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KMID : 0362720100480030196
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Journal of the Korean Dental Association
2010 Volume.48 No. 3 p.196 ~ p.204
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The effect of premolar extractions on tooth-size discrepancy in malocclusion patients
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Kim Hee-Hun
Sung Sang-Jin
Moon Yoon-Shik
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Abstract
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To establish the ideal occlusal relationship, the values of tooth size and ratio must be in a normal range.
In this study, the means and standard deviations of Bolton’s anterior ratio and overall ratio using mesiodistal dimensions of
teeth measured on diagnostic models of 334 Korean malocclusion patients were calculated and differences in Bolton ratio
according to the groups of malocclusion patients were studied. Also the changes that can occur in overall ratio before and after hypothetical tooth extractions were observed.
The results are as follows. 1. The mean anterior ratio of Korean malocclusion patients was 78.0± 2.69%, and the mean
overall ratio was 91.56± 2.28%. 2. The largest value of tooth size ratio could be found in Class III group, followed by Class I
and Class II groups in order. However there was no statically significant difference. 3. The values of overall ratio reduced
significantly after premolar extractions in all malocclusion groups, which was much more significant in the extraction of
upper second premolar and lower first premolar(U5L4) or upper second premolar and lower second premolar(U5L5). 4. The values of overall ratio reduced significantly after premolar extractions in all 3 groups divided based on Bolton ratio, which was much more significant in the extraction of upper second premolar and lower first premolar(U5L4) or upper second premolar and lower second premolar(U5L5).
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KEYWORD
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Bolton tooth-size ratio, premolar extractions, tooth size discrepancy
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