Effects of orthodontic extraction on facial soft and hard tissue changes among average-angle skeletal class Ⅰ Chinese adults females:A 3D geometric morphometric study

Abstract

Abstract Background: This study aimed to investigate changes in the facial soft and hard tissues changes among the average-angle skeletal class Ⅰ Chinese adult females receiving extraction orthodontic treatment, as well as the correlations between them. Methods: The 3dMD® stereo photography technology was used to explore facial soft tissue changes, and lateral cephalograms and cone beam computed tomography (CBCT) to explore hard tissue changes. A total of 23 adult females were recruited, among which 11 patients were with teeth extraction, 12 patients without teeth extraction treatment. Results: Among the 3D distance measurements, decreased soft tissue changes of 1/3 Face height, Stomatological height, Chin height and Lip width were observed (p<0.005), in which Lip width was found to have a moderate correlation with the decreased hard tissue change of upper inter-first molar width (d5) (ra=0.619, p<0.005). Among the 3D angle measurements, decreased soft tissue changes of Chin-lips angle and Lip angle, were found, in which Lip angle was found to have a moderate correlation with the decreased hard tissue changes of ∠U1-SN (ra=0.659, p<0.005). While the Soft tissue angle and Nasolabial angle increased post-orthodontics (p<0.005). In addition, moderate negative correlations between Nasolabial angle and hard tissue changes of ∠U1-SN and d1 were found (ra=-0.668; -0.763, p<0.005). Conclusion: Extraction orthodontic treatment showed a good control for facial protrusion cases, making the patients profile more attractive and harmonious. Changes in position and inclination of anterior teeth were also related to changes of facial soft tissues. There is no significant collapse in buccal and temporal region of patients with teeth extraction treatment compared with those without teeth extraction.