Intracanal temperature changes during bone preparations close to and penetrating the inferior alveolar canal: Drills versus piezosurgery.

PURPOSE: The aim of this in vitro study was to investigate temperature increases in the inferior alveolar canal (IAC), when different bone preparation methods approximate and penetrate the IAC. MATERIALS AND METHODS: In pig mandible, buccal bone removals were performed until the neurovascular bundle became visible. Temperatures were registered with thermocouple probes and with infrared thermometer. Preparations were performed with diamond drills (DD), tungsten carbide drills (TCD), piezoelectric diamond sphere (PT_D) and saw (PT_S) tips, and a combined preparation method was also performed whereby the superficial three-fourths of the bone was removed with TCD and the deepest one-fourth of the bone with PT_D (TCD + PT_D_7 degrees C) or PT_S (TCD + PT_S_7 degrees C), using cooled irrigation (7 degrees C). RESULTS: Preparations using room temperature irrigation caused significantly less heat on the bone surface than in the IAC. Piezosurgery in the IAC produced significantly higher temperatures (>13 degrees C) than the drills (<4 degrees C). Heat productions of the piezoelectric tips were reduced significantly by applying the combined bone removal methods. The speed of PT_S and TCD + PT_S_7 degrees C were comparable to the speed of TCD, whereas TCD + PT_D_7 degrees C was found to be significantly slower. CONCLUSION: The speed of piezosurgery is comparable to that of the drills; however, it produces the highest, potentially nerve-harming temperatures. To eliminate the heat consequences during piezosurgery in the IAC, the use of cooled irrigation at 7 degrees C and predrilling is recommended.