Effects of Implant Drill Wear, Irrigation, and Drill Materials on Heat Generation in Osteotomy Sites
This study evaluated the effects of drill wear on bone temperature during osteotomy preparation with 3 types of drills and compared heat production between drills. The drills used in this study were titanium nitride-coated metal, tungsten carbide carbon-coated metal, and zirconia ceramic drills. An osteotomy 11 mm in depth was formed in bovine scapular bone following the manufacturer's recommended drill sequences. Drilling was performed without irrigation and repeated 20 times; temperature was measured every 5 times. Next, 200 rounds of drilling during irrigation were performed for each drill, with temperature change monitored until round 200. Analysis of variance statistics were used for analyses of the measured data. Drilling without irrigation showed significant thermal increase at all time points compared to drilling with irrigation (P < .001). No significant difference was found between drill materials. Under irrigation, the frequency of previous drilling had minimal effects on thermal change. The repeated-measures analysis of variance revealed major thermal change at the initial time point (P < .0001), and the multiple comparison tests revealed a significant difference in temperature between the initial drills that had been used 50 or fewer times and those that had been used more than 50 times, irrespective of the drill material. The results of this study indicate that the initial drill should be changed in osteotomy preparation with irrigation after they have been used 50 times. Irrigation may be a more critical factor for the control of temperature elevation than is the drill material.
The implant drill systems. (a) The TiN-coated drill served as a control. The diameters for each drill sequence were 1.8, 2.0, 2.5, 3.2, and 4.2 mm (left to right). The color of the TiN coating was gold, as is typical. (b) The WC/C-coated drill had a black coating. The diameters were 1.5, 2.0, 3.0, 3.4, and 4.3 mm (left to right). Note that the third drill was not a twist drill but a pilot drill that enlarged a hole from 2.0 mm to 3.0 mm in diameter; the pilot drill was used as recommended by the manufacturer. (c) The zirconia ceramic drill was white in color. The diameters were 1.7, 2.0, 2.8, 3.5, and 4.2 mm (left to right).
Schematic diagram of the drill sequence and location of the thermocouples. Sticky wax (gray rectangle) was used to protect the thermocouples from environmental effects, such as the cool water.
Schematic representation of the equipment used to measure temperature, plus photos of a data logger, thermostat, and handpiece. The data logger recorded the bone temperature during drilling. The thermostat maintained a temperature of 36.5°C in the water bath.
Contributor Notes