Assessment of Thermal Alteration During Caries Removal Using Er:YAG Laser

Objective: The aim of this study was to evaluate in vitro the thermal alterations during dentin caries removal using Er:YAG laser. Methods: sixty fragments (2.5-mm thick), from thirty human molars, were randomly assigned into two groups (n=30): artificial dentin caries or sound dentin (control group). The caries lesion (± 1-mm-deep) was obtained with S.mutans (Strains ATCC 25175) cultures through six weeks. The specimens of both groups were assorted into 3 subgroups (n=10), according to the irradiation frequency used (4, 6, or 10Hz) at a constant energy level of 200mJ and an irradiation time of 20s. Before irradiation, a thermocouple, adapted to the tooth fragment, recorded the initial temperature value (°C); then, the temperature was measured the 10s during irradiation and after finishing irradiation. A caries detection system (DIAGNOdent) was employed to evaluate the demineralized dentin removal. Data were analyzed by Kruskal-Walis' and Friedman's tests. Results: temperature increased gradually over time for all groups; there was no difference between the temperatures obtained with 4 and 6Hz; the highest temperature values were achieved with 10Hz; concerning both types of substrate, there was no difference between carious and sound dentin; the caries detection system revealed that the caries removal was similar with 4 and 6Hz, and was superior with 10Hz. Conclusions: the frequency of 10Hz, although removed the caries lesion more adequately, promoted the highest temperature increase.