| Objective:The aims of the present study were to investigate the soft tissue profiles response to the bimaxillary orthognathic surgery. In addition, the relationship between the soft tissue and the skeletal movements during the bimaxillary orthognathic surgery was discussed, and the influence of preoperative soft tissue thickness to the predictability of soft tissue behavior was examined.Materials and methods:Twenty skeletal classⅢmalocclusion patients(6 male,14 female) from the orthodontic department of Tianjin Stomatological Hospital from 2006 to 2010 were selected. A comparative cephalometric study on the pre-and post-treatment was performed to evaluate the soft tissue responses after surgery and the treatment performance in terms of soft tissue profiles.The relationships between the soft tissue and the hard tissue changes was evaluated by a linear regression methodology.To evaluate the treatment performance of 20 patients based on the changes during pretreatment and posttreatment, Pearson's coefficients of correlation were calculated to examine the relationships between the thicknesses of subnasale, indentation of lower lip, red part of the upper and lower lip, soft chin and the changes of soft tissue.Results1 The convexity of the soft tissue and the full soft tissue, comparing T1 and T2 surgry, was significantly reduced (P<0.01).The full soft tissue convexity was changed by 2.08°in one year after surgery. Comparing TO and T3, the soft tissue convexity and the full sotr tissue convexity were both decreased. The changes of the parameters evaluating the status of the upper lip were also observed. The length and the thickness of the upper lip were changed at the stage of T2 compared with the stage of T3. A mean decreased UL/Prn-Pos of 2.67mm was also observed at the stage between TO and T3. T0-T1, The lower lip was significantly changed by 4.9mm and the thickness of the soft chin was also increased. TO and T1 compared with T2 and T3, the change of all landmard of lower lip and the chin in sagittal measurements was indicated. One year after surgery, a significant decrease of soft tissue thickness at lower lip and the soft chinwere registered.2 The relationship between Prn and A movements was significant correlated which was indicated by r with 0.866(P<0.01). The relation between A' and U1 movements for corresponding landmarks was strongly correlated as indication of the highest r with 0.935(P<0.001). The closely correlationship between UL and U1, L1, B Pog were also observed, especially L1 (r=0.919). All mandibular soft tissue landmarks were strongly correlated with hard tissue landmarks.3 The poor correlation between the thickness of subnasale and the change of the soft tissue was indicated. The correlation between the thickness of chin and the change of the soft tissue was shown to be negative. The negative correlation was also shown between thickness of indentation of lower lip and the change of the soft tissue.Conclusion1 The effects of the bimaxillary surgery on the soft tissue profile were mainly presented as the increase of facail convexity, the significant change of the lower facial, particularly the lower lip and the soft chin. One year after the surgery, there were a tendency of relapse at the length and the thickness in soft tissue, particularly in the upper lip.2 The correlation between nasal tip and maxillary was high. The correlation of upper lip to incisal was more significant than other hard tissues. The moderate correlation occurred for the landmark in the lower lip. The high correlation occurred for landmark in the chin, which should help to predict the changes of the soft tissue after the surgery.3 The changes of the soft tissues after surgery was highly negative correlated with the thickness of lower lip and soft chin before surgery, e.g. more significant change of soft tissue was often observed with thin lower lip and chin. |
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