Intrapulpal temperature changes during root surface irradiation with an 809-nm GaAlAs laser.

Abstract

The aim of this study was to explore, in vitro, whether the irradiation of human root surfaces with a diode laser might induce nonphysiologic intrapulpal temperature elevations and, therefore, jeopardize pulp vitality. The pulps were removed from human maxillary and mandibular incisors extracted for periodontal reasons. The root canals were enlarged to an apical size #60 file. The teeth were radiographed with standard dental films and a millimeter grid to determine root thickness. The thickness of dentin between the root surface and the pulp in the irradiation areas was 1, 2, and 3 mm. To determine intrapulpal temperature changes during laser irradiation, 0.5-mm K-type thermocouples were inserted. An 809 nm GaAlAs laser with a 400-micron optical fiber was used. The power output varied between 0.5 and 2.5 W in the continuous-wave mode (0 Hz). Irradiation was continued for up to 120 seconds. Temperature elevations between 0.5 and 32.0 degrees C were registered in an energy- and time-dependent manner. Dentin thickness had a significant effect on intrapulpal temperature changes (Mann Whitney U test, P <.05), with a thinner dentin layer resulting in higher temperature elevations. Diode-laser irradiation may jeopardize pulp vitality. It must be recommended to limit power output to 0.5 W and the time of irradiation to 10 seconds when lasing the root surfaces of lower incisors and first maxillary premolars. With other teeth, a power output of 1.0 W and an exposure time of 10 seconds must not be exceeded to ensure a safe clinical application.