Changes of the transverse dental arch dimension, overjet and overbite after rapid maxillary expansion (RME)

Abstract

Objective: The aim of this study was to evaluate changes of the transverse dental arch dimension, overjet and overbite after the patients underwent the rapid maxillary expansion. Materials and methods: The upper and lower dental models of the patients who showed maxillary constriction with posterior crossbite and underwent maxillary expansion were collected. The transverse dental arch dimensions at canine, first premolar, second premolar and first molar were measured before (T1) and after the expansion (T2). The overjet and overbite of both before and after expansion (T1,T2) were also recorded. Moreover, the dental models of patients with no posterior crossbite were collected as control. Paired t-test was performed to evaluate the changes of the dental arch dimensions after the expansion. The student t-test of the independent samples, treated and untreated groups, were selected for the statistical analysis. Results: The maxillary interdental arch widths of canines, premolars and molars significantly increased after the expansion when compared to these before treatment. The amount of the expansion were 3.52±2.25 mm, 4.55± 2.34 mm, 5.18±1.80 mm, and 5.03±2.04 mm for intercanine, inter-first premolar, inter-second premolar and intermolar widths, respectively. The changes on the lower arch were evaluated, although only the upper arch was expanded. The statistical significant increase in the mandibular interdental arch widths except the intercanine width, was found. The overjet and overbite decreased which showed the clinical changes after the maxillary expansion in the sagittal dental arch dimension. The upper and lower interdental arch widths of the maxillary constricted patients after maxillary expansion, were enlarged to be similar to the patients with no posterior crossbite. Conclusion: The efficiency of the expansion therapy is to correct the constricted maxilla and enlarge both maxilla and mandibular transverse dental arch dimensions. After maxillary expansion, the posterior crossbite and the excessive overjet improved.