The Study of Soft-Tissue Profile Changes in Patients with Class III Malocclusion after Premolar Extraction Therapy / 天津医药

ABSTRACT

Objective To investigate the change and correlation between hard-tissue and soft-tissue in patients with class III malocclusion after premolar extraction treatment. Methods Thirty-four adult patients with skeletal classⅢmalocclusion who met the including criteria were included in this retrospective study. The lateral cephalographs were traced and analysed before and after the treatment. Results After orthodontic treatment,the values of long axis of upper incisors and S-N angle (U1-SN) and long axis of lower incisors-mandibular plane (L1-MP) were decreased, and the angle of man-dibular plane (MP-FH) was increased (P<0.01). The SL line was used as a reference, the protrusion of upper incisor (UI-SL) and upper lips (UL-SL) was decreased, and the protrusion of lower incisors (LI-SL) and lower lips (LL-SL) was also de-creased after orthodontic treatment (P<0.05 or P<0.01). There was no significant difference in the relevant measurements of chin. The retraction of upper incisor (△UL-SL) was the only measurement that was positively correlated with upper lip re-traction (△UI-SL). The retraction of upper incisor (△UI-SL) and lower incisor (△LI-SL) were positively correlated with the lower lip retraction (△LL-SL). There was a positive correlation between△UI-SL and△LL-SL. Conclusion The soft-tissue profile improved significantly after four premolars extraction. The change of soft-tissue profile was moderate correlated with hard-tissue.