Abstract: Objective To metrically assess the vertical changes of the occlusal landmarks for biogenerically reconstructed inlays in CEREC CAD/CAM system. Methods Stone replicas of 20 untreated maxillary first molars were scanned and measured with Infinite Focus system. Relative heights of the tip of mesiopalatal cusp (MPC) and the central pit (CP) to the tip of mesiobuccal cusp were calculated and the inclination of the line passing through MPC and CP was measured as a representation of the mesiopalatal cuspal inclination (MPCINC). The casts were prepared for mesiopalatal inlay restoration and restored with CEREC chair-side system using biogeneric tooth model. Inlays seated on the corresponding casts were scanned again. The same items were measured and calculated. Differences between the restorations and natural teeth (△MPC, △CP and △MPCINC) were tested by paired Student’s t test (P=0.05). Bland-Altman plots were used to assess agreements between the two occlusal surfaces. Relationships between the differences and MPCINC of natural tooth were evaluated using Pearson’s correlation coefficient. Results The vertical differences of occlusal landmarks between natural teeth and biogeneric reconstructions were (101.87±33.21) μm for MPC, (-201.72±55.28) μm for CP and (4.66°±0.31°) for MPCINC. All three differences were statistically significant (P<0.05). There was a significant correlation between △MPCINC and MPCINC of natural tooth (P<0.01) while △MPC and △CP were independent from MPCINC. Conclusions Significant differences associated with three occlusal landmarks exist between the automatic occlusal reproduction by biogeneric tooth model and the natural occlusal morphology.

Key words: CAD/CAM, occlusal morphology, inlays, reproducibility, biogeneric tooth model, maxillary first molars