The purposes of this study were to compare the soft tissue changes following hard tissue change after surgery between the one jaw and two-jaw surgery in skeletal class III patients and to get the reference of the incisal inclination at presurgical orthodontics. For this study 24 patients for the two-jaw surgery group and 18 patients for one jaw surgery group were selected. Lateral cephalograms were taken at pretreatment, after presurgical orthodontic treatment, immediately after surgical treatment and at least 6 months after surgery. They were traced and analyzed on skeletodental structure and soft tissue.
The results were as follows:
1. After surgery, maxilla, maxillary incisors and upper lip were moved anteriorly and superiorly in two-jaw surgery group. Mandible and mandibular incisors were moved posten3rly and superiorly, and thickness of lower _lip was . .
p ....s
increased in both group but there were no statistically significant difference. Anterior facial height was more decreased in two-jaw surgery group (p<0.05). At least 6 months after surgery, by the postorthodontic treatment, maxillary incisors were moved labially 1.44mm, mandible and mandiibular incisors were moved lingually 1.43mrn, 1.26mm respectively in one jaw surgery group. But there was no statistically significant changes of hard tissue in two :jaw surgery group.
2. The correlation coefficients of maxillary hard and soft tissue horizontal changes were high in two jaw surgery group and the ratios for soft tissue to A point were 19% at Sri, 80% at SLS, 82% at LS. The ratios for soft tissue to B point were 92% at Ll, 104% at iiS in one jaw surgery group, 89% at LI, 101% at ILS in two-jaw surgery group.
3. The correlation coefficients and change ratios of mandibular incisors and LL HS on lower lip horizontal changes were 0 0.89 and 75%, 85% in one jaw surgery group, 0.93, 0.90 and 76%, 87% in two-jaw surgery group. The correlation coefficients of maxillary incisors and Sn, SLS and LS on upper lip horizontal changes were 072, 0.76 and 0.75 in two jaw surgery group and ratios of changes were 57%, 58%o and 59%.
4. The regression equations between skeletal horizontal discrepancy and incisal inclinaton were taken in one jaw surgery group. Those were FM1A=57.48-2.17ANB, U1-SN=-75.02+2.17SNB and R2 were 0.63, 063 respectively. So if there is skeletal horizontal discrepancy by mandibular prognathism in one jaw surgery case, we consider attaining more labial inclination of maxillary incisors than normal and more lingual inclination of mandibu ar incisors than nonnal. But correlation coefficient of the regression equations in two jaw surgery group was low, so, that equation was not reliable.
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