Effect of preheating of low shrinking resin composite on intrapulpal temperature and microtensile bond strength to dentin

Abstract

The effect of preheating of the silorane-based resin composite on intrapulpal temperature (IPT) and dentin microtensile bond strength (μTBS) was evaluated. For the IPT, teeth (n=15) were sectioned to obtain discs of 0.5mm thickness (2 discs/tooth). The discs were divided into three groups (n=10/group) according to the temperature of the Filtek LS™ silorane-based resin composite during its placement, either at room temperature (23±1°C) or preheated to 54°C or 68°C using a commercial Calset™ device. Discs were subjected to a simulated intrapulpal pressure (IPP) and placed inside a specially constructed incubator adjusted at 37°C. IPT was measured before, during and after placement and curing of the resin composite using K-type thermocouple. For μTBS testing, flat occlusal middentin surfaces (n=24) were obtained. P90 System Adhesive was applied according to manufacturer’s instructions then Filtek LS was placed at the tested temperatures (n=6). Restorative procedures were done while the specimens were connected to IPP simulation. IPP was maintained and the specimens were immersed in artificial saliva at 37°C for 24h before testing. Each specimen was sectioned into sticks (0.9±0.01mm2). The sticks (24/group) were subjected to μTBS test and their modes of failure were determined using scanning electron microscope (SEM). For both preheated groups, IPT increased equally by 1.5–2°C upon application of the composite. After light curing, IPT increased by 4–5°C in all tested groups. Nevertheless, the IPT of the preheated groups required a longer time to return to the baseline temperature. One-way ANOVA revealed no significant difference between the μTBS values of all groups. SEM revealed predominately mixed mode of failure. Preheating of silorane-based resin composite increased the IPT but not to the critical level and had no effect on dentin μTBS.