Individual "alveolar phenotype" limits dimensions of lateral bone augmentation.

Aim: Alveolar ridge resorption following tooth extraction often renders a lateral bone augmentation inevitable. Some patients, however, suffer from severe early (during graft healing, E ) and/or late (during follow-up, L ) graft resorption. We explored the hypothesis that the "individual phenotypic dimensions" may partially explain the degree of such resorptions.

Materials And Methods: Patients who underwent a guided bone regeneration (GBR) procedure were screened for inclusion according to the following criteria: (1) a relatively symmetrical maxillary arch; (2) an intact contra-lateral alveolar bone dimension; (3) the availability of a pre-operative cone-beam CT (CBCT); (4) a CBCT taken immediately after GBR, and (5) at least one CBCT scan ≥6 months after surgery. CBCT scans from different timepoints were registered and imported into the Mimics software (Materialise, Leuven, Belgium). Bone dimensions of the contra-lateral site of the augmentation, representing the "individual phenotypical dimension (IPD) of the alveolar crest", were superimposed on the augmented site and registered accordingly. As such, E and L could be measured over time, in relation to the IPD (in two dimensions; per millimetre apically from the alveolar crest, in the centre of the GBR), as well as in three dimensions (the entire GBR, 2 mm away from the mesial, distal, and apical border for standardization).

Results: A total of 17 patients (23 augmented sites) were included. After E , the outline of the augmentation was in general located ±1 mm outside the IPD, but ≥1.5 years after GBR, it further moved towards the IPD (85% within 0.5 mm distance).

Conclusions: Within the limitations of this study, the results indicate that the dimensions of a lateral bone augmentation are defined by the "individual phenotypic bone boundaries" of the patient.