Dento-skeletal response to three different protocols of rapid maxillary expansion in hyperdivergent growing subjects: a longitudinal retrospective study.

Abstract

The aim of this study was to evaluate the dento-skeletal response in hyperdivergent growing patients comparing Rapid Maxillary Expansion (RME) using three different protocols. Three groups of hyperdivergent subjects treated with RME were analyzed. In 41 patients (23F, 18M) the RME was bonded on the maxillary deciduous second molars (E-RME group); in 40 patients (24F, 16M) the RME was bonded on the first permanent maxillary molars (6-RME group); in 45 patients (26F,19M) the RME was bonded on the first permanent maxillary molars with a removable mandibular Bite-Block (6-RME/BB group). Lateral cephalograms and dental casts were scanned and digitally measured before treatment (T1), at the appliance removal (T2) and at least 1 year after the appliance removal (T3). The comparison was made within the same group and between the groups. Statistical comparisons were assessed with analysis of variance multi-comparison test (*P = 0.05). A significant increase of upper molars buccal tipping was observed in 6-RME group when compared with E-RME and 6-RME/BB groups in the short-term (T2-T1) and long-term (T3-T1); a significant intercanine width increase was observed in E-RME group at the same times. No significant differences in dentoalveolar variables were observed comparing E-RME group versus 6-RME/BB group. The E-RME protocol allows for a greater skeletal expansion and produces a lower buccal tipping of the first permanent upper molars. The use of the BB in 6-RME/BB group shows a similar attitude to the E-RME protocol then can be considered an effective therapeutic alternative.