下顎前突症に対する顎矯正手術後の軟組繊側貌の予測に関する研究

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In order to make predictions for softtissue profile of lower face after orthognathic surgery for mandibular prognathism, lateral radiographic cephalograms of 23 subjects of skeletal class III malocclusion who were given mandibular body ostectomy were used and the following study was made. 1. The subjects for this study consisted of 23 females with an average age of 18 years and 9 months. All subjects had skeletal Class III malocclusion and 11 of these had a complication of open bite. Twenty subjects were given step ostectomy of the mandibular body and the other three vertical ostectomy. Right lateral radiographic cephalometric films were taken as reference at five points in time : before, immediately after, 3 months after, 6 months after, and a year after operation. 2. For cephalometric measurement, coordinates with the straight line originating from S and parallel to FH plane as X axis and the line at right angle to it as Y axis were prepared and 13 landmarks of hardand softtissue were measured on a digitizer. 3. Changes with time in hard and soft tissue profile were plotted on the coordinates as changes of the landmarks and their average movements were examined and the following results were obtained. 1) Marked posterosuperior displacement of the mandible as a result of operation was seen as a change in the hard tissue profile. Until 3 months after operation, superoanterior displacement of the mandible along with occlusal reconstruction was observed. Thereafter, until 6 months after operation, a trend for relapse consiting mainly of anterior displacement continued. However, after 6 months, no significant changes were seen and changes were about stabilized. 2) During the period before and 3 months after operation, Ls and Sto were displaced posteroinferiorly and 6 points below Li posterosuperiorly reflecting the displacement of the hard tissue. During the period 3 to 6 months after operation, slighte displacement anteroinferiorly 6 points below Li was seen. However, after 6 months no significant changes were seen and the changes were about stabilized. 4. With a view to making predictions for soft tissue profile after orthognathic surgery for mandibular prognathism, multiple regression analysis was made of hard and soft tissue landmarks before and over 6 months after operation, five items of thickness of soft tissue before operation, and overjet and overbite before operation, as variables. For selection of independent variables, stepwise selection at F level 2.0 to enter or remove variables was chosen. As a result, the linear multiple regression equation as shown in Table 12 was obtained, and factors of change for each soft tissue landmark after operation were analyzed. Then, a multiple regression equation which shows a multiple correlation coefficient of over 0.95 with as little variables as possible and is statistically significant at 0.01 by F-test was determined as the predicting equation. Furthermore, in order to visually examine accuracy of the predicted soft tissue profile, a computer program which allows simultaneous graphic presentation of pre- and post-operative hard and soft tissue profiles obtained from the actual values and the predicted profiles was prepared. With use of this program, the predictinig equation was applied to the 23 cases used to derive the regression equations and to the 3 additional cases which were not included in the original material as an external check, and visual comparison with the postoperative profiles obtained from the actual values was made. This comparsion showed fair accuracy in all these samples and indicated its general applicability in clinical use.
九州歯科学会の論文

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升井一朗
福岡歯科大・口腔外科II

下顎前突症に対する顎矯正手術後の軟組繊側貌の予測に関する研究

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