| Abstract: | The soft-tissue profile response to maxillary surgery (impaction and advancement) at the Le Fort I level was evaluated. Data were derived from quality-controlled preoperative and postoperative cephalograms of nongrowing patients with their lips in repose. A standardized tracing technique was used, and this was followed by landmark identification and digitization. Computer measurement of the linear distance of each cephalometric point from horizontal and vertical reference lines was then obtained. Soft-tissue change to hard-tissue change ratios, as well as single and multiple regression equations, were calculated from a patient pool representing fourteen impactions and seven advancements. The results demonstrated many statistically significant correlations. The soft-tissue response to maxillary surgery appeared to be predictable, and the anticipated changes following both impaction and advancement surgical procedures were summarized. Prediction schemes for soft-tissue change evaluation were presented and tested, with a mean error value of approximately 22 percent. In addition, the results of this study led to the following abbreviated conclusions: For the impaction group, (1) the upper lip closely followed the movement of the maxillary central incisor in the horizontal plane, (2) the mandibular soft tissue followed the skeletal mandibular autorotation on an approximately 1:1 basis, (3) the lower border of the upper lip moved superiorly approximately 40 percent of the vertical maxillary change, and (4) there was a superior vertical change in all of the maxillary soft-tissue points. For the advancement group, (1) a progressive increase in the horizontal soft-tissue movement from the tip of the nose to the free end of the upper lip was observed and (2) vertical change in the soft-tissue and horizontal movement of the mandibular soft tissue was unpredictable. |
