RESUMO
OBJECTIVE: The aim of this research was to evaluate, under the scanning electron microscope, the role of different parameters and angles of incidence of the Nd:YAG laser on the morphology of the radicular dentine. BACKGROUND DATA: Irradiation of dentine with Nd:YAG laser removes smear layer and promotes its fusion and recrystallization, thus decreasing permeability. METHODS: Forty-eight human maxillary canines were randomly divided in four groups of 12 teeth each, according to the following parameters of irradiation: 1 Wand 10 Hz; 1 Wand 20 Hz; 3 Wand 10 Hz; 3 Wand 20 Hz. Two teeth of each group were split longitudinally and the laser was applied perpendicularly to the root canal. Specimens were observed under the SEM, and the morphological alterations in dentine were recorded. RESULTS: The increase of power and frequency of the laser produced more structures that characterize the irradiation of dentine by Nd:YAG laser, such as globular formations, melting and glazing, and ebullitions. Such structures were especially frequent when 3 Wand 20 pps were used as parameters. The removal of the smear layer produced root canals with more dentinal tubules visible under the SEM. CONCLUSIONS: The increase in power and frequency of the Nd:YAG laser irradiation produced more visible morphological alterations than the lower settings. The removal of the smear layer increased the number of visible dentinal tubule openings.