Effects of Palatal Morphology on Rapid Maxillary Expansion during the Rapid Expansion Stage

Abstract

A narrowed maxillary dental arch can be treated by laterally expanding either the maxillary arch or maxillary bone with a RME appliance. But, the effects of RME on maxillary and mandibular dental arches, palatal morphology, and oral function have not been sufficiently clarified. Therefore, to investigate if differences in palatal morphology affect changes brought about by maxillary expansion, we examined post-expansion changes in maxillary and mandibular dental arches and palatal morphology. We also examined the direction of the width of mastication pathway and tongue elevation pressure. The study was composed of 12 pediatric patients; they were treated using a rapid maxillary expansion appliance. Maxillary and mandibular dental models, width of mastication pathway, and tongue elevation pressure were taken at T1, T2, and T3 ; lateral cephalograms were also taken at T1. Dental model measurement results indicated greater palatal width and lower palatal height in G1 than those in G2. Lateral cephalograms indicated significant differences between G1 and G2 for the gonial angle, Frankfort mandibular plane angle, lower facial height, and occlusal plane. The above findings revealed that the rapid expansion stage for RME varies according to palatal morphology: in patients with rectangular dental arches, expansion occurred mainly in the palatal base area,whereas in patients with high palates, expansion occurred mainly in the shallow palatal areas. In addition, we found that width of mastication pathway, tongue elevation pressure,lower molar dental arch width, and lower tooth bucco-lingual inclination increased in patients with rectangular dental arches.