Design of occlusal wear facets of fixed dental prostheses driven by personalized mandibular movement

Existing virtual articulators simulate mandibular movement by using various parameters and are used to design restorations. However, they are not able to reproduce actual patient movements, and the designs of occlusal wear facets by them and by personalized mandibular movement have not been compared.

The purpose of this clinical study was to establish a clinical application protocol for a virtual articulator based on previous research and to evaluate the accuracy of the occlusal wear facets designed by it.

The gypsum casts of 12 participants were scanned with a cast scanner as the original data. A single crown, 3-unit splinted crowns, a 5-unit fixed partial denture, and a fixed complete denture were virtually prepared on the digital mandibular casts by using the Geomagic Studio 2013 software program. High points were created at the wear facets, and corresponding digital wax patterns with occlusal interferences were generated. The exocad software program was used to design corresponding restorations with the copy method. Static (STA restoration) and dynamic (DYN restoration) occlusal adjustments were carried out with the built-in virtual articulator. The mandibular movements of participants were recorded by the novel virtual articulator system, and the occlusal surfaces of the digital wax patterns were adjusted (FUN restoration). The restorations adjusted with the 3 methods were compared with the original data. The mean value and root mean square (RMS) of 3D deviation and positive volumes (V+) in the occlusal direction were measured. Depending on the normality, 1-way ANOVA and the Kruskal-Wallis test were used to analyze the influence of occlusal surface design methods on the morphology of occlusal wear facets (α=.05).

The mean deviation of the 4 kinds of STA restorations ranged from 0.19 mm to 0.22 mm, the DYN restorations from 0.13 mm to 0.17 mm, and the FUN restorations from 0.03 mm to 0.09 mm. A significant difference was found between the STA and FUN restorations of the 3-unit splinted crowns and 5-unit fixed partial dentures (Ρ=.013, Ρ=.021). The mean values of 3D deviation and V+ decreased from the STA group to the DYN group and then to the FUN group. The RMS and V+ were statistically similar (Ρ>.05).

The preliminary results of the study indicate that the FUN 3-unit splinted crowns and 5-unit fixed partial dentures designed with the self-developed virtual articulator were better than the STA restorations. The FUN restorations were more coincident with the morphology of the wear facets on the original teeth.