Crack Extension Analysis and Parameter Optimization in Robot-Assisted Cracked Tooth Preparation Process: Finite Element Analysis and Experiment

Existing robot-assisted cracked tooth preparation systems often result in crack extension or even tooth fracture due to inappropriate parameter settings. In order to solve this problem, a thermal–mechanical coupling model was developed to optimize the grinding parameters for a cracked tooth preparation robot. The grinding force model, based on an empirical formula, was established and analyzed. Using this model, the grinding temperature field of the tooth surface under a moving heat source was also determined. The optimal feed speed and rotational speed of the bur were identified through analysis. After verifying the model's accuracy through experiments, the stress intensity factor at the crack tips for various preparation parameters was calculated using the established thermal–mechanical coupling model, enabling the determination of a safe parameter range. Robot-assisted tooth preparation experiments were conducted based on the optimized preparation parameters, which resulted in a 19.32% reduction in normal grinding force and a 56.26% reduction in surface grinding temperature, and consequently a reduction in pulpal thermal damage compared to conventional preparation parameters. Crack extension following tooth preparation was observed by Micro-CT scanning, and the success rate of preventing crack extension was 73.33%, 93.33%, and 86.67% in xoz, yoz, and xoy sections.