Purpose: to calculate probabilities for tissue injury and to measure effective- ness of various coolant strategies in countering heat buildup produced by dry ultrasonic vibration during post removal.
N= 10 single canal (premolars or canines).
Materials & Methods:
- All teeth were standardized; access, C/S, and obturation.
- Post spaces were prepared 10 mm in depth with #5 ParaPost drill. Posts cemented with Panavia 21. adhesive resin cement .
- Two K-type Chromega-Alomega thermocouples attached to tooth and post. Data set consisted of cervical and apical measures of temperature increase at 1-second intervals from baseline during continuous ultrasonic instrumentation until a 10oC increase in temperature at the cervical site was registered and the teeth were allowed to cool under the assistance of 5 cooling methods. : (1) air only from 3-way syringe; (2) water spray from 3-way syringe; (3) small cotton pellet #3 sprayed for 2 seconds with Endo-Ice and applied; (4) large cotton pellet #0 sprayed for 2 seconds with Endo-Ice applied to the post; (5) cooling by ambient air.
•Most highlighted Results:
1.Injurious temperatures are easily reached in less than 1 minute during dry ultrasonic instrumentation of metallic posts.
2.Endo-Ice applied with large cotton pellet was the most efficient coolant method, but this was not statistically significant over less costly options. 3.The 4 active coolants used in this study were all effective in reducing the probability of temperature damage caused by instrumentation.
Clinical significance: Cycles of short instrumentation times with active coolants are effective in reducing the probability of tissue damage when teeth are instrumented dry.