Operative Dentistry Adhesive Dentistry I PDF

Operative Dentistry Adhesive Dentistry I Kostis Giannakopoulos, DDS, PhD Assistant Professor, Department of Dentistry 24-10-2023  A new era in Operative Dentistry was introduced by enamel and dentin adhesion  Adhesion allowed The use of new materials. More conservative tooth pre...

Operative Dentistry Adhesive Dentistry I Kostis Giannakopoulos, DDS, PhD Assistant Professor, Department of Dentistry 24-10-2023  A new era in Operative Dentistry was introduced by enamel and dentin adhesion  Adhesion allowed The use of new materials. More conservative tooth preparation. Less removal of unsupported enamel. Repair of restorations. Conservative esthetic procedures. Resin based dentistry would not be possible without the use of dental adhesives.  Adhesion The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking forces or both. American Society for Testing and Materials (specification D907)  Mechanisms of adhesion in Dentistry Mechanical—penetration of resin and formation of resin tags within the tooth surface. Adsorption—chemical bonding to the inorganic component (hydroxyapatite) or organic components (mainly type I collagen) of tooth structure. Diffusion—precipitation of substances on the tooth surfaces to which resin monomers can bond mechanically or chemically. A combination of the previous three mechanisms.  Failure of adhesion Cohesive failure in the substrate. Cohesive failure within the adhesive. Cohesive failure in the restorative material. Adhesive failure (failure at the interface of the substrate or the restorative material and the adhesive).  What bonding system???? Adhesive Strategy??? Dry or wet bonding? Direct? Indirect? Silica based porcelain? Zirconia? Solvent? Compatibility? Dual cure? Sensitivity?  Enamel adhesion Buonocore MG. A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces. J Dent Res 1955;34:849-53  Michael Buonocore Eastman Dental Center - USA Sealing of pits and fissures with an adhesive resin: its use in caries prevention. Cueto EI, Buonocore MG. J AM Dent Assoc. 1967 Jul;75(1):121-8  Acid etching Acid etching transforms the smooth enamel into an irregular surface and increases its surface-free energy.  Resin tag formation A fluid resin-based material is applied to the irregular etched surface and the resin penetrates into the surface. Monomers in the material polymerize, and the material becomes interlocked with the enamel surface. The formation of resin micro-tags within the enamel surface is the fundamental mechanism of resin-enamel adhesion.  Enamel adhesion Acid Etch (phosphoric acid 35% for at least 30 sec). Resin tags. High bond strength. Reliable bond.  Dentin adhesion – Total Etch Significant debate at that time in Europe and the U.S.A. Fusayama T. New Concepts in operative dentistry. Chicago,IL: Quintessence Publishing Co,Inc; 1980 Takao Fusayama 1916-2003  Dentin adhesion Materials can interact with dentin mechanically or chemically or both. Major mechanism of adhesion is micromechanical interlocking of resin into the network of collagen fibrils left exposed by acid etching. Glass ionomer cements and some phosphate- based self-etch adhesives, offer some chemical bonding. Dentin is a dynamic substrate and consequently, adhesion is difficult and unpredictable. Dentin adhesion is not reliable Challenges in dentin adhesion Dentin contains water and organic substance, mainly type I collagen. Enamel contains mainly hydroxyapatite.  Dentin contains a dense network of tubules that connect the pulp with the DEJ. The number of tubules is increasing closer to the pulp in number and size. The quality of adhesion gets lower. The tubules occupy an area of only 1% of the total surface near the DEJ, whereas they occupy 22% of the surface close to the pulp. Challenges in dentin adhesion Dentin is an intrinsically hydrated tissue. Fluid filled tubules with a collagen network lining the inter-tubular dentin. Resins are hydrophobic. Challenges in dentin adhesion Degradation of collagen by dentin proteinases is known to negatively affect the bonded interface. It happens in varying time after the etching and application of the adhesive.  Smear Layer Whenever tooth structure is prepared with a bur or other instrument, residual organic and inorganic components form a “smear layer” of debris on the surface. The smear layer fills the orifices of dentin tubules, forming “smear plugs”. Smear plugs decrease dentin permeability by nearly 90% in vitro.  Dentin Adhesion Step 1. Etch for 15 seconds to: – remove the smear layer. – Demineralize inter-tubular and peri-tubular dentin. – Expose collagen fibrils. Ca10(PO4)6(OH)2+H3PO4 = Ca3(PO4)2 + H2O  Hybrid Layer formation Resin infiltration of acid etched dentin transforms the surface from crystalline, acid-sensitive and relatively hydrophilic to an organic structure, acid resistant and relatively hydrophobic Nakabayashi N, Kojima K, Masuhara E. The promotion of adhesion by the infiltration of monomers into tooth substrates. J Biomed Mater Sci 1982;16:265–73. Nobuo Nakabayashi 1936 -  Dentin Adhesion Step 3. Liquid acrylic monomers (hydrophobic) as a last layer.  HYBRID D LAYER B A DENTIN COMPOSITE  DENTIN ETCHED DENTIN HYBRIDIZED AGED DENTIN DENTIN INORGANIC (HΑp) % 50 0 0 0 COLLAGEN % 25 25 25 0 – 25 WATER % 25 75 0 0 – 35 RESIN % 0 0 75 20 – 50 Pashley DH et al. State of the art etch and rinse adhesives. Dent Mater 2011;27:1 - 16  Wet Dentin Adhesion A method for bonding to tooth structure using phosphoric acid as a dentin-enamel conditioner. Quintessence Int. 1991;22:285-290 Improved bond strength through acid-etching of dentin and bonding to wet dentin surfaces. J Am Dent Assoc. 1992;123:35-4 John Kanca  Wet Dentin Adhesion Drying etched dentin results in a 2/3rds reduction of its volume. The collagen fiber network in etched dentin literally floats in water. If dentin is dried, the hybrid layer cannot be formed.