Crowded group is composed of 60 subjects who visited Yonsei University for orthodontic treatment and has no history of orthodontic treatment. Noncrowded group is composed of 26 subjects who has no crowding, considered to have a normal occlusion and no history of orthodontic treatment. Currently available and approved analytic method was used. Interrelationship between tooth size and arch size, and it´s correlation on tooth crowding was studied and the following results were obtained.
1. In comparison of sum of mesiodistal width, of crown size of teeth was greater in noncrowded group than that of crowded group on both arch. (p < 0.01:;.
2. In comparison of arch lengths, the values measured from arch length 2 showed greater in noncrowded group (p < 0.01). Also in crowded group, arch length 1 showed greater value than arch length-2 on both arch (p < 0.01).
3. In comparison of arch widths, upper interlateral (p < 0.01) and upper intercanine width (p < 0.05) showed greater value in noncrowded group on upper arch and intermolar width showed greater value in noncrowded group on both upper and lower arches (p < 0.05).
4. In comparison of arch perimeters, arch perimeter 2 was greater value in noncrowded group on both upper and lower arches (p < 0.01).
5. Dentoalveolar disproportion was greater in noncrowded group on both upper and lower arches (p < 0.01).
6. In lower incisors MD/FL ratio, the central and lateral incisors were greater in crowded group, but statistial significance was only in lateral incisors (p < 0.01)
7. The irregularity index of lower incisors showed greater value in crowded group (p < 0.01).
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