bond resin application steps.priming and bond resin application steps. Although these systems are marketed as fasterAlthough these systems are marketed as faster and easier to use, all require several proceduraland easier to use, all require several procedural steps, including acid conditioning for maximalsteps, including acid conditioning for maximal adhesion to enamel and dentin. Similar to theadhesion to enamel and dentin. Similar to the fourth-generation materials, these materials relyfourth-generation materials, these materials rely on the Hybridization of dentin for achievingon the Hybridization of dentin for achieving adhesion. These materials also generally relyadhesion. These materials also generally rely on residual moisture in the dentin andon residual moisture in the dentin and hydrophilic water-chasing compositions to effecthydrophilic water-chasing compositions to effect resin penetration into the dentin. One-stepresin penetration into the dentin. One-step (Bisco Inc, Illinois) and Prime & Bond (Dentsply /(Bisco Inc, Illinois) and Prime & Bond (Dentsply / Caulk, Delaware) were among the first one-Caulk, Delaware) were among the first one- bottle adhesive systems marketed. Shear bondbottle adhesive systems marketed. Shear bond strength values of these materials in laboratorystrength values of these materials in laboratory exceeds 20 MPa.exceeds 20 MPa. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 144.  None of these systems is truly a one-None of these systems is truly a one- component system because they requirecomponent system because they require an acid treatment priming step for enamelan acid treatment priming step for enamel and in some case dentin. The shortand in some case dentin. The short comings of of the 4th and 5th generationcomings of of the 4th and 5th generation dentin bonding agents or the so calleddentin bonding agents or the so called ‘total etch’ bonding system are post-‘total etch’ bonding system are post- operative sensitivity. The total etchoperative sensitivity. The total etch technique lead to collapse of thetechnique lead to collapse of the demineralized matrix when it was air dried.demineralized matrix when it was air dried. So the use of primer pretreatment wasSo the use of primer pretreatment was necessary to re-expand the matrix prior tonecessary to re-expand the matrix prior to applying the final bonding agent.applying the final bonding agent. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 145. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 146. Sixth Generation Dentin AdhesivesSixth Generation Dentin Adhesives ::  Recently several bonding systems haveRecently several bonding systems have been developed and proposed as thebeen developed and proposed as the Sixth generation of adhesive materials.Sixth generation of adhesive materials. Two categories of bonding agentsTwo categories of bonding agents represent the self-etching primer concept.represent the self-etching primer concept. One category involves a combined acidOne category involves a combined acid etching / priming solution and a bondingetching / priming solution and a bonding agent. The other involves a singleagent. The other involves a single component, a combined acid etching,component, a combined acid etching, priming and bonding material.priming and bonding material. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 147.  The bonding mechanism of self-etchingThe bonding mechanism of self-etching primers is based on the simultaneousprimers is based on the simultaneous etching and priming of enamel and dentinetching and priming of enamel and dentin without rinsing, forming a continuum in thewithout rinsing, forming a continuum in the substrate and incorporating smear plugssubstrate and incorporating smear plugs into the resin tags. In addition tointo the resin tags. In addition to simplifying the bonding technique, thesimplifying the bonding technique, the elimination of rinsing and drying stepselimination of rinsing and drying steps reduces the possibility of over wetting orreduces the possibility of over wetting or over drying, thus eliminate the risk ofover drying, thus eliminate the risk of collagen collapse, which can have acollagen collapse, which can have a negative influence in adhesion.negative influence in adhesion. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 148.  All of these self-etching primers areAll of these self-etching primers are hydrophilic and they all contain somehydrophilic and they all contain some water. Although it would be desirable towater. Although it would be desirable to remove that water at the end of theremove that water at the end of the etching time, the presence of HEMA,etching time, the presence of HEMA, acidic monomers and dissolved calciumacidic monomers and dissolved calcium and phosphate ions may lower the vaporand phosphate ions may lower the vapor pressure of water, making it difficult topressure of water, making it difficult to remove all residual water prior toremove all residual water prior to polymerization.polymerization. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 149.  SEPs are attractive in that removal ofSEPs are attractive in that removal of smear layer and smear plugs is notsmear layer and smear plugs is not required. This reduces the potential forrequired. This reduces the potential for postoperative sensitivity, as well as thepostoperative sensitivity, as well as the bonding problems associated with thebonding problems associated with the transudation of dentinal fluid throughtransudation of dentinal fluid through patent dentinal tubules.patent dentinal tubules. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 150.  . The technique sensitivity associated with. The technique sensitivity associated with bonding to a dehydrated collapsedbonding to a dehydrated collapsed collagen matrix is also eliminated, ascollagen matrix is also eliminated, as water is an essential component in thesewater is an essential component in these systems. As they do not require asystems. As they do not require a separate acid-etching step, they are lessseparate acid-etching step, they are less likely to result in a discrepency betweenlikely to result in a discrepency between the depth of demineralization and thethe depth of demineralization and the depth of resin infiltrations since bothdepth of resin infiltrations since both processes occur simultaneously.processes occur simultaneously. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 151.  Self-etch adhesives are usually formed bySelf-etch adhesives are usually formed by increasing the concentration of acidic adhesiveincreasing the concentration of acidic adhesive monomers such as Phenyl-P, 4AET, 4 METAmonomers such as Phenyl-P, 4AET, 4 META etc. and dissolving them in HEMA with enoughetc. and dissolving them in HEMA with enough water to ionize the acidic functional groups.water to ionize the acidic functional groups. Within the last few years, numerous sixthWithin the last few years, numerous sixth generation dentin bonding systems have beengeneration dentin bonding systems have been introduced, such as One-up Bond F (Tokuyamaintroduced, such as One-up Bond F (Tokuyama Corp. Tokyo, Japan ), XENO CF Bond (DentsplyCorp. Tokyo, Japan ), XENO CF Bond (Dentsply Sankin, Tokyo, Japan ), Adper Prompt (3MSankin, Tokyo, Japan ), Adper Prompt (3M ESPE ), G-BOND (GC America ), Prompt L-popESPE ), G-BOND (GC America ), Prompt L-pop (3M ESPE, Seefeld, Germany ), Xeno IV(3M ESPE, Seefeld, Germany ), Xeno IV (Dentsply Caulk ), Clearfil SE Bond (Kuraray(Dentsply Caulk ), Clearfil SE Bond (Kuraray Dental, Japan)Dental, Japan) www.indiandentalacademy.comwww.indiandentalacademy.com
  • 152. Mechanism of actionMechanism of action  All adhesive formulations used in total-All adhesive formulations used in total- etch bonding systems contain 5-10 wt%etch bonding systems contain 5-10 wt% acidic monomers along with other mono oracidic monomers along with other mono or dimethacrylates. The pH of thesedimethacrylates. The pH of these formulations is between 2.5 and 4.5.formulations is between 2.5 and 4.5. These are too high to demineralize smearThese are too high to demineralize smear layers or etch dentin, hence thelayers or etch dentin, hence the requirement for a separate step of acidrequirement for a separate step of acid etching with 32-37% phosphoric acid (pHetching with 32-37% phosphoric acid (pH 0.1 – 0.6).0.1 – 0.6). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 153.  However, if the concentration of acidicHowever, if the concentration of acidic monomers was increased from the usualmonomers was increased from the usual 5-10wt% to 30-40wt%, and if these acidic5-10wt% to 30-40wt%, and if these acidic monomers were dissolved in 30-40wt%monomers were dissolved in 30-40wt% Hydroxyethyl methacrylate (HEMA), a veryHydroxyethyl methacrylate (HEMA), a very water soluble priming monomer, a newwater soluble priming monomer, a new formulation would be obtained that is bothformulation would be obtained that is both a self-etching, and self-priming adhesivesa self-etching, and self-priming adhesives system with a pH low enough (i.e., pH 1-2)system with a pH low enough (i.e., pH 1-2) to etch through smear layers into theto etch through smear layers into the underlying dentin.underlying dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 154.  The smear layers are either incorporatedThe smear layers are either incorporated into the hybrid layer or they are completelyinto the hybrid layer or they are completely dissolved. The surfaces are scrubbed fordissolved. The surfaces are scrubbed for 20 seconds and then gently air dried to20 seconds and then gently air dried to evaporate the small amount of water thatevaporate the small amount of water that is in the product to ionize the acidicis in the product to ionize the acidic monomers and facilitate solubilization ofmonomers and facilitate solubilization of calcium and phosphate ions from thecalcium and phosphate ions from the etched smear layer and the underlyingetched smear layer and the underlying intact tooth structure. The dried surface isintact tooth structure. The dried surface is then covered with a relatively hydrophobicthen covered with a relatively hydrophobic adhesive layers that is light cured. Someadhesive layers that is light cured. Some in vitro studies using SEPs reported bondin vitro studies using SEPs reported bond strengths of 20-28 MPa.strengths of 20-28 MPa.www.indiandentalacademy.comwww.indiandentalacademy.com
  • 155. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 156. SEVENTH GENERATION BONDINGSEVENTH GENERATION BONDING AGENTS:AGENTS:  This is the latest addition in the series ofThis is the latest addition in the series of bonding systems. This was the first trulybonding systems. This was the first truly one- step bonding agent for use with directone- step bonding agent for use with direct and indirect restoration. By using I- Bond,and indirect restoration. By using I- Bond, time can be saved and this product istime can be saved and this product is simple to apply, no mixing, no mess.simple to apply, no mixing, no mess. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 157. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 158.  I- bond is the only all- in- one etch-I- bond is the only all- in- one etch- disinfect- desensitize- prime- bonddisinfect- desensitize- prime- bond system. I- bond is the only bonding systemsystem. I- bond is the only bonding system with Gluma desensitizer. The patentedwith Gluma desensitizer. The patented chemistry used in I- bond is based onchemistry used in I- bond is based on UDMA and 4 – META in an acetone /UDMA and 4 – META in an acetone / water solvent.water solvent. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 159. MODERN CLASSIFICATION OF DENTINMODERN CLASSIFICATION OF DENTIN ADHESIVES:ADHESIVES:  Generation classification for bondingGeneration classification for bonding agents no longer exist as it was officiallyagents no longer exist as it was officially withdrawn by its introducer Dr. Vargas inwithdrawn by its introducer Dr. Vargas in the year 2000 with the advent of Clearfilthe year 2000 with the advent of Clearfil SE bond. The introducer Dr. Vargas hasSE bond. The introducer Dr. Vargas has officially accepted after introduction ofofficially accepted after introduction of Clearfil SE bond that there are only 2-Clearfil SE bond that there are only 2- systems : Total etch and self-etch.systems : Total etch and self-etch. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 160. Total etch Dentin Adhesive SystemsTotal etch Dentin Adhesive Systems  Simultaneous application of an acid toSimultaneous application of an acid to enamel and dentin seperately, known asenamel and dentin seperately, known as the total-etch technique. The total-etchthe total-etch technique. The total-etch technique was initiated in Japan bytechnique was initiated in Japan by phosphoric acid etching of dentin beforephosphoric acid etching of dentin before the application of a phosphate ester typethe application of a phosphate ester type of bonding agent. But there was noof bonding agent. But there was no significant improvement in bond strengths,significant improvement in bond strengths, possibly because of the hydrophobicpossibly because of the hydrophobic nature of the phosphonated resin.nature of the phosphonated resin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 161.  In addition, in the mid-1970s, some researchersIn addition, in the mid-1970s, some researchers had hypothesized that the application of acids tohad hypothesized that the application of acids to dentin might trigger inflammatory pulpaldentin might trigger inflammatory pulpal responses. Based on these concerns, acidsresponses. Based on these concerns, acids were believed to be contraindicated for directwere believed to be contraindicated for direct application on dentin and the total-etchapplication on dentin and the total-etch technique did not gain acceptance in Europe ortechnique did not gain acceptance in Europe or the United States. However, newer adhesivethe United States. However, newer adhesive systems (the fourth and fifth generationsystems (the fourth and fifth generation materials described earlier) based on the total-materials described earlier) based on the total- etch philosophy have proved successful both inetch philosophy have proved successful both in vitro and in vivo. Laboratory bond strengthsvitro and in vivo. Laboratory bond strengths usually vary from 17 MPa to 30 MPa, which areusually vary from 17 MPa to 30 MPa, which are very close to the values commonly obtained onvery close to the values commonly obtained on enamel.enamel. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 162.  Based on application procedure, total etchBased on application procedure, total etch technique may be of 3 steps or 2 stepstechnique may be of 3 steps or 2 steps  a) Three steps etch adhesives (Etching +a) Three steps etch adhesives (Etching + primer + adhesive)primer + adhesive)  b) Two step etch adhesives (Etching +b) Two step etch adhesives (Etching + primer, adhesive)primer, adhesive) www.indiandentalacademy.comwww.indiandentalacademy.com
  • 163. Interaction with tooth substrateInteraction with tooth substrate  A) To Enamel: Bonding to acid etched enamelA) To Enamel: Bonding to acid etched enamel theoretically requires an air-dried surface totheoretically requires an air-dried surface to allow the photo polymerizable hydrophobicallow the photo polymerizable hydrophobic bonding agent to be drawn by capillary attractionbonding agent to be drawn by capillary attraction into the pits created by acid etching. As a resultinto the pits created by acid etching. As a result two kinds of tag like extensions are formed.two kinds of tag like extensions are formed.  1. micro tags are circularly formed between1. micro tags are circularly formed between enamel prism peripheries.enamel prism peripheries.  2. micro tags are formed at the cores of enamel2. micro tags are formed at the cores of enamel prisms.prisms. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 164. B) To Dentin:B) To Dentin:  Primarily dentin smear layer produced duringPrimarily dentin smear layer produced during cavity preparation is removed by the etch andcavity preparation is removed by the etch and rinse phase, which results in a 3-5 um deeprinse phase, which results in a 3-5 um deep demineralization of the dentin surface anddemineralization of the dentin surface and collagen fibers are nearly completely uncoveredcollagen fibers are nearly completely uncovered from hydroxyl apatite at this state when afrom hydroxyl apatite at this state when a successive application of primer and adhesivesuccessive application of primer and adhesive results in interlocking between collagen networkresults in interlocking between collagen network and monomers. This network was first describedand monomers. This network was first described in 1982 and is commonly referred to as “Hybridin 1982 and is commonly referred to as “Hybrid layer”. Concurrently with hybridization, resin tagslayer”. Concurrently with hybridization, resin tags seal the unplugged dentin tubules and offerseal the unplugged dentin tubules and offer additional retention through hybridization of theadditional retention through hybridization of the tubule orifice wall.tubule orifice wall.www.indiandentalacademy.comwww.indiandentalacademy.com
  • 165. MERITS AND DEMERITS OF TOTALMERITS AND DEMERITS OF TOTAL ETCH ADHESIVESETCH ADHESIVES  Merits :Merits :  In-vitro and in-vivo study had shown effectiveIn-vitro and in-vivo study had shown effective adhesion to enamel and dentin.adhesion to enamel and dentin.  Best bond to enamel.Best bond to enamel.  Demerits :Demerits :  Risk of over etching dentin.Risk of over etching dentin.  Time consuming application procedure.Time consuming application procedure.  Risk of surface contamination when not usingRisk of surface contamination when not using rubber dam.rubber dam.  Sensitive to “over wet” or “over dry” dentinSensitive to “over wet” or “over dry” dentin surface conditions.surface conditions.  May lead to nanoleakage and early debonding.May lead to nanoleakage and early debonding.www.indiandentalacademy.comwww.indiandentalacademy.com
  • 166. Self- etching adhesive systemsSelf- etching adhesive systems  In Japan, self-etching adhesives have beenIn Japan, self-etching adhesives have been introduced in an attempt to simplify theintroduced in an attempt to simplify the application of dentin adhesive systems. Theseapplication of dentin adhesive systems. These self-etching systems are generally considered toself-etching systems are generally considered to be less technique sensitive. Furthermore, inbe less technique sensitive. Furthermore, in addition to simplifying the bonding technique,addition to simplifying the bonding technique, they eliminate the rinsing and drying steps thatthey eliminate the rinsing and drying steps that reduce the possibility of over wetting or overreduce the possibility of over wetting or over drying, both of which can negatively influencedrying, both of which can negatively influence adhesion (Jin, Kim & Park, 2002).adhesion (Jin, Kim & Park, 2002). www.indiandentalacademy.comwww.indiandentalacademy.com
  • 167.  These dentin bonding agents have a reducedThese dentin bonding agents have a reduced number of components and application steps,number of components and application steps, and this reduces the risk of saliva contaminationand this reduces the risk of saliva contamination in the field of operation. The mechanism ofin the field of operation. The mechanism of action, composition etc. is already described inaction, composition etc. is already described in previous section. These self-etching primers canprevious section. These self-etching primers can be devided into two subgroups, “mild”,be devided into two subgroups, “mild”, “moderate” and “strong”/ “aggressive”,“moderate” and “strong”/ “aggressive”, depending on their pH and thus on their abilitydepending on their pH and thus on their ability to penetrate dentin smear layers and their depthto penetrate dentin smear layers and their depth of demineralization into the subsurface dentin..of demineralization into the subsurface dentin.. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 168.  Theoretically, in an adhesive system thatTheoretically, in an adhesive system that simultaneously demineralizes dentin andsimultaneously demineralizes dentin and infiltrates it with monomers and are theninfiltrates it with monomers and are then polymerized in situ, no gaps would be leftpolymerized in situ, no gaps would be left between the primed dentin and thebetween the primed dentin and the demineralization front of the underlyingdemineralization front of the underlying dentin matrix. This results in a simplifieddentin matrix. This results in a simplified bonding procedure that improves thebonding procedure that improves the marginal seal and adhesion to dentin.marginal seal and adhesion to dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 169.  The goal of simultaneously etching andThe goal of simultaneously etching and priming dentin assumes that the adhesivepriming dentin assumes that the adhesive resin will penetrate beyond the smearresin will penetrate beyond the smear layer into the underlying sound dentin. Aslayer into the underlying sound dentin. As the pH of self-etching primer solution isthe pH of self-etching primer solution is sufficiently low to demineralize the smearsufficiently low to demineralize the smear layer and underlying dentinal surface,layer and underlying dentinal surface, etching and priming of the cavity can beetching and priming of the cavity can be accomplished simultaneously and wateraccomplished simultaneously and water rinsing after etching is eliminated.rinsing after etching is eliminated. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 170.  Scanning Electron Microscopic study hasScanning Electron Microscopic study has shown that there may be three types ofshown that there may be three types of bond failure.bond failure.  1. Adhesive failure (between the dentin1. Adhesive failure (between the dentin bonding agent and the tooth structure).bonding agent and the tooth structure).  2. Cohesive failure (within tooth2. Cohesive failure (within tooth structure).structure).  3. Mixed failure (adhesive and cohesive3. Mixed failure (adhesive and cohesive fracture of the material with part of itfracture of the material with part of it remaining on the tooth structure).remaining on the tooth structure).  According to Pashley et al. (Apr., 1999)According to Pashley et al. (Apr., 1999) there is no true adhesive failure in self-there is no true adhesive failure in self- etching bonding system.etching bonding system.www.indiandentalacademy.comwww.indiandentalacademy.com
  • 171.  There is an ongoing trend to move away fromThere is an ongoing trend to move away from the classical multi-component bonding systemsthe classical multi-component bonding systems toward simplified, consolidated adhesives thattoward simplified, consolidated adhesives that are more user-friendly. The combination ofare more user-friendly. The combination of hydrophilic primers and the comparativelyhydrophilic primers and the comparatively hydrophobic bonding resin components inhydrophobic bonding resin components in contemporary single-bottle, total-etch systemscontemporary single-bottle, total-etch systems and single-step, self-etch systems reflects moreand single-step, self-etch systems reflects more of the clinician - consumer’s desire forof the clinician - consumer’s desire for operational efficiency and time-saving ratheroperational efficiency and time-saving rather than genuine technological breakthrough. Fromthan genuine technological breakthrough. From a logistics perspective, the transition froma logistics perspective, the transition from functionality to procedural simplification signifiesfunctionality to procedural simplification signifies a continuing escalation in the hierarchy ofa continuing escalation in the hierarchy of product design and manufacturing.product design and manufacturing. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 172. ROLE OF PROTEINS IN DENTINROLE OF PROTEINS IN DENTIN BONDINGBONDING::  Another important issue in dentin bondingAnother important issue in dentin bonding is that drying demineralized dentinis that drying demineralized dentin effectively increases the potential for theeffectively increases the potential for the subsequent remineralization of that dentin.subsequent remineralization of that dentin. It may, therefore, be debatable to stateIt may, therefore, be debatable to state that air-drying has a deleterious effect onthat air-drying has a deleterious effect on long-term stability and durability of dentinlong-term stability and durability of dentin – resin bonded interfaces. In fact, no– resin bonded interfaces. In fact, no clinical study has ever supported thisclinical study has ever supported this theory.theory. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 173.  By becoming insoluble upon air – drying,By becoming insoluble upon air – drying, collagen may remain less susceptible tocollagen may remain less susceptible to degradation. These exposed collagendegradation. These exposed collagen fibers might be able to stretch uponfibers might be able to stretch upon tension and provide an elastic interface.tension and provide an elastic interface. Therefore this is one of numerousTherefore this is one of numerous questions addressed in the area of dentinquestions addressed in the area of dentin adhesion research. These questionsadhesion research. These questions pertain especially to extrapolationspertain especially to extrapolations obtained form only empirical observation sobtained form only empirical observation s of bond strength studies.of bond strength studies. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 174.  The partial removal of phosphoprotiensThe partial removal of phosphoprotiens from root lesions may enhance thefrom root lesions may enhance the remineralization potential of those lesions.remineralization potential of those lesions. This is important because acid – etchingThis is important because acid – etching deminieralizes dentin and may leave ademinieralizes dentin and may leave a layer of exposed collagen at the bottom oflayer of exposed collagen at the bottom of the hybrid layer (Kato G and Nakabayashithe hybrid layer (Kato G and Nakabayashi 1996) If this collagen had the ideal1996) If this collagen had the ideal environmental conditions for undergoingenvironmental conditions for undergoing reminerlization, nanoleakgae at thereminerlization, nanoleakgae at the bottom of the hybrid layer might be only anbottom of the hybrid layer might be only an initial temporary phenomenon that couldinitial temporary phenomenon that could be arrested by the demineralizationbe arrested by the demineralization process.process. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 175.  It has been reported that could beIt has been reported that could be arrested by remineralization process. Itarrested by remineralization process. It has been reported that whenhas been reported that when demineralized dentin is restored with andemineralized dentin is restored with an adhesive system, demineralized layeradhesive system, demineralized layer undergoes remineralization with in 4undergoes remineralization with in 4 months. Further studies are warranted tomonths. Further studies are warranted to determine the effect of etching on thedetermine the effect of etching on the concentration of non – collagenousconcentration of non – collagenous proteins and the role that these proteinsproteins and the role that these proteins have for the stability and durability of thehave for the stability and durability of the resin – dentin interfaces.resin – dentin interfaces. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 176. MICROLEAKAGE:MICROLEAKAGE:  Microleakage is the passage of bacteria andMicroleakage is the passage of bacteria and their toxins between restoration margins andtheir toxins between restoration margins and tooth preparation walls. Clinically, micro leakagetooth preparation walls. Clinically, micro leakage becomes important when one considers thatbecomes important when one considers that pulpal irritation is more likely caused by bacteriapulpal irritation is more likely caused by bacteria than by chemical toxicity of restorative materials.than by chemical toxicity of restorative materials. An adhesive restoration may not bondAn adhesive restoration may not bond sufficiently to etched dentin to prevent gapsufficiently to etched dentin to prevent gap formation at margins. The smear layer aloneformation at margins. The smear layer alone may be a pathway for micro leakage through themay be a pathway for micro leakage through the nanochannels within /’its core.nanochannels within /’its core. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 177.  Several studies have demonstrated thatSeveral studies have demonstrated that the pulpal response to restorativethe pulpal response to restorative materials is related to the degree ofmaterials is related to the degree of marginal leakage. Bacteria are able tomarginal leakage. Bacteria are able to survive and proliferate with in the fluid –survive and proliferate with in the fluid – filled marginal gaps under compositefilled marginal gaps under composite restorations. If the restoration isrestorations. If the restoration is hermetically sealed, bacteria will nothermetically sealed, bacteria will not survive.survive. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 178.  In some cases, pulpal inflammation mayIn some cases, pulpal inflammation may occur in the absence of bacteria. Someoccur in the absence of bacteria. Some bacterial by – products such asbacterial by – products such as endotoxins, material from cell walls, andendotoxins, material from cell walls, and some elements derived from bacterialsome elements derived from bacterial lipopolysaccharides, can cause damage tolipopolysaccharides, can cause damage to the pulpal tissue. This damage is initiatedthe pulpal tissue. This damage is initiated when leukocytes migrate into the pulp,when leukocytes migrate into the pulp, some times as early as 72 hours after thesome times as early as 72 hours after the pulp has been challenged.pulp has been challenged. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 179.  A useful property of dentin adhesives thatA useful property of dentin adhesives that remove the smear layer is that they may seal theremove the smear layer is that they may seal the resin-dentin interface and thus prevent exposureresin-dentin interface and thus prevent exposure of the pulp – dentin complex to bacteria andof the pulp – dentin complex to bacteria and their toxins. Several in vitro reports havetheir toxins. Several in vitro reports have demonstrated such sealing capacity for total –demonstrated such sealing capacity for total – etch dentin adhesives systems, but other studiesetch dentin adhesives systems, but other studies have shown the occurrence of severe leakagehave shown the occurrence of severe leakage associated with similar dentin adhesives. Recentassociated with similar dentin adhesives. Recent research also has demonstrated the presence ofresearch also has demonstrated the presence of nanometer-sized pores underneath or within thenanometer-sized pores underneath or within the resin – dentin inter diffusion area, despite theresin – dentin inter diffusion area, despite the presence of gap free restoration margins.presence of gap free restoration margins. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 180.  Therefore, it is debatable whether the absenceTherefore, it is debatable whether the absence of marginal opening will result in a perfect sealof marginal opening will result in a perfect seal between resin and dentin. Bonding the resin to abetween resin and dentin. Bonding the resin to a preparation with cavosurface margins in enamelpreparation with cavosurface margins in enamel is still the best way to prevent micro leakage.is still the best way to prevent micro leakage.  The occurrence of gaps at the resin – dentinThe occurrence of gaps at the resin – dentin interface may not cause immediate debonding ofinterface may not cause immediate debonding of the restoration. For example: in spite of havingthe restoration. For example: in spite of having demonstrated excellent marginal seal in vitro,demonstrated excellent marginal seal in vitro, opti bond (Kerr corporation, orange, California)opti bond (Kerr corporation, orange, California) does not completely seal the interface in vivo.does not completely seal the interface in vivo. Inspite of the probability of incomplete seal ofInspite of the probability of incomplete seal of dentin margins class V clinical studies usingdentin margins class V clinical studies using total – etch dentin adhesives systems report nototal – etch dentin adhesives systems report no findings of pulpal inflammation and. or necrosis.findings of pulpal inflammation and. or necrosis. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 181.  In vitro micro leakage studies generallyIn vitro micro leakage studies generally involve class V restorations. Specimensinvolve class V restorations. Specimens usually are thermo cycled and some timesusually are thermo cycled and some times mechanically loaded to stimulate oralmechanically loaded to stimulate oral conditions. To quantify micro leakageconditions. To quantify micro leakage specimens are immersed in a disclosingspecimens are immersed in a disclosing solution, such as silver nitrate, basicsolution, such as silver nitrate, basic fuchsin or methylene blue. The dyefuchsin or methylene blue. The dye penetrates the resin – dentin interfacepenetrates the resin – dentin interface wherever gap occurs. Some authors havewherever gap occurs. Some authors have speculated that in vivo leakage is lessspeculated that in vivo leakage is less than the corresponding dye penetration inthan the corresponding dye penetration in vitro.vitro. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 182. MICROLEAKAGEMICROLEAKAGE www.indiandentalacademy.comwww.indiandentalacademy.com
  • 183.  Sano et al (1995)Sano et al (1995) observed that most adhesiveobserved that most adhesive interface studies have involved SEMinterface studies have involved SEM demonstration of the penetration of adhesivedemonstration of the penetration of adhesive resins into demineralized dentin surfaces withresins into demineralized dentin surfaces with subsequent creation of hybrid layers.subsequent creation of hybrid layers. Nanoleakage is a term that describes theNanoleakage is a term that describes the diffusion of small ions or molecules within thediffusion of small ions or molecules within the hybrid layer in the absence of gap formation.hybrid layer in the absence of gap formation. This microscopic study examined theThis microscopic study examined the nanoleakage of the hybrid layer using a silvernanoleakage of the hybrid layer using a silver nitrate staining technique. It is important tonitrate staining technique. It is important to determine the location and morphology of thesedetermine the location and morphology of these nanometer-sized porosities that may permit thenanometer-sized porosities that may permit the hybrolysis of collagen fibers and degradation ofhybrolysis of collagen fibers and degradation of adhesive monomers.adhesive monomers.www.indiandentalacademy.comwww.indiandentalacademy.com
  • 184. BIOCOMPATIBILITY:BIOCOMPATIBILITY:  Besides demineralizing the dentin surface,Besides demineralizing the dentin surface, phosphoric acid removes the smear layerphosphoric acid removes the smear layer and opens the orifices of the tubules.and opens the orifices of the tubules. Despite past apprehension about potentialDespite past apprehension about potential acid penetration into the dentin tubulesacid penetration into the dentin tubules and pulp space, the interaction of etchantsand pulp space, the interaction of etchants with dentin is limited to the superficial 1.9with dentin is limited to the superficial 1.9 to 5.8to 5.8 µµm.m. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 185.  Thus, it is unlikely that the acid is directlyThus, it is unlikely that the acid is directly responsible for any injury to the pulp. Acidresponsible for any injury to the pulp. Acid penetration occurs primary along thepenetration occurs primary along the tubules, with penetration of intertubulartubules, with penetration of intertubular dentin occurring at a lower rate. Thedentin occurring at a lower rate. The effects of etchants on dentin are limited byeffects of etchants on dentin are limited by the buffering effect of hydroxyapatite andthe buffering effect of hydroxyapatite and other dentin components including theother dentin components including the collagen, which may act as a barrier thatcollagen, which may act as a barrier that reduces the rate of demineralization.reduces the rate of demineralization. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 186.  Marshall and others have elucidated theMarshall and others have elucidated the importance of pH regarding the effect ofimportance of pH regarding the effect of acids on dentin surfaces. Etching ratesacids on dentin surfaces. Etching rates increases dramatically with lower pH.increases dramatically with lower pH. Small differences in pH between acidicSmall differences in pH between acidic gels of similar phosphoric acidgels of similar phosphoric acid concentration may be responsible forconcentration may be responsible for distinct depths of dentin demineralization.distinct depths of dentin demineralization. Manufacturers add thickeners to facilitateManufacturers add thickeners to facilitate handling and other modifiers (such ashandling and other modifiers (such as buffers, surfactants etc.) to their etchingbuffers, surfactants etc.) to their etching gels, and these may contribute to thatgels, and these may contribute to that phenomenon.phenomenon. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 187.  Another problem associated with etchingAnother problem associated with etching dentin with acids is that current geldentin with acids is that current gel etchants are hypertonic. Application ofetchants are hypertonic. Application of hypertonic gel could osmotically draw fluidhypertonic gel could osmotically draw fluid from the dentin toward the surface andfrom the dentin toward the surface and alter the exposed collagen fibers. Ideally,alter the exposed collagen fibers. Ideally, one would use isotonic acids as dentinone would use isotonic acids as dentin etchants, which have been reported to beetchants, which have been reported to be well tolerated both by cell cultures and bywell tolerated both by cell cultures and by monkey pulps.monkey pulps. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 188.  For several decades, the development ofFor several decades, the development of adhesives systems was limited by the belief thatadhesives systems was limited by the belief that acids applied to dentin during proceduresacids applied to dentin during procedures caused pulpal inflammation. The use of basescaused pulpal inflammation. The use of bases and liners was considered essential to protectand liners was considered essential to protect pulp from the toxicity of restorative materials.pulp from the toxicity of restorative materials. This concept however, has changes over theThis concept however, has changes over the last 20 years. Even some clinical studies alsolast 20 years. Even some clinical studies also have been reported normal pulp responses afterhave been reported normal pulp responses after the application of adhesive on the dentin pulpthe application of adhesive on the dentin pulp complex when the pulp is macroscopicallycomplex when the pulp is macroscopically exposed. Another recent study showed that theexposed. Another recent study showed that the newest dentin adhesive systems are not harmfulnewest dentin adhesive systems are not harmful when applied to exposed pulps.when applied to exposed pulps. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 189.  Adverse pulpal reactions after aAdverse pulpal reactions after a restorative procedure may not be causedrestorative procedure may not be caused by the material used in that procedure, butby the material used in that procedure, but by bacteria remaining in, or penetratingby bacteria remaining in, or penetrating the preparation. In some cases, adversethe preparation. In some cases, adverse reactions are caused by a combination ofreactions are caused by a combination of factors, such as following:factors, such as following:  Bacterial invasion of pulp, either from theBacterial invasion of pulp, either from the tooth preparation or from an existingtooth preparation or from an existing carious lesion.carious lesion.  Bacterial penetration the pulp caused byBacterial penetration the pulp caused by faulty restoration.faulty restoration. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 190.  Pressure gradient caused by excessivePressure gradient caused by excessive dessication or by excessive pressuredessication or by excessive pressure during cementation.during cementation.  Traumatic injuriesTraumatic injuries  Iatrogenic tooth preparation – excessiveIatrogenic tooth preparation – excessive pressure, heat or friction.pressure, heat or friction.  Stress derived from polymerizationStress derived from polymerization contraction of composites andcontraction of composites and adhesives.adhesives.  www.indiandentalacademy.comwww.indiandentalacademy.com
  • 191. BONDING AMALGAM TO TOOTHBONDING AMALGAM TO TOOTH STRUCTURESTRUCTURE  Amalgam bonding systems may be usedAmalgam bonding systems may be used to seal underlying tooth structure andto seal underlying tooth structure and bond amalgam to enamel and dentin.bond amalgam to enamel and dentin. They require dual characteristics toThey require dual characteristics to achieve optimal wetting. Amalgam isachieve optimal wetting. Amalgam is strongly hydrophobic, whereas enamelstrongly hydrophobic, whereas enamel and dentin are hydrophilic.and dentin are hydrophilic. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 192.  Therefore the bonding system must beTherefore the bonding system must be modified with a wetting agent that has themodified with a wetting agent that has the capacity to wet both hydrophobic andcapacity to wet both hydrophobic and hydrophilic surfaces. Typical dentinhydrophilic surfaces. Typical dentin bonding systems may be used, but specialbonding systems may be used, but special 4-methyloxy ethyl trimellitic anhydride (4-4-methyloxy ethyl trimellitic anhydride (4- META) based systems are usedMETA) based systems are used frequently. This monomer moleculefrequently. This monomer molecule contains both hydrophobic and hydrophiliccontains both hydrophobic and hydrophilic ends.ends. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 193.  Macroshear bond strengths for joining amalgamMacroshear bond strengths for joining amalgam to dentin are relatively low (2 to 6 Mpa).to dentin are relatively low (2 to 6 Mpa). Although good bonding occurs to tooth structure,Although good bonding occurs to tooth structure, micromechanical bonding at the interface of themicromechanical bonding at the interface of the amalgam with the bonding system is poor. Mostamalgam with the bonding system is poor. Most debonding occurs by fracture along thisdebonding occurs by fracture along this interface. Since no chemical bonding occurs atinterface. Since no chemical bonding occurs at the interface, it is important to developthe interface, it is important to develop micromechanical bonding. To accomplish this,micromechanical bonding. To accomplish this, the bonding system is applied in much thickerthe bonding system is applied in much thicker layers (10 to 50 um), so that amalgam beinglayers (10 to 50 um), so that amalgam being condensed against the resin adhesive layer willcondensed against the resin adhesive layer will force fluid components of the amalgam toforce fluid components of the amalgam to squeeze into the unset bonding adhesive layersqueeze into the unset bonding adhesive layer and produce micromechanical laminations of theand produce micromechanical laminations of the two materials.two materials. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 194.  In a recent literature on “BONDINGIn a recent literature on “BONDING AMALGAM TO TOOTH STRUCTURE”,AMALGAM TO TOOTH STRUCTURE”, Gordon J. Christensen has stated thatGordon J. Christensen has stated that studies vary on the effectiveness ofstudies vary on the effectiveness of various amalgam bonding materials invarious amalgam bonding materials in strengthening prepared teeth or even instrengthening prepared teeth or even in bonding effectively to tooth structure.bonding effectively to tooth structure. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 195.  However, the views of thousands of dentistsHowever, the views of thousands of dentists participating in continuing education coursesparticipating in continuing education courses confirm that amalgam bonding agents definitelyconfirm that amalgam bonding agents definitely reduced postoperative tooth sensitivity. At thisreduced postoperative tooth sensitivity. At this time, bonding amalgam is growing in developedtime, bonding amalgam is growing in developed countries, but all amalgam bonding agents arecountries, but all amalgam bonding agents are not equal. Although most will reduce or eliminatenot equal. Although most will reduce or eliminate postoperative tooth sensitivity, only a few bondpostoperative tooth sensitivity, only a few bond amalgam to tooth structure. And even thoseamalgam to tooth structure. And even those bond at a significantly lower bond strength thanbond at a significantly lower bond strength than resin bonds to dentin.resin bonds to dentin. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 196. RECENT ADVANCEMENTS INRECENT ADVANCEMENTS IN BONDED AMALGAMBONDED AMALGAM RESTORATIONSRESTORATIONS www.indiandentalacademy.comwww.indiandentalacademy.com
  • 197. CONCLUSION:CONCLUSION:  Reliable bonding of resins to enamel and dentinReliable bonding of resins to enamel and dentin has revolutionized the practice of operativehas revolutionized the practice of operative dentistry. To satisfy demands of today’s dentaldentistry. To satisfy demands of today’s dental patients, improvements in materials andpatients, improvements in materials and procedures have been made to make it possibleprocedures have been made to make it possible to reproduce the natural appearance of naturalto reproduce the natural appearance of natural teeth with direct and / or indirect estheticteeth with direct and / or indirect esthetic restorations. Esthetic techniques involve arestorations. Esthetic techniques involve a bonding step to ensure durability and reliability.bonding step to ensure durability and reliability. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 198.  Thus, the ideal bonding system should beThus, the ideal bonding system should be indifferently to enamel and dentin, haveindifferently to enamel and dentin, have sufficient strength to resist failure as asufficient strength to resist failure as a result of masticatory forces, haveresult of masticatory forces, have mechanical properties close to those ofmechanical properties close to those of tooth structures be resistant totooth structures be resistant to degradation in the oral environment anddegradation in the oral environment and easy to use for the clinician.easy to use for the clinician.  Although important improvement inAlthough important improvement in bonding have been made in the last 30bonding have been made in the last 30 years, proper attention to technique and ayears, proper attention to technique and a good understanding of the bondinggood understanding of the bonding process remain essential for clinicalprocess remain essential for clinical success.success. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 199. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com

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