Dental Tribune Denmark

Digital bone augmentation in posterior mandibles: A retrospective CBCT study and proposal of a 2-step bone augmentation protocol

The objective was to analyze bone resorption patterns in posterior mandibles and the dimensions of their corresponding digital bone grafts. This could allow the fabrication of bone grafts with standardized dimensions that can be applied in the majority of clinical cases. Cone beam computed tomography scans (n = 120) were analyzed to evaluate the frequency of Cawood and Howell (C&H) classes. The most frequent class needing bone augmentation was virtually regenerated using specific software. Dimensions of the grafts were calculated. Class V was the most frequent atrophic class needing augmentation in posterior mandibles (20.4%). Severe atrophic stages were more frequent in females (adjusted P value = 0.001), in older people (adjusted P value = 0.31) and in the right mandible (adjusted P value = 0.03). After virtual regeneration of Class V cases (n = 36), 3 clusters based on the number of missing teeth were evident. The mean length of the grafts was 20 mm when 2 teeth were missing (reference), 23.9 mm in the case of 3 missing teeth (P < 0.001) and 29.6 mm for 4 missing teeth (P < 0.001). Height and width were comparable across the 3 clusters (P-values = 0.39–0.93). The mean graft volume was 1,469 mm3 in the case of 2 missing teeth (reference), 1,814 mm3 for 3 missing teeth (P = 0.001) and 2,177 mm3 for 4 missing teeth (P < 0.001). These volumes corresponded to those of soft-tissue expanders, suggesting the possibility of a 2-step augmentation protocol: soft-tissue expansion, followed by regeneration with prefabricated grafts of the corresponding volume. Class V was the most frequent resorption pattern requiring augmentation in posterior mandibles. Virtual regeneration revealed 3 clusters of grafts, differing only in length based on the number of missing teeth. A 2-step augmentation protocol is proposed using soft-tissue expanders and prefabricated grafts with corresponding volumes. This protocol might be more applicable in the right mandible, females and older patients. Keywords Mandible; alveolar bone grafting; bone graft; cone beam computed tomography; soft-tissue expansion.

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