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Dentin bonding agents / rotary endodontics courses

The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
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Dentin bonding agents / rotary endodontics courses

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing Dental Education WWW.INDIANDENTALACADEMY.COM
  2. 2. • Introduction • Criteria For Bonding Agent • Terminologies • Contents of Bonding System • Bonding to dentin is Challenging! • History • Classifications • Generations Of DBA • Newer DBA • Conclusion • References WWW.INDIANDENTALACADEMY.COM
  3. 3. Introduction • Today operative dentistry primarily involves “minimal invasive or “minimum intervention” . Only the lost or diseased tooth tissue is replaced by restorative material that is directly bonded to remaining sound tissue. • While effective bonding to enamel has been achieved with relative ease, bonding to dentin has proved to be more difficult. • Dentin presents a less favorable substrate, for resin bonding, with its higher organic content, tubular nature and inherent wetness . WWW.INDIANDENTALACADEMY.COM
  4. 4. • Dentin adhesive systems can react with intertubular and peritubular dentin only when the smear layer is removed or when adhesive system is capable of difussing through this layer of debris. • In an attempt to improve adhesion of composite restorative materials to dentin, research in chemical bonding has led to the development of dentin adhesives WWW.INDIANDENTALACADEMY.COM
  5. 5. Criteria for Ideal Dental Adhesive System (Philips and Rage) 1961 - Provide a high bond strength to dentin that should be present immediately after placement and that should be permanent. - Provide a bond strength to dentin similar to that to enamel. - Show good biocompatibility to dental tissue including pulp. - Minimize micro leakage at the margins of restorations. - Prevent recurrent caries and marginal staining - Be easy to use and minimally technique sensitive - Possess good shelf life - Be compatible with a wide range of resins - System should not be toxic or sensitizing to the operators and patients. - Should seal the tooth surface from oral fluids. WWW.INDIANDENTALACADEMY.COM
  6. 6. TERMINOLOGIES • Adhesion ~ the attraction between two atoms and molecules at the contacting surfaces of different materials; it can be chemical (ionic), physical (van der Waals’), and/or mechanical (micro- or macro- interlocking) • Adhesive ~ monomer (or related) that penetrates and establishes intimate contact with the conditioned tissue substrate, polymerises, and forms a strong bond between such substrate and the restorative material • Priming ~ cleaning, structural alteration, and increasing adhesiveness of the substrate. WWW.INDIANDENTALACADEMY.COM
  7. 7. • Etching ~ dissolution of the substrate, removed by rinsing to enhance intimate contact of adhesives with collagen. • Wetting ~ the ability of a liquid to come into intimate contact with solid substrate; facilitates bonding WWW.INDIANDENTALACADEMY.COM
  8. 8. Etchants, Primers & Adhesive in Bonding system: - Etchant is an acid which selectively dissolves the tooth structure to provide retention for the restoration. - They are also known as conditioners. - The most popular etchant is 37% phosphoric acid. - Primers are hydrophilic monomers usually carried in a solvent. - Because of their hydrophilic nature they are able to penetrate the moist tooth structure especially the dentin and its collagen mesh thus improving the bond. - Thus they serve as a bridge connecting the tooth structure to the adhesive. - The solvent used are acetone, ethanol or water. Some are used without solvents. WWW.INDIANDENTALACADEMY.COM
  9. 9. Etchants, Primers & Adhesive in Bonding system: • Adhesive are generally hydrophobic monomers. • Being hydrophobic they do not wet the tooth leading to air entrapment, air inhibition and thereby poor bonding. • Thus they have to be used in combination with primers to form an effective bond to tooth structure. • The adhesive bonds the resin to the primer which in turn penetrates and binds to the tooth structure thus completing the bonding sequence. WWW.INDIANDENTALACADEMY.COM
  11. 11. Bonding to dentin is a challenge!! Due to complexities of dentin . . . • Complex histologic structure and variable composition of the dentin. • Enamel is 92% inorganic hydroxyapatite by volume, Whereas dentine is (on average) only 45% inorganic. • Also dentinal hydroxyapatite is randomly arranged in an organic matrix that consists primarily of collagen, which is permeated throughout by tubules. • These tubules contain vital processes of the pulp odontoblasts. Hence, vital dentine is a sensitive structure. • The high water content provides competition with any adhesive biomaterial for bonding to dentine.WWW.INDIANDENTALACADEMY.COM
  12. 12. SMEAR LAYER • Presence of smear layer on prepared dentin surface. This smear layer fills the orifices of dentinal tubules (forming smear plugs and decreases dentin permeability by 80%) • To achieve a strong bond, it is necessary to either strengthen this smear-layer in situ or to remove it entirely. • In the latter, it is imperative to ensure an adequately adhesive restoration otherwise the open tubules may allow irritants or bacteria greater access to the pulp. WWW.INDIANDENTALACADEMY.COM
  13. 13. • Removal of the smear layer and smear plugs with acidic solutions may result in an increase of the fluid flow onto the exposed dentin surface. • This fluid may interfere with the adhesion, because the hydrophobic resins do not adhere to the hydrophilic substrate even if resin tags are formed in dentin tubules. WWW.INDIANDENTALACADEMY.COM
  14. 14. • Stresses at the Resin- Dentin interface:- - Composites shrink as they polymerize, creating stresses of up to 7 MPa within the composite mass depending on the configuration of the preparation. - Unrelieved stresses in the composite may cause internal bond disruption as well as marginal gaps around restoration that increases microleakage. - Immediate bond strength of approx. 17 MPa may be necessary to resist these contraction stresses to prevent marginal debonding. WWW.INDIANDENTALACADEMY.COM
  15. 15. Development of Dentin Bonding Agents:- • 1951 – Dr. Oscar Hagger introduced Sevitron cavity seal (Amalgamated dental company). This was glycerophosphoric acid dimethacrylate (GPDM) chemically activated with sulfinic acid. • 1956 – Buonocore et al reported that glycerophosphoric acid dimethacrylate (GPDM) could not bond to hydrochloric acid etched dentinal surfaces. Limitations:- - Low bond strength of 2-3 MPa. - Bond was unstable in water. WWW.INDIANDENTALACADEMY.COM
  16. 16. • 1962 – R.L. Bowen developed bis-GMA molecule. • 1965 – Bowen introduced N- Phenylglycine Glycidyl methacrylate (NPG-GMA), to overcome the limitations of GPDM. • Late 60’s to 70’s – 1st generation DBA’s. • Late 70’s – 2nd generation DBA’s. • 1979 – Fusayama dentin etching (total etch technique). • 1982 – Nakabayashi “Hybrid Layer”. • Mid 80’s – 3rd generation DBA’s. • 1991 – 1st adhesion Symposium, Nebraska, Omaha. - Kanca popularized total etching in U.S. - Dentin etching gained worldwide acceptance. • Early 1990’s - 4th generation DBA’s. WWW.INDIANDENTALACADEMY.COM
  17. 17. CLASSIFICATION OF DENTIN BONDING AGENTS (DBA) 1) Based on chemistry:- - Phosphate/ Phosphonate system - Oxalate system - NPG-PMDM system - Isocyanate system - Gluteraldehyde system - 4- META – Tributyl borane system 2) Based on generations of dentin bonding agents:- Generation I to VII 3) Scientific classification:- Based on treatment of smear layer and the number of clinical steps:- Smear layer –modifying adhesives (one/two step) Smear layer –removing adhesives (two/three step) Smear layer –dissolving adhesives (one/two step) (Self-etching adhesives) WWW.INDIANDENTALACADEMY.COM
  18. 18. 4) Based on solvents:- - Acetone based - Water based - Ethanol based 5) Based on fillers:- - Filled adhesives 6) Based on fluoride release:- - Fluoride releasing adhesives 7) Based on type of activation:- - Light activated - Dual activated 8) Based on type of substrate:- - Enamel, dentin, amalgam, porcelain, base and noble metals. WWW.INDIANDENTALACADEMY.COM
  19. 19. CLASSIFICATION OF BONDING AGENTS BASED ON THEIR SHEAR BOND STRENGTH: (EICK ET AL, 1991) Three categories of dentinal adhesives are proposed: • Category I includes adhesives with shear bond strength values between 5 and 7 Mpa; • Category II includes dentinal adhesives with shear bond strengths between 8 and 14 Mpa; and • Category III includes adhesives with shear bond strength values above 20 Mpa . WWW.INDIANDENTALACADEMY.COM
  20. 20. CLINICAL SIGNIFICANCE OF THIS CLASSIFICATION: • Polymerization shrinkage • 2.9 to 7.1% by volume • contraction gap • 17-20 MPa bond strength to overcome (Davidson et al) WWW.INDIANDENTALACADEMY.COM
  21. 21. EVOLUTION OF DENTIN BONDING AGENTS: • First Generation. • Second Generation. • Third Generation. • Fourth Generation. • Fifth Generation. • Sixth Generation. • Seventh Generation. WWW.INDIANDENTALACADEMY.COM
  22. 22. FACTORS INFLUENCING THE EVOLUTION OF BONDING SYSTEMS: • Etching/conditioning Dentin • Smear Layer Treatment • Handling properties According to generations: Evolution of bondingagents from No etch to total etch and self etch. WWW.INDIANDENTALACADEMY.COM
  23. 23. FIRST GENERATION DBA • Ignored the smear layer. • Achieved deeper penetration in D’ tubules • These bonded to the enamel and dentin by chelation with calcium on the tooth surface. • They included NPG-GMA (N- Phenylglycine Glycidyl methacrylate), the polyurethanes and the cyanoacrylates. • NPG-GMA is a bifunctional molecule or coupling agent. • This means that one end of this molecule bonds to dentin while the other bonds (polymerizes) to composite resin. WWW.INDIANDENTALACADEMY.COM
  24. 24. • An example of an NPG-GMA bonding agent was S.S.White’s Cervident which became available in 1965. • Bond strengths of first generation DBA’S was 2-3 MPa. WWW.INDIANDENTALACADEMY.COM
  25. 25. Limitations:- • Low bond strength of 2-3 MPa • Loss in bond strength over time • Lack of stability of individual components during storage • Based on carbon-13 NMR analysis – No ionic bonding develops between NPG-GMA and hydroxyapatite WWW.INDIANDENTALACADEMY.COM
  26. 26. SECOND GENERATION DBA • These products depended upon smear layer for bonding. • The majority of these incorporated halophosphorous esters of unfilled resins such as bisphenol- A glycidyl methacrylate, or bis-GMA, or hydroxyethyl methacrylate, or HEMA. • The mechanism by which these bonded to dentin were postulated to be through an ionic bond to calcium by chlorophosphate groups. • Clearfil Bond system F (Kuraray) introduced in 1978, was the first product. • Bond strength range from 4.5-6 MPa. WWW.INDIANDENTALACADEMY.COM
  27. 27. • Limitations :- - Primary bonding was to the smear layer which prevented intimate resin- dentin contact, which is a pre-requisite for a chemical reaction. - Low Bond Strength 4.5 to 6 Mpa Only WWW.INDIANDENTALACADEMY.COM
  28. 28. THIRD GENERATION DBA • Three step systems. • Dentin etching was introduced by Fusuyama. • Followed by a primer application. • Application of an unfilled resin. • These systems alter or remove the smear layer prior to bonding. • Bond strength range between 12-15 MPa. • Three component system consisting of – - Conditioner - Primer - Adhesive WWW.INDIANDENTALACADEMY.COM
  29. 29. Conditioner (Cleanser, Etchant)- Is usually • a weak organic acid (maleic acid), • a low concentration of a stronger inorganic acid (phosphoric or nitric acid), or • a chelating agent (EDTA). • Actions:-Heavily alters or removes the smear layer. - Demineralizes peritubular and intertubular dentin and thereby exposes collagen fibrils - Increases dentin permeability by 4-9 times. WWW.INDIANDENTALACADEMY.COM
  30. 30. DENTIN PRIMER: • The primer contains hydrophilic resin monomers which include hydroxyethyl trimellitate anhydride, or 4- META, and biphenyl dimethacrylate, or BPDM. • The primers contain a hydrophilic group that infiltrates the smear layer, modifying it and promoting adhesion to dentin, and • the hydrophobic group of the primer creates adhesion to the resin. • Dentin primers may be 6 % phosphate penta-acrylate, (PENTA) ; 30 % HEMA; and 64 % ethanol. WWW.INDIANDENTALACADEMY.COM
  31. 31. • Actions:- Links the hydrophilic dentin to the hydrophobic adhesive resin. - Promotes infiltration of demineralized peritubular and intertubular dentin by its own monomers and those of the adhesive resin. - Increase wettability of the conditioned dentin . WWW.INDIANDENTALACADEMY.COM
  32. 32. • Adhesive (Bonding resin, sealing resin):- 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. • Actions:- - Combines with the primer monomers to form a resin- reinforced hybrid layer (resin- dentin interdiffusion zone) 1-5 microns thick. - Forms resin tags to seal the dentin tubules. - Provide methacrylate groups to bond with the subsequently placed resin composite. WWW.INDIANDENTALACADEMY.COM
  33. 33. • Representative brands:- - Scotch bond 2 - Universal bond - Syntac - Tenure WWW.INDIANDENTALACADEMY.COM
  34. 34. FOURTH GENERATION DBA EARLY 990’S • 3- component system. • Fusayama and colleagues tried bonding to enamel and dentin by total etching the preparation with 40 percent phosphoric acid. • The mineralized tissues of the peritubular and intertubular dentin are dissolved by the acidic action; the initial surface penetration exposes the collagen fibers. • In this area, for a depth of 2 to 4 micrometers, hybridization takes place, and resin tags can seal the tubule orifices firmly. WWW.INDIANDENTALACADEMY.COM
  35. 35. FOURTH GENERATION DBA’S EARLY 990’S • Ability to bond as strongly to dentin as to enamel. • “Wet bonding” (Ability to bond strongly to moist dentin and technique insensitivity). • “Multi purpose bonding” (Ability to bond to many different substrates, e.g.- enamel, dentin, porcelain, base and noble metals, amalgam). • Bond strength ranges between 17-24 MPa. WWW.INDIANDENTALACADEMY.COM
  36. 36. • Representative brands:- Etchant First step Primer Adhesive Second step Third step All Bond 2 Pro-Bond Liner Bond 2 WWW.INDIANDENTALACADEMY.COM
  37. 37. • The hybrid layer is defined as “the structure formed in dental hard tissues (enamel, dentin, cementum) by demineralization of the surface and subsurface, followed by infiltration of monomers and subsequent polymerization.” Nakabayashi et al (1982) Hybrid zoneWWW.INDIANDENTALACADEMY.COM
  38. 38. Wet bonding • Introduced by Kanca and Gwinnett in 1992. • After conditioning, the enamel and dentin surfaces should be properly treated to allow full penetration of adhesive monomers. • On the enamel surface – A dry condition is preferred. • On the Dentin surface – A certain amount of moisture is needed to avoid collapse of exposed collagen scaffold, which impedes effective penetration of adhesive monomers. • Consequently it is difficult to achieve the optimal environment for both substrates. WWW.INDIANDENTALACADEMY.COM
  39. 39. WET VERSES DRY BONDING Air drying demineralized dentin reduces its volume by 65% WWW.INDIANDENTALACADEMY.COM
  40. 40. Keep the substrate field dry and use adhesive systems with water based primers to rehydrate Keep the acid etched dentin surface moist and rely on water chasing capacity of acetone based primers WWW.INDIANDENTALACADEMY.COM
  41. 41. Etchant Primer Adhesive+ + Etchant + Primer Adhesive Primer and adhesive 3 step total etch IV Generation 2 step V Generation WWW.INDIANDENTALACADEMY.COM
  42. 42. FIFTH GENERATION DBA’S • Unique feature is the combination of the priming and bond resin application steps, resulting in a one component formula. • Also rely heavily on wet bonding. • Most commonly used and probably the most successful system. • These bonding systems create a mechanical interlocking with etched dentin by means of resin tags, adhesive lateral branches and hybrid layer formation.. WWW.INDIANDENTALACADEMY.COM
  43. 43. • Bond strength - > 20MPa • Representative brands:- - Prime and bond - Prime and bond 2.1 - One step - Optibond solo - Single bond Prime & Bond- NT Adper Single Bond Optibond Solo Gluma Comfort Bond WWW.INDIANDENTALACADEMY.COM
  44. 44. INTER-COMPARISON OF V GENERATION: Adhesive Mean Shear Bond Strength ( MPa ) Single Bond 30.0±5.5 Opti Bond Solo 23.4±3.4 One-Step 22.5±3.8 Prime & Bond 2.1 21.1±5.0
  45. 45. SIXTH GENERATION DBA’S • They are self etching adhesives ( Etch & prime simultaneously). • They involve a somewhat different mechanism in that, as soon as the decalcification process is initiated, the infusion of the evacuated spaces by dentin bonding agent is begun. • As a result, the potential for residual vacancies amongst the collagenous fibers is dramatically reduced or eliminated altogether. Etchant Primer Adhesive WWW.INDIANDENTALACADEMY.COM
  46. 46. Etchant Primer Adhesive Etchant Primer Adhesive + + + + Self etching primer All in one adhesive Sixth Generation Type I Sixth Generation Type II WWW.INDIANDENTALACADEMY.COM
  47. 47. ADVANTAGES AND DISADVANTAGES OF SELF- ETCHING ADHESIVES • Advantages :- - Simultaneous demineralization and resin infiltration. - No post conditioning rinsing. - Not sensitive to diverse dentin-wetness conditions. - Time saving application procedure. - Consistent and stable composition. - Hygienic application (Unidose). - Effective dentin desensitizer. WWW.INDIANDENTALACADEMY.COM
  48. 48. • Disadvantages :- - Insufficient long term clinical research. - Adhesion potential to enamel yet to be clinically proven. Xeno IIIPrompt L PopClearfil SE Bond WWW.INDIANDENTALACADEMY.COM
  49. 49. Etchant Primer Adhesive+ + Etchant Primer Adhesive = All in one adhesive Seventh Generation DBA’s Seventh Generation DBA’s WWW.INDIANDENTALACADEMY.COM
  53. 53. NEWEST PRODUCT • Nanofilled :- - Recently, bonding agents have been marketed that contain extremely small filler particles. These are called nanofilled DBA’s. E.g.- Prime and bond NT (7nm fillers) - Excite (12nm fillers) Advantages- Make DBA stronger and tougher - Able to cover adequately with a single coat - Improved marginal integrity. WWW.INDIANDENTALACADEMY.COM
  54. 54. • Newer Antibacterial Dentin Bonding Agents:- - Recently, bonding agents have been marketed that contain methacryloyloxy dodecyl pyridinium bromide (MDPB), has been developed (Imazato et al., 1994).. And also Nano-silver! E.g.- Clearfil Protect Bond and Prime Bond NT Advantages- The incorporation of MDPB is considered to be a potential method of providing dentin adhesive systems with antibacterial activity before and after curing. Eradication of residual bacteria that invade the tooth-adhesive interface by microleakage. WWW.INDIANDENTALACADEMY.COM
  56. 56. References:- • Sturdevant’s art and science of operative dentistry, 4th edition. • Fundamentals of operative dentistry, James B. Summitt, 2nd edition. • Phillips’ science of dental materials, Kenneth J. Anusavice, 11th edition. • Swift ED, Perdigao J, Heymann HO. Bonding to enamel and dentin: A brief history and state of the art. Quintessence Int 1995:26:95-110. • Walshaw PR, McComb D. Clinical considerations for optimal dentinal bonding. Quintessence Int 1996:27:619- 625. • Meerbeek BV et al. Adhesion to enamel and dentin: current status and future challenges. Operative Dentistry 2003:28:215-235. WWW.INDIANDENTALACADEMY.COM