The influential bony factors and vectors for predicting soft tissue responses after orthognathic surgery in mandibular prognathism

Publication date: Available online 31 January 2018
Source:Journal of Oral and Maxillofacial Surgery
Author(s): Yoon-Sic Han, Ho Lee
PurposeTo identify hard tissue points and vectors that have the greatest effect on soft tissue movements after orthognathic surgery in patients with mandibular prognathism.Patient and MethodsThis retrospective study involved patients who underwent mandibular setback surgery with or without maxillary advancement. Multiple linear regression models were adapted to evaluate the association between the eight hard tissue landmark (predictor variables) changes and 11 soft tissue responses (outcome variables) based on the x and y coordinates assessed from superimposed pre- and postoperative three-dimensional computed tomography images.ResultsA total of 50 patients (42 patients underwent two-jaw surgery; eight patients underwent one-jaw surgery; mean age, 23 ± 4 years) were included in the present study. Our statistical models demonstrated that horizontal hard tissue changes had a greater influence on the soft tissue responses than the vertical changes did, and these changes were more notable in the lower facial area (lower lip contour and chin profile) than the midfacial area (nasal profile, upper lip contour, upper lip length, and nasolabial angle). In the horizontal soft tissue response model, the ratio of soft tissue A point to A point was 0.86 (95% CI, 0.674-1.049):1; the ratio of soft tissue B point to B point was almost 1 (95% CI, 0.919-1.071):1; and the ratio of the soft tissue pogonion to the pogonion was 0.88 (95% CI, 0.805-0.963):1.ConclusionsHorizontal or vertical bone tissue changes affected both the horizontal and vertical soft tissue changes in most areas. Our study demonstrated that the soft tissue response is not a linear change, but a more complicated and dynamic reaction.



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