The effect of pre-etching of dentine, cut and uncut enamel on the shear bond strength of silorane-based and methacrylate-based composite resin systems

INTRODUCTION: Modern composites are exceptional physically and aesthetically, but success is dependent on effective bonding to tooth structures, possibly enhanced by phosphoric acid pre-etching. AIMS: To determine the effect pre-etching of tooth surfaces has on the shear bond strengths of silorane-based and of methacrylate-based composite resin systems METHOD: To 120 recently extracted human molars and pre-molars, composite resin stubs were bonded with Silorane System Adhesive or Scotchbond Universal, to pre-etched or to non-pre-etched tooth surfaces, using an Ultradent jig. After thermocycling, each specimen was debonded under a shear force, in an Instron Universal testing machine (crosshead speed 0.5mm/minute. RESULTS: Data were subjected to an analysis of variance and when significant, to pairwise comparisons. The silorane-based system achieved significantly higher mean shear bond strengths (MPa) on pre-etched surfaces of: uncut enamel (15.204 vs 9.424), cut enamel (21.352 vs 12.110) and dentine (19.787 vs 8.278). Methacrylate-based bonds to pre-etched uncut enamel were significantly stronger (28.898 vs 18.451). Pre-etching cut enamel enhanced the bond (20.548 vs 16.384, not significant). Pre-etched dentine recorded lower mean bond strengths (15.288 vs 19.645) also not significantly CONCLUSIONS: The effect of pre-etching on the shear bond strength to uncut enamel, cut enamel, and dentine was product-specific.