Objectives: Recently, it has become possible to reconstruct complete occlusal surfaces using the biogeneric tooth model. This study aimed to mathematically assess and compare the morphologic agreement between original morphology and CAD-reconstructed, waxed-up and CAM partial crowns.
Materials and methods: Thirty-nine intact first permanent molars (39 participants) were included. Impressions, bite registrations and three gypsum replicas were made. Preparations for CAD/CAM partial crowns were performed and scanned. The restorations were biogenerically reconstructed (CEREC® v3.80) and milled. Wax-ups of these preparations were scanned as well as the milled restorations and original teeth. Discrepancies were evaluated by matching the scans with the original morphologies (Match3D, output: volume/area, z difference) and by contact patterns. The discrepancies were compared between CAD-reconstructions and either wax-ups or milled restorations (paired t test, α = 0.025 for two multiple tests).
Results: The mean differences between natural tooth morphology (triangular stabilisation 71.8%) and biogeneric reconstructions, wax-ups and milled restorations (triangular stabilisation 87.2%) were: 184 ± 36 μm (volume/area), 187 ± 41 μm (z difference); 263 ± 40 μm (volume/area), 269 ± 45 μm (z difference) and 182 ± 40 μm (volume/area), 184 ± 41 μm (z difference). Differences associated with biogeneric reconstructions were significantly less than those of wax-ups (volume/area and z difference, p < 0.0001), but not significantly different than those of milled restorations (p = 0.423 (volume/area), p = 0.110 (z difference)).
Conclusions: CAD software enables a closer reconstruction of teeth than do wax-ups, even when no cusps remain. The milling device is precise enough to transfer CAD into the final restoration.
Clinical relevance: This study shows that state of the art CAD/CAM can effectively produce natural tooth morphology and may be ideal for fixed partial dentures.