Temperature elevation on root surfaces during Nd:YAG laser irradiation in root canals

Abstract

The purpose of this study was to evaluate the temperature elevation on the root surfaces when Nd:YAG laser was irradiated in the root canals. Ten extracted human teeth were used. The tip of laser fiber through a 23-G needle was fixed at 1.0 mm shorter than the working length, and then Nd:YAG laser (2 W 1 s, 2 W 3 s, 3 W 1 s, 3W 3 s) was irradiated in the root canals under three conditions (with water irrigation, within water and without water). The temperature elevation on the root surfaces was measured at the root apex and lateral surface point of the laser tip level by infrared thermometer. The intracanal surfaces of irradiated teeth were observed using microscopy. The highest temperature under the condition of without water was more than 500 °C. The temperature elevation without water was significantly higher than that with water irrigation and within water ( p<0.01). The temperature elevation of five teeth whose depression defects were confirmed was higher than the other five teeth. This study suggests that the temperature elevation on the root surfaces during Nd:YAG laser irradiation in the root canals undergoes changes greatly according to the various conditions and may cause thermal periodontal tissue injuries.