How Does RME Affect Maxillary Arch Width Long Term? Long-Term Effects of Rapid Maxillary Expansion Followed by Fixed Appliances

Background: Maxillary expansion is a routine procedure performed to correct narrow maxillary arch width and posterior cross-bite. We assume, as orthodontists, that our expansion will be stable long term, but is that assumption correct? Objective: To evaluate the long-term changes in maxillary dental arch widths in patients who were treated with rapid maxillary expansion (RME) appliances followed by edgewise appliances. Design: This was a retrospective analysis of the records of 41 patients who had been treated for maxillary constriction. Methods: Maxillary dental casts were available at 4 time periods: before treatment, after maxillary expansion, after complete nonextraction orthodontic therapy, and approximately 5 years later. The maxillary intercanine, interpremolar, and intermolar widths were measured at all 4 intervals. These widths were then compared over time. Results: The maxillary intermolar, interpremolar, and intercanine widths all increased during palatal expansion treatment. During the time of full-banded, edgewise orthodontic therapy, the intermolar, interpremolar, and intercanine widths decreased. After appliance removal, these widths continued to decrease, with the greatest decrease occurring in the intercanine width, which nearly reached its original pretreatment distance. Conclusions: A significant amount of relapse occurs after RME during a second phase of orthodontics, as well as long term. Reviewer's Comments: I found the information in this study to be useful. I have had similar experiences in patients I have treated using RME followed by routine orthodontics. Long term, these arch widths tend to decrease with time. I believe it is probably due to the stretching of the palatal gingiva, which simply does not accommodate to these greater widths in all patients. It is good to be aware of this information before correction of posterior cross-bites and to consider long-term retention for patients who have been treated for significant palatal constriction. (Reviewer-Vincent G. Kokich, DDS, MSD).