# Direct Measurement of Heat Produced during Drilling for Implant Site Preparation
## 3 Results  
The average maximum temperature for each rotating speed and region are shown in Figure 2, and the temperature changes at 500, 1200 and 2000 rpm are shown in Figure 3. The direct drilling temperature without the rotating slip ring on the thermosensor, used in previous works, recorded an average 8 \({}^{\circ}\)C higher than our method with the rotating slip ring at all speeds. The mean values of peak temperature by drill speed and measuring depth is shown in Table 1.  
Figure 2: Comparison of implant drilling temperature measured at drill with/without slip ring or inside bone at a depth of 1, 5, and 10 mm, respectively, as a function of rotation speed. When the drilling speed was 500 rpm, the temperature of the drill increased rapidly once the drilling started, and the mean maximum temperature of 51.4 \({}^{\circ}\)C, SD (standard deviation) 3.8, was reached in 5 s when the drill reached a depth of 10 mm. On the other hand, the thermocouples in the bone reached the maximum temperature (mean 42.7 \({}^{\circ}\)C, SD 2.7) after 7 s.  
When the drilling speed was 1200 rpm, the temperature of the drill increased rapidly once the drilling started, and the maximum temperature (mean 68.5 \({}^{\circ}\)C, SD 3.9) was reached in 5 s when the drill reached a depth of 10 mm. On the other hand, the thermocouples in the bone reached the maximum temperature (mean 44.0 \({}^{\circ}\)C, SD 1.9) after 9 s.  
When the drilling speed was 2000 rpm, the temperature of the drill increased rapidly once the drilling started, and the maximum temperature (mean 82.7 \({}^{\circ}\)C, SD 5.7) was reached in 4 s when the drill reached a depth of 10 mm. On the other hand, the thermocouples in the bone reached the maximum temperature (mean 50.6 \({}^{\circ}\)C, SD 4.2) after 9 s.  
The patterns of temperature change at all speeds were very similar to one another. The maximum temperature measured inside the bone was at 10 mm depth compared to those at 5 mm and 1 mm depths. \begin{table}
\begin{tabular}{c c c c c c} \hline
**RPM** & **Drill** & **1 mm Depth** & **5 mm Depth** & **10 mm Depth** & **IR** \\ \hline
500 & \({}^{\mathrm{a}}\) 51.4 \(\pm\) 3.8 & \({}^{\mathrm{a}}\) 34.5 \(\pm\) 1.6 & \({}^{\mathrm{a}}\) 37.9 \(\pm\) 2.5 & \({}^{\mathrm{a}}\) 42.7 \(\pm\) 2.7 & \({}^{\mathrm{a}}\) 37.7 \(\pm\) 2.9 \\
1200 & \({}^{\mathrm{b}}\) 68.5 \(\pm\) 3.9 & \({}^{\mathrm{a}}\) 36.1 \(\pm\) 1.0 & \({}^{\mathrm{a}}\) 39.4 \(\pm\) 1.8 & \({}^{\mathrm{a}}\) 44.0 \(\pm\) 1.9 & \({}^{\mathrm{a}}\) 38.1 \(\pm\) 2.4 \\
2000 & \({}^{\mathrm{c}}\) 82.7 \(\pm\) 5.7 & \({}^{\mathrm{b}}\) 38.1 \(\pm\) 2.4 & \({}^{\mathrm{b}}\) 45.0 \(\pm\) 1.5 & \({}^{\mathrm{b}}\) 50.6 \(\pm\) 4.2 & \({}^{\mathrm{a}}\) 39.9 \(\pm\) 3.4 \\ \hline \end{tabular} \({}^{\mathrm{a}}\)b,c Different letters in each column indicate statistical significance among groups (\(p<0.05\)).  
\end{table} 
Table 1: Mean values of peak temperature by drill speed and measuring depth. Figure 3: (**a**) The mean values of thermal change during drilling at 500 rpm; (**b**) at 1200 rpm; (**c**) at 2000 rpm. The temperature differences at 1 mm depth as a function of drilling speed were very small (mean 34.5 \({}^{\circ}\)C, SD 1.6, to mean 38.1 \({}^{\circ}\)C, SD 2.4), whereas those at 5 mm depth (mean 37.9 \({}^{\circ}\)C, SD 2.5, to mean 45.0 \({}^{\circ}\)C, SD 1.5) and 10 mm (mean 42.7 \({}^{\circ}\)C, SD 2.7, to mean 50.6 \({}^{\circ}\)C, SD 4.2) depth were much more pronounced. The surface temperature measured using the infrared ray sensor was corroborated to the temperature measured at 1 mm depth in bone. The maximum drill temperature increased rapidly within 4-5 s, whereas the temperature measured inside the bone reached the maximum temperature after 7-9 s regardless of the drill rotating speed. The thermocouple located in the bone indicated the maximum temperature at a depth of 10 mm when the drill temperature started decreasing, showing the disparity.