Purpose: To compare the effect of rapid palatal expansion (RPE) and Damon technique on the correction of dental crowding with non-extraction approach.
Methods: 19 adolescent patients with non-extraction orthodontic treatment were reviewed. They had Class I skeletal pattern and moderate crowding. Nine subjects were treated with RPE followed by straight wire appliance, and 10 subjects were treated with Damon appliance only. The dental casts and cephalometric radiophotographs were measured before and after the treatment. The difference between two groups was analyzed for Student's t test with SPSS15.0 software package.
Results: Upper and lower inter-canine width increased 2.9mm and 1.3mm respectively in RPE group (P<0.05), while there was no significant change in Damon group. A significant posterior expansion of upper and lower arch width was noted in both RPE and Damon groups (P<0.05). The increase in upper inter-bicuspid width and lower inter-molar width was comparable in two groups. The upper inter-molar width in RPE group expanded 5.3mm, which was significantly larger than that of 3.1mm in Damon group(P<0.05). The increase in lower inter-bicuspid width in Damon group, on the other hand, was larger than that of RPE group (4.5mm vs. 1.5mm). (P<0.05) Both groups showed buccal tipping of bicuspids and molars, with more extend of bicuspid tipping in Damon group (P<0.05). The maxillary base width increased 2.1mm in RPE group, which was significantly larger than that of 0.6mm in Damon group (P<0.05). The upper and lower incisors in Damon group were tipped forward by 9.2 degrees and 7.5 degrees respectively, while the change in RPE group was not significant (P<0.05).
Conclusion: Both RPE and Damon technique can successfully increase the arch width and correct moderate dental crowding with non-extraction approach. Damon appliance protrudes the upper and lower incisors and expands the dental arch by buccal tipping of bicuspids and molars. RPE expands the maxillary base along with the whole upper dental arch and could maintain the incisors in upright position.