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. RME significantly decreased overbite and increased overjet, and a statistically significant decrease was observed in both overbite and overjet at the postretention assessment.