Microtensile bond strength of silorane or methacrylate resin-based composites associated to self-etching or conventional adhesives to dentin after different storage times

Abstract Objectives The aim of this study was to evaluate the bond strength of methacrylate-based (Filtek Z350-3M/ESPE) or silorane-based (Filtek P90-3M/ESPE) resin composites associated with self-etching adhesive systems (Adper SE Plus-3M/ESPE, Adper P90-3M/ESPE and Clearfil SE Bond-Kuraray) or with a conventional adhesive system (Scotchbond MultiUso-3M/ESPE) to dentin after 24 h and 180 days storage times, and also to determine the fracture pattern. Materials and methods The occlusal enamel was removed from 48 recently extracted impacted third molars to expose the superficial dentin. The teeth were divided into eight groups (n=6) according to the adhesive system applied and to the resin composite used for block fabrication. The specimens were cut into sticks with an area of approximately 1 mm² and separated into two groups according to storage time in distilled water (24 h or 180 days). The test specimens were subjected to microtensile bond strength tests in a universal testing machine (EMIC) at a speed of 0.5 mm/min. The results were analyzed by the three-factor analysis of variance and the Tukey test. Results No significant difference was found between “24 h” and “180 days” storage times for any resin and adhesive system evaluated (p=0.9113). The Filtek P90 and Filtek Z350 resin composites showed no statistical differences in the mean microtensile bond strength values, in the different associations with the adhesive systems assessed (p=0.28). There were significant differences in microtensile bond strength mean values between the Filtek P90 and Filtek Z350 resin composites when these were used with the same type of adhesive system (p=0.02). It was observed that higher bond strength values were obtained when Filtek Z350 resin composite was used. There was a predominance of adhesive fractures in all groups tested after 24 h, except for Filtek Z350 resin associated with Scotchbond MultiUso adhesive, and for Filtek P90 associated with Adper SE Bond system, in which case there was predominance of the mixed fracture type. After 180 days, Filtek P90 resin associated with the Adper SE Bond system presented 100% mixed fractures, whereas a larger number of adhesive fractures were obtained in the other groups. Conclusions The methacrylate-based resin presented higher bond strength values than the silorane-based resin. The association of resin P90 with Adper SE Plus adhesive is not recommended. The other associations presented similar bond strength values among one another.