抄録
The purpose of this study was to investigate changes in the upper and lower lip vermilion areas and the relevant factors in mandibular prognathism patients treated with orthognathic surgery.
The samples were diagnosed as a mandibular protrusion and collected from mandibular prognathism patients before treatment with orthognathic surgery from 2000 to 2007.
Subjects with congenital disease including cleft lip and palate, syndrome and severe facial asymmetry with jaw deviation were excluded. All subjects were divided into two groups by surgical procedure. Eighteen and 16 patients underwent mandibular setback surgery (one-jaw group) and two-jaw surgery (two-jaw group), respectively. Lateral cephalograms and standardized frontal facial photographs were taken before and after surgery and used for the analysis. Cephalometric analysis of the changes of skeletal and dentoalveolar structures was conducted.
Upper and lower lip vermilion areas were measured by using NIH Image software (National Institute of Health, Bethesda, MD, USA). A paired t-test was used to identify significant changes in skeletal components and lip vermilion areas before and after surgery. Pearson correlation analysis was also used to discriminate skeletal changes responsible for lip vermilion changes before and after surgery.
The following results were obtained.
1. In the one-jaw group, the lower lip vermilion area exhibited a decreasing tendency, whereas the upper lip vermilion area was almost invariable. Thus, the ratio of vermilion area (upper lip vermilion area/lower lip vermilion area) showed a slight increase.
2. In the two-jaw group, the upper vermilion area exhibited an increasing tendency, while the lower vermilion area was almost unchanged. As a result, the ratio of vermilion area increased similarly to that in the one-jaw group.
3. In the one-jaw group, a significant negative correlation was found between overjet and lower lip vermilion area.
4. In the two-jaw group, a significant positive correlation was found between changes in vertical position of Point A and upper vermilion area. Moreover, there was a significant negative correlation between changes in FMA and upper vermilion area.
These results suggested that although the ratio of vermilion area increased in the one-jaw and two-jaw groups after orthognathic surgery, the mechanism of lip morphological improvement was quite different in the two groups. It is also considered that the counter-clockwise rotation of the mandible following upward movement of the maxilla achieved by two-jaw surgery affects the change in upper lip vermilion area.
