Available online 5 December 2022

Author links open overlay panelAbstractStatement of problem

The use of digital interocclusal registration scans for virtual articulation and mounting has been studied extensively; however, the accuracy of the cross-mounting procedures in a digital workflow is not well understood.

Purpose

The purpose of this in vitro study was to compare the accuracy of digital and conventional cross-mounting by measuring the 3-dimensional deviation at each step of sequential cross-mounting.

Material and methods

A set of reference casts and complete-arch interim restorations was prepared for complete-arch complete-coverage restorations, hand-articulated, and mounted in an articulator. The reference casts were then scanned with and without the interim restorations to generate 4 reference casts for cross-mounting. For the conventional group, 15 sets of the 4 casts were printed. Polyvinyl siloxane interocclusal registration records were made of the reference casts for each set, and casts were sequentially cross-mounted. For the digital workflow, 15 sets of bilateral interocclusal registration scans were made of the mounted reference casts and used to align the cast scans. Three-dimensional deviations at 2 anterior and 2 posterior points were recorded between the experimental mountings and the reference casts on each set of casts. Nonpaired t test and analysis of variance (ANOVA) were used to compare the average discrepancy between the 2 groups, and the pooled anterior versus posterior discrepancies were compared (α=.05).

Results

A significant difference was found between conventional and digital cross-mounting procedures (P<.001), but no significant difference was found in either group, conventional (P=.116) or digital (P=.987), at each step of the sequential mountings. The mean ±standard deviation at the final set of related casts in the conventional workflow was 201.6 ±137.0 μm and that in the digital group was 50.3 ±47.5 μm, with a significant difference between anterior and posterior deviations in the digital group (P=.028), but not in the conventional group (P=.143). The mean ±standard deviation anterior conventional deviation was 175.6 ±119.2 μm and that in the digital group was 36.9 ±30.9 μm. The mean ±standard deviation posterior conventional deviation was 227.6 ±50.2 μm and that in the digital group was 63.7 ±57.2 μm.

Conclusions

Digital cross-mounting was more accurate than conventional cross-mounting, although increased deviation was found in the anterior region compared with the posterior region.

Section snippetsMaterial and methods

A set of reference casts (Fig. 1) was prepared simulating a patient undergoing a complete mouth rehabilitation and consisting of maxillary (MxPp) and mandibular (MnPp) preparation casts and a set of milled complete-arch maxillary and mandibular interim restorations (DWX-52D 5-Axis Dental Milling Machine; Roland DGA Corp). The interim restorations were seated firmly on the preparation casts, hand-articulated, and then mounted with a Bonwill triangle as a reference for the occlusal plane by using

Results

The mean ±standard deviation between the reference casts and experimental casts in the digital and conventional study groups is presented in Table 1. The conventional group demonstrated a higher mean ±standard deviation at 201.6 ±137.0 μm than the digital group which demonstrated a mean ±standard deviation of 50.3 ±47.5 μm. The difference was statistically significant (P<.001). Figure 5 demonstrates the means and ranges of deviations for the conventional and digital cross-mounting groups. The

Discussion

A significant difference was found when analyzing the mean deviation in the conventional and digital workflows; therefore, the null hypothesis was rejected. The digital workflow was more accurate than conventional cross-mounting methods. Errors inherent in conventional procedures contribute to this greater overall deviation. Such errors include stone expansion and the elastomeric behavior of the occlusal registration material.

PVS interocclusal registration materials have shown clinically

Conclusions

Based on the findings of this in vitro study, the following conclusions were drawn:

1.

Digital cross-mounting was found to be significantly more accurate than conventional cross-mounting.

2.

No significant difference in deviation was found between different cross-mounting steps in either conventional or digital workflow.

3.

In digital cross-mounting, a significant difference was found in the anterior versus the posterior deviation.

4.

This study provides evidence to support incorporating cross-mounting into a

Acknowledgments

The authors thank Mr Jack Jeong from 3D BioCAD and B&B Dental Ceramic Arts Inc for their lab and technical support and Mr Joel Pollet from Cimquest Inc for his technical support.

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© 2022 by the Editorial Council for the Journal of Prosthetic Dentistry.