RESUMEN
This research was performed to study the shear bond strengths of resin composite to normal and sclerotic dentin using total-etch and self-etch techniques. Four types of adhesive systems were used in this study, in which two adhesives utilized the total-etch technique, namely three-step and two-step total-etch adhesives. The other two adhesives utilized the self-etch technique, namely two -step and one-step self-etch adhesives.The structure of both normal and sclerotic dentin was identified by visual examination, according to the dentin sclerosis scale, and was confirmed by light microscopic examination and SEM. The nature of hybrid layer and resin tags, produced by total-etch and self-etch adhesives, were ex- : amined by SEM.The shear bond strengths data obtained was converted to MPa unit and statistically analyzed with one-way, two-way analysis of variance [ANOVA] and least significant difference at 99% confidence interval. In general, total-etch technique produced superior bond strength values than self-etch technique. The three-step total-etch adhesive produced the highest bond strength to normal dentin while the two-step total-etch adhesive produced the highest bond strength to sclerotic dentin. One-step self-etch adhesive produced the lowest bond strengths to both normal and sclerotic dentin. Bond strengths to normal dentin were double those to sclerotic dentin. Generally, total-etch adhesive systems provided higher bond strengths than self-etch adhesive systems, demonstrating that a possible advantage of reducing clinical application steps resulted in lower bond strengths. Three-step total-etch adhesive system produced the highest bond strength to normal dentin. Two-step total-etch adhesive system, based on ethanol solvent, produced the highest bond strength to sclerotic dentin. One-step self-etch adhesive produced the lowest bond strength to both normal and sclerotic dentin. As regard the type of dentin, the structure of sclerotic dentin provided a less reliable substrate for adhesion