ABSTRACT
The purpose of this study was to evaluate whether the basal bone of maxilla was expanded transversely by rapid palatal expansion through the posteroanterior cephalometric analysis. Thirty patients with the maxillary deficiency were utilized in this study, The posteranterior cephlometric X-ray film taken twice, before and after rapid palatal expansion. The obtained results were as follows : 1. There was a significant increase of the maixllary width by rapid palatal expansion in male and female.(p<0.001) 2. there was no significant difference between the male and female in the expansion of the maxillary width by rapid palatal expansion. 3. There was a significant increase of the mixillary by rapid palatal expansion in th both of before and after the puberty. 4. There was no significant difference between before and after the puberty in the expansion of the maxillary width by rapid palatal expansion.