Real-time Temperature Monitoring During Light-Curing of Experimental Composites

To investigate the real-time temperature rise during light-curing of experimental composite materials containing bioactive glass 45S5 (BG) and compare it to the temperature rise in three commercial composites.

Five light-curable composite materials containing 0-40 wt% of BG and a total filler load of 70 wt% were prepared. Cylindrical composite specimens 6 mm in diameter and 2 mm thick were cured using Bluephase G2 (Ivoclar Vivadent) at 1200 mW/cm² for 30 s. The rise in temperature during light-curing was measured at the bottom of the specimens using a T-type thermocouple at the data collection rate of 20 s ^-1. An additional illumination for 30 s was performed after the specimen temperature returned to the baseline in order to record the temperature rise due to the heating from the curing unit. Statistical analysis was performed using the one-way ANOVA and Pearson correlation analysis with α=0.05.

Temperature rise during light-curing of experimental composites amounted to 12.2-14.0 °C and was comparable to that of the flowable commercial composite (12.5 °C) but higher than that of nano- and micro-hybrid commercial composites (9.6-10.3 °C). The temperature rise during the second illumination was similar for all composites (7.8-9.1 °C). In experimental composites, the temperature rise which was attributable to the polymerization exotherm amounted to 3.1-5.8 °C and was negatively correlated to the BG fraction (R²=0.94). Times at which temperature reached maximum values were in the range of 6.5-19.8 s and were positively correlated to the BG fraction (R²=0.98).

Temperature rise during light-curing of experimental composites was comparable to that of commercial composites, suggesting that the amount of heat released is tolerable by dental pulp.