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BONDING

BONDING. Dr. Raghuwar D Singh Associate Professor. Prosthodontic Department King George’s Medical University UP, Lucknow. ADHESION. Sound tooth structure must be conserved. Optimal retention must be achieved. Microleakage must be prevented. MECHANISM OF ADHESION.

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BONDING

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  1. BONDING Dr. Raghuwar D Singh Associate Professor Prosthodontic Department King George’s Medical University UP, Lucknow

  2. ADHESION • Sound tooth structure must be conserved. • Optimal retention must be achieved. • Microleakage must be prevented.

  3. MECHANISM OF ADHESION Factors in achieving adhesive bonds – • Wetting • Interpenetration (formation of a hybrid zone) • Micromechanical Interlocking • Chemical bonding

  4. ACID ETCHING TECHNIQUE – • Most effective ways of improving the marginal seal & mechanical bonding b/w Resin and Enamel . Mode Of Action :: • It creates micro-porosities by etching of the enamel .

  5. Etching increase the surface area . • Etched enamel has a high surface energy and allows a resin to wet the surface & penetrate into micro- porosities. • Resin Tags are approx 6microm in diameter and 10-20micro m in length.

  6. Acid Used :: • 37 % Phosphoric acidis most commonly used acid . • Supplied in gel form . • Brush or Syringe is used for application on the enamel .

  7. Procedure :: • Dry the enamel surface completely . • Length of application = 60 sec. but may be 15 sec. • After etching , dried enamel shows white , frosted appearance . • If enamel surface is contaminated, re-etching for 10 sec .

  8. BONDING AGENTS: • Enamel bond agents • Dentin bond agents

  9. ENAMEL BOND AGENTS: • Hydrophobic • Unfilled resin • Bis GMA • TEGDMA

  10. DENTIN BOND AGENTS: Dentin

  11. Problems in bonding to dentin: • Dentin is a dynamic tissue that shows changes due to ageing, caries or restorative procedures. • Dentinal tubules are filled with dentinal fluid which constantly flow outward from the pulp. • Dentin has considerable amount of organic material & water. • Dentin is close to pulp, so different chemical used for bonding and etching may irritate the pulp.

  12. role of smear layer :- • Whenever tooth surface is cut with hand or rotary instruments, it causes small particles of the cut tooth surface to the tooth producing the smear layer. • Smear layer is defined as any debris, calcific in nature produced by reduction or instrumentation of enamel of dentin or cementum.

  13. Retention of smear layer:- • 1) lowers dentin permeability • 2) prevent decrease in bond strength • 3) lowers effect of pulpal pressure on bond strength ** Recent generations adhesives involves modification of smear layer to facilitate bonding.

  14. It has two phases - • Solid phase- made up of cutting debris, primarily denaturated collagen and mineral. • Liquid phase- made up of tortuous fluid filled channels around the cutting debris. • Bacteria entrapped in smear layer can survive and multiply beneath the restoration.

  15. Conditioning of dentin: • It is defined as an alteration of dentin surface including the smear layer with the objective of producing a substrate capable of micromechanical and possibly chemical bonding to dentin adhesive. • Acid conditioners: • Phosphoric acid, • Citric acid, • Nitric acid, • Oxalic acid, and • Hydrochloric acid.

  16. Chelators- Remove the smear layer without decalcification or significant physical changes on underlying dentin substrate. • Best known chelator conditioner is EDTA. • Thermal conditioning- Recent trend is to use lasers in conditioning of teeth. • Studies have conformed increased bond strengths with lased dentin compared to those with unlased dentin.

  17. The molecule designed for dentin bonding were represented by an M-R-X molecule. • M- methacrylate group for bonding to resin matrix of composite resin • R- spacer such as hydrocarbon chain • X- functional group for bonding to organic or inorganic component of dentin.

  18. ETCHENTS / CONDITIONERS • ORGANIC ACID:- Maleic acid, EDTA, Citric acid, Tartaric acid. • POLYMERIC ACID:- Poly acrylic acid. • INORGANIC ACID:- Phosphoric acid, Nitric acid.

  19. Hydrophilic Primers/ Conditioners Bonding liquid

  20. PRIMERS • NTG-GMA • PMDM • BPDM • PENTA • HEMA

  21. ADHESIVE RESINS Hydrophobic monomers - • BIS-GMA • UDMA Diluent - • TEGDMA Wetting agent - • HEMA

  22. DENTIN BONDING AGENTS: • First generation • Second generation • Third generation • Forth generation • Fifth generation

  23. MCQs: • Most effective way of improving the marginal seal and bonding between restorative resin and Enamel is: 1. Using adhesive 2. Acid etching 3. Using both adhesive and acid etching 4. None of the above

  24. Most commonly used acid for acid etching technique: 1. 35% Phosphoric acid 2. 37% Phosporic acid 3. 37% Hydrochoric acid 4. 35% Citric acid

  25. Chelators most commonly used to remove the smear layer: 1. EDTA 2. BIS GMA 3. HEMA 4. Oxalic acid

  26. The nature of enamel bonding agents should be: 1. Hydrophilic 2. Hydrophobic 3. Depending on the condition of enamel 4. Neutral

  27. The length of application of acid in acid etching technique should be: 1. 10 Second 2. 60 Second 3. 90 Second 4. 120 Second

  28. THANK YOU

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