The effect of premolar extractions on tooth-size discrepancy in malocclusion patients

Kim,  Hee-Hun; Sung,  Sang-Jin; Moon,  Yoon-Shik

J Korean Dent Assoc > Volume 48(3); 2010 > Article

The Journal of The Korean Dental Association 2010;48(3):196-204.
Published online March 31, 2010.

Original Article 1 - 부정교합과 차등적 소구치 발치가 치아 크기 부조화에 미치는 영향

김희헌¹, 성상진², 문윤식³

^¹울산의대 서울아산병원 치과교정과
^²울산의대 서울아산병원 치과교정과
^³울산의대 서울아산병원 치과교정과

The effect of premolar extractions on tooth-size discrepancy in malocclusion patients

Hee-Hun Kim¹, Sang-Jin Sung², Yoon-Shik Moon³

¹Department of Dentistry, Asan medical center, College of Medicine, University of Ulsan
²Department of Dentistry, Asan medical center, College of Medicine, University of Ulsan
³Department of Dentistry, Asan medical center, College of Medicine, University of Ulsan

Abstract

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;pm;2.69%, and the mean overall ratio was 91.56;pm;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).

Key Words: Bolton tooth-size ratio;Premolar extractions;tooth size discrepancy;