title: [Influence of the mandibular second premolar extraction on the angulation of the mandibular third molar].
abstract: OBJECTIVE
  To compare the angular changes in the developing mandibular third molars in the mandibular second premolar extraction and non-extraction cases and to determine whether the mandibular second premolar extraction causes favorable rotational changes in the angulations of the  developing mandibular third molars and benefits its later eruption.
  
  
  METHODS
  Pretreatment and posttreatment panoramic radiographs were taken from 45  subjects who had been treated by the extraction of the mandibular second premolars and 48 subjects who had been treated without extraction. The  horizontal reference plane was used to measure and compare the changes in the angulations of the developing mandibular third molars.
  
  
  RESULTS
  The  mean uprighting of the mandibular third molars seen in the extraction group was (5.9±2.5) degrees on the right side and (8.0±3.4) degrees on the left side  following treatment. For the nonextraction group the mean uprighting was (1.8±2.4) degrees on the right side and (1.5±2.1) degrees on the left side. There  was a statistically significant difference between the groups (P<0.05).
  
  
  CONCLUSIONS
  Mandibular second premolar extraction might be a helpful procedure  on the angulations of the developing mandibular third molars.
authors: The First Dental Center, Peking University School and Hospital of Stomatology, Beijing, China.
authors: Guang-yao
authors: GY
authors: Feng
authors: Bing-shuang
authors: BS
authors: Zou
authors: Xue-mei
authors: XM
authors: Gao
authors: Xiang-long
authors: XL
authors: Zeng
authors: Xiu-jing
authors: XJ
authors: Wang
authors: Yan
authors: Y
authors: Yan
mesh_terms: D000293:Adolescent; D001641:Bicuspid / Q000000981:diagnostic imaging / Q000601:surgery*; D002648:Child; D003766:Dental Occlusion; D005260:Female; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000628:therapy; D008334:Mandible; D008964:Molar, Third / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011859:Radiography; D014081:Tooth Extraction; D014087:Tooth Movement Techniques