Effect of premolar extraction on mandibular rotation

Various types of appliances have been tried by the Orthodontists for the fixed orthodontic treatment. Irrespective of the appliance used the main goal of retraction of anterior teeth in extraction cases is to keep the vertical dimension stable so as not to allow downward and backward rotation of mandible. The aim of this study was to compare changes in mandibular rotation following fixed orthodontic treatment on subjects who have undergone extraction of all first premolars. Pre and post treatment lateral cephalogram of 25 subjects were taken (13 females and 12 males), aged 18-25 years and the tracings were done using Nemoceph software. Parameters assessed were facial height (anterior and posterior), mandibular plane angle (FMA & SN-GoGn), and Jaraback ratio. Student t-test was used to make statistical comparison. Mean difference of SN-GoGn(0.15 ±0.07), FMA(0.23 ±0.52), Anterior facial height(0.18±0.01) and posterior height(0.45±0.01) and Jaraback ratio(0.47±0.32) did not show statistically significant difference between pre and post treatment. Mandibular plane did not alter during treatment. When adequate mechanics is followed during treatment desirable treatment outcome with insignificant alteration of mandibular plane can be achieved.