Evaluation the Actual and Effective Symphysis to Detect the Direction of Mandibular Rotation in Iraqi Sample (Cephalometric Study)


This study is attempted to find out if the actual and effective symphysis are correlated with the measurements of mandibular rotation and can be used to detect the direction of mandibular growth. Ninety five Iraqi adult patients (54 females and 41 males)with an age ranged between 18-31 years collected among patients having Cl I skeletal and occlusal relations and full permanent dentition regardless the third molars were chosen for this study. Each person was subjected to clinical examination and digital true lateral cephalometric radiograph. The radiographs were analyzed by using AutoCAD 2007 computer program to measure the two symphyseal measurements with eleven measurements for mandibular rotation. Descriptive statistics were obtained from the measurements of both genders; independent samples t-test was performed to evaluate the gender differences, while Pearson’s correlation coefficient test was used to find the correlation of actual and effective symphysis with the mandibular rotation measurements. Actual and effective symphysis were not significantly differing between genders, while facial heights were significantly higher in males. Regarding the mandibular rotation angles, only SN-MP, saddle (N-S-Ar), and the sum of the posterior angles (Sum PA)were significantly higher in females, while PP-MP, FMA, articular (S-Ar-Go), and gonial (Ar-Go-Me) angles showed non-significant higher mean values in males. For both genders and the total sample, the actual symphysis didn’t show any significant correlation with the facial heights and the mandibular rotation angles, on the contrary the effective symphysis showed in both genders and the total sample significant positive correlations with Jarabak ratio, and significant negative correlations with SN-MP, PP-MP, FMA, and the sum of the posterior angles. In males and the total samples, the saddle angle (N-S-Ar) significantly positively correlated with the effective symphysis, while gonial angle (Ar-Go-Me) was significantly negatively correlated with it. Articular angle (S-Ar-Go) only significantly negatively correlated with the effective symphysis in the total sample. Effective symphysis is a good predictor of the direction of mandibular rotation, while actual symphysis is a poor predictor.