Effect of preheating on the microtensile bond strength of the bulk-fill resin composite to dentin of the floor of class 1 cavities.

Abstract

Title: Effect of preheating on the microtensile bond strength of the bulk-fill resin composite to dentin of the floor of class 1 cavities. Purpose:Due to the lack of the articles about the effect of preheating on the microtensile bond strength of the bulk-fill resin composite in cavities with high C-Factor, purpose of this study was to evaluate the effect of preheating on the microtensile bond strength of the bulk-fill resin composite to dentin of the floor of class 1 cavities. Material and methods: 36 extracted sound human lower third molars with similar dimensions were collected, cleaned and stored. The cusps were sectioned to form a flat occlusal surface. After etching and bonding, a 1mm thick layer of Filtek Z250 microhybrid resin composite was applied on occlusal surface. In the middle of the occlusal surface a class 1 cavity (3.5×3.5×4 mm) was prepared in a way that pulpal floor was placed in middentin. The teeth were randomly divided into two groups (n=18).The tubes of X-tra fil composites were stored in distilled water with temperatures of 23˚C and 60˚C for 30 minutes, then it was packed in cavities. A 500 round thermocycling procedure was carried out with 5 and 55˚C. Then every 3 teeth were mounted in a block of self-cure acrylic resin and the blocks were glued to the plates, afterword they were sectioned into 1mm × 1mm species with a trimming device under water coolant, providing at least 3 species per tooth, therefore there were 110 species in total. The species were glued at the end of the microtensile testing machine’s jig and they were loaded in tension until breaking. The load at failure was recorded in Newton. For determination of mean difference of preheating on microtensile bond strength, independent T test was used (p<0.05). Results: The independent T test showed that there was significantly statistical difference between preheating and non preheating groups (p=0.002). The meaning of the microtensile bond strength in preheated group significantly increased compared to other group.