Automatic adjustment of dental crowns using Laplacian mesh editing

Abstract

Currently, the restoration of missing teeth by means of dental implants is a common treatment method in dentistry. Ensuring optimal contact between teeth (occlusion) when designing the occlusal surface of an implant-supported crown is crucial for the patient. Although there are various occlusal concepts and guidelines for achieving optimised occlusion, adapting an occlusal surface is challenging. The contact points must be established in certain areas of the occlusal surface without impairing the aesthetics of the teeth and the masticatory function. A computer-aided, automated modelling approach can assist in the design process and can reduce the reliance on manual labour. This study aimed to develop a modelling approach that enables the automatic adaptation of an occlusal surface to specific occlusal concepts while preserving the natural appearance. In this study, the occlusal surface of an implant-supported crown based on a scanned first right mandibular molar was adopted. Nominal contact points were determined based on occlusal concepts by Ramfjord and Ash (RA) and Thomas (T). The shape of the occlusal surface was then adapted concerning the desired contact points using Laplacian mesh editing. The modification results were validated for different forces and crown materials (3Y-TZP and PMMA) using a finite element contact analysis. The contact analysis results showed that locations with high compressive stresses correspond with the locations of the nominal contact points. The reaction forces were more evenly distributed in PMMA crowns, due to the lower Young's modulus of PMMA compared to 3Y-TZP. Furthermore, the occlusal scheme with fewer contact points (RA) showed higher maximum reaction forces per contact area. The presented method enables the automated adaptation of an (implant-supported) crown to specific occlusal schemes, proving to be valuable in dental CAD.