Midpalatal suture density ratio: Assessing the predictive power of a novel predictor of skeletal response to maxillary expansion

Introduction: Rapid maxillary expansion (RME) is a common orthodontic treatment to correct maxillary transverse deficiency; however, the inability to determine the precise timing of fusion of the midpalatal suture creates difficulty for clinicians to prescribe the appropriate treatment, surgical or nonsurgical expansion. The purpose of this study was to assess the predictive power of the midpalatal suture density ratio (MPSD) for a skeletal response to RME. Methods: Preand posttreatment cone-beam computed tomography scans were obtained from 78 orthodontic patients aged from 8 to 18 years treated with RME. MPSDs were calculated from pretreatment scans, and a prediction was made for the amount of skeletal expansion obtained at the level of the palate after comprehensive orthodontic treatment. Predicted values were compared with actual outcomes as assessed from posttreatment scans, followed by regression analyses to investigate correlations between MPSD and skeletal expansion and equivalence testing to analyze the performance of the predicted measurements. Results: The MPSDs were not statistically significantly (P>0.05) correlated with the amount of skeletal expansion achieved. In addition, the predicted skeletal expansion using MPSD was not statistically equivalent to the skeletal expansion achieved using an equivalence margin of +/- 0.05. Conclusions: The results suggest that the MPSD obtained from pretreatment cone-beam computed tomography scans were not correlated well enough with the amount of skeletal expansion achieved to be an effective predictor of the amount of long-term skeletal expansion after RME.