Effect of smear layer thickness and selfadhesive resin cements PH on the shear bond strength of self-adhesive resin cements to dentin

Abstract

Although self- adhesive resin cements have resulted in bond strength to dentin comparable to that with conventional resin luting agents, some concerns remain regarding bonding efficacy to dentin covered by the smear layer. The purpose of this study was to determine the effect of the smear layer thickness and self adhesive resin cement pH on shear bond strength to dentin. Material and methods: Buccal and lingual enamel of 48 healthy premolars was removed after the samples were mounted in self-cured acrylic resin. Buccal surface dentin of samples was ground with 60 Grit silicon carbide paper to obtain a thick smear layer and lingual surface dentin was ground with 600 Grit silicon carbide paper to obtain a thin smear layer and then the samples were randomly divided into 3 groups of 16 depending on cement variety (cement pH): first group: Relyx Unicem; second group: Clearfil SA; third group: Speed CEM. In each group composite resin blocks measuring 3 mm in diameter and 3 mm in height were bonded to buccal and lingual surfaces of teeth using self-adhesive resin cement according to the manufacturerEs instructions. After 24 hours in distilled water at a temperature of 37C, shear bond strength was measured in Mpa and failure modes of the specimens were examined under a stereomicroscope. Data were analyzed using two-way ANOVA and LSD post hoc tests (p< 0.05). Results: The analysis showed that cement pH effect was significant on the shear bond strength, (p=0.02) but the effect of the smear layer thickness (p=0.11) and the interaction between cement pH and smear layer thickness were not significant (p=0.11). The highest mean bond strength was obtained with Relyx Unicem and thin smear layer. Conclusion: Shear bond strength of self-adhesive resin cements to dentin was affected by pH, and shear bond strengths of Clearfil SA and Speed CEM Cement were similar, but significantly less than that of Relyx. Smear layer thickness did not affect the shear bond strength of self-adhesive resin cements.