LONG-TERM STABILITY AND PREDICTION OF SOFT-TISSUE CHANGES AFTER LEFORT-I SURGERY

Many evaluations of soft tissue changes after orthognathic surgery hav e been undertaken, and many correlations of soft tissue to hard tissue movements have been established. These studies have not, however, spe cifically discussed the long-term stability or characteristics of the soft tissue changes. The objectives of this study were (1) to determin e the long term stability of soft tissue changes 5 years after LeFort I osteotomy, (2) to determine reliable correlations, if any, of soft t issue changes to bony movements effected in surgery, and (3) to determ ine the predictability of soft tissue changes as an aid to orthodontic treatment planning. Cephalometric data from 25 patients who were trea ted with LeFort I osteotomy with or without a concurrent mandibular pr ocedure were analyzed retrospectively. Cases were selected from the pa tient records of the Department of Oral Surgery of the Vrije Universit eit in Amsterdam, the Netherlands. These patients were followed up at four time points, the last being a mean of 6.1 years after surgery. An alysis of stability data revealed that most horizontal and vertical so ft tissue change after LeFort I surgery occurred in the first year aft er surgery. Significant (>10%) change continued to occur for subnasale , labrale inferius, upper lip protrusion, lower lip protrusion, and so ft tissue convexity during the subsequent 5 years. Hard tissue to soft tissue correlations were calculated and ratios of soft tissue to hard tissue movement were determined for appropriate hard and soft tissue landmarks at four time intervals. Reliable correlations of hard tissue change at surgery to 5-year soft tissue change could be made for 10 v ariables, which was considerably less frequently than for 1-year soft tissue change. The relatively low reliability of long-term prediction correlations suggests that soft tissue movements may be more independe nt of hard tissue over time. One-year prediction values were similar t o 5-year values and thus could be used for prediction purposes in orth odontic treatment planning. Most short-term hard to soft tissue correl ations found in the present study were in the range of those establish ed by previous authors. Long-term hard tissue to soft tissue correlati ons gave higher ratios of soft tissue movement secondary to maxillary surgery, approaching ratios of 1.0:1.0 for some variables. This findin g, as well as the long-term stability data, suggest that soft tissue s ettling or equilibrium after surgery may take several years to complet e.