Evaluation of the effects of mandibular growth direction determined by roth-jarabak analysis on the fixed functional therapy outcomes

The purposes of this study are: 1. To investigate the relationship between mandibular growth direction determined by Roth-Jarabak analysis and the forward movement of the mandible followed by fixed functional therapy. 2. To identify possible biomarkers to predict successful outcomes of fixed functional therapy in prepubertal children with Class II malocclusion. Lateral cephalometric radiographs of 90 patients at the prepeak skeletal maturation (CVM II and CVM III) with Class II malocclusion treated with fixed functional appliance were selected from the database of Çukurova University, Faculty of Dentistry, Department of Orthodontics. Pre-treatment and post-treatment radiographs were analyzed. The patients were divided into two groups according to posttreatment increment in SNB angle which was used as the discriminant factor for successful treatment. "Group 1" (mean age 12.62± 1.07) consisted of 61 patients who demonstrated an increase in SNB angle of equal to or less than 1.3° and "Group 2" (mean age 12.7±1.1) consisted of 29 patients who demonstrated an increase in SNB angle more than 1.3° . ROC analysis was used to assess the relationship between pre-treatment cephalometric variables and forward mandibular movement. The mean amount of mandibular growth (Co-Gn) in the two groups were not different (p˃0.5). However, statistically significant differences were found in terms of vertical rotation parameters of mandible between the two groups (Sum of Angles, SN/GoGn, Y axis p≤0.001). According to ROC analysis, the pretreatment gonial ratio has identified as the most strongly related parameter to SNB increment. Pretreatment gonial ratio equal or smaller than %72 can predict an unfavorable movement of mandible followed by fixed functional therapy in prepubertal patients with Class II malocclusion.