Effect of changes in mandibular plane angle on soft tissue profile during orthodontic treatment

Abstract

Among soft tissue analysis methods used in orthodontic diagnosis, the one invented by Yamawaki is of particular interest. Although this analysis predicts the soft tissue A-Po to FH angle from the hard tissue A-Po to FH angle, the relationship between these angles does not apply for high or low angle patients. We studied the relationship between these two angles in 50 high angle patients and 50 low angle patients. The correlation between the hard tissue A-Po to FH angle and the soft tissue A-Po to FH angle was analyzed for each group using linear regression. We required a significant difference at the p=0.01 level between the hard tissue A-Po to FH angle and the soft tissue A-Po to FH angle for inclusion in the analysis.
For high angle patients post-treatment, the correlation equation was y=0.87x+8.9, while for low angle patients it was y=0.89x+8.21. The change in the soft tissue A-Po to FH angle in both groups was smaller than that for normal orthodontic patients. Our equations provide the relationship between the hard tissue A-Po to FH angle and the soft tissue A-Po to FH angle for high and low angle patients.Shika Igaku(J Osaka Odontol Soc) 2003 Sep; 66(3): 241-246.