Soft-Tissue Changes Related to Mandibular Advancement Surgery

This retrospective study assessed the relationship between the soft-tissue contours of the lower lip and chin and the underlying hard tissues consequent to surgical advancement of the mandible in the endeavour to enhance prediction in treatment planning. Cephalometric head films of 25 cases, 7 of which had advancement genioplasties, were available at presurgical, early postsurgical, intermediate, and long-term stages. Nineteen cephalometric landmarks were located and the data measured relative to X-Y coordinates constructed on the head films and were recorded on a Kontron video plan computer (Kontron Messgerate, GmbH, Image-analysis-systems, Eching/München, West Germany). The data were organized and tabulated with Statgraphics version 4.0 software and statistically analyzed at the Institute of Medical Biostatistics, University of the Witwatersrand. No significant differences were found in the data between the patients who had undergone advancement genioplasties and those who had not. The soft-tissue chin advanced in a 1:1 ratio with the bony chin and a significant correlation was found between the horizontal change at labrale inferius relative to the lower incisor tip with a ratio of 0.77:1, but only marginally improved when tissue thickness was incorporated into a multiple regression analysis. Vertical changes of the lower lip did not show significant correlations with any hard tissue changes. Only when presurgical tissue thickness was included into a multiple regression analysis did the vertical change at labrale inferius demonstrate a fairly good correlation with the vertical change at menton. No significant changes occurred in the upper lip, and there was no significant relapse recorded at a minimum of 12 months after surgery.