Resorption of retromolar bone grafts after alveolar ridge augmentation—volumetric changes after 12 months assessed by CBCT analysis

Abstract In this pilot study, a volumetric analysis of retromolar onlay bone grafts over a period of 12 months was conducted, using repeated CBCT imaging combined with automated image registration. Eleven patients being treated with 16 bone grafts taken from the retromolar area were examined by CBCT scanning prior to bone augmentation (T0), immediately after bone augmentation (T1) and after a healing time of 12 months after augmentation (T2). Graft volumes were measured at each time point after automated image registration of consecutive CBCT scans. The mean volume of the augmented site was 372.2 ± 179.4 mm3. Resorption relative to the original augmented volume was 43.7% ± 19.0% after 12 months. Three-dimensional graft resorption could be precisely depicted by the use of automated image registration for CBCT data over a period of 12 months and demonstrated extensive volumetric changes of bone grafts taken from the ascending ramus of the mandible. Graft resorption and continuous bony remodeling of the grafted site before and after implant insertion have to be carefully considered by the clinician.