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.

1. Bills DA, Handelman CS, BeGole EA. Bimaxillary dentoalveolar protrusion: Traits and orthodontic correction. Angle Orthod2005;75:333-9.
2. Lamberton CM, Reichart PA, Triratananimit P. Bimaxillary protrusion as a pathologic problem in the Thai. Am J Orthod 1980;77:320-9.
3. Diels RM, Kalra V, Deloach N, Powers M, Nelson S. Changes in soft tissue profile of African-Americans following extraction treatment. Angle Orthod. 1995;65:285–292.
4. Keating PJ. Bimaxillary protrusion in the Caucasian: A cephalometric study of the morphological features. Br J Orthod1985;12:193-201.
5. Al Maaitah E, El Said N, Abu Alhaija ES. First premolar extraction effects on upper airway dimension in bimaxillary proclination patients. Angle Orthod2012;82:853-9.
6. Jones AG, Bhatia S. A study of nasal respiratory resistance and craniofacial dimensions in white and West Indian black children. Am J Orthod Dentofacial Orthop1994;106:34-9.
7. Sharma JN. Skeletal and soft tissue point A and B changes following orthodontic treatment of Nepalese class I bimaxillary protrusive patients. Angle Orthod2010;80:91-6.
8. Taylor M, Hans MG, Strohl KP, Nelson S, Broadbent BH. Soft tissue growth of the oropharynx. Angle Orthod1996;66:393-400.
9. Linder-Aronson S, Leighton BC. A longitudinal study of the development of the posterior nasopharyngeal wall between 3 and 16 years of age. Eur J Orthod1983;5:47-58.
10. Germec-Cakan D, Taner T, Akan S. Uvulo-glossopharyngeal dimensions in non-extraction, extraction with minimum anchorage, and extraction with maximum anchorage. Eur J Orthod2011;33:515-20.
11. Wang Q, Jia P, Anderson NK, Wang L, Lin J. Changes of pharyngeal airway size and hyoid bone position following orthodontic treatment of class I bimaxillary protrusion. Angle Orthod2012;82:115-21.
12. Bhatia S, Jayan B, Chopra SS. Effect of retraction of anterior teeth on pharyngeal airway and hyoid bone position in class I bimaxillary dentoalveolar protrusion. Med J Armed Forces India 2016;72 Suppl1:S17-23.
13. Hang WM. Obstructive sleep apnea: Dentistry’s unique role in longevity enhancement. J Am Orthodon Soc 2007;7:28-32.
14. Valiathan M, El H, Hans MG, Palomo MJ. Effects of extraction versus non-extraction treatment on oropharyngeal airway volume. Angle Orthod2010;80:1068-74.
15. LaMastra SJ. Relationships between changes in skeletal and integumental points A and B following orthodontic treatment. Am J Orthod1981;79:416-23.
16. Goldin B. Labial root torque: Effect on the maxilla and incisor root apex. Am J Orthod Dentofacial Orthop1989;95:208-19.
17. Roos N. Soft tissue profile changes in Class II treatment. Am J Orthod. 1977;72:165–175.

Dr Parul Agarwal