Incisor positions and soft-tissue profile in skeletal class III patients before and after surgical-orthodontic treatment

Abstract

Objective To investigate the changes in incisor inclination and soft tissue profile before and after surgical-orthodontic treatment and the effect of extraction treatment planning on the curative effect of skeletal class Ⅲ patients. Methods The subjects consisted of 51 skeletal Class Ⅲ patients treated with the surgical-orthodontic approach. They were divided into 2 groups: extraction group (n=21) had an extraction of the maxillary premolars, and non-extraction group (n=30) had no extractions. Lateral cephalograms were analyzed before treatment (T0), 1 month before surgery (T1), and after debonding (T2). 9 items of hard tissue indexes, 10 items of dental indexes and 15 items soft tissue indexes were selected. After the measurement of variables, SPSS 19.0 was used to analyze and compare the data. Results The cephalogram analyses showed that there was no obvious difference between extraction group and non-extraction group before treatment. In pre-operation treatment, maxillary incisors' decompensation and the decrease of protrusion were more obvious in the extraction group (U1-NA/° reduced by 4.38°, U1-NA/mm reduced by 2 mm) ; conversely, there was an increasing trend of compensation of maxillary incisors in the non-extraction group. The mandibular incisors in both groups were significantly decompensated(L1-NB / ° increase of 12.4 ° and 9.52 ° respectively) and the lower lip thickness was thinner. After treatment, the position of upper and lower lip in the extraction group were more posterior than those in the non-extraction group, and the changes of ANB Angle were more obvious after surgery. Conclusions For skeletal Class Ⅲ patients with similar craniofacial features, pre-surgery extraction decompensates incisor inclination better, which may results in greater improvement of soft and hard tissue morphology after orthognathic surgery. Key words: Skeletal Class Ⅲ malocclusion; Surgical-orthodontic treatment; Extraction orthodontic therapy; Cephalometric analyses; Compensatory