title: [Effects of premolar extractions on Bolton index overall ratios].
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Orthodontics, Jinan Dental Hospital. Jinan 250001, Shandong Province, China.E-mail:wzljnkqzj@126.com.
authors.forename: Zhu-liang
authors.initials: ZL
authors.lastname: Wei
authors.forename: Yi-ling
authors.initials: YL
authors.lastname: Wang
authors.forename: Wen-mei
authors.initials: WM
authors.lastname: Zhang
mesh_terms: D001641:Bicuspid; D006801:Humans; D008310:Malocclusion; D009811:Odontometry; D014081:Tooth Extraction