Heat Generation During Implant Site Preparation: An In Vitro Study

Thermal changes elicited during drilling and tapping procedures used in site preparation for screw-shaped and cylindrical implants were measured in vitro in blocks of bovine cortical femure bone. Heat-senstivie thermocouples were placed in the bone specimens at 4- and 8-mm depths and at a constant distance from the periphery of the drilling site; this distance was preset for each type of bur used. Rotary cutting was performed with 10-mm-long twist drills (2- and 3-mm diameter) and triflute drills (3.3- and 4-mm diameter) running at 4,500 rpm with external irrigation. A special guide drill was used to ensure unidirectional continuous drilling with a load of 2,000 g. In addition, the effect of irrigation was evaluated during tapping procedures with 10-mm-long taps used at 20 rpm. The greatest temperature increase was observed with the 2-mm twist drill at both 4- and 8-mm depths. Significantly greater temperature increase was noted at the 8-mm depth versus the 4-mm depth with the twist d rills. Such significant difference between temperature rise at the two different drilling depths was not observed with the triblute burs. The time interval require d for the maximum temperature reached during rotary cu tting to return to baseline values was two times longer for the 2-mm twist drill than for the 3.3-mm triblute bur at both drilling depths. No statistically significant differences could be found between the maximum temperatures generated when tapping was performed with and without irrigation at both 4- and 8-mm depths. It can be suggested that the geometry of triblute burs combines cutting efficacy with greater heat dissipation capabilities than twist drills at the drilling depths of 4 and 8 mm used in this study.