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Restorative dentistry is mainly based on good adhesion between restorative materials and dental substrates; while adhesion to enamel is generally reliable, adhesion to dentin is less predictable (1) because of the presence of dentinal tubulis and the perfusion of liquids from it.
Adhesion to dentin requires demineralization of peritubular and intertubular dentin to replace the demineralized layer of dentin with monomers.
The main role of adhesive materials is to insure good adhesion between tooth tissues and restorative materials while maintaining good marginal seal.
Formation of hybrid layer between adhesive material and dentin depends on penetration of monomers through collagen fibers, this can be seen with total etch adhesive techniques.
The obstacle with this technique is the collapse of collagen fibers due to rinsing and air drying procedures after the application of acid which makes the use of total etch adhesive technique sensitive and results in poor penetration of monomers to the full depth of the demineralized layer of dentin. Because of the complexity and sensitivity of total etch adhesive technique, a new generation of dental bonding was needed and self-etch adhesive was introduced.
Evaluation of shear bond strength is performed using a shear stress machine (e.g. Testometric; (Testometric Company Ltd, Lancashire, UK) on prepared samples by considering multiple factors that affect this evaluation...