Effect of power settings on temperature change at the root surface when using a holmium YAG laser in enlarging the root canal

The aim of this study was to determine the maximum amount of power, in watts, that a Holmium YAG laser could deliver via a 245-mu m fiberoptic to the canal surface and still not raise the temperature (Delta T) of the cementum by >5 degrees C. Sixty single-rooted teeth were divided into three groups according to power selection (0.50, 0.75, and 1.00 W). The three main outcome variables were: change in apical temperature, change in coronal temperature, and maximum size of an endodontic file that could fit into the canal after lasing. The group means for apical Delta T were: 1.00 W = 2.2 degrees C, 0.75 W = 2.68 degrees C, and 0.50 W = 1.58 degrees C. The group means for coronal Delta T were: 1.00 W = 1.15 degrees C, 0.75 W = 0.99 degrees C, and 0.50 W = 0.56 degrees C. The group means for file size were: 1.00 W = 41.25, 0.75 W = 38.75, and 0.50 W = 40.75. The canal size was increased from a size 25 file up to approximately a size 40 file with all power groups. There were no significant differences between the groups for change in apical temperature (p = 0.32), coronal temperature (p = 0.17), or maximum file size (p = 0.86) when adjustments were made for tooth dimensions. In all groups studied, the Delta T was <5 degrees C. This represents a safe and predictable laser procedure.