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ADHESION IN DENTISTRY

ADHESION IN DENTISTRY. ADHESION Is defined as the state in which two surfaces are held together by interfacial forces which consist of valence forces or interlocking forces or both Is defined as attachment of one substance to another. Adherend :

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ADHESION IN DENTISTRY

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  1. ADHESION IN DENTISTRY

  2. ADHESION Is defined as the state in which two surfaces are held together by interfacial forces which consist of valence forces or interlocking forces or both Is defined as attachment of one substance to another

  3. Adherend : The surface or substrate to which adhesive is applied • Adhesive: A material that can join substances together, resist separation and transmit loads across the bond

  4. Adhesive Adherend

  5. DENTIN BONDING AGENTS: • Are di-functional or multifunctional organic molecules that contain a reactive group which interacts with dentin and monomer of restorative material

  6. MECHANISM OF ADHESION • 1. Mechanical theory: State that the solidified adhesive interlocks micromechanically with the roughness and irregularities of the surface of the adherend. 2. Adsorption theory: This includes all kinds of chemical bonds between the adhesive and adherend including primary & secondary bonds

  7. Diffusion theory: • Proposed that adhesion is a result of bonding between mobile molecules . • Polymers from each side of the interface can cross over and react with molecules on other side. • Eventually interface disappears and two parts merge into one.

  8. Electrostatic theory: • States that an electrical double layer forms at the interface between a metal & a polymer. • The interfacial phenomena to occur, the two materials being joined must be sufficiently close & have intimate contact. • Sufficient wetting of adhesive will occur only if it’s ST is less than Surface free energy of adherend

  9. ADVANTAGES OF ADHESIVE TECHNIQUE • 1) Minimal tooth preparation………… • 2) Reduces microleakage at restoration tooth interface….. • 3) Better transmission & distribution of functional stresses across restoration tooth interface • 4) Reinforcement of weakened tooth structure • 5) Repair of restoration is possible • 6) Replacement of debonded restoration with little loss of tooth structure……

  10. Requirements of good bonding: (Dental materials and their selection: William J O’ Brien Third edition.Sturdevant.) 1.Good Wetting; degree of spreading of a liquid drop on a solid surface Low contact angle : Good wetting High contact angle : Poor wetting

  11. 2.SURFACE ENERGY FOR SUBSTRATE • 3. SURFACE TENSION OF LIQUID • 4. SURFACES JOINED SHOULD BE CLEAN • Liquid with low viscosity, low surface tension, low contact angle & substrate should have high surface energy.

  12. Indications of adhesive dentistry: • Restoring carious and fractured tooth structure, abrasion, erosion, cervical restorations • Indirect resin based restoration. • All ceramic restoration. • Prefabricated/ cast posts. • Ortho brackets. • Perio splints • Pit and fissure sealants. • Re attachment of fractured tooth.

  13. History of dentinal bonding: Oscar Hagger( 1951):GPA DMA. Buonocore: (1955): Acid etching technique ……. Bowen ( 1957) : Development of BISGMA.

  14. Nakabayashi et al( 1975) Hybrid layer . Ferrari et al( 1997- 2003) Development of one bottle bonding systems. Sixth and Seventh generation bonding systems. Fusayama ( 1979) Concept of total etching and bonding.

  15. Ideal requirements of dentin bonding agents: • High bond strength to dentin • Provide bond strength to dentin similar to that of enamel • Biocompatibility to dental tissue including the pulp • Minimize microleakage at the margins of the restorations.

  16. Prevent recurrent caries and marginal staining. • Easy to use and minimally technique sensitive. • Good shelf life. • Be compatible with a wide range of resins. • Non toxic and non sensitizing to the operators or patients. • Bonding agents should seal the tooth surfaces from oral fluids.

  17. Enamel adhesion: • Bonding to enamel is achieved mainly by micro mechanical retention after acid etching which removes the smear layer and dissolves hydroxy apatite crystals in the outer surface. • The formation of resin tags with enamel surface is the basis.

  18. Resin tags : 2 types • Macrotag: formed between enamel rod peripheries. (2-5µ) • Microtag: fine network of tags across the end of each rod where HA are dissolved. • More important & contribute to bond strength….

  19. Macrotags • Microtags

  20. Etching: • Process of increasing surface reactivity by de-mineralising the superficial calcium layer and thus creating the enamel tags. • Enamel etching transforms smooth enamel into irregular enamel with a high surface free energy.

  21. Pattern of enamel etching: • Type I: removal of enamel prism core, prism periphery intact • Type II: Prism periphery removed • Type III: Mixed pattern

  22. Enamel etching patterns

  23. Effect of acid etch on enamel: • Kind of acid used • Acid concentration • Etching time • Form of etchant • Rinse time • Way in which etching is activated– Rubbing, agitation, repeated application • Primary or permanent dentition • Flouridated, demineralised or stained enamel.

  24. Etchants: • INORGANIC ACIDS • Phosphoric Acid 30%-40% • Nitric Acid • ORGANIC ACIDS • Maliec acid • Citric acid • Oxalic acid

  25. Phosphoric acid: • Buonocore suggested 85% PA RECOMMENDED 30-40% • This is because calcium dissolution & etching depth increases as the conc of PA increases until it reaches 40%. At higher conc, a reverse effect is seen.

  26. Etching time: • Not less than 15 secs Washing time: 5-10secs ETCHING RESULTS IN: • Cleanses debris from enamel • Produces a complex 3D microtopography at enamel surface. • Increases enamel surface area for bonding • Produces micro-pores for resin. • Exposes more reactive surface layer thus increasing its wettability

  27. Steps of enamel etching: • 1) oral prophylaxis • 2) Clean & wash the teeth with water • 3) Isolation • 4) Apply acid etch in the form of liquid or gel for 10-15secs • 5)Wash etchant for 5-10secs • 6) frosty white appearance on drying • 7) Repeat procedure if contaminated • 8) Apply Bonding agent • 9) Formation of micro & macro tags constitute the fundamental of enamel resin adhesion

  28. Hybrid layer • Defined as structure formed in dental hard tissue due to de-mineralisation of dentinal surface followed by infiltration of monomer & its polymerisation. • It is the zone in which resin of adhesive system micro mechanically interlocks with dentinal collagen.

  29. Tubule wall hybridization Refers to extension of hybrid layer into tubule wall. Hermetically seals pulp dentin complex. Lateral tubule hybridization Refers to formation of tiny hybrid layer into the walls of lateral tubule. This hybrid layer typically surrounds central core of resin called micro resin tag .

  30. Reverse Hybrid layer: Seen when acid etch dentin is treated with NaOCL.Hybrid layer is surrounded by more inorganic materialunlike the normal hybrid layer where collagen is encapsulated by resin. Ghost hybrid layer: Formed due to incorporation of air bubbles at the substrate adhesive interface These micro space are then open to micro leakage.

  31. Hybrid layer Resin tag Dentinal tubule

  32. Composition of dentin bonding agents • Etchants • Primers • Adhesives • Initiators and accelerators • Fillers

  33. The various acid etchants used are: • Organic • Maliec acid • Tartaric acid • Citric acid • EDTA • Acidic monomers • Polymeric • Polyacrylic acid • Mineral acids • Hydrochloric acid • Nitric acid • Hydrofluoric acid

  34. Primers Also called adhesion promoters. Monomers used is HEMA-HYDROXY ETHYLE METH ACRYLATE

  35. The solvents used in primers • Acetone • Ethanol • water. • Acetone – H2O • Eg: Tenure- quick • Acetone- ethanol • Eg: All bond 2 ( Bisco) • Ethanol- water • Eg: Gluma comfort bond • Scotchbond

  36. Adhesives Bis GMA, UDMA, TEGDMA, Methacrylatedphosphates Initiators and Accelerators Light cured: camphoroquinone and an organic amine. Dual cured bonding agents :catalyst to promote self curing.

  37. Fillers: • Most unfilled • inorganic fillers 0. 5% to 40% by wt. • microfillers, or nanofillers, and submicron glass. • Advantages ….

  38. Classification of dentin bonding agents:

  39. I Generation Bonding agents • Buonocore :GPA-DMA could bond to HCl etched dentin • Bowen 1965 :N- Phenylglycineglycidylmethacrylate( NPG- GMA) • .

  40. Agents used in this generation: • NPG-GMA. • Glycerophosphoric acid dimethacrylate.( GPA-DMA). • Cyanoacrylates • Polyurethanes • Commercial product • Cervident( S.S White, Lake wood, NJ) First commercially available bonding agent. • Cosmic bond( Amalgamated Dental Company) • Palakav( Kulzer, USA). D e n t i n B o n d i n g S y s t e m s

  41. II generation bonding agents: • 1978, the Clearfil Bond System F( Kuraray, Osaka, Japan) • Systems • Scotch bond dual cure( 3M ESPE). • Bondlite ( Kerr). • Prisma Universal Bond. • Mechanism of action: • Major Disadvantage : Interaction occurred at the smear layer D e n t i n B o n d i n g S y s t e m s

  42. Third Generation Dentin Adhesives • mid to late 1980s • Two approaches : • Modification of smear layer to improve its properties • Removal of smear layer partially without disturbing the plugs that occluded the dentinal tubules D e n t i n B o n d i n g S y s t e m s

  43. 3 step process Advantages: Better clinical performance. Disadvantages . D e n t i n B o n d i n g S y s t e m s

  44. The agents used were: • Scotch bond2 ( 3M Dental) • Gluma( Bayer/ Miles) • Tenure( Den- Mat) • Prisma Universal Bond 3( Caulk/ Dentsply), • Syntac( Ivoclar Vivadent) • XR Bond( Kerr) • Clearfil New Bond( Kuraray) D e n t i n B o n d i n g S y s t e m s

  45. Fourth Generation Bonding agents: Total etch concept : Fusayama in 1979 D e n t i n B o n d i n g S y s t e m s

  46. Bonding via resin tag formation in the tubules of conditioned dentin. • Formation of precipitate on pre treated dentin surfaces followed by chemical or mechanical bonding of resin. • Chemical union to either • organic or inorganic • components of dentin. • Hybrid layer : Nakabayashi D e n t i n B o n d i n g S y s t e m s

  47. 3 step total etch 4 Th Generation Etchant + Primer Adhesive +

  48. Advantages: • Bond strength: 18 Mpa • Can bond to mineralized tissue as well as metal, amalgam, composite and porcelain. • Disadvantages: • Multiple steps: Technique sensitive. • Unless the primer and adhesive are applied consecutively, the overlying composite resin will not bond to the surface. • light cure to dual cure. D e n t i n B o n d i n g S y s t e m s

  49. Agents used in this generation • All bond 2( Bisco Dental) • Amalgam- bond( Parkell) • Clearfil Liner Bond( Kuraray) • Imperva Bond( Shofu Dental) • Optibond( Kerr) • Scotch bond multipurpose( 3M Dental) D e n t i n B o n d i n g S y s t e m s

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