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.
Highlights
Influenced by the most diverse social contexts, physical appearance has become a great concern of people, which include a perfect smile with white and lined up teeth
The crowns of human teeth were submitted to 35% hydrogen peroxide bleaching (Whiteness HP, FGM Produtos Odontológicos Ltda, Joinvile, PR, Brazil) activated by different light sources (Table 1)
Halogen light induced the highest temperature rise (1.41±0.64oC) (p
Summary
Influenced by the most diverse social contexts, physical appearance has become a great concern of people, which include a perfect smile with white and lined up teeth. Sodium perborate and carbamide peroxide are generally used for bleaching procedures[25], being effective for bleaching teeth. Side effects, such as changes in the tooth structure[19], microleakage in restorations[7], external root resorption and pulpal irritation[18] have been reported. The in-office technique using bleaching agents at high concentrations associated with thickening, catalysts or light-activated[11] agents is faster and more effective, but requires the use of heat or light source for activation of the hydrogen peroxide[4]. In an attempt to achieve the bleaching of several types of tooth stains, an external heat source was associated to hydrogen peroxide in discolored teeth[6,14]. Consequences of direct applications of heat on tooth structures may be mild, but may be extremely severe, leading to irreversible pulp damage[28]
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