Abstract:

Objective:The purpose of this studywas to evaluate the effects of the pulsed Nd:YAG laserirradiation in root canals on tem- perature changes on the root surface in vitro and optimize the parameters of laser irradiation in root canal treatment.Methods:A total of 108 extracted single-root human teeth were divided into A, B and C groups, after the preparation of root canals and re- moval of their crowns. GroupAwas evaluated the surface temperature changes of differentteeth irradiatedwith the same outputen- ergy. The teeth inGroup B and Cwere irradiated respectivelywith the frequencies of 15 Hz and 20 Hz, and 7 differentoutput en- ergy, and the inner root canal surface inGroup Bwas coatedwith a layerof ink, whichworked as the initiator.Results:The tooth surface temperature of the mandibular incisor increased more obviously than that of the maxillary incisor, canine and premolar, during root canal irradiation treatment (P<0101). Significant difference was shown on the temperature elevation when the teeth were irradiated with 2W or higher output power (P<0101). Temperature increased significantly higher in the teeth with initiator than thatwithout it (P<0101). With the same parameters of output energy, the surface temperature demonstrated higher on the apical partof the root canal than thatin the middle.Conclusion:There is significantly positive correlation between the temperature elevation on the root surface and the average output power and frequency of the pulsed Nd:YAG laserirradiation in the root canal. The shape of tooth, initiator and different parts of the root may also play important roles in the temperature changes of the tooth surface. This study may help optimize the parameters of clinical laser irradiation treatment.

Key words: rootcanaltreatment, pulsedNd:YAGlaserirradiation, rootsurfacetemperature