Bone Drilling Simulation: Effects of Drill Bit Material on Bone Temperature

Bone drilling is a critical surgical procedure in orthopaedic, dental, and maxillofacial surgery, during which excessive bone temperature elevation at the tool-bone interface can cause thermal osteonecrosis (bone temperature > 47 °C). The subsequent effects compromise osseointegration and implant stability. Drill coating material could regulate both frictional heat dissipation and mechanical cutting resistance. However, the comparative thermomechanical performance of titanium nitride (TiN), titanium carbonitride (TiCN), titanium carbide (TiC), and diamond coatings across multiple simultaneous drilling responses has not been systematically quantified under designed experimental conditions. A Box-Behnken Design (BBD) comprising 60 finite element simulation runs (15 per coating block, 3 centre points per block) was employed to develop second-order response surface methodology (RSM) models for maximum bone temperature and thrust force. Analysis of variance (ANOVA) revealed that the quadratic model was highly significant (F = 137.79, p < 0.0001), with coating material (D) as the dominant factor (F = 497.40), followed by spindle speed (A, F = 702.67), feed rate (B, F = 412.86), and drill diameter (C, F = 177.92). All three coating-by-continuous-parameter interactions (AD, BD, CD) were insignificant (p > 0.19), which indicates that the thermal advantage of diamond over TiN reveals as a uniform absolute offset independent of continuous parameter levels. Multi-objective desirability optimization identified a diamond coating at 944 rpm, 0.020 mm/rev, and 2.8 mm diameter as the optimal condition (d = 0.981), producing the lowest bone temperature (59.8 °C). These findings provide statistically validated guidance for coating selection and the design of surgical drilling protocols to minimize thermal bone damage.