Bone formation after surgically assisted rapid maxillary expansion: comparison of 2 distraction osteogenesis protocols

Objective: The aim of this study was to compare bone formation between 2 distraction osteogenesis protocols by analyzing cone beam computed tomography (CBCT) scan data. Study Design: In this retrospective study, the efficacy of 2 different surgically assisted rapid maxillary expansion protocols (group 1 [G1], 3 × 0.25 mm/d; group 2 [G2], 1 mm start followed by 2 × 0.25 mm/d) was analyzed using CBCT scans obtained at 3 time points: preoperatively (T0), immediately after surgery (T1), and 6 months after surgery (T2). Bone formation at T0, T1, and T2 was analyzed using the Dolphin Imaging 11 program. Results: At T1, both groups had significantly higher bone volume than at T0 (G1, 135.6 vs 124.65 mm3, respectively; G2, 153.49 vs 118.9 mm3, respectively), with no significant difference between groups (P = .6). Moreover, bone density measured in the region of interest was similar between groups at all 3 time points; however, in both groups, bone density was significantly lower at T1 and T2 than at T0 (P < .01), with no difference between T1 and T2. Conclusions: Bone density between the incisors decreased with progressive distraction (i.e., increasing volume), regardless of the distraction protocol used; thus, both protocols can be used safely in clinical practice. Nevertheless, our results indicate that stress should not be applied to the incisors within 6 months of surgery, regardless of the protocol used. Surgeons and orthodontists should therefore consider immature bone formation and avoid using excessive force to close a diastema.