Fully automatic CAD design of the occlusal morphology of partial crowns compared to dental technicians' design

The aim of this study was to compare the occlusal morphology of partial crown reconstructions made by dental technicians with reconstructions made by a fully automatic software process (biogeneric tooth model) in relation to the original natural tooth shape. Stone replicas of natural teeth were measured three-dimensionally before preparing inlay and onlay cavities for ceramic restorations (n = 5). For each preparation, five reconstructions (in total n = 25) were made by five dental technicians. Additionally, reconstructions were calculated automatically by a software based on the biogeneric tooth model (Cerec 3D). In order to compare the two different kinds of reconstruction, an objective metrical similarity measure (shape similarity value, SSV) based on calculated volumes between compared datasets was used. In 22 of 25 cases, the reconstructions made by the CAD software were closer to the original situation than the reconstructions made by the technicians. Mean average SSV of reconstructions made by the technicians (310.2 +/- 78.8 mu m) was significantly higher (p < 0.05) than mean SSV of CAD reconstructions (biogeneric model) (222.0 +/- 47.7 mu m). In the design of naturally shaped occlusal inlay/onlay surfaces, a fully automatic CAD system can be at least as good as conventional wax-ups by dental technicians. The adjustment of a dental restoration to fit the morphology of surrounding tooth structures, still presents challenges for the dentist.