Modeling and characterization of the CEJ for optimization of esthetic implant design

This study evaluated the dimensions and characteristics of the cementoenamel junction (CEJ) of maxillary anterior teeth; the natural CEJ was compared to current implant design and used for design optimization. Standardized digital images of 137 extracted human teeth (45 central incisors, 46 lateral incisors, and 46 canines) were used to measure cervical dimensions, CEJ curvature, and distance from zenith of CEJ to interdental contact on proximal views. The x- and y-coordinates of the CEJ contour were digitized before mathematic processing to allow the representation of a single average curve for buccal, palatal, mesial, and distal surfaces for each tooth type. These measurements were combined to existing data related to dentogingival and "implantomucosal" junction to extrapolate specific biologic landmarks around teeth and implants. Mean cervical dimensions, distance from zenith of CEJ to interdental contact, and CEJ curvature were compared. Cervical dimensions significantly differed, with a more symmetric cervical cross-section for central incisors, slightly more rectangular shape for lateral incisors, and distinctly rectangular shape for canines. CEJ curvature was statistically different between all tooth groups (centrals > laterals > canines); within groups, curvature value was always superior at the mesial aspect compared to distally (3.46 mm vs 3.13 mm for centrals, 2.97 mm vs 2.38 mm for laterals, and 2.55 mm vs 1.60 mm for canines). Tooth-implant biologic width discrepancies ranged from 4.10 to 5.96 mm and were different between all groups of teeth (centrals > laterals > canines); within groups, the discrepancy was always superior at the mesial aspect compared to distally. Current implant design featuring a flat, rotation-symmetric shoulder should be reconsidered in view of natural CEJ contour to improve biologic considerations and related esthetics.