Three-Dimensional Static Articulation Accuracy of Virtual Models – Part I: System Trueness and Precision

Abstract

Purpose

To evaluate the 3D static articulation accuracy of 3 model scanner-CAD systems (Ceramill Map400 [AG], inEos X5 [SIR], Scanner S600 Arti [ZKN]) using a coordinate measuring machine (CMM). Trueness and precision for each system will be reported in Part I.

Materials and Methods

The master model simulated a single crown opposing a 3-unit fixed dental prosthesis. Five mounted stone cast sets were prepared, and one set was randomly selected. Reference values were obtained by measuring interarch and interocclusal reference features with the CMM. The stone cast set was scanned 5 times consecutively and articulated virtually with each system (3 test groups, n = 5). 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

For trueness values, mean interarch global distortions ranged from 13.1 to 40.3 μm for dR_R, –199.0 to –48.1 μm for dR_C, and –114.1 to –47.7 μm for dR_L. Mean percentage error of interarch distortion did not exceed 0.6%. Mean interocclusal distortions ranged from 16.0 to 117.0 μm for dR_M, -33.1 to 101.3 μm for dX_M, 32.9 to 49.9 μm for dY_M and –32.0 to 133.1 μm for dZ_M. ANOVA of trueness found statistically significant differences for dR_C, dR_L, dR_M, dX_M, and dZ_M. For precision values, absolute mean difference between the 10 superimposition combinations ranged from 25.3 to 91.0 μm for dR_R, 21.5 to 85.5 μm for dR_C, 24.8 to 70.0 μm for dR_L. Absolute mean difference ranged from 49.9 to 66.1 μm for dR_M, 20.7 to 92.1 μm for dX_M, 86.8 to 96.0 μm for dY_M, and 36.5 to 100.0 μm for dZ_M. ANOVA of precision of all test groups found statistically significant differences for dR_R, dR_C, dR_L, dX_M and dZ_M, and the SIR group was the least precise.

Conclusion

The overall interarch global distortion of all three model scanner-CAD systems was low and did not exceed 0.6%. Variations in scanner technology, virtual articulation algorithm, and use of physical articulators contributed to the differences in distortion observed among all three groups.

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