Three-Dimensional Static Articulation Accuracy of Virtual ModelsPart 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. dRR, dRC, and dRL, represented interarch global distortions at right, central, and left sides, respectively, while dRM, dXM, dYM, and dZM represented interocclusal global and linear distortions between preparations. Results: Mean interarch 3D distortion ranged from –348.7 to 192.2 μm for dRR, –86.3 to 44.1 μm for dRC, and –168.1 to 4.4 μm for dRL. Mean interocclusal distortion ranged from –257.2 to –85.2 μm for dRM, –285.7 to 183.9 μm for dXM, –100.5 to 114.8 μm for dYM, and –269.1 to –50.6 μm for dZM. ANOVA showed that articulation method had significant effect on dRR and dXM, while system had a significant effect on dRR, dRC, dRL, dRM, and dZM. There were significant differences between 6 test groups for dRR, dRL dXM, and dZM. dRR and dXM 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.