The objective of this in vitro study was to evaluate the amount of heat generated on the external root surface during retrieval of NiTi instrument using ultrasonics. This study checked the temperature rise at higher and lower power settings in presence and absence of coolants at the junction of separated NiTi instrument & the ultrasonic tip, and near the apex of root. Method: 60 permanent human maxillary first molars were decoronated from the cemento-enamel junction using diamond disc such that 8-10mm of mesiobuccal roots of maxillary first molars were obtained. Cleaning & shaping of canals was done using 2.5% sodium hypochlorite & 17% EDTA. The canals were enlarged upto size F1 Protaper. 4mm of Pro-Taper F1 file was fractured & left in the mesiobuccal canal, 4-5 mm from the coronal access. K type thermocouples connected to digital thermometer were attached to external root surface to measure temperature rise. These teeth were divided in 4 equal groups (n=15) : Group 1-With water as coolant/lower power setting ,Group 2 Without coolant/lower power setting ,Group 3 With water as coolant/higher power setting, Group 4 Without coolant/higher power setting. Ultrasonic tip ET 20 was activated for 30 sec, and temperature rise was recorded. The highest temperature rise was seen in the group without coolant at higher power setting whereas lowest temperature rise was seen in the group with coolant at lower power setting.
