Effects of early treatment of maxillary incisor crowding by using two bands and four brackets (2×4) mechanotherapy

Abstract

The purpose of the present study was to investigate effects of early treatment of maxillary incisor crowding on anteroposterior skeletal and dental changes. Treatment group comprised 17 patients with maxillary incisor crowding treated with the two bands and four brackets (2×4) mechanotherapy, and with an initial mean age of 8 years and 10 months. Control group consisted of 17 patients with the same type of malocclusion as the treatment group and with an initial mean age of 8 years and 7 months. Lateral cephalograms in the treatment group were obtained at three time periods: T1, at the start of the 2×4 mechanotherapy; T2, at the end of the 2×4 mechanotherapy; T3, at the end of posttreatment observation. In the control group, lateral cephalograms were obtained at two time periods: T1, at the start of observation; T3, at the end of observation. Ten linear and 10 angular measurements were made for each cephalogram and the cephalometric data obtained were analysed statistically. The significantly large retroclination of the mandibular incisors was found at T1 in both groups compared with Japanese norms, resulting in the obtuseness of the interincisal angle. The resolution of maxillary incisor crowding during T1–T2 produced the retrusive movement of maxillary central incisor tips and the retroclination of mandibular incisors. There were no statistically significant differences for the T1–T3 changes in any linear and angular measurements between both groups. The mandibular incisors were, however, inclined labially during T1–T3 in the treatment group, which were, on the contrary, inclined lingually in the control group. These results suggested that the resolution of maxillary incisor crowding mostly produce the anteroposterior dental effects, and that its effect on the correction of the retroclination of mandibular incisors which was observed at the start of the 2×4 mechanotherapy was not so significant.