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Introduction: Suture expansion stimulates bone growth to correct craniofacial deficiencies but has a high potential of treatment relapse. The objective of this study was to investigate whether there is a dose-dependent relationship between the recombinant human bone morphogenetic protein-2 (rhBMP-2) and bone formation during suture expansion., Methods: Fifty 6-week-old male New Zealand white rabbits were randomly assigned to 5 groups to receive 0 (control), 0.01, 0.025, 0.1, or 0.4 mg/mL of rhBMP-2 delivered by absorbable collagen sponge placed over the interfrontal suture. The suture was expanded for 33 days by 200 g of constant force via a spring anchored with 2 miniscrew implants. Distance of suture expansion, suture volume, and cross-sectional area after expansion were measured using radiographs with bone markers and microcomputed tomography. Suture widths and mineralization appositional rates were calculated based on the widths between bone labels under an epifluorescent microscope. Software (Multilevel Win 2.0; University of Bristol, Bristol, United Kingdom) was used to model distance of suture expansion over time as polynomials to compare group differences. Wilcoxon signed rank tests were performed to compare the suture volume and cross-sectional area, mineral apposition rate, and suture width between groups. The significance level was set at P = 0.05., Results: Whereas the sutures were expanded in all groups, sutures were expanded by significantly greater amounts in the control and the 0.01 mg/mL groups without fusing the sutures than in the 0.025, 0.1, and 0.4 mg/mL groups with fusing sutures. Compared with the controls, the 0.01 mg/mL group showed significantly lower suture volumes, cross-sectional areas, and suture widths after expansion. The mineral apposition rate was significantly higher in the 0.01 mg/mL group than in the controls from days 10 to 30., Conclusions: The 0.01 mg/mL dose of rhBMP-2 delivered by absorbable collagen sponge can stimulate bone formation at the bony edges of the suture during suture expansion; however, higher concentrations cause suture fusion. With an appropriate concentration, rhBMP-2 might facilitate suture expansion for clinical uses., (Copyright © 2013 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Introduction: The aim of this experimental study was to evaluate the effects of systemically applied zoledronic acid on bone regeneration in response to expansion of the sagittal suture and relapse in rats., Methods: Thirty-six male Wistar rats were divided into 3 groups. In the first and second groups, saline solution was given subcutaneously after expansion, and the retention periods lasted 14 and 7 days, respectively. In the third group, 0.1 mg of zoledronic acid was diluted with saline solution and given subcutaneously after expansion; the retention period lasted for 7 days. Expansion and relapse amounts were measured by using computed tomography. After the retention period, 6 rats from each group were killed for histologic and immunohistochemical assessments. The other 6 rats from each group were used for observation of the relapse., Results: The histologic evaluation showed that, in groups 1 and 2, the numbers of osteoblasts were less than observed in group 3. When scores of staining intensity were compared, immunoreactivities were statistically significantly increased in group 3 compared with groups 2 and 1. Statistically significant differences were found when the relapse percentages were compared between the groups (P <0.05). The smallest relapse occurred in group 3., Conclusions: Zoledronic acid has positive effects on bone formation in the sagittal suture in response to expansion and decreases the relapse ratio after expansion in rats., (Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)