The evaluation of the dentofacial effects obtained with the application of class iii elastics from the symphyseal miniplates

The aim of this prospective study is to evaluate the dentofacial effects of the intermaxillary Class III elastics applied from the symphyseal miniplates to the maxillary acrylic expansion appliance in growing skeletal Class III patients in comparison with the untreated Class III control group.The material obtained from 34 subjects in prepubertal or pubertal skeletal growth periods were included in the study. All subjects had skeletal Class III malocclusion with maxillary deficiency, vertically normal or decreased growth pattern, anterior cross-bite, positive overbite and retrusive nasomaxillary complex. Prior to application of Class III elastics rapid maxillary expansion (2 times/day) with a bonded appliance was performed in the treatment group comprised of 17 subjects. In the treatment group (mean chronological age:11.3±1.5; mean skeletal age: 10.6±1.4; 7 girls, 10 boys) intermaxillary Class III elastics were applied from the miniplates which were surgically placed between lateral and canine teeth bilaterally in the mandibular symphysis. The materials of the control group (mean chronological age:9.9±1.2; mean skeletal age: 9.9±1.4; 9 girls, 8 boys) consists of the lateral cephalometric radiographs which were selected from the archive of Başkent University Department of Orthodontics which were appropriate for the selection criteria of this study. Lateral cephalometric and posteroanterior cephalometric radiographs, study models were obtained and temporomandibular joint was evaluated at the beginning and end of treatment periods in treatment group. Lateral cephalometric radiographs were analysed according to the structural superimposition method of Björk and the airway was evaluated in both groups. Additionally, posteroanterior cephalometric radiographs, study models and temporomandibular joint disorder symptoms were evaluated in the treatment group. Measurements were evaluated statistically via Student?s t test and dependent t test.In the treatment group maxilla moved 3.82±1.46 mm forward and mandible moved 4.21±1.58 mm backward (p<0.001). The differences between the groups were significant (p<0.001). Maxilla showed significant anterior (p<0.001) and mandible showed significant posterior (p<0.001) rotation in the treatment group. Overjet increased 6.62±1.08 mm and overbite decreased 4.29±2.32 mm in the treatment group, whereas overjet decreased 0.15±0.52 mm and overbite increased 0.62±0.86 mm in the control group. Both maxillary and mandibular incisors were protruded significantly in the treatment group whereas the inclination changes were not significant in the control group.Airway dimensions were increased significantly after the treatment. The significant increase in the maxillary width was accompanied with significant increase in the nasal width.Significant decrease was observed in the maxillary arch discrepancy due to the maxillary molar mesialization and significant increase was observed in the mandibular arch discrepancy due to the protrusion of mandibular incisors in the treatment group.No statistically significant changes related with the temporomandibular joint disorders were observed in the treatment group patients after the protraction therapy.