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Dentin bonding agents sneha


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seminar on dentin bonding agents

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Dentin bonding agents sneha

  2. 2.  Introduction  Principles of adhesion  Indications for Use of Adhesives  Advantages of Bonding Techniques  Mechanisms of adhesion  Factors affecting adhesion  Challenges in adhesion  Dentin bonding systems  Evolution of bonding agents  Classification of bonding agents  Conclusion  References
  3. 3.  The dental profession has spent most of its history restoring the effects of dental disease, but currently, the majority of restoration work is replacement or repair of prior treatment.  One reason for the change is population’s burgeoning interest in health and beauty, which is driving increased demand for cosmetic dental procedures.  Historically, for many adults, the achievement of a pretty smile has meant submission to extensive invasive procedures and high-cost fixed prosthodontics.  Improvements in tooth-colored restoratives and bonding technology have made cosmetic dental procedures more palatable and feasible.  In addition, newer technology allows the general practitioner to handle many previously complex esthetic problems more simply, conservatively, and economically. Introduction
  4. 4.  The fundamental objective of all restorations since centuries has been to create adhesion between two dissimilar surfaces: mineralized tooth structure and the restorative materials.  The invention of dentin bonding agent is like a - dream come true for dentistry, which led to the beginning of new era of adhesive dentistry.  The concept of dentistry with the introduction of adhesives has changed from - Extension for Prevention to PREVENTION OF EXTENSION !!!
  5. 5. Theprinciplesof adhesivedentistrydatesbackto 1955 whenbuonocore,afterobservingindustrialuse of phosphoricacidto improveadhesionof paintsandresin coatingsto metalsurfaces, appliedacidto theteethto ‘renderthetoothsurfacemorereceptiveto adhesion’ Michael Buonocore
  6. 6. The traditional “drilland fill”approachis fading now because of numerous advancements taking place in restorative dentistry.
  8. 8. Adhesion: The state in which two surfaces are held together by interfacial forces, which may consists of valence forces or interlocking forces or both. (The American Society for Testing and Materials; specification D 907) Adherend: The surface or substrate that is adhered Adhesive/adherent: A material that can join substances together, resist separation and transmit loads across the bond Adhesive failure: The bond that fails at the interface between the two substrates. Cohesive failure: The bond fails within one of the substrates, but not at the interface.
  9. 9. Adherend 1 Adherend 2 Adhesive System or Luting Cement Interface 2Interface 1 DENTAL JOINT ENAMEL, DENTIN > Liner, Base, Cement > Post and Core > Dental Amalgam > Implant > < Composite, Amalgam < Cast Inlay, Onlay, or Crown < All-Ceramic Inlay, Onlay, or Crown < Veneers, Maryland Bridges < Orthodontic Brackets AdhesiveInterface 1 DENTAL ADHESION
  10. 10. Diagrammaticrepresentation of dental adhesive system, where Adherend 1 is enamel, dentinor both. Adhesive is bondingagent, Adherend 2 is compositeresin
  12. 12. Adhesive restorative techniques are currently used to accomplish the following:  1. Restore Class I, II, III, IV, V, and VI carious or traumatic defects  2. Change the shape and the color of anterior teeth  3. Improve retention for metallic crowns or for porcelain-fused-to-metal crowns  4. Bond all-ceramic restorations  5. Bond indirect resin-based restorations  6. Seal pits and fissures  7. Bond orthodontic brackets  8. Bond periodontal splints and conservative tooth replacement prostheses
  13. 13.  9. Repair existing restorations (composite, amalgam, ceramic, or ceramometal)  10. Provide foundations for crowns  11. Desensitize exposed root surfaces  12. Seal beneath or bond amalgam restorations to tooth structure  13. Impregnate dentin that has been exposed to the oral fluids, making it less susceptible to caries  14. Bond fractured fragments of anterior teeth  15. Bond prefabricated and cast posts  16. Reinforce fragile roots internally  17. Seal apical restorations placed during endodontic surgery
  14. 14. Four different mechanisms of adhesion has been described: Mechanical adhesion – interlocking of the adhesive with irregularities in the surface of the substrate, or adherend. Adsorption adhesion – chemical bonding between the adhesive and the adherend. The forces involved may be primary (ionic or covalent) or secondary (hydrogen bonds, dipole interaction or van der Waals) valence forces. Diffusion adhesion – interlocking between the mobile molecules, such as adhesion of two polymers through diffusion of polymer chain ends across an interface. Electrostatic adhesion – an electric double layer at the interface of a metal with a polymer that is part of the total bonding mechanism.
  15. 15.  Wetting is the ability of the liquid to flow easily over the entire surface and adhere to the solid.  If the adhesive does not wet the surface of the adherend, adhesion between the adhesive and adherend will be negligible or nonexistent.  Wetting is principally influenced by: – Cleanliness of the adherend : Cleaner surface, greater adhesion. – Surface energy of the adherend: More surface energy, greater adhesion
  16. 16.  The extent to which an adhesive wets the surface of the adherend may be determined by measuring the contact angle, which is the angle, formed by the adhesive with the adherend at their interface.  The stronger the attraction of the adhesive for the adherend, the smaller will be the contact angle.  The zero contact angle is the best to obtain wetting
  17. 17.  Surface Energy ◦ The surface tension of the liquid and the surface energy of the adherend, ultimately determine the degree of wetting that occurs. ◦ Generally, the harder the surface , the higher the surface energy will be, which means that adhesive properties of the material will be higher.
  18. 18.  Surface Contamination ◦ The substrate surface should be clean as contamination prevents the adhesion. ◦ Adhesive should be able to fill their regularities making the surface smooth allowing proper or intimate contact
  19. 19.  Water ◦ The higher the water content, the poorer is the adhesion. ◦ Water canreact withbothmaterialsby the high polargroupandhydrogenbond whichcan hamper the adhesion
  20. 20. Steps in Forming Good Adhesion (1) Clean adherend (2) Good wetting (3) Intimate adaptation (4) Bonding (5) Good curing physical bonding chemical bonding mechanical bonding + –
  21. 21. • To bond to enamel, it is very important to focus on the mineral component (hydroxyapatite) of enamel. • Buonocore, 1955 – was the first to reveal the adhesion of acrylic resin to acid etched enamel. – used 85 percent phosphoric acid for etching • Silverstone revealed that the optimum concentration of phosphoric acid should range between 30 to 40 percent to get a satisfactory adhesion to the enamel.
  22. 22.  If the concentration is greater than 50 percent ◦ Monocalcium phosphate monohydrate may get precipitated  Concentrations lower than 30 percent, ◦ Dicalcium phosphate monohydrate is precipitated which interferes with adhesion.
  23. 23.  Percentage of etchants used: ◦ %35 to 40%  Use of lower concentrations of phosphoric acid and reduced etching time has shown to give an adequate etch of the enamel while avoiding excessive demineralization of the dentin
  24. 24.  Acid application time: ideally 10 seconds ◦ studies show that enamel should not be etched for more than 15 to 20 seconds Scanning electron micrograph of enamel etched with 35% phosphoric acid (3M ESPE, St. Paul, Minn) for 15 seconds.
  25. 25. Enamel acid etching – removes 10 micron of enamel Creates microporous layer 5 to50 microns deep Smooth surface – irregular surface with high surface energy 72dynes/cm Unfilled liquid acrylic resin (enamel bonding agent) Wets the surface Enters into microporosities by capillary action Two types of resin tags are formed Macrotags microtags  (form between enamel prisms peripheries ) (form at the core of enamel prisms )
  26. 26. Removes residual pellicle exposure to the inorganic crystallite component of enamel. Creates a porous layer with the depth of the pores ranging from 5-10 µm. Increases as the wettublity and surface area of the enamel substrate. Raises the surface energy of enamel with creation of reactive polar sites.
  27. 27.  Silverstone et al (1975) studied the morphological changes in SEM produced on the acid etched enamel surface.  Exposure of human enamel to conditioning solutions produces 3 basic etching patterns.
  28. 28.  Type I: (Preferential prism center etching) Dissolution of prism cores without dissolution of prism peripheries resulting in a honey comb appearance. The average diameter of the hollowed prism core is measured as about 3µm. This is the most commonest type of etching pattern.  Type II: Dissolution of peripheral enamel without dissolution of prism cores resulting in a cobblestone appearance  Type III : Mixed pattern. Etching pattern is less distinct and includes areas resembling type I and type II patterns as well as regions in which the etching pattern appears unrelated to prism morphology.This type of etching in general is associated with the presence of prism less enamel and appears as a generalized surface roughening.
  29. 29. Clinically a uniform dull appearance is an indication that the tooth surface has been adequately etched.  Silverstone in 1974 showed that etched enamel surface under polarized light resulted in 3 zones.  1. Etched Zone 2. Qualitative Zone 3. Quantitative Zone
  30. 30.  1. Etched Zone This is the narrow zone of enamel at about 10µm in depth, that is removed by etching. The fully reacted mineral crystals are removed resulting in the exposure of more reactive surface. This increased surface area and a reduced surface tension allows resin to wet in the etched surface more readily.  2. Qualitative Zone: This zone is about 20µm in depth and it is rendered porous during acid etching of the enamel when identified qualitatively using polarized light.  3. Quantitative Zone: This third zone is almost up to 20µm depth. It is qualitatively indistinguishable from adjacent enamel and can be detected with quantitative polarized light. In human enamel, the pores may be spherical, elongated or sometimes as large chamber that are connected to smaller channels called ink bottle systems.
  31. 31.  .
  32. 32.  Clean and wash the teeth with water.  Isolate to prevent any contamination from saliva or gingival crevicular fluid  Apply acid etchant in the form of liquid or gel for10 to 15 seconds.  Deciduous teeth require longer time for etching than permanent teeth because of the presence of aprismatic enamel in deciduous teeth
  33. 33. • Now apply bonding agent and low viscosity monomers over the etched enamel surface. • Generally, enamel bonding agents contain Bis-GMA or UDMA with TEGDMA added to lower the viscosity of the bonding agent. • The bonding agents due to their low viscosity, rapidly wet and penetrate the clean, dried, conditioned enamel into the microspaces forming resin tags.
  34. 34.  Fluorosed teeth have an altered structure, composition and appearance.  With the increase in severity of fluorosis enamel becomes more porous and sub-surface lesion extends towards the inner enamel.  Several studies have shown that composites can be bonded successfully to fluorosed enamel depending on the degree of fluorosis.  It is always recommended to grind the enamel before bonding as it is seen that bond strength of composites to ground enamel of teeth with moderate fluorosis is similar to that of normal teeth.  Acid etching is good for enamel bonding but not for dentin bonding in fluorosed teeth. As a consequence a good choice of adhesive, it would be a two-step self etch adhesive with an additional acid etching step for the enamel.
  35. 35. .
  36. 36.  Adhesion of restorative materials to enamel has become a routine and reliable aspect of modern restorative dentistry,  But adhesion to dentin has proved to be more difficult and less predictable.  Much of the difficulty in bonding to dentin is the result of the complex microstructure and variable composition of dentin in different areas of the tooth.
  37. 37.  Thus, the composition of dentin is much different than that of enamel, and one would expect it to behave differently when etched with acid.  The presence of water and organic components lower the surface energy of dentin and make bonding with hydrophobic resins essentially impossible.
  38. 38.  Dentin also contains a dense network of tubules that connect the pulp with the dentinoenamel junction (DEJ) .  A cuff of hypermineralized dentin called peritubular dentin lines the tubules.  The less mineralized intertubular dentin contains collagen fibrils with the characteristic collagen banding.  The intertubular dentin is penetrated by submicron channels, which allow the passage of tubular liquid and fibers between neighboring tubules, forming intertubular anastomoses
  39. 39.  Dentin is an intrinsically hydrated tissue, penetrated by a maze of 1- to 0.25-μm-diameter fluid-filled dentin tubules.  Movement of fluid from the pulp to the DEJ is a result of a slight but constant pulpal pressure  Pulpal pressure has a magnitude of 25 to 30 mm Hg or 34 to 40 cm H2O.  Dentinal tubules enclose cellular extensions from the odontoblasts and are in direct communication with the pulp .  Inside the tubule lumen, other fibrous organic structures are present, such as the lamina limitans, which substantially decreases the functional radius of the tubule.
  40. 40. Relative number of dentin tubules and tubule volume at different dentin levels as measured at different distances from the dentinoenamel Junction. Adapted from Heymann 1995. Distribution of tubules in dentin Dentin close to the pulp shows a higher tubule density than in dentin remote from the pulp. The higher the tubule density, the lower the bond strength values of the dentin adhesives to the dentin The relative area occupied by dentin tubules decreases with increasing distance from the pulp
  41. 41.  Created whenever dentin is cut or ground with hand or rotary dental instruments and is about 1 to 5 μm thick (Brannstrom, 1982).  It consists of debris that presumably reflects the composition of the underlying dentin.  Thus, the composition of superficial versus deep smear layers would be expected to be quite different.  It has a uniform, amorphous structure, which appears to completely occlude the orifices of all dentinal tubules.  Smear plugs are projections of the smear layer that extend to variable distances into dentinal tubules when the smear layer is created
  42. 42.  The smear layer has both advantages and disadvantages in the bonding process (Yap et al, 1994). Advantages include :  Reduction of dentin permeability to toxins and oral fluids;  Reduction of diffusion (usually inwards) and convection of fluids (outwards by hydrostatic pressure or inwards, for example, while restorations are cemented),  Reduction of wetness of cut dentin surfaces, and  Prevention of bacterial penetration of dentinal tubules.
  43. 43.  Wetness and the harboring of bacteria or their products,  It reduces the surface energy which compromises surface wetting,  Prevents the intimate surface contact between the adhesive and dentin substrate, and  Prevents resin penetration into dentinal tubules (Gwinnett, 1984; Rees and Jacobsen, 1990).  It acts like a separating agent since it is an intrinsically weak structure (5 to 6 MPa cohesive strength) that bond weakly to the underlying dentin (Tao and Pashley, 1988).  Further, the mineral component of the smear layer may dissolve slowly under a leaking restoration or may be removed by acid produced by bacteria to leave a gap which in turn increases marginal leakage and possibly secondary caries.
  44. 44. Factors such as :  radius and length of the tubules,  the viscosity of dentin fluid,  the pressure gradient,  the molecular size of the substances dissolved in the tubular fluid, and  the rate of removal of substances by the blood vessels in the pulp affect permeability. All of these variables make dentin a dynamic substrate and consequently a difficult substrate for bonding.
  45. 45. The factors important in understanding the over all ‘bonding equation’ is  Dentin factors  Tooth factors  Patient factors  Material factors  Clinical factors
  46. 46.  Quality of dentin Higher bond strength is achieved for younger teeth compared to the dentin of elderly patients. Altered dentin (sclertic or carious). Variation in density of the tubules. Location of dentin (whether peripheral or close to pulp)  Etching of dentin (too long etching results in impeded hybrid layer formation and produces a weaker bond strength.  The dentin should not be desiccated; it must be kept moist during the entire procedure. If it dries up, the collagen structure collapses.
  47. 47. Tooth factors: The tooth factors include Lesion size and shape Enamel and dentin structure Tooth flexure Tooth location Fluoride content Surface roughness Patient factors: Patient factors associated with dentin adhesion are: •The degree of occlusal stress •Patient’s age
  48. 48.  Saliva and/or blood contamination  Moisture contamination from handpieces or air-water syringes  Oil contamination from handpieces or air-water syringes  Surface roughness of tooth surface  Mechanical undercuts in tooth preparation  Fluoride content of teeth  Presence of plaque, calculus, extrinsic stains or debris  Presence of bases and liners on the prepared teeth
  49. 49. Conditioner (Cleanser, Etchant) Conditioner is usually a weak organic acid (e.g. maleic acid), a low concentration of a stronger inorganic acid (e.g. phosphoric or nitric acid), or a chelating agent (e.g. EDTA). Main Actions:  Heavily alters or removes the smear layer  Demineralizes peritubular and intertubular surface dentin and, thereby, exposes collagen fibrils.  Demineralizes up to a depth of 7.5 microns  Depth of demineralization depends on type of acid, its concentration, and etching time  More mineralized peritubular dentin is etched more deeply than the intertubular dentin  Increases dentin permeability by 4 to 9 times.
  50. 50.  Primer is usually a bifunctional monomer in a volatile solvent such as acetone or alcohol; a bifunctional monomer is one that has a hydrophilic end (i.e., one with an affinity for water) and a hydrophobic end (one lacking an affinity for water); Examples of bifunctional monomers include  HEMA (hydroxyethyl methacrylate),  NMSA (N-methacryloyl-5- aminosalicylic acid),  NPG (N-phenylglycine),  PMDM (pyromellitic diethylmethacrylate), and  4-META (4- methacryloxyethyl trimellitate anhydride).
  51. 51.  Links the hydrophilic dentin to the hydrophobic adhesive resin; is able to do this because of its bifunctional nature (i.e., primer's hydrophilic end bonds to the wet dentin and its hydrophobic end bonds to the adhesive resin)  Promotes infiltration of demineralized peritubular and intertubular dentin by its own monomers and those of the adhesive resin.  Increases wettability of the conditioned dentin surface and increases contact between the dentin and resin
  52. 52.  Adhesive is an unfilled or partially filled resin; may contain some component of the primer (e.g. HEMA) in an attempt to promote increased bond strength. Main Actions:  Combines with the primer’s monomers to form a resin-reinforced hybrid layer (resin-dentin interdiffusion zone) from 1 to 5 microns thick.  Forms resin tags to seal the dentin tubules provides methacrylate groups to bond with the subsequently placed resin composite
  53. 53.  One of the first products that used this method for enamel and dentin treatment was Scotchbond Multi-Purpose Adhesive, which used 10% to 12% maleic acid.  Scotchbond MPA and most other current-generation products now use the same acid for etching dentin that they use for etching enamel (i.e., concentrations of phosphoric acid that range from 32 to 40%).  This method of etching dentin with a 32 to 40% concentration of phosphoric acid is called the total-etch technique and was first discussed by Fusayama in 1977.
  54. 54. Acid washing / rinsing Removes smear layer Dissolves HA Drying shrinks remaining Collagen polymer molecules Rehydration / priming Swells collagen Mechanism of dentine bonding
  55. 55. Monomer penetration Mechanism of dentine bonding Monomer polymerisation And collagen entanglement
  56. 56.  Ideally a dentin bonding agent should have both hydrophilic and hydrophobic ends. The hydrophilic end displaces the dentinal fluid, to wet the surface. The hydrophobic end bonds to the composite resin. • Mechanism of Bonding M R X • Where, M is the double bond of methacrylate which copolymerizes with composite resin. • R is the spacer which makes the molecule large. • X is a functional group for bonding which bonds to inorganic or organic portion of dentin
  57. 57.  Bonding to the inorganic part of dentin involves ionic interaction among the negatively charged group on X ◦ for example, phosphates, amino acids and amino alcohols, or dicarboxylates) and the positively charged calcium ions.  Commonly used bonding systems employ use of phosphates.
  58. 58. • Bonding to the organic part of dentin – Interaction with • Amino (–NH), • Hydroxyl (–OH), • Carboxylate (–COOH), • Amide (–CONH) groups • Dentin bonding agents have – isocyanates, – aldehydes, – carboxylic acid – anhydrides and – carboxylic acid chlorides which extract hydrogen from the above mentioned groups and bond chemically. present in dentinal collagen.
  59. 59.  Developed in 1960s  Relied on adhesion to smear layer  No. of steps involved were two; etching of enamel + application of adhesive  Did not recommend dentin etch  Bowen formulated Cervident containing N- phenylglycine glycidyl methacrylate (NPG-GMA).  NPG-GMA is a surface-active comonomer that theoretically could mediate water- resistant chemical bonds of resin to dentinal calcium. Smear layer
  60. 60.  This means that one end of this molecule bonds to dentin while the other polymerizes with composite resin.  bond strengths - 2 to 3 MPa .  The clinical results with these systems were poor .  No improvement in marginal leakage when compared to conventional unfilled enamel bonding resins (Barkmeier and Cooley, 1991).  Based on Carbon-13 NMR analysis, it appears that no ionic bonding actually develops between NPG-GMA and hydroxyapatite. (Jorge Perdigao, Edward Swift).
  61. 61.  In the late 1970s the second-generation systems were introduced ,  Incorporated halophosphorus esters of unfilled resins such as bisphenol-A glycidyl methacrylate (Bis-GMA), or hydroxyethyl methacrylate (HEMA), which substituted methacrylate.  Mechanism by which they bond to dentin was postulated to be through an ionic bond to calcium by chlorophosphate groups.  The clinical performance of these bonding agents was relatively poor,  Shear dentinal bond strengths of only 2 to 6 MPa were reported
  62. 62.  A major reason for the poor performance of these bonding agents is the fact that they bond to the smear layer rather than to the underlying dentin hence,  Their bond strength is limited by the cohesive strength of the smear layer or the adhesion of the smear layer to the dentin below (Tao et al, 1988).  These bond strengths were not great enough to counteract contraction stress generated by shrinking composites, which is estimated to exceed 20 MPa in some cavities.  Furthermore, some studies indicate that bonds between phosphate esters and dentin may also be hydrolyzed by immersion in water.  Therefore, composite resin tends to separate from dentin, forming gaps at restoration margins and increasing the microleakage at margins in dentin or cementum
  63. 63.  Etched tubule dentin bonding agents Representative brand: Dentin Bonding System (Den-Mat).  Phosphate ester dentin bonding agents ◦ Representative brands: Bondlite (SDS/Kerr), Creation Bond (Den-Mat), Prisma Universal Bond (Caulk), and Scotchbond (3M).  Polyurethane dentin bonding agents Representative brand: Dentin-Adhesit (Ivoclar Vivadent).
  64. 64.  In third generation the smear layer was partially removed or modified rather than complete removal.  In most of the systems, the phosphate primer modifies the smear layer by softening it; after penetration, it cures, forming a hard surface.  The adhesive is then applied, attaching the cured primer to the composite resin.  Bonding to smear layer-covered dentin was not very successful before 1990, however, because the resins did not penetrate through the smear layer, bond was weak approached 10-12 MPa (Leinfelder, 1993)
  65. 65.  The basis of third generation systems was laid in 1979 when the Japanese philosophy of acid-etching the dentin to remove the smear layer gained acceptance.  The acid opens dentinal tubules partially and increases their permeability to form micromechanical attachment.  Based on this total-etch concept Clearfil New bond was introduced in 1984, which contains HEMA and 10-methacryloyoxy-decyl-dihydrogen phosphate (10-MDP), which had long hydrophobic and short hydrophilic components as active components.
  66. 66. 1st step: -Total etching Leaving free minerals on surface -Rinse surface -Total drying of surface 2nd step : adding primer 3rd step: Adding adhesive resin ,Then adding Composite Smear layer Residual water Primer Adhesive Composite
  67. 67.  Fourth-generation dentin adhesives were introduced for use on acid etched dentin.  Because the clinical technique involves simultaneous application of an acid to enamel and dentin, this method is commonly known as the total-etch technique.  Also called the etch and rinse technique, it was the most common strategy for dentin bonding during the 1990s and remains popular today.  Application of acid results in partial or total removal of smear layer and demineralization of underlying dentine up to depth of 7.5 microns
  68. 68. Application of acid to dentin partial or total removal of the smear layer and demineralization of intertubular and peritubular dentin, open dentin tubules, and exposed collagen fibers, increased microporosity of the intertubular dentin  Dentin is demineralized by up to 7.5 μm depending on the type of acid, application time, and concentration  The primer in a three-step system is designed to increase the critical surface tension of dentin.  When primer and bonding resins are applied to etched dentin, they penetrate the intertubular dentin, forming a resin-dentin interdiffusion zone, or hybrid layer.  They also penetrate and polymerize in the open dentinal tubules, forming resin tags
  69. 69. In the three-bottle total etch bonding technique, acid is used to remove the smear layer and smear plugs from the dentin and to remove peritubular dentin, increasing the diameter of the tubules thereby (Fig. A) that will form stronger resin tags. The etched surface is then primed with dilute methacrylates (red) in a volatile solvent (Fig. B) to insure that the matrix is expanded and precoated with methacrylates. Then a solvent-free adhesive (green) is applied that diffuses into the primed surface and down into the tubules where it polymerizes with the primer (Fig. C).
  70. 70.  Fourth-generation adhesives such as All-Bond 2, OptiBond FL and Scotchbond Multipurpose are basically composed of  An acid etching gel that is rinsed off;  A solution of primers that are reactive hydrophilic monomers in ethanol, acetone, and/or water  An unfilled or filled fluid boding agent- hydrophobic monomer such as Bis-GMA combined with hydrophilic HEMA.
  71. 71.  All-Bond 2 and Scotchbond Multipurpose are two of the first fourth-generation adhesive systems, which rely on the hydration of dentin as a critical parameter for effective bonding.  All-Bond 2 uses a phosphoric acid enamel/dentin conditioning step to be followed by the application of hydrophilic primers containing N-tolyglycine-glycidyl methacrylate (NTG-GMA) and biphenyl methacrylate (BPDM) in acetone.  This priming layer is followed by an unfilled resin containing Bis-GMA and HEMA.  The original Scotchbond Multipurpose conditioned dentin with 10% maleic acid solution followed by a primer consisting of an aqueous layer of HEMA and Vitrebond copolymer.  The adhesive resin system is also a Bis-GMA resin containing HEMA. Later, maleic acid was replaced by phosphoric acid to generate more consistent results.
  72. 72.  Other fourth-generation adhesive systems include  Imperiva Bond (acid treatment – primer containing HEMA & 4-acryloxyethyltrimeric acid - Triethylene glycol dimethacrylate (TEGDMA), dimethylamino ethylmethacrylate and butylated hydroxytolune (BHT),  Permaquik (acid conditioning- ethanol based primer (naturally occurring elastic resin+ Canada balsam+HEMA)- adhesive resin (Bis-GMA+glass filler).  Optibond and Solidbond employs partially filled adhesive resins, use of fillers in the adhesive resin exhibits less shrinkage in the bonding layer  It is hypothesized that generating less residual shrinkage stress in the adhesive reduces bond failures.
  73. 73. ProBOND is unique in that it does not require dentin conditioning.  It consists of an acetone/ethanol primer with a phosphate adhesion promoter, PENTA and an adhesive containing a urethane dimethacrylate resin (UDMA), PENTA and glutaraldehyde. Liner Bond 2 introduced the concept of a no-rinse self-etching primer.  The primer consisted of pheny-P, HEMA, and N-methacryloyl 5-aminosalicyclic acid (5-NMSA) and  a bonding resin containing 10-methacryloyldecyl dihydrogen phosphate (MDP), Bis-GMA and colloidal silica
  74. 74.  An additional feature of fourth-generation systems is the claim for their utility in multipurpose applications.  In addition to dentin and enamel adhesion, bond strength claims were made for cast alloys, amalgam and porcelain,  Mean shear bond strength of the fourth-generation systems are reported to range from 17MPa to great than 34MPa.  If the clinician carefully adhered to the specific recommendations made regarding the methods and times required for application of the bonding agent, the results were highly effective.  Shear bond strengths to both enamel and dentin routinely approximated 25 MPa.  Such a process has permitted forms of esthetic and functional treatment not previously conceived.
  75. 75. 1st step: -Total etching(removal of smear layer) Leaving free minerals on surface -Rinse surface -Without drying of surface (residual water left) 2nd step : adding primer 3rd step: Adding adhesive resin & then composite Composite Smear layer Residual water Primer Adhesive resin
  76. 76.  Ethanol-based adhesives Eg: OptiBond Solo (and later OptiBond Solo Plus),  Acetone-based adhesives All- bond 2 and One-Step (BISCO)  Water-based adhesives Scotchbond MP and ScotchBond 1
  77. 77.  These also are called the “one bottle” systems because they combine the primer and bonding agent into a single solution.  A separate etching step still is required.  .The first of these products was LD Caulk’s Prime & Bond. When originally introduced, it was to be used only when placing direct composite resin restorations.  Recently, it underwent two changes and has been renamed Prime & Bond 2.1.  The changes were addition of fluoride and inclusion of an elastomeric monomer to reduce the DBA‘s rigidity.
  78. 78.  Other fifth-generation products include OptiBond Solo (SDS/Kerr), Single Bond (3M ESPE), PQ1 (Ultradent), and Gluma One Bond (Heraeus Kulzer).  In general, these products have limitations.  Many require at least as much time to apply or even more time than three-component products and they lack many of the components necessary to perform multisubstrate bonding.  It also appears important to apply multiple coats of these agents so that there is an adequately thick resin layer on top of the hybrid layer.  This helps protect the DBA from early failure when the resin composite shrinks during polymerization.
  79. 79.  Recently have been marketed  Contains extremely small filler particles.  Include the products Prime & Bond NT (Dentsply/Caulk) and Excite (Ivoclar Vivadent).  Prime & Bond NT contains 7 nanometer fillers , has a greater concentration of resin and a smaller molecular weight resin.  These changes, are said to make the DBA tougher, stronger, and able to cover adequately with a single coat;  it is also claimed to penetrate dentin better, provide improved marginal integrity, and have a low film thickness.  Ivoclar Vivadent’s Excite contains 12-nanometer fillers and is packaged in a single-use capsule. It is very fast to apply, covers dentin in one coat, and comes with a graphics-only instruction card.
  80. 80.  Introduced in the late 1990s and early 2000s .  Self-etching primer and adhesive: ◦ Available in two bottles:  Primer  Adhesive ◦ Primer is applied prior to the adhesive ◦ Water is the solvent in these systems. Self etching adhesive ◦ Available in two bottles:  •Primer  Adhesive ◦ A drop from each bottle is taken, mixed and applied to the tooth surface, for example, Prompt L-pop.
  81. 81.  Mechanism of bonding: In these agents as soon as the decalcification process starts, infiltration of the empty spaces by the dentin bonding agent is initiated
  82. 82.  Comparable adhesion and bond strengths to enamel and dentin  Reduces postoperative sensitivity because they etch and prime simultaneously  They etch the dentin less aggressively than total etch products  The demineralized dentin is infiltrated by resin during the etching process
  83. 83.  Since they do not remove the smear layer, the tubules remain sealed, resulting in less sensitivity  They form a relatively thinner hybrid layer than traditional product which results in complete infiltration of the demineralized dentin by the resin monomers. This results in increased bond strength  Much faster and simpler technique  Less technique sensitive as fewer number of steps are involved for the self etch system
  84. 84. XenoIII Clearfilse bond promptl pop Examples:
  85. 85.  They achieve the same objective as the sixth generation systems except that they simplified the multiple sixth generation materials into a single component, single bottle one-step self- etch adhesive, thus avoiding any mistakes in mixing.  Developed in late 2000s  All in one concept, i.e. components available as single component  Uses self etch primer  Good bond strength.  No postoperative sensitivity.  Also have disinfecting and desensitizing properties.  They have attained consistently lower bond strengths than the fourth and fifth-generation adhesives
  86. 86.  Laboratory studies show that bond strengths and margin sealing to be equal to the sixth-generation systems.  iBondTM is a seventh-generation, single-component, no-mix, one- step application dental adhesive with an etchant, adhesive, desensitizer, and photoinitiator.  Laboratory testing confirms that iBondTM has physical characteristics similar to other self-etching adhesives and may be used in all clinical situations where dental adhesives are required.
  87. 87.  GC has also introduced one component self-etching light-cured adhesive under trade name of G-BOND.
  88. 88. STEP 4TH GEERATION 5TH GENERATION 6TH GENERATION 6TH GEN (MIXING REQUIRED) 7TH GEN SELF ETCHING ADHESIVE SELF ETCHING ADHESIVE Etching of enamel dentine Etchant Etchant Self etching primer Self-etching, self-priming resin/sealer Self-etching, self-priming resin/sealer desensitizer, disinfectant Priming of dentin Primer Self-priming resin/sealer Self –etching primer Self-etching, self-priming resin/sealer Self-etching, self-priming resin/sealer desensitizer disinfectant Sealing of enamel and dentine Resin/sealer Self-priming resin/sealer Resin/sealer Self etching, self priming resin/sealer Self-etching, self-priming resin/sealer desensitizer disinfectant
  89. 89.  A new category of composite resin restorative materials, which include what could be referred to as an “eighth-generation” bonding system, has just become available for use.  This new technology features a bonding agent which is contained within the composite resin restorative material.  A self-etching, self-adhering flowable composite technology eliminates the need for a separate bonding application step with composites for direct restorative procedures.  Utilizing previous adhesive technology (found in the OptiBond system [Kerr]), this new self-etching, self-bonding flowable composite resin system (Vertise Flow [Kerr]), simplifies the placement of direct composite restorations.
  90. 90.  Since fifth-, sixth- and seventh-generation systems are incompatible with self- cure materials and dual-cure materials that cannot be effectively light-cured  Futura bond DC dual cured  It is dual-cured and works with all light-, self- or dual-cured resins  It takes only 35 sec. from start to finish  It needs only one coat .  Futurabond DC cures without any light in the self-cured mode. This is a big advantage for root canal cementation.  Futurabond DC eliminates the problem of the “pooling effect” with moisture
  91. 91.  A new system would be developed that had the best attributes of the fourth generation and the ease of the sixth-generation bonding systems, and that system is Surpass® from Apex  Surpass is an eighth-generation material because it is very different from other generations.  It consists of three bottles: an etchant/conditioner, a primer, and a separate hydrophobic bonding resin.  In that regard, it resembles fourth-generation materials but the etchant/conditioner is not rinsed from the tooth.  Thus, Surpass also has characteristics of the sixth generation—the ease of a no-rinse system but the performance of a fourth-generation system.
  92. 92.  Surpass 1 is applied to the dentin and enamel for about 10 seconds, agitating gently.  Three brushfuls of Surpass 2 are then applied right onto the wet preparation.  Once the three brushfuls have been applied, the preparation is dried thoroughly for 10 seconds. It cannot be overdried and the drier the tooth is following application of Surpass 2, the better the result.  Then a layer of Surpass 3 is applied to the preparation and light-cured for 10 seconds.  This is the only technique for Surpass no matter what kind of procedure is being performed..
  93. 93.  Surpass may be used with any resin materials—dual-cure, self-cure, and light- cure—and no catalysts are required.  For use with indirect restorations, Surpass is simply made very thin prior to light- curing.  For direct restorations, the bonding resin can be made to the desired thickness, although a thin uniform layer is recommended.  Surpass dentin bond strengths have been demonstrated to be in the mid-50 MPa range
  94. 94.  A dentin bonding agent is a low viscosity unfilled or semifilled resin for easy penetration and formation of a hybrid layer.  When a bonding agent is applied, part of it penetrates into the collagen network, known as intertubular penetration and the rest of it penetrates into dentinal tubules called intratubular penetration.  In intertubular penetration, it polymerises with primer monomers forming a hybrid layer/resin reinforced layer
  95. 95.  Hybridization is the process of formation of a hybrid layer.  The hybrid layer is the phenomenon of formation of a resin interlocking in the demineralized dentin surface. The hybrid layer is responsible for micromechanical bonding between tooth and resin
  96. 96.  When dentin is treated with a conditioner, it exposes the collagen fibril network with interfibrillar microporosities.  These spaces are filled with low viscosity monomers when primer is applied.  This layer formed by demineralization of dentin and infilteration of monomer and subsequent polymerization is called the hybrid layer.  Hybridoid layer is that area of demineralized dentin into which resin fail to penetrate
  97. 97. 1. Top layer: Consists of loosely arranged collagen fibrils and interfibrillar spaces filled with resin. 2. Middle layer: Consists of interfibrillar spaces in which hydroxyapatite crystals have been replaced by resin monomer because of the hybridization process. 3. Bottom layer: Consists of almost unaffected dentin with a partly demineralized zone of dentin
  98. 98.  The hybrid layer promotes good bond strength,  Behaves like an impermeable membrane that can prevent noxious stimuli from invading pulpal tissue through dentinal tubules. Hybridized dentin reduces the  risk of microleakage,  incidence of secondary caries and  post-operative sensitivity.
  99. 99. Diagrammatic presentation of different zones of hybrid layer
  100. 100.  Concerns have been raised that aggressive etching of the dentin may cause demineralization to a depth that might be inaccessible to complete resin impregnation.  If this occurred, a collagenous band at the base of the hybrid, not impregnated by resin, would dramatically weaken the resin-dentin bond and consequently, the durability of bond.  Incomplete resin penetration has been described as causing a microporous dentinal zone at the base of hybrid layer (Sano et al, 1994) , which is thought to be a pathway for nanoleakage of fluids, causing hydrolysis of collagen and a reduction in longevity of bond.
  101. 101. • By etching dentin, the smear layer and minerals from it are removed, exposing the collagen fibers • Areas from where minerals are removed are filled with water. • This water acts as a plasticizer for collagen, keeping it in an expanded soft state. • Thus, spaces for resin infiltration are also preserved. But these collagen fibers collapse when dry and if the organic matrix is denatured. • This obstructs the resin from reaching the dentin surface and forming a hybrid layer
  102. 102. • The desired effect of acid etching, which is increased permeability • For this reason, presence of moist/wet dentin is needed to achieve successful dentin bonding. • When primer is applied to wet/moist dentin, water diffuses from the primer to the organic solvent and the solvent diffuses along with the polymers into the demineralized dentinal matrix and tubules.
  103. 103. Schematic (on the left) and transmission electron micrograph, on the right, of the “over-wet” phenomenon. In the total-etch, wet bonding technique, there is the danger that some regions in complex cavity preparations (such as proximal boxes) may be too wet. When single bottle primer/adhesives are applied, the solvent may diffuse into the water, forcing adhesive monomers to undergo phase changes, forming blisters, resin globules, etc. Note that although the etched intertubular dentin has taken up resin to form hybrid layers (red zone on left) the adhesive (blue) did not form resin tags, but left the tubules in communication with microblisters filled with water (light blue). These blisters may compress when the restoration is under occlusal function, forcing dentinal fluid toward the pulp and causing post-operative sensitivity. This is one of the possible complications of this technique-sensitive bonding method.
  104. 104. Transmission electron micrographs of dentin bonded with an all-in-one adhesive, then placed in 37ºC water for 24 hrs prior to soaking in silver nitrate to demonstrate the presence of water-filled (now silver-filled) channels called “water trees” (finger-pointers) extending from the hybrid layer (H) and passing through the cured adhesive layer. The black silver deposits indicate where there were water-filled channels. Such water trees do not form in self-etching primer adhesives.
  105. 105. Modern dentin adhesives systems are classified as  Group one: Modify the smear layer and incorporate in the bonding process. They are further classified in one step and two step smear layer modifying system.  Group two: Complete removal of the smear layer. Again they are further classified in two and three step removing systems, depending on a combined or a separate application of a primer and adhesive resin.  Group three: Dissolve the smear layer.
  106. 106. 3-COMPONENT SYSTEMS (E + nP + B)  Scotchbond Multipurpose Plus (3M)  Permaquick (Ultradent)  Bond-It (Jeneric / Pentron)  All-Bond 2 (BISCO)  Tenure A/B/S (Denmat)  ProBond (Dentsply) 2-COMPONENT SYSTEMS (nEP + B)  Clearfil SE Bond & LinerBond 2v (Kuraray)  Tyrian SPE (Bisco)  Optibond Solo SE Plus (Kerr)  Fluoro Bond (Shofu)  UniFil Bond (GC)  Mac Bond II (Tokuyama)  NanoBond (Pentron) 2-COMPONENT SYSTEMS (E + nPB)  Syntac Single Component (Ivoclar)  Ecusit Primer/Mono (DMG Hamburg)  One Coat Bond (Coltene / Whaledent)  Bond-1 (Jeneric / Pentron)  Tenure Quik with Fluoride (Denmat)  Solid Bond (Hereaus-Kulzer)  Imperva Bond (Shofu)  EG Bond (Sun Chemical)  PQ1 (Ultradent)  Easy Bond (Parkell)  Paama 2 and Stae (SDI)  Prime&Bond NT (Dentsply)  Single-Bond (3M)  Optibond Solo and Solo Plus (Kerr)  One-Step (BISCO)  Excite (Ivoclar/Vivadent)  OSB Bonding System (ESPE)  IntegraBond (Premier) 1-COMPONENT SYSTEMS (nEPB)  AQBond (Sun Medical)  or Touch-and-Bond(Parkell)  Adper Prompt or LP3 (3M-ESPE)  Solist (One-bottle-bond) (DMG Hamburg)  iBond (Hereaus-Kulzer)  Xeno III (Dentsply)
  108. 108.  Besides the use of dentin bonding agent as a normal part of resin bonding, they have other clinical applications like: ◦ Metal-Resin bonding of indirect resin-bonded inlay, onlay, crown or veneer. ◦ As amalgam bonding agent. ◦ Prevention and treatment of hypersensitivity. ◦ In establishing apical and coronal seal of the root along with resin ◦ Pulp capping agent ◦ As a protective coat for glass ionomer restorations
  109. 109. Amalgam Bonding A technique to bond amalgam to the cavity.
  110. 110.  Conserve more tooth structure by reducing the need to remove sound tooth tissue for mechanical retention.  Increased Amalgam retention.  Reduce marginal leakage  Reduce the need for dentine pins.  Potentially reduce sensitivity  Improve fracture resistance  Improved amalgam margins
  111. 111.  Resin Cements ( Panavia)  Adhesive Bonding Agents -initially designed for composites -OptiBond solo -Amalgambond -Scotchbond multipurpose
  112. 112.  Etching dentine opens up dentinal tubules enabling adhesive resin to flow into dentine and is retained micromechanically  Adhesive resin adheres to amalgam roughness micromechanically and by 4-META adhesive
  113. 113.  Decreased microleakage  YES  Increased amalgam retention ◦ YES, if cavity lacks mechanical retention  Avoids risk of using pins ◦ YES, 20% of pins perforate, 80oC rise
  114. 114.  Improved amalgam margins ◦ Depends on adhesive used. Panavia weakens amalgam at margins ◦ Technique may reduce incidence of ditching  Tooth reinforcement ◦ YES, if large cavity ◦ NO, if small cavity
  115. 115.  Not recommended for routine amalgam cavities with sufficient mechanical retention and undercuts. No evidence of increased benefit to balance increased costs.  Useful for large multisurface amalgams to avoid use of pins  Useful for amalgam repairs  Some easier to use than others
  116. 116. Technique  Place matrix band ( lightly vaselined)  Etch 10% phosphoric acid  Wash and dry  Apply adhesive ( Kerr Optibond solo)  Blow off excess solvent  Light cure  Pack amalgam
  117. 117.  Increased cost of restoration  Technique sensitive?  Not in use long enough to permit adequate evaluation of clinical performance  Adhesion may breakdown over time
  118. 118. Summary  Amalgam is an excellent core build-up material for posterior teeth  Excellent interim restoration for posterior teeth .  Adhesives can be used to improve retention in large amalgam restorations and cores.  Adhesives and preparation features can often substitute for pin retention for cores
  119. 119. The choice may be Confusing. It is easy for the clinician to believe that a newsystemis betterover the old onesbut this may not alwaysbe true. SO: Chemistryis more important than the company. Technique is more important than the material. What we have to choose:
  120. 120. Thank you