Comparing the accuracy of occlusal vertical dimension transfer in CAD-CAM dentures

PurposeThere are different methods to transfer occlusal vertical dimension (OVD) when fabricating complete dentures, but it is not clear which method yields the most accurate transfer. This study investigated the accuracy of transferring the OVD of the maxillary/mandibular relationship when designing and fabricating digital dentures by evaluating two commonly used workflows: duplicate dentures (DDs) and occlusion rims (ORs). Materials and methodsMounted edentulous casts were used to simulate a completely edentulous patient. These casts were used in two workflows: (1) DD workflow where complete dentures were fabricated and relined (n = 15), and (2) OR where final impressions and ORs were constructed (n = 15). Relined dentures and ORs with fiduciary markers were then scanned and virtually articulated, then exported as STL files. A scan of the articulated casts (simulated patients) with fiduciary markers embedded was also exported as an STL file and used as a control. STL files for each workflow were superimposed over the control and analyzed in 3D inspection software (Geomagic Control X, 3D Systems, NC) for deviations (mm) at three different locations. Average 3D deviations were compared among the groups using a two-way ANOVA (alpha-0.05). ResultsThe average deviation for OR was significantly larger than DD at all locations of measurement [F = 46.00, p < 0.0001]. The majority of the measurements (98.9%) had a positive deviation value, indicating increased OVD. The overall deviation for the OR group from the control was 0.72 +/- 0.13 mm versus 0.45 +/- 0.23 mm for the DD group. There was no difference in deviation between the points of measurement and no interaction between the location and method [F = 0.02, p < 0.98]. ConclusionsThe DD workflow exhibited less deviation in the transfer of OVD than the OR workflow. However, the deviation was small and may not be clinically significant.