Changes of the Nasolabial Angle Due to Orthodontic Treatment and Facial Growth

Abstract

This study addressed the quantitative changes of the Nasolabial angle, lip retraction and columellar changes due to treatment with concomitant growth. Sixty initial and final lateral headplates were examined on prepubertal children who underwent comprehensive orthodontic treatment. The angular changes in the Nasolabial angle (△NLA), Labial angle (△A) and Nasal angle (△B) were measured along with the horizontal (△H) and vertical (△V) linear changes of maxillary central incisor. Each of these five measurement changes was tested for the effects of extraction and gender. Correlations were drawn between the △NLA: △AH, △NLA: △V, NLA: △A, △NLA: △B, and △A: △H.

Analysis of variance showed that extraction therapy exhibited a larger treatment change than non-extraction therapy for the NLA and upper lip, with the NLA increasing in magnitude and the Labial angle showing upper lip retraction. There was also a sex difference for the treatment change in the lower border of the nose. The only high correlation found was between the opening of the NLA and the retraction of the upper lip (NLA: △A gave r = -0.84). The other correlations were significant but low. These findings could aid in orthodontic treatment planning when changes in the upper lip and NLA will affect the facial esthetics.