Factors influencing the predictability of soft tissue profile changes following mandibular setback surgery

The objective of this cephalometric study was to assess long-term changes i n the soft tissue profile following mandibular setback surgery and investig ate the presence of factors that may influence the soft tissue response to skeletal repositioning. The subjects enrolled were XO consecutive mandibula r prognathism patients operated with bilateral sagittal split osteotomy and rigid fixation. Lateral cephalograms were taken at 6 occasions: immediate presurgical, immediate postsurgical, 2 and 6 months postsurgical, and 1 and 3 years postsurgical. The subjects were grouped according to gender and ma gnitude of setback. Ratios of soft tissue to hard tissue movements were cal culated for the subgroups. Females generally demonstrated greater ratios th an males with a statistically significant difference for the upper lip and chin (P < .05). Postsurgical alterations in the profiles were more predicta ble in patients with larger setbacks compared to patients with smaller ones . Skeletal relapse had a profound influence on long-term profile changes. B ased on these findings, it is proposed that the database used in prediction software be adjusted to account for such factors in an attempt to improve the accuracy of computerized treatment simulations.