ABSTRACT

To compare the skeletal and dental effects of twin-block appliances with or without expansion.

From our archives, patients using twin-block appliances were selected. A total of 20 patients with expansion screws were classified as group 1 (10 male, 10 female; mean age 12.48 ± 1.38 years), and 18 patients without screws as group 2 (8 male, 10 female; mean age 12.81 ± 1.16 years). Cephalometric radiographs at pre-and post-treatment were used to evaluate skeletal and dentoalveolar parametric changes; study models and posteroanterior radiographs were used for transverse evaluation. The initial measurements and the treatment-related mean changes within the study groups were analyzed using the Student’s t-test.

Changes in maxillary skeletal measurements were not statistically significantly different between groups except for A-VRL (P > .05). Mandibular measurements showed an increase in SNB (º) and Co-Gn distance in both groups. However, these changes were similar for both groups (P > .05). The maxillary measurements showed that incisors were proclined in the expansion group and retroclined in the non-expansion group. No significant difference was found between the groups in terms of changes in the skeletal transversal measurements (P > .05). On the study models, the changes in maxillary intercanine and intermolar widths, and in arch length differed to a statistically significant degree between groups (P < .05).

The skeletal effects of 2 different types of twin-block appliances in the transversal direction were similar; it was determined that dental expansion was obtained in the maxilla by adding screws to the twin-block appliances.

Keywords: Twin-block, expansion, posteroanterior, cephalometrics