Skeletal and Soft Tissue Point A and B Changes Following Orthodontic Treatment of Nepalese Class I Bimaxillary Protrusive Patients

Abstract

To test the hypothesis that there is no correlation in the interrelationships of skeletal and soft tissue points A and B with anterior teeth retraction. Thirty adult Class I bimaxillary protrusion patients treated with preadjusted appliances after first premolar extraction were included. Pretreatment and posttreatment variables were compared using paired t-test, and the relationship of soft and hard tissue variables was studied using Pearson correlation coefficient and linear regression equation. Mean point A and soft tissue point A (sA) were retracted 2.7 mm (P < .001) and 1.7 mm (P < .001), and mean point B and soft tissue point B (sB) were retracted 2.1 mm (P < .001) and 1.2 mm (P < .001), respectively. Mean ratio of retraction of point A with sA and point B with sB was 1.5:1 and 1.7:1, respectively. A significant degree of correlation existed between retraction of point A and soft tissue point A (r = 0.648, P < .01) and point B and soft tissue point B (r = 0.806, P < .01). Linear regression analysis used to predict the changes in sA and sB showed significant relationship between point A and sA (r = 0.543, F = 11.7, R2 = 0.29, P < .001) and point B and sB (r = 0.825, F = 59.7, R2 = 0.68, P < .001). Decreases in hard and soft tissue convexity were due to the retraction of the skeletal and soft tissue points A and B in addition to the lips retraction. The hypothesis is rejected. Retraction of skeletal point A and B lead to retraction of sA and sB under controlled root positions. Nearly proportionate changes existed in the skeletal points and overlying corresponding soft tissue points.