METHODS: 49 single-rooted extracted human teeth were sectioned at the cemento-enamel junction. Root canals were prepared with step-back technique to file size #45 apically and obturated with laterally condensed gutta percha and zinc oxide eugenol based sealer. The root tip was resected at 90° 3 mm from the apex. Teeth were randomly divided into 3 groups each of 13 teeth (10 for leakage, 3 for SEM analysis), and 2 groups each of 5 teeth served as controls. In the 3 experimental groups, apical cavities were prepared using an ultrasonic retrotip and contact tips of an Er:YAG laser with two different power settings (80 and 100 mJ at 10 pps). Working time was recorded. The surfaces of the retrograde cavity walls were examined using SEM. Leakage was measured after retrograde filling with SuperEBA cement; after immersion in India ink for 7 days, teeth were cleared and evaluated for linear leakage under x20 magnification. Microleakage and working time were analyzed by ANOVA and Scheffe test.
RESULTS: There were no significant differences in dye leakage among ultrasonic and laser-treated groups. Significantly (p<0.05) more working time was required in the 80 mJ laser group than in the ultrasonic and 100 mJ laser groups. Morphological examination of prepared dentin walls showed no debris or smear layer in the laser-treated groups but slight to moderate smear layer was present in the ultrasonic group. Dentin walls in the lased groups were irregular and scale-like.
CONCLUSIONS: Er:YAG laser has the potential to be applied to root end preparation. This research was partially supported by NRCT-JSPS Core University Program.