Thermal effects caused by the association of hybrid light and incorporation of titanium dioxide into 37% carbamide peroxide for dental bleaching.

Abstract

This study monitored the thermal changes in the pulp chamber and on the buccal surface of teeth during in-office bleaching with 37% carbamide peroxide (CP) either with or without the incorporation of titanium dioxide (TiO₂) and with or without activation with a hybrid light (HL). A total of 50 bovine incisors were prepared and randomly separated into 5 treatment groups (n = 10): 35% hydrogen peroxide (HP); CP; CP + HL; CP + TiO₂; and CP + TiO₂ + HL. The bleaching gels were applied for 30 minutes. In the groups with HL activation (infrared laser diodes + violet LEDs), 1-minute applications of active light were alternated with 1-minute pauses for the entire duration of bleaching. Type K thermocouples were positioned directly within the pulp chamber and on the buccal surface of the incisors to measure the temperature changes at different timepoints over the course of 30 minutes. Statistical analysis was performed with Kruskal-Wallis and post hoc Dunn tests for comparisons between treatments and Friedman and post hoc Nemenyi tests for comparisons between timepoints (α = 5%). The CP + HL and CP + TiO₂ + HL groups showed significantly higher pulp chamber temperatures than the other groups (P < 0.05). The CP + TiO₂ + HL group showed a significantly higher buccal temperature (median of 42.55°C) after 30 minutes of application than all of the other groups (P < 0.05) except CP + HL (P > 0.05). The use of HL raised the pulp chamber and buccal surface temperatures during bleaching, and these changes could exceed the 5.5°C limit for safe temperature increases. When activated by HL, the incorporation of TiO₂ potentiated the increase in temperatures.