Three-dimensional assessment of transverse dentoskeletal mandibular dimensions after utilizing two designs of fixed mandibular expansion appliance: A prospective clinical investigation

The aim of this clinical study was to evaluate and compare the dentoskeletal transverse mandibular arch dimensions following the use of two designs of fixed mandibular expanders using cone beam computed tomography (CBCT). Twenty orthodontic patients, 12 females and 8 males, with mean age of 13.4 ± 0.5 years were selected and randomly divided into two equivalent groups; group A consisted of 10 patients (4 boys, 6 girls) who were treated with modified Williams expander and group B consisted of 10 patients (4 boys, 6 girls) who were treated with a two-arm fixed expander. Consistent expansion instructions were given to all patients according to a standardized slow protocol of one quarter turn twice/week for both expanders. Routine orthodontic records as well as mandibular CBCTs were obtained before (T1) and immediately after expansion (T2) to estimate changes in dentoskeletal mandibular transverse dimensions. The data was statistically analyzed and the significance level was set at p ≤ 0.05. Mandibular intercanine, inter-premolar, intermolar widths; and arch perimeter were significantly increased (p ≤ 0.05) following expansion with both fixed expanders. However, the changes in inter-premolar width, intercanine width, and arch perimeter were significantly augmented in two-arm fixed expander group than modified Williams’s group. In contrast, their effects on the skeletal mandibular body width were non-significant (p > 0.05). Both expanders yielded significant and equivalent dentoalveolar effects that were more evident with two-arm fixed expander than the William one. Both fixed designs enhanced mandibular transverse dental dimensions; however, they were unsuccessful to create any considerable skeletal effects.