The purposes of this study are to evaluate the Korean mandibular dental arch and classify the mandibular dental arch shape and size based on the incisal angle, canine angle, inter second molar width and height. In this study the mandibular study models were fabricated using irreversible hydrocolloid impression material from 225 volunteers with a mean age 23.62 (range 19-29). And the study models were measured with 3-dimensional measuring device and the mandibular dental arch was classified by means of K-means clustering method and visual inspection, then obtained data were analyzed with t-test for the statistical analysis.
The results `were as follows ;
1. The average canine height was 5.19mm(s.d. 1.17) in both sex, 5.34mm in male, and 35.83mm in female. And the sexual difference was significant(02. The average second molar height was 39.81mm(sd. 2.44) in both sex, 40.19mm in male, and 39.21mm in female. And the sexual difference was significant(03. The average inter-canine width was 27.16mm(s.d. 1.78) in both sex, 27.41mm in male, and 26.77mm in female. And the sexual difference was significant(04. The average inter-first molar width was 46.93mm(s.d. 2.67) in both sex, 47.72mm in male, and 45.7mm in female And the sexual difference was significant(05. ´the inter-second molar width was average 56.09mm(s.d. 3.01) in both sex, 57.24mm in male, and 54.32mm in woma. And the sexual difference was significant(06. The arch form was classified into three shapes based on the incisal and canine angle. V-shape showed 124.88 of incisal angle and 141.64 of canine angle, U-shape showed 152.76° and 125.35° , and 0-shape showed 138:03° and 133.66° respectively. Each arch shape distribution was that the V-shape was 142%, the Ushape was 14.7%, and the 0-shape was 71.1% of the 225 study models.
7. It was thought that the use of second molar width is more reasonable than height for classifying the dental arch size. The arch size was classified into four sizes based on the 2nd molar width. Size 1 showed range of 42.24-48.´23 mm, size 2 showed 48.24-54.23mm, and size 3 showed 54.24-60.23mm size 4 showed 60.24-66.23mm respectively Each arch size distribution was that the size I was 1.3%, the size 2 was 27.1%, the size 3 was 63.6%, and the size 4 was 8:0% of the 225 study models.
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