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From 1965 to 1974, the total number of the orthodontic patients who visited Seoul National University Hospital was only about 1000. But in the last several years the number has been increasing so rapidly that we have about 1000 new orthodontic patients every year. This made it necessary to undertake an epidemiologic study on them so that we can accommodate their orthodontic needs adequately. Accordingly, the present study was done in an attempt to provide reliable quantitative information regarding the characteristics of malocclusion-Angle's classification etc.--of patients who visited Department of Orthodontics, Seoul National University Hospital from 1985 to 1989. The total number was 3305. This study sought to determine the annual trend in total number during 5 years, frequency in each age and sex group and distribution according to Angle's classification. It was found that: 1. Total number of orthodontic patients has been increasing and the number of female patients was 1.55 times as high as that of male. 2. Percentage of Class III malocclusion has been increasing, but that of Class I decreasing. Each percentage of Class I, Class II div. 1, Class II div. 2 and Class III was 35.92%, 13.40%, 1.54%, and 49.14%. 3. Percentages of 8 to 12-year-old group and 12 to 18-year-old group showed decreasing trends, but that of adult patients showed increasing trend.

This study was undertaken to ascertain the changes of fetuses in craniofacial dimension and to evaluate the growth and development during fetal period. Lateral cephalograms by soft X-ray were taken from 64 fetuses and were measured in linear and angular aspects. The following conclusions were obtained. 1. The linear increase rates of anterior cranial base length exceeded those of the posterior cranial base length. 2. Growth increments on horizontal dimension were greater than vertical dimension in the maxilla. 3. The cranial base angle was almost constant after fetal period 13 weeks with the average angle of 130 degrees. 4. The angle between anterior cranial base and palatal plane was decreased gently during fetal period.