ENAMEL AND DENTINE BONDING AGENTS

Prof. Alsayed Abdelhafez BDS, MD , PhD Zagazig Univeristy.

Items to be covered. 2. Introduction Uses Problems associated with bonding Ideal requirements Composition Classification Development (Generation) of bonding agents Based on number of steps of application Based on etching mode Based on mode of application Manipulation New clinical indications for dentin adhesives Properties.

3. Introduction Traditional mechanical methods of retaining restorative materials have been replaced to a large extent by tooth conserving adhesive restorative techniques which allow more conservative tooth preparation. Which depend on micro- mechanical retention and less removal of unsupported enamel. There has been dramatic progression in the adhesion of dental adhesives and resins to enamel and dentin in the last 40 years..

—WII/. Adhesive restorative technique is used to :.

Enamel challenges. Hydrophobicity of enamel ; 85 % inorganic, 12 % organic and water 3 % microstructure..

6. Dentine challenges Hydrophobicity; 45 % inorganic , 33 % organic and 22 % water. Complex composition and histological structure . High organic content mainly of collagen fibers . The presence of pulpal fluid and odontoblastic processes. Smear layer presence interferes with adhesive bonding to dentine Smear layer : It is a loosely attached layer of debris, left on dentine surface following instrumentation. It is a weak substrate for adhesion..

Ideal requirements of bonding agents. 7. High bond strength to enamel and dentin immediately after placement. Contain hydrophilic part to bond to wet dentine and hydrophobic part to bond to copolymerize with subsequently applied resin. Biocompatibility: Minimize microleakage at the margins Should be of low viscosity for better diffusion. Easy to use and minimally technique sensitive. Good shelf life. Be compatible with a wide range of resins.

Composition of bonding agents. 8. Modern bonding agent contains three major ingredients ( etchant , prime r and adhesive ) that may be packed separately or combined. Etchants (Conditioner) Used to produce roughness of the surface by exposing it to an acid and thoroughly rinsing the residue to promote micromechanical bonding of an adhesive to the surface. Chemical etchant using different acids with concentrations Inoraganic as phospforic acid (most common) (27-37%) Organic (maleic & citric acids) Polymeric ( polyacrylic acid) Minera l (hydrofluoric & phosphoric acids which is the most common in 37 % concentration). Other etchants; Lasers and air abrasion may be used either intra or extraorally ..

9. Rinsing and drying to remove etchant Over-drying of etched dentine collapse of collagen fibers and poor resin infiltration. Excess water within collagen competes with resin infiltration into etched dentine..

10. . . NB: Conditioning of the surface means alteration of the surface without removal of calcium. Etching means preferential demineralization. Etching is used with resin restorations while conditioning is used with glass ionomer restorations..

Syntacø Pnmer. 11. 2. Primers Bifunctional monomers carried in a solvent. (HEMA) Provides a mean of bonding hydrophobic composites to hydrophilic dentine. The solvents are acetone, ethanol-water, or water. Primers have different evaporation rates, drying patterns, and penetration characteristics → affect bond strength. Advantages Enhances monomer penetration. Increases surface wettability and energy. Stabilizes collagen fibers. Acidic primers containing carboxylic acid groups are used in self-etching bonding agents..

Composie indng Resintags eeu. 12. 3. Adhesives Include monomers that are mostly hydrophobic, as Bis -GMA with a small percentage of hydrophilic monomers. Copolymerizes with the primer molecules, penetrates and polymerizes into interfibrilar spaces→ hybrid layer, and penetrates into dentin tubules → resin tags. 4. Initiators and accelerators such as camphorquinone and organic amine. 5. Fillers 0.5−40% wt (micro and nanofillers ). 6. Other ingredients such as fluoride and antimicrobial agent..

Acid—etching + Dentin Smear Layer with Bur + Cornposite Etched Dentin with Collagen Dentin Adhesive Hybrid Layer.

Classification of dentin bonding agents. 14. I. Bonding generation. II. Number of steps of application. III. Etching approach. IV. Dealing approach with smear layer..

15. B.Generation Time Period Development First generation 1950 -1970 Liquid acrylic monomer onto acid etched enamel. Resin penetrates into the surface, polymerize and interlocked with the enamel surface. No bonding with dentine. Second generation Early 1970 s No dentin etching. Adhesion to smear layer. Weak bond strength. Third generation Late 1970s Hydrophbic enamel bonding agent Hydrophilic dentine bonding agent Acid etching of dentin. Separate primer. Increased bond strength. Fourth generation Total etch, Multiple bottles ( Phosphoric acid, Primer, Adhesive). 3 steps Mid to late 1980s Removal of smear layer. Etching and rinsing. Hybrid” layer of dentin and collagen Concept of “wet bonding” introduced. Technique sensitive..

16. Generation Time Period Development Fifth generation Total etch, Single-bottle, (phosphoric acid &) 2 steps Early 1990s Etch and rinse. Hybrid layer formation. Combined primer and adhesive in one bottle. Maintained high bond strengths. Sixth generation, Self-etch primer & adhesive (Type I), Self-etch adhesive & primer (Type II) Early 2000 s (Type I) two steps for application & (Type II) needs mixing. Reduced incidence of post-treatment sensitivity. Bond strengths lower than fourth- and fifth-generations Seventh generation, One-Bottle System, All in one. Late 2002s Self-etch & dual cure. Combines etching, priming and bonding in single solution. Good bond strength and margin sealing Eighth generation Nanofilled adhesive Latest Self-etching. Nanofilled . Fluoride releasing . No post-operative sensitivity..

II.Based on number of application steps. 17. Three steps Self-primhg steps Sir* Step etching Prirner primer Mix 11 pnmtng.

Acid F,tching. Etch & rinse.. 18. III. Based on etching approach:.

/ According to number of clinical applications Three steps Etch and rinse system Convensional system. Seperate etchant, primer adhesive (multiple bottles. Total etch technique. Fourth generation. Two steps Etch & rinse appmach Single bottle system. . Primer & adhesive in single bottle. . Total etch technique. . Fifth generation. Self-etch approach . Self etch primer a& seperate adhesive. . sixth generation type I. One step Self-etch approach . Self etch adhesive. . Needs mixing before application. . Sixth generation type II. . One bottle (all in one) syste . Etchant, primer & adhesive in one solution. . Seventh generation..

IV. Based on mode of application and dealing with smear layer:.

Recent advances in dentine bonding system are available nowadays, e.g.,.

Other clinical indications for dentin adhesives. 22.

Manipulation. abstract. abstract. Figure view:. c.l+ter.

Manipulation. 24. 1. Etching: Gel etchants are dispensed from a syringe onto tooth surfaces, to enamel first and then to dentin . Etching times for enamel vary depending on the type and quality of enamel. Generally, a15-second etch with 37% phosphoric acid. The gel is rinsed away and the tooth structure is maintained in a moist surface condition for the next stage of bonding. Use gentle air-drying to check the enamel for a frosty appearance, but guard against over-drying of etched dentin as you do so. If necessary, rehydrate the dentin to a glistening appearance before applying primer..

25. 2.Primer application & evaporation of solvents : In contrast to enamel, dentin contains more water and is strongly hydrophilic. To manage this problem, primers have hydrophilic components that wet dentin and penetrate the surface. The process of resin infiltration or impregnation of etched dentin by the primer is called hybrid layer formation. The result of this process has been called the resin interpenetration zone or resin-inter diffusion zone. This layer is critical to bonding and creates the necessary microtags . Primer with solvent enhances surface wettability. Most of the solvent evaporates after placement. Several layers usually must be applied to produce a persisting glistening appearance on dentin..

26. 3.Adhesive application layers: Once the primer is applied adequately, an adhesive is applied and light cured. Surfaces of the cured bonding agents are initially air inhibited and do not immediately react. However, as composite is placed against the surface, the air is displaced and copolymerization occurs..

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