Objective: 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.
Study design: 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.
Result: 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.
Conclusion: 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.