LAUSR

In the fixed prosthesis process dental prosthesis treatment, the dentist needs to conceive the morphology of the tooth preparation and make numerous micro-adjustments by manual operation. This study aims to establish a digital design system for accurate designing of veneer preparation and study the trajectory planning of the robot-assisted preparation. According to the standard operation requirements, the projection line segmentation method based on point drawing is proposed for interactive selection to ensure the margin smoothness of the preparation area. The preparation depth is parameterized, and the foldback point correction method based on secondary segmentation is used for repairing the offset preparation area to ensure surface smoothness. The fenestration preparation model was obtained in the digital interactive design software. The model is divided into two feature areas which are interpolated by the B-spline curve and NURBS surface, respectively. The isoparametric curve method is used to plan the preparation trajectory. The experimental and theoretical values of the target feature points from the X, Y and Z coordinate directions were also calculated and analyzed. The experiment is carried out by the physical prototype of the tooth preparation robot. The maximum error of the feature points on the preparation are 0.180 mm, 0.104 mm and 0.142 mm in X, Y and Z directions, respectively. The confidence interval of the system error is stable within 0.30 mm. The error of the feature points verifies the feasibility of the digital interactive design system and the correctness of the trajectory planning of tooth veneer preparation. The system could have the potential to assist dentists in the precise design of the veneer preparation, improve the processing efficiency and ensure the effect of tooth veneer prosthesis.