Influence of occlusal plane inclination and digital camera type on the accuracy of maxillary cast transfer to a virtual articulator.

STATEMENT OF PROBLEM: Two-dimensional (2D) photographs have been described to transfer the maxillary cast to a virtual articulator. However, the influence of occlusal plane inclination and camera type on the accuracy of the maxillary cast transfer remains uncertain.

PURPOSE: The purpose of this in vitro study was to assess the influence of the occlusal sagittal plane inclination and camera type on the accuracy of the maxillary cast transfer.

MATERIAL AND METHODS: A dentate maxillary stone cast was mounted in an articulator (Panadent PCH) using the mounting table so that the occlusal plane was horizontal. Fiducial markers were attached to the stone teeth. The cast was digitized with a laboratory scanner (T710). The stone cast was positioned on a calibrated table to control the sagittal tilting of the cast. Twelve groups were created: 0, +1, +2, +3, +4, +5, +6, +7, +8, +10, +12, and +14 degrees. Two subgroups were created: a mirrorless camera (Z8) with a macro lens or a smartphone (iPhone 17 Pro Max) (n=30). In the 0-degree group, the maxillary scan was transferred into the articulator by registering the mounting plate with the mounting platform using a dental program (DentalCAD). A total of 10 linear measurements (3 in the posterior right, 4 in the anterior, and 3 in the posterior left) were obtained between the fiducial markers and an additional plane coincident with the mounting table. The mounted maxillary scan was exported while maintaining the software program's coordinate system (reference 0-degree scan file). The 0-degree images of mirrorless and smartphone subgroups were then used to transfer the maxillary scan into the same articulator, followed by obtaining the same 10 measurements for each specimen. To obtain the reference mounted scan of the tilted groups, the reference 0-degree scan file was imported into a program (Meshmixer) to tilt the occlusal plane, reproducing the inclinations generated by the calibrated table. In the +1-degree group, the reference +1-degree scan file was imported into the dental program while maintaining the coordinate system, thereby allowing automatic mounting in the articulator. The same 10 linear measurements were obtained for each specimen. In the +2, +3, +4, +5, +6, +7, +8, +10, +12, and +14-degree groups, the same procedures were followed as in the +1-degree group, using the corresponding reference scan file. The measurements obtained in the reference scan files were used as a reference to obtain discrepancies with the maxillary scan transfer for each subgroup specimen in the maxillary plane transfer into the virtual articulator. Trueness was analyzed by using 2-way ANOVA followed by the Tukey tests. Precision was evaluated by using the Levene and pairwise comparisons Wilcoxon rank sum tests (α=.05).

RESULTS: Significant posterior right and anterior and posterior left trueness discrepancies were found between the groups (P<.001) and subgroups (P<.001), with a significant group×subgroup interaction (P<.001). Overall, the higher the degree of occlusal plane inclination, the higher the posterior right and anterior and posterior left discrepancies. The mirrorless subgroup obtained significantly better posterior right (P<.001) and anterior (P<.001) and posterior left (P<.001) trueness than the smartphone subgroup. The Levene test showed significant posterior right (P<.001) and anterior (P<.001) and posterior left (P<.001) precision discrepancies among the groups and anterior precision discrepancies among the subgroups (P=.024) tested.

CONCLUSIONS: The occlusal plane inclination and the type of digital camera tested influenced the accuracy of the maxillary posterior right and anterior and posterior left plane transfer.