Drilling- and withdrawing-related thermal changes during implant site osteotomies

Intrabony temperature increase is not only dependent on shearing energy and mechanical friction between bone and surgical drill but is also related to heat capacity and thermal conductivity of the surrounding bone and the applied surgical instrument. Thus time of occurrence of the highest temperature rise can be expected after the shearing process of the osteotomy, potentially affecting the process of osseointegration.

The aim of this study was to evaluate temperature changes during the shearing and withdrawing processes during osteotomies.

An overall 160 automated intermittent osteotomies (10/16 mm drilling depth) with 2 mm diameter twist drills and 3.5 mm diameter conical drills and different irrigation methods (without/external/internal/combined) were performed on standardized bone specimens. The drilling cycles were operated by a computer-controlled surgical system, while a linear motion potentiometer and multichannel temperature sensors in various intrabony levels ensured the real-time documentation of temperature changes during the shearing and withdrawing processes.

The highest temperature changes were invariably recorded during the process of withdrawal. Significantly lower temperature changes (p < .02) could be recorded at maximum drilling depths during the shearing process regardless of drilling depth, diameter or irrigation method. During coolant supply, 2 mm diameter twist drills showed higher temperatures (10 mm, p < .01/16 mm, p < .03) compared with 3.5 mm diameter conical implant drills. Internal (10 mm, p < .01) or combined irrigation (16 mm, p < .01) was associated with significantly lower temperatures compared with external irrigation by the use of conical implant drills.

Considering that heat generation during osteotomies is a multifactorial scenario, this study could demonstrate that the highest temperature rise during implant osteotomies occurs during the withdrawing process and that the time of occurrence is influenced by predominant factors such as osteotomy depth and mode of irrigation.