Edge damage prediction and analysis of ceramic restorations in ultrasonic-assisted dental grinding based on a multi-grit finite element model

Abrasive machining is heavily used to fabricate ceramic restorations in dentistry. The machining-induced edge damage on ceramic surfaces has been a persistent challenge for reliable restorations. This paper presents a new three-dimensional (3D) finite element analysis (FEA) modeling to visually evaluate and quantitatively predict edge chipping damage of ceramic restorations. In this model, a randomly distributed multi-grit model was built instead of most single-grit or uniform models widely used in the past. Meanwhile, axial ultrasonic vibration was first added to the model to investigate the effects of rotary ultrasonic on surface quality. Dental grinding testing was carried out using a robot arm and a high-speed dental handpiece with and without ultrasonic assistance. The experimentally measured results were in agreement with the FEA predictions. The results indicate that the reasonable rotary-ultrasonic assistance could achieve a clear reduction of edge chipping damage in the brittle dental ceramics, especially at high cutting depths without compromising cutting efficiency, compared with conventional dental grinding. This research has first proved the feasibility of applying the rotary ultrasonic technique to dental high-speed grinding for improving the surface quality of ceramic restorations. Furthermore, the proposed multi-grit FEA model for edge damage prediction is applicable not only to dental grinding but also to other abrasive machining in engineering.