Heat Generation During Guided and Freehand Implant Site Preparation at Drilling Speeds of 1500 and 2000 RPM at Different Irrigation Temperatures: An In Vitro Study

Purpose: The purpose of our study was to evaluate the impact of different irrigation fluid temperatures on intraosseous temperature increment during guided and freehand implant site preparation. Materials and Methods: Bovine rib segments were used. Temperature was detected using K-type thermocouples. The studied groups were defined as combinations of the following: drilling speed (1500, 2000 RPM), drill diameter (2.0, 2.5, 3.0, 3.5 mm), surgical method (guided, freehand), and irrigation fluid temperature (10°C, 15°C, 20°C). The data were analysed with Kruskal-Wallis analysis of variance (ANOVA) and ANOVA, as appropriate. Results: At 1500 RPM, guided drilling with 20°C irrigation fluid yielded temperature values exceeding the necrotic threshold (47°C) when performed with bits of 3.0 and 3.5 mm diameters. Meanwhile, 15°C irrigation managed to keep the mean increment below 8.0°C at the diameter of 3.5 mm for both guided and freehand surgery. However, 10°C irrigation cancelled every statistically significant difference between guided and freehand groups. At 2000 RPM and with 20°C irrigation, mean peak temperatures exceeded the necrotic threshold at the diameters 3.0 and 3.5 mm (guided) and 3.5 mm (freehand). When applying 10°C irrigation, though, all measurements indicated peak temperatures in the safe zone. Conclusion: Drillings at 1500 and 2000 RPM, in a guided setting, cause temperature elevations that exceed the necrotic threshold. A speed of 2000 RPM drilling may produce potentially harmful temperatures also in a freehand setting. 10°C and 15°C irrigation kept temperature increments in the safe zone at 2000 RPM and 1500 RPM, respectively. Keywords: dental implants, heat production, osteonecrosis, osteotomy