Influence of different parameters on bone heating and drilling time in implantology.

The influence of various parameters on bone heating during drilling and drilling time was studied in vitro in a bovine cortical femur model. Drilling using a standard, a surgical or a laboratory motor unit did not affect bone temperature elevation. For a given speed, low 1/40 reduction contra-angle was more effective in moderating temperature elevation when compared to 1/10 reduction; but drilling time in this case (1/40) had to be doubled. Enhancing the drilling load from 0.8 kg to 2 kg had little effect on temperature elevation at 400 rpm and 800 rpm (< 3 degrees C). Drilling time drastically decreased and was inversely proportional to the square of the load. Predrilling did not affect temperature elevation, but decreased drilling time. From 400 rpm to 10,000 rpm, temperature elevation was positively correlated with drilling speed. It further decreased up to 24,000 rpm and then was constant up to 40,000 rpm. Drilling time was proportionally reduced with increased rotation speed. Strikingly, heat was largely dissipated within 10 s at high rotation speed. The use of a cryogenic spray at 24,000 rpm allowed the reduction of temperature elevation. Finally, protection from temperature elevation according to above parameters is suggested.