Experimental evaluation of heat generation in bone drilling using SS316L and ZrO ₂ drill bits across multiple speeds and drill diameters

Overheating of the bone during drilling may raise intraosseous temperature to more than 47°C, leading to osteonecrosis and compromising implant stability. Tool material, geometry and operating conditions play an important role in heat generation. Stainless steel (SS316L) is commonly used, but ZrO ₂ has become a possible alternative due to its biocompatibility and lower thermal impact. Custom drill bits (2.5, 3.0 and 3.5 mm diameter; two flutes; 90° point angle; 25° helix angle) were manufactured. A five-axis CNC machine was used to perform drilling experiments on standardized polyurethane bone blocks. A feed rate of 30 mm/min and spindle speeds of 900, 1100 and 1300 r/min were used. Temperatures T _max and T _avg were measured using thermocouples and recorded in two trials per condition. For T _max and T _avg , the temperature values obtained in two repeated trials were reported as mean ± standard deviation. SS316L drills produced greater, more fluctuating thermal profiles, reaching a T _max of ∼37°C at 900 r/min (2.5 mm) to 58.75°C at 1300 r/min (3.0 mm), exceeding the osteonecrosis threshold. The T _avg reached up to 39°C at 1300 r/min. On the contrary, ZrO ₂ drills generated lower temperatures with a T _max of 31–46°C and a T _avg of 29–35°C irrespective of the diameter and speed. It is worth noting that ZrO ₂ drills did not surpass 47°C. Thermal response is highly dependent on drill diameter and spindle speed, but material properties are the decisive factor. ZrO ₂ drills operated at lower T _max and T _avg than SS316L and exhibited greater thermal control, minimizing the risk of thermal osteonecrosis. Results suggest that ZrO ₂ may provide a safer thermal response during the test dry-bone drilling process.