Effect of energy (J) on temperature changes at apical root surface when using Er:YAG laser to enlarge root canals

The use of lasers for cleaning, shaping and disinfecting root canals must not produce heat which damages periapical tissue and alveolar bone. The aim of the present study was to determine the increase of external temperature at the apical surface of the root canal after Er:YAG laser irradiation with a 250 mu m diameter fiberoptic guide with and without distilled and deionized water at 3 different total energies. Thirty single-rooted teeth were instrumented to #25 It-file using distilled and deionized water for irrigation. They were divided into three groups according to total energy (15J, 30J and 45J with 15 Hz and 140 mi per pulse). Each group nas irradiated with water and then without water. The increase in temperature at the apical root surface was measured with a multimeter and a thermocouple. Changes in apical temperature were significantly different in all groups (p<0.01, 15J<45J<30J). Less time was necessary for return to initial room temperature at 15J. We conclude that in vitro use of the Er:YAG laser (total energy of 15, 30, and 45J) increased external apical root temperature and that the root canal must be filled with distilled and deionized water to reduce the risk of an increase in temperature.