The effect of different broken file removal techniques on strengt of roots after dynamic loading

The aim of the study is to evaluate the fracture resistance of teeth restored after instrument removal from root canals with ultrasonic-BTR-Pen or trephine bur BTR-Pen techniques after aging in a chewing simulator. Fifty four human single rooted teeth were divided into 4 groups (2 control groups and 2 study groups) according to the removal method of the broken instrument. Broken instruments were extracted either with ultrasonic+ BTR-Pen system or removed using trephine bur BTR-Pen techniques. The success rate of instrument removal and consumed time were recorded. The teeth, which were restored after the removal of instruments from their canals, were loaded by chewing simulator. In this study, 120,000 cycles (1.6 Hz) corresponding to 6 months. After aging procedures the teeth were cut and the root sections were subjected to a lood at a 1mm/min. rate in on universal testing device. Broken instrument removal success rate, duration and root fracture resistance of the teeth were statistically analyzed. The success of removing the broken instrument with Trephine bur + BTR Pen and ultrasonic system + BTR Pen was found to be 95.50% and 86.40%, respectively, and there was no statistically significant difference between the two techniques (p>0.05). When the time is compared, the ultrasonic+BTR-Pen system (23,97±8,35 min) showed similar results to that of the trephine bur+BTR-Pen (24.1 ± 8.28 min) (p > 0.05). When the root fracture resistance of the teeth were examined, there were no statistically significant difference between the trephine and ultrasonic groups (p=0.989).Both trephine group and ultrasonic group were statistically significantly lower than the positive and negative control groups (p<0.0001). İn conclusion, there was no significant difference between the trefan bur + BTR Pen and ultrasonic system + BTR Pen groups in terms of the success, duration and root fracture resistance of the broken instrument. Keywords: BTR-Pen, broken instrument, ultrasonic, trepan bur