In vitro thermographic measurement in pulpal chamber during diode laser bleaching

Abstract

Thermographic was employed to determine the temperature rise in lower incisors pulpal chambers during diode laser bleaching. Two methods were used: a thermocouple for 72 teeth and a infrared (IR) thermographic camera for 36. Two bleaching agents, both 35% hydrogen peroxide- Whiteness HP (HP) and Hi Lite (HL) - were applied to the specimens buccal surfaces and irradiated with a diode laser (808 5nm), CW for 30s. Intensities tested were 21.W/cm2, 29.8W/cm2, 35.8W/cm2, 38.2W/cm2, 52.9W/cm2 e 63.7W/cm2. Means of the greatest temperature rises with the HL were statiscally lower than the HP (p<0.01). When HP was irradiated with 50.9W/cm² and 61.1W/cm², the temperature registered was over 5.5ºC, considered as the limit to avoid pulp damage. The IR thermacam analysis showed that, when the HP was used, the temperature rise in pulp chamber was similar to the target area on the buccal surface. Evaluation of tooth color was done using a VITAshade guide at baseline and at the end of the bleaching treatment. Both products proved to be efficient, however HP produced statiscally higher shade changes than HL (p<0.01). It can be concluded that the diode laser bleaching associated with the HP was safe when intensities below 50mW/cm2 were employed. Higher parameters can cause damage to pulp vitality of the lower incisors, fact that did not occurred with the HL gel. Both gels were efficacious to the bleaching technique proposed, but the HP showed better results.