Determinants of alveolar ridge preservation differ by anatomic location

Aim To investigate and compare outcomes following alveolar ridge preservation (ARP) in posterior maxilla and mandible. Methods Twenty-four patients (54 +/- 3years) with single posterior tooth extraction were included. ARP was performed with freeze-dried bone allograft and collagen membrane. Clinical parameters were recorded at extraction and re-entry. Harvested bone cores were analysed by microcomputed tomography (micro-CT), histomorphometry and immunohistochemistry. Results In both jaws, ARP prevented ridge height loss, but ridge width was significantly reduced by approximately 2.5mm. Healing time, initial clinical attachment loss and amount of keratinized tissue at extraction site were identified as determinants of ridge height outcome. Buccal plate thickness and tooth root length were identified as determinants of ridge width outcome. In addition, initial ridge width was positively correlated with ridge width loss. Micro-CT revealed greater mineralization per unit volume in new bone compared with existing bone in mandible (p<0.001). Distributions of residual graft, new cellular bone and immature tissue were similar in both jaws. Conclusion Within the limitations of this study, the results indicate that in different anatomic locations different factors may determine ARP outcomes. Further studies are needed to better understand determinants of ARP outcomes.