Title: Evaluating the effects of first premolar extraction on Point A, Point B and Nasolabial angle in patients with bimaxillary protrusion
Authors: Dr Parul Agarwal, Dr Sunil Kumar Puiluri, Dr Akash Lavate, Dr Sneha Hoshing, Dr Sneha Shinde, Dr Shreya Aradhey, Dr Vaishnavi Gadhave
DOI: https://dx.doi.org/10.18535/jmscr/v11i3.04
Abstract
Objective: The aim was to determine the effects of first premolar extraction on point A, point B and nasolabial angle in patients with bimaxillary protrusion.
Materials and Methods: The following study included pre- and post-orthodontic treatment cephalograms of fifty bimaxillary protrusion patients. First premolars were extracted and all the cases were treated with maximum anchorage. Cephalometric radiographs were used to measure the changes in point A, point B and nasolabial angle. Pre- and post-treatment variables comparison was done using paired t-test and study of relationship between soft- and hard-tissue variables was carried out using Pearson correlation coefficient and linear regression equation.
Results: Mean point A and soft tissue point A (sA) were retracted 2.8 mm (P < .001) and 1.8 mm (P < .001), and mean point B and soft tissue point B (sB) were retracted 2.2 mm (P< .001) and 2.2 mm (P < .001), respectively. Mean increase in nasolabial angle was 14.96 degree.
Mean ratio of retraction of point A with sA and point B with sB was 1.5:1 and 1:1, respectively. Mean ratio of retraction of point A with NLA was 1:5.
A significant degree of correlation existed between retraction of point A and soft tissue point A (r = 0.917, P < .001), point B and soft tissue point B (r = 0.929, P < .001), point A and NLA (r= 0.420, P< .05).
Linear regression analysis used to predict the changes in sA and sB showed significant relationship between point A and sA (R2 = 0.842, P < .001) and point B and sB (R2 = 0.863, 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 and increase in nasolabial angle.
Conclusions: Retraction of skeletal point A and B lead to retraction of sA,sB and increase in nasolabial angle under controlled root positions. Nearly proportionate changes existed in the skeletal points and overlying corresponding soft tissue points.
Keywords: Point A, Point B, Premolar extractions, Soft tissue point A, Soft tissue point B, Nasolabial angle, Bimaxillary protrusion.
