Comparison of transverse changes during maxillary expansion with 4-point bone-borne and tooth-borne maxillary expanders.

INTRODUCTION: The purposes of this study were to evaluate and compare the dentoskeletal changes concurrent with 4-point bone-borne and tooth-borne rapid maxillary expanders in growing children. METHODS: The study was conducted with 20 growing girls (ages, 12 +/- 0.6 years) with posterior crossbite. They were divided into 2 equal groups; patients in one group were treated with a tooth-borne maxillary hyrax expander (TBME), and those in the other group received a bone-borne maxillary hyrax expander (BBME) anchored directly to the palatal bone. Changes were assessed using cone-beam computed tomography. Images were taken before and immediately after expansion. RESULTS: Superimpositions of the 3-dimensional palatal images showed significant increases in skeletal widths at the canine, first premolar, and first molar areas in both groups. The TBME group had greater nasal width expansion. Regarding the transverse dentolinear measurements, significant increases were seen in both groups, whereas the TBME group showed a greater increase than the BBME group. Significant increases in the dentoangular measurements were seen in the TBME group only and were significantly greater than in the BBME group at the first premolars. CONCLUSIONS: There were significant increases in facial and maxillary widths for the BBME group and in nasal width for the TBME group. Both expanders produced basal bone expansion at the level of the hard palate. The TBMEs produced more dental expansion, buccal rolling, and a greater increase in nasal width than did the BBMEs.