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[Effects of premolar extractions on Bolton index overall ratios]
Zhu-liang Wei1, Yi-ling Wang, Wen-mei Zhang
1Department of Orthodontics, Jinan Dental Hospital. Jinan 250001, Shandong Province, China.E-mail:wzljnkqzj@126.com.
Purpose:
To investigate the effect of premolar extraction on Bolton index overall ratios.
Methods:
Bolton index overall ratios were measured in 198 randomly chosen dental casts of three types of Angle's malocclusions before and after 4 combinations of hypothetical premolar extractions. The data was processed using SPSS 17.0 software package.
Results:
The overall ratios decreased in each class of Angle's malocclusion after all combinations of premolars extraction, and the decreases in combinations of 5/5 and 5/4 extractions were significantly greater than that of 4/4 and 4/5 combinations (P<0.05), but no significant difference was found between different types of malocclusion (P>0.05).
Conclusions:
When formulating a treatment plan involving premolar extractions, orthodontists should consider that the Bolton overall ratios may decrease.
