Osteopenia in Corticotomy-Assisted Tooth Movement and Stability

Periodontally Accelerated Osteogenic Orthodontics (PAOO) induces osteopenia of alveolus adjacent to surgically injured cortical bone (corticotomy) allowing more rapid tooth movement. Objective: To evaluate osteopenia-related events in alveolar bone induced by corticotomy with/without tooth-movement using MicroCT-analysis. Methods: Sixty nine CRL-CD male rats were included and grouped as corticotomy alone (upper left first molar); tooth-movement alone; and “combined” therapy with right side of each animal serving as the untreated control. Tooth-movement was performed utilizing a 25-gram Sentalloy spring secured to a micro-screw palatal to the incisors. There was a 6-week active tooth movement (active phase); appliances were removed, and reversal of osteopenia and bone stability were assessed for additional 6 weeks (stability phase). Animals were sacrificed at 1, 2, 3, 4, 6, 7, 8, 9 and 12 weeks. Maxillae were removed, stripped and fixed in formaldehyde. MicroCT-imaging was performed at 36μm/voxel; samples were binarized using the same parameters for filter and threshold. Bone volume (BV), bone volume fraction represented by bone volume/total volume (BV/TV), average mineral density of hydroxyapatite (BMD), and bone mineral content (BMC) were calculated. Statistical analysis was performed using ANOVA with Tukey post-hoc tests. Results: During the active phase, combined treatment led to significantly reduced BV (p=0.009) and BMC (p=0.008) at 2 and 6 weeks while corticotomy had greater BV/TV compared to tooth-movement and combined groups (p=0.001) at the same time intervals. During the stability phase, week-7 samples in the combined group had significantly reduced BV/TV compared to weeks 8 and 12 (p=0.003). No significant intra-group differences were found among samples at either 8 or 12-weeks. Conclusion: Corticotomy combined with tooth-movement enhances the osteopenia that leads to faster orthodontic tooth movement with no significant difference in stability of bone volume and mineral content.