Nonextraction treatment with rapid maxillary expansion and mandibular symphyseal distraction osteogenesis and vertical skeletal dimensions

Objective: To investigate the effects of rapid maxillary expansion (RME) and mandibular symphyseal distraction osteogenesis (MSDO) on vertical dimensions of the face. Materials and Methods: Fourteen patients, nine girls and five boys, underwent RME and MSDO procedures. Distraction was carried out at a rate of 1 mm per 24 hours with a tooth-borne appliance. The amount of distraction was 7 mm for each patient. Standardized lateral cephalograms were taken at the following time periods: before treatment (T0), after RME (T1), at the completion of MSDO (T2), and at the end of fixed orthodontic treatment (T3). The data were evaluated by using a general linear model of repeated-measures analysis of variance and paired t-tests at the 95% confidence level. Results: RME significantly increased the vertical dimensions of the face and decreased the overbite (P < .001). Although the vertical parameters of the face on the lateral cephalogram decreased after MSDO, these decreasing effects were statistically insignificant just for the distances measured from the horizontal reference line to the chin points. In other words, MSDO decreased the vertical skeletal dimensions that were increased by RME, but this neutralizing effect of MSDO was not as much as the increase caused by RME. Conclusion: Treatment modalities (RME, MSDO, and fixed orthodontic treatment) described in this study, in total, had little effect on the vertical skeletal measurements of the face.