Three-Dimensional Static Articulation Accuracy of Virtual Models—Part II: Effect of Model Scanner-CAD Systems and Articulation Method

Abstract

Purpose

Accurate maxillomandibular relationship transfer is important for CAD/CAM prostheses. This study compared the 3D-accuracy of virtual model static articulation in three laboratory scanner-CAD systems (Ceramill Map400 [AG], inEos X5 [SIR], Scanner S600 Arti [ZKN]) using two virtual articulation methods: mounted models (MO), interocclusal record (IR).

Materials and Methods

The master model simulated a single crown opposing a 3-unit fixed partial denture. Reference values were obtained by measuring interarch and interocclusal reference features with a coordinate measuring machine (CMM). MO group stone casts were articulator-mounted with acrylic resin bite registrations while IR group casts were hand-articulated with poly(vinyl siloxane) bite registrations. Five test model sets were scanned and articulated virtually with each system (6 test groups, 15 data sets). STL files of the virtual models were measured with CMM software. dR_R, dR_C, and dR_L, represented interarch global distortions at right, central, and left sides, respectively, while dR_M, dX_M, dY_M, and dZ_M represented interocclusal global and linear distortions between preparations.

Results

Mean interarch 3D distortion ranged from –348.7 to 192.2 μm for dR_R, –86.3 to 44.1 μm for dR_C, and –168.1 to 4.4 μm for dR_L. Mean interocclusal distortion ranged from –257.2 to –85.2 μm for dR_M, –285.7 to 183.9 μm for dX_M, –100.5 to 114.8 μm for dY_M, and –269.1 to –50.6 μm for dZ_M. ANOVA showed that articulation method had significant effect on dR_R and dX_M, while system had a significant effect on dR_R, dR_C, dR_L, dR_M, and dZ_M. There were significant differences between 6 test groups for dR_R, dR_L dX_M, and dZ_M. dR_R and dX_M were significantly greater in AG-IR, and this was significantly different from SIR-IR, ZKN-IR, and all MO groups.

Conclusions

Interarch and interocclusal distances increased in MO groups, while they decreased in IR groups. AG-IR had the greatest interarch distortion as well as interocclusal superior-inferior distortion. The other groups performed similarly to each other, and the overall interarch distortion did not exceed 0.7%. In these systems and articulation methods, interocclusal distortions may result in hyper- or infra-occluded prostheses.

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