A mathematical representation of occlusal surfaces called the biogeneric tooth model has been developed (Mehl et al. 2003). Objective: The objective of this study was to investigate the automatic occlusal reconstruction of CAD-inlay restorations using the biogeneric tooth model. Methods: Impression and stone replicas of 40 intact and carious-free posterior molar teeth of young patients were made. After scanning the surfaces with a 3D laser device, various types of inlay cavities were simulated by two experts. After selecting some starting points, the linear parameters of the biogeneric tooth model were adapted iteratively to the remaining tooth substance by minimizing an error function. This error function comprises both a distance measure and a probability distribution of the calculated occlusal surface, which was derived from the learning process of a tooth library. The calculated CAD-surfaces were compared to the original surfaces and rated according to standardized criteria. Results: For all inlay cases a molar surface was calculated (100%). Compared to the original tooth morphology the congruence of the fissure lines was excellent or acceptable for 95%, the cusp areas exhibit a excellent or acceptable ranking for 92%. Concerning the ridge line including the mesial- distal dimensions, morphological conformity was rated for 87%. Whereas in all cases of first molars and second lower molars the process results in acceptable and excellent reconstructions, more problems arised for the second upper molar due to the high variability of shape. Conclusions: The new mathematical process affords a fully automated reconstruction of occlusal surfaces during the CAD/CAM- process.

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