Long-Term Effects of Rapid Maxillary Expansion Followed by Fixed Appliances

Objective: To evaluate the long-term changes in maxillary arch widths, overjet, and overbite in patients who were treated with rapid maxillary expansion (RME) followed by edgewise appliances. Materials and Methods: The material for the study consisted of study casts taken from 41 patients (19 males, 22 females) on four different occasions (before treatment, T1; after RME, T2; after treatment, T3; and during follow-up period, T4). The upper intercanine, interpremolar, and intermolar widths and overjet and overbite were measured on each set of study casts. Mean age of the subjects was 13.2 +/- 1.3 years (range, 11.2-16.9 years) at T1, 13.3 +/- 1.3 years (range, 11.3-17 years) at T2, 15.5 +/- 1.4 years (range, 13.1-18.8 years) at T3, and 20.4 +/- 1.6 years (range, 17.9-24.8 years) at T4. Results: The net increase in intercanine width, interpremolar width, intermolar width, overjet, and overbite was 1.4 +/- 2.4 mm, 4.6 +/- 2.6 mm, 4.3 +/- 2.5 mm, 0.1 +/- 0.6 mm, and 0.2 +/- 0.6 mm, respectively, and the relapse rates were 37% for intercanine width, 19% for interpremolar width, and 17% for intermolar width at the end of the follow-up period. Conclusions: A significant amount of relapse occurred in maxillary arch widths at the postretention assessment, the greatest being in intercanine width. RIME significantly decreased overbite and increased overjet, and a statistically significant decrease was observed in both overbite and overjet at the postretention assessment. (Angle Orthod. 2010;80:5-9.)