Microleakage and adhesion / endodontic courses
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The document discusses microleakage and adhesion in dental materials, highlighting microleakage's effects and causes, alongside strategies for bacterial prevention. It covers adhesion's critical factors, including wettability and surface interaction, and provides a historical overview of resin bonding advancements. The document also details the properties of various dental cements and their applications in restorative dentistry.
Microleakage and adhesion / endodontic courses
- 1. INDIAN DENTAL ACADEMY Leader in continuing Dental Education Microleakage and adhesion WWW.INDIAN DENTAL ACADEMY.COM
- 2. Microleakage and adhesion • Microleakage – Definition – Effects – Causes • Bacterial microleakage reduction – Water sorption enhanced expansion and F- release – Improved adhesion • Resins • cements WWW.INDIAN DENTAL ACADEMY.COM
- 3. Nano and Micro - leakage • Nanoleakage – Passage of fluid / dissolved species in nano - sized (10-9 m) gaps • Microleakage – Passage of fluid and bacteria in micro gaps (10-6 m) between restoration and tooth • “Most significant hazard in restorative dentistry” and “greatest risk to the pulp” WWW.INDIAN DENTAL ACADEMY.COM
- 4. Effects of nano and micro - leakage Nano leakage Sensitivity during thermal occlusal stress Bacterial leakage Discoloration Recurrent caries Pulpal irritation / infection WWW.INDIAN DENTAL ACADEMY.COM
- 5. Causes of micro gaps • During placement due to – Polymerisation shrinkage – Air bubbles during mixing – Poor adhesion and wetting • Cracks may develop with time due to – Mechanical loading – Thermal stresses WWW.INDIAN DENTAL ACADEMY.COM
- 6. Bacterial microleakage prevention • Matching of tooth / restorative dynamic – thermal – mechanical props • Restorative water sorption induced – Expansion – Fluoride release – Increased set • Improved adhesives / sealing of tubules WWW.INDIAN DENTAL ACADEMY.COM
- 7. Thermal expansion and conductivity Amalgam 22-28 9.4 Composite resin 20-60 0.25 GIC 10-11 0.15-0.35 Tooth 11.4 0.18-0.47 Thermal expansion coefficient e 10-6 / C Thermal conductivity K 10-6 / C(mm2/s) K = quantity of heat passing per s through a block of unit thickness and cross sectional area for a temp. difference of 1C E = volume expansion for unit rise in temperature WWW.INDIAN DENTAL ACADEMY.COM
- 8. Water sorption and mechanical properties • Composites and compomers – – mechanical properties decrease via • Polymer plasticisation • Silane hydrolysis • Cements – – mechanical properties increase via • Closing of cracks due to swelling • Continuing acid / base reaction promotion WWW.INDIAN DENTAL ACADEMY.COM
- 9. Water Sorption levels and effects • Water sorption –RMGIC > GIC > compomer >composite • Expansion –RMGIC > GIC > compomer ~composite • Fluoride release –RMGIC ~ GIC > compomer Biomaterials 19 (6) 1998 WWW.INDIAN DENTAL ACADEMY.COM
- 11. Microscopic processes required for formation of strong adhesive joint Clean / stable / rough surface formation Good wetting of adhesive High contact in pores Extensive liquid / solid interactions Strong cured / set adhesive WWW.INDIAN DENTAL ACADEMY.COM
- 12. Criteria for adhesion between liquid and solid • Wettability – Low surface tension g (Acetone / alcohol 23) – High surface energy E – Strong liquid / solid interaction • To fill pores / roughness – High surface tension • Rapid flow – Low viscosity • For adhesives – Favourable liquid / solid interactions – Low viscosity – Chemical reaction for set Steel PTFE E = 230 E = 18mJ / m2 Water g = 73 hexane g = 18 Wetting Capillary action Water hexane q q WWW.INDIAN DENTAL ACADEMY.COM
- 13. Physical interactions and Chemical reactions • Physical Van de Waals interactions – None permanent • ion / ion • dipole / ion • dipole / dipole – H-bond (particularly strong) • Chemical Reactions – Ionic (eg acid + base salt + water) – Covalent (eg in C-C backbone in polymers) - + - + + - C=O ------H-OR (CH2-CH2)n + - - + - + - Like attracts like - materials generally either hydrophilic or hydrophobic d- d+ WWW.INDIAN DENTAL ACADEMY.COM
- 14. Types of adhesion • Chemical bonding between surfaces • Micro - mechanical attachment • Polymer entanglements WWW.INDIAN DENTAL ACADEMY.COM
- 15. Dentine and enamel adhesion with resins WWW.INDIAN DENTAL ACADEMY.COM
- 16. Composition of enamel and dentine Enamel Dentine wt% Water 3 10 Noncollagenous proteins 1 2 Collagen - 18 Hydroxyapatite 95 70 Enamel wet by hydrophobic or hydrophilic monomers Dentine requires hydrophilic monomers Both surfaces need roughening for good adhesive contact WWW.INDIAN DENTAL ACADEMY.COM
- 17. History of resin bonding • Pre 1970 – Acid etch enamel (not dentine) – self cured bonding agents • 1970s – Hydrophobic enamel adhesives – Hydrophilic dentine adhesives – light cure systems • 1980s – Acid etch of dentine – Acidic hydrophilic monomers for dentine priming – Hydrophobic low viscosity resin adhesive • 1990s – Common hydrophilic dentine and enamel adhesives – Light and dual cure systems – 5th generation 2 component combining primer and adhesive – 6th generation 1 component to etch, prime and form adhesive bond. WWW.INDIAN DENTAL ACADEMY.COM
- 18. Some basic polymerisable acids 4th generation mainly have lower acidity carboxylic acid groups on polymerisable Hydrophilic monomers 5th and 6th generation adhesives often have more acidic phosphoric acid group on polymerisable monomersWWW.INDIAN DENTAL ACADEMY.COM
- 19. 4th generation bonding agents • Etchant – 37% Phosphoric acid (gel with silica particles or cellulose) • Primer – Hydrophilic monomer + initiators • HEMA or MMA – Polymerisable carboxylic acid (COOH) • 4-META (anhydride) or BPDM, GPDM (acid containing dimethacrylates) – Solvent • Acetone or ethanol / water • Adhesive • BISGMA (resin) TEGDMA (diluent) + initiators • Inorganic fillers (0.5 to 40 wt%) • Fluoride WWW.INDIAN DENTAL ACADEMY.COM
- 20. Effect of etchant on enamel • Addition of phosphoric acid for 30s – Frosty appearance – SEM structure show preferential etching of hydroxyapatite prism • Cores • Periphery • Penetration of monomer into rough surface gives micromechanical bonding WWW.INDIAN DENTAL ACADEMY.COM
- 21. Dentine bonding • Phosphoric acid etch for 10s gives – Smear layer removal – Hydroxyapatite dissolution • Drying causes – Collagen collapse • Priming gives – Collagen rehydration • Intra and inter tubular Monomer penetration provides – Micromechanical adhesion on polymerisation – Tubule sealingWWW.INDIAN DENTAL ACADEMY.COM
- 22. Bond strength and fatigue • Initial resin bond strengths to enamel and superficial dentine can be 15-35 MPa • Deep dentine bond strengths generally lower • Combined mechanical and thermal cycling can rapidly decrease bond strength WWW.INDIAN DENTAL ACADEMY.COM
- 23. Cements Hydrophilic and react / associate with dentine / enamel structures ZnO PAA Sr F Al Si OP(OH)3 Zinc polycarboxylate GIC Silicates Zinc phosphates Acid + base salt + water High acidity Small molecule Lower acidity Polymer has less mobility Base Base WWW.INDIAN DENTAL ACADEMY.COM
- 24. GIC types I Luting cementation of crowns 1.5 orthodontic etc. II Restorative aesthetic low stress >3 III a)Lining thermal barrier under metal restoration 1.5 b)Base dentine substitute >3 under composite Type Uses Powder / liquid wt. fraction WWW.INDIAN DENTAL ACADEMY.COM
- 25. Cement Strengths GIC 90-220 4 70-210 4-8 RMGIC 85-120 13 150-200 20-40 Zn phosphate 96-130 4 130-160 8 Zn polycarboxylate 55-96 4 80 16 Adhesive resin 50-210 40 Cementation Bases Compressive Tensile Compressive Tensile WWW.INDIAN DENTAL ACADEMY.COM
- 26. Low strength neutral and basic cements Zinc oxide eugenol (neutral) OH O Acid + Base ZnO Sedative effect on pulp polymerisation inhibitor Calcium hydroxide with glycol salicylate gives calcium disalicylate Calcium hydroxide (base) cements Light cure cements contain CaOH and UDMA WWW.INDIAN DENTAL ACADEMY.COM
- 27. Glass ionomer bonding • Pre - Dentine conditioning with PAA – cleans surface of debris • PAA in cement neutralised by – Glass to solidify cement – hydroxyapatite to provide chemical bond to tooth structures WWW.INDIAN DENTAL ACADEMY.COM
- 28. Texts • R. Van Noort, “Introduction to Dental Materials” Mosby 1994 (2nd ed. June 2002) • R.G. Craig, J.M. Powers, “Restorative Dental Materials” 11th ed. Mosby 2002 • W. J. O’Brien, “Dental Materials and Their Selection” 2nd ed. Quintessence 1997 • N. Nakabayashi, D.H. Pashley, “Hybridisation of dental hard tissues”, Quintessence 1998. • G.J. Mount, RW, Bryant, “ Preservation and restoration of tooth structure” Mosby 1998. • Biomaterials special issue vol 19 (6), “Proceedings of the 1st European Union Conference on Glass – Ionomers” 1998 WWW.INDIAN DENTAL ACADEMY.COM