Multitomographic evaluation of the dental effects of two different rapid palatal expansion appliances

Rapid palatal expansion (RPE) is widely used in the treatment of transverse maxillary deficiencies. Generally, there are two types of RPE appliances: banded and bonded expanders. The purpose of this prospective study was to compare the dental effects of banded and bonded appliances. The study consisted of 23 patients (13 females and 10 males) with a bilateral maxillary deficiency. Twelve patients (seven females and five males) with a mean age of 14.8 +/- 0.3 years were treated with banded RPE and 11 patients (six females and five males) with a mean age of 15.1 +/- 0.7 years with bonded RPE. Multitomographic radiographs were taken before (T0) and at the end (T1) of expansion while the patients were wearing an acrylic mandibular appliance in which ball bearings and bars were embedded. Statistical analyses of the measurements at T0 and T1 were undertaken with a paired t-test, and the difference between the groups assesed with a Student's t-test. In both groups, the angle between the radiographic image of the bar and the axial inclination of the upper first premolar and molar teeth was (5.34 and 2.73 degrees for the right premolars, 5.17 and 2.28 degrees for the left premolars, 11.83 and 3.73 degrees for the right molars, and 9.75 and 5.64 degrees for the left molars in the banded and bonded groups, respectively. The distance from the vestibular cortical plate to the palatal root of these teeth (1.17 and 1.23 mm for the right premolars, 2.46 and 1.09 mm for the left premolars, 2.75 and 0.64 mm for the right molars, 2.23 and 0.96 mm for the left molars in the banded and bonded groups, respectively) increased (both P < 0.01). These increases indicated buccal tipping of the teeth. Comparison of the two groups showed that tipping of the first molar and premolar teeth in the banded group was significantly more than in the bonded group (P < 0.01 and P < 0.001, respectively).