COMPARISONS OF POSTSURGICAL STABILITY OF THE LEFORT-I MAXILLARY IMPACTION AND MAXILLARY ADVANCEMENT

The purpose of this study was to determine retrospectively the stability of the LeFort I osteotomy after a one-piece maxillary impaction or advancement. Cephalograms of 31 patients were evaluated before surgery, immediately after surgery, in fixation, and after fixation. Descriptive statistics for the absolute and the relative changes of the various linear and angular parameters were calculated for the different stages. The analysis of variance general linear models procedure was used to compare the impaction group (n = 23) with the advancement group (n = 8). The findings indicated that the two groups could be studied independent of age, sex, surgeon, the presence of pretreatment open bite, and the length of the postsurgical fixation. The findings further indicated the presence of significant differences in the postsurgical changes between the maxillary impaction and the maxillary advancement groups. As an example, during fixation, the maxilla moved superiorly more at point A in the advancement group (xBAR = 1.89 mm) than in the impaction group (xBAR = 0.67 mm). The upper incisor movements showed a similar pattern, moving more superiorly for the advancement group (xBAR = 2.30 mm) than for the impaction group (xBAR = 0.96 mm). Therefore care should be taken to avoid "burying" the incisors beneath the lip in patients undergoing maxillary advancement, who have minimal exposure of the maxillary incisors before surgery.