In vitro study of the pulp chamber temperature rise during light-activated bleaching

Abstract

This study evaluated in vitro the pulp chamber temperature rise induced by the light-activated dental bleaching technique using different light sources. The root portions of 78 extracted sound human mandibular incisors were sectioned approximately 2 mm below the cementoenamel junction. The root cavities of the crowns were enlarged to facilitate the correct placing of the sensor into the pulp chamber. Half of specimens (n=39) was assigned to receive a 35% hydrogen peroxide gel on the buccal surface and the other halt (n=39) not to receive the bleaching agent. Three groups (n=13) were formed for each condition (bleach or no bleach) according to the use of 3 light sources recommended for dental bleaching: a light-emitting diode (LED)-laser system, a LED unit and a conventional halogen light. The light sources were positioned perpendicular to the buccal surface at a distance of 5 mm and activated during 30 s. The differences between the initial and the highest temperature readings for each specimen were obtained, and, from the temperature changes, the means for each specimen and each group were calculated. The values of temperature rise were compared using Kruskal-Wallis test at 1% significance level. Temperature rise varied significantly depending on the light-curing unit, with statistically significant differences (p<0.01) among the groups. When the bleaching agent was not applied, the halogen light induced the highest temperature rise (2.38±0.66°C). The LED unit produced the lowest temperature increase (0.29±0.13°C); but there was no significant difference between LED unit and LED-laser system (0.35±0.15°C) (p>0.01). When the bleaching agent was applied, there were significant differences among groups (p<0.01): halogen light induced the highest temperature rise (1.41±0.64°C), and LED-laser system the lowest (0.33±0.12°C); however, there was no difference between LED-laser system and LED unit (0.44±0.11°C). LED and LED-laser system did not differ significantly from each other regardless the temperature rise occurred with or without bleaching agent application. It may be concluded that during light-activated tooth bleaching, with or without the bleaching agent, halogen light promoted higher pulp chamber temperature rise than LED unit and LED-laser system. The tested light-curing units provided increases in the pulp chamber temperature that were compatible with pulpal health.

Influence of whitening gel on pulp chamber temperature rise by in-office bleaching technique

“…This probably occurred due to the presence of the purple coloring, with peak absorption of 521nm, in the whitening gels evaluated. In the present study, the Whiteness HP (FGM) and Whiteness HP Maxx (FGM) groups also showed significant temperature increase when irradiated with the blue light, as was found in the literature 6,35 . Still, it should be emphasized that the lowest temperature variation was observed with the Whiteness HP Maxx (FGM) whitening gel, when compared to the Whiteness HP (FGM), even though this difference was not shown to be significant.…”

“…The present study adopted 5mm distance between the tip of the light and the surface of the tooth covered by the whitening gel, which allowed a greater increase in temperature 6,28 .…”

“…Several authors working with LEDs with power density between 500 and 950mW/cm 2 , using whitening gel and following the recommended protocol, have observed the increase in temperature 6,35 . This output may be applied to the data obtained in the present study in which the light from the LED, with a mean intensity of 600mW/cm 2 , raised the temperature for all groups studied, although not surpassing the critical value of 5.5°C necessary to cause changes in the pulp 16 .…”

“…To this end, LEDs have been widely used to emit energy in a narrow range of the visible spectrum, guaranteeing greater safety in heat generation [6][7][8][9][10] . However, although traditionally considered as light sources that do not generate heat 11 , LEDs have been questioned recently as to their capacity to raise the temperature of the tooth 5,12,13 .…”

Comparative clinical and psychosocial benefits of tooth bleaching: different light activation of a 38% peroxide gel in a preliminary case–control study

“…Erikkson et al 33 found that 42°C might be a critical temperature to the pulp when sustained for 1 min; Baldissara et al 34 reported that an intrapulpal temperature rise of 8.9–14.7°C in humans does not induce pulpal pathology. As there is no agreement about which is the lowest value of pulp chamber temperature rise that would cause pulp damage, it is rational to use a light source that minimizes possible iatrogenic problems during clinical treatments 35.…”