Ultrasonic vibration: temperature rise on external root surface during broken instrument removal

The effect of 2 ultrasonic tips and power settings on temperature rise of external root surface was investigated during ultrasonic vibration of intracanal broken instruments. Thirty maxillary human central incisors had lingual coronal access. The apical 5 mm of size 40 K-files was separated at apical region. Two thermocouples connected to digital thermometer were attached to external root surface to measure temperature rise. Central incisors were divided into 3 equal groups: group 1 in which Satelec ET 40 ultrasonic tip at power 1 was used, group 2 in which ET 40 at power 5 was used, and group 3 in which CPR 5 ultrasonic tip at power 1 was used. Ultrasonic vibration without coolant was activated for 2 minutes, and temperature rise was recorded at 1 and 2 minutes. At 1 minute, CPR 5 and ET 40 at power 1 showed statistically significant less temperature rise. CPR 5 demonstrated lower temperature rise compared with ET 40 when used for 2 minutes. ET 40 showed less temperature at power 1 compared with power 5. Significant increase in temperature from 1 minute to 2 minutes was observed in all groups.