Methods: The sample included 15 males and 15 females that were balanced regarding age, dental and skeletal maturation. Skeletal asymmetries were excluded from the study. A mandibular kinesiograph was used to record both the mandibular resting position and opening-closing movements. Changes in the lateral mandibular shift from maximum opening (MO) to centric occlusion (CO) and from rest position (RP) to CO after maxillary expansion (T1-T2) were compared between genders using Student t-test. T1-T2 comparisons were performed using paired t-test.
Results: Before treatment, no differences in lateral shift (mm) from MO-CO were found between genders (males: 3.15; females: 3.92; diff: -0.77; 95%CI: -2.30, 0.75). After treatment, lateral shift from MO-CO was similar in both genders (males: 1.64; females: 1.68; dif: -0.04; 95%CI: -1.69, 1.61). A significant reduction was found after treatment for both groups (1,89mm; p=0.002). The lateral shift from MO to RP was similar for males and females before (males: 2.46; females: 2.87; diff: -0.41; 95%CI: -1.75, 0.93) and after treatment (males: 1.52; females: 1.50; diff: 0.014; 95%CI: -1.42, 1.46). The mean post-treatment reduction (1.24mm) was significant for both groups (p=0.013). T1 lateral displacement of the mandible at rest position was similar in males and females (males: 0.8; females: 1.09; diff: -0.29; 95%CI: -0.81, 0.22). Similar results were found at T2 (males: 0.34; females: 0.48; diff: -0.13; 95%CI: -0.54, 0.27). T1-T2 changes were significant for both groups (0.48mm; p=0.012)
Conclusions: Orthodontic treatment of FUCB showed a reduction in the mandibular shift from MO-CO, MO-RP and RP-CO. No differences were found between genders at any stage of the study.
This study was funded by the Fundación Investigación Médica Mutua Madrileña.