Temperature Rise During Experimental Light-Activated Bleaching

Objectives: The aim of this study was to evaluate the surface and intrapulpal temperature variation after bleaching treatment with 25% hydrogen peroxide (ZOOM 2, Discus Dental, USA) using different light sources. Methods: A K-type thermocouple was used to measure the temperature increase in the pulp chamber while infrared termometer was used for surface mesurements of extracted upper incisors and canines. Experimental LED 405 (400mW/cm2), OLED (200 mW/cm2) and femtosecond laser (800 mW/cm2) were tested and compared to ZOOM2 (Discus Dental, USA). Specimens were divided into 8 groups (n=10) ; for intrapulpal temperature: (G1) control – bleaching gel without light activation, (G2) without gel + light activation, (G3) vaseline + light activation, (G4) bleaching gel + light activation, and for surface temperature: (G5) bleaching gel without light activation, (G6) without gel + light activation, (G7) vaseline + light activation, (G8) bleaching gel + light activation. The temperatures were recorded at 5 time points: before, 5, 10, 15 and 30 minutes during light activation. Data were analyzed by the Friedman's test and Wilcoxon Signed Rank test. Results: Without bleaching gel, increase in surface temperature readings ranged from 5.3°C (LED), 2.2°C (OLED), 5.5°C (femtosecond laser-unfocused), 20.4°C (femtosecond laser-focused) to 26.2°C (ZOOM 2) and in pulp chamber temperature increases ranged from 3.7°C (LED), 1.8°C (OLED), 4.9°C (femtosecond laser-unfocused), 18.7°C (femtosecond laser-focused) to 23.9°C (ZOOM 2). The presence of the bleaching gel or vaseline with light sources significantly reduced temperature increas at the surface and within the pulp (p<0.05) except when using OLED (p˃0.05). Conclusions: The increase in the pulp chamber temperature with the LED, OLED and femtosecond laser (unfocused) was below the critical temperature increase of 5.5°C. Femtosecond laser (focused) as well as the ZOOM 2 produced a pulp chamber temperature increase above this threshold. Caution is advised when using this type of light activation. This abstract is based on research that was funded entirely or partially by an outside source: Ministry of Science, Education and Sport, Republic of Croatia (project No. 065-0352851-0410).