Dentinal microcrack formation during root canal preparations by er,cr: Ysgg laser

The purpose of this study was to compare the formation of microcracks following root canal preparation performed with hand files and erbium, chromium:yttrium, scandium, gallium, garnet (Er;Cr:YSGG) laser (Waterlase iPlus; Biolase Technology, Inc., San Clemente, CA, USA) irradiation with the EndoLase Radial firing tip (RFT) Root Canal Therapy Kit. In this study one hundred and fifty extracted single-rooted human mandibular premolar teeth were decoronated by using a diamond coated bur with water-cooling, leaving roots 13 mm in length. A silicon impression material was used for coating the cemental surface of roots to simulate periodontal ligament space. All roots were then embedded in acrylic blocks. The working length was set at 12 mm, 1 mm short of the anatomical apex. 150 samples prepared for shaping are divided into 5 separate groups. In the hand instrumentation group (n=30 teeth), the samples were prepared conventionally using standard K-files enlarged up to master apical file ISO size 40. Other 120 samples to be expanded by laser are divided into 4 groups. Instrumentation of samples in these 4 groups was done up to #25 K-file and then the canals of each group were irradiated by an Er;Cr:YSGG laser using (RFT2 and RFT3, Endolase, Biolase Technology) with the different power settings (1.25 W, 2 W, 3 W, 4 W) and the other panel settings; 50 Hz frequency, 34 % water, and 24% air according to manufacturers' recommendations. Roots were then sectioned at 3, 6, and 9 mm from the apices, and the cut surfaces were observed under a microscope and checked for presence of dentinal microcracks. As a result, the prevalence of microcracks showed no significant difference (p>0.05) between the roots prepared with the hand files when compared with the other grups prepared with the Er;Cr:YSGG laser. In conclusion the Er,Cr:YSGG laser technique facilitated enlargement of root canals and showed similar microcrack formation when compared with the hand instrumentation technique.