title: Effect of premolar extraction and presence of the lower third molar on lower second molar angulation in orthodontic treatment.
abstract: OBJECTIVE
  To evaluate the change in mandibular second-molar (M2) angulation in orthodontic treatment with premolar extraction and lower third molar (M3).
  
  
  METHODS
  Panoramic radiographs were evaluated in 3 groups of 129 participants: (1) control, no orthodontic treatment (n = 65); (2) extraction, orthodontic treatment with premolar extraction (n = 30); and (3) nonextraction, orthodontic treatment without premolar extraction (n = 34). The angular difference and ratio of M2 to the first molar (M1), the change in the angulation of M2 between pre- and postorthodontic treatment, and the distal bone level of M2 were assessed.
  
  
  RESULTS
  The angular difference and ratio of M2 to M1, the angulation change of M2 between pre- and postorthodontic treatment, and the distal bone level of M2 were higher in the nonextraction group than in the control and extraction groups.
  
  
  CONCLUSIONS
  The successful orthodontic alignment of the M2 may not be achieved in nonextraction cases when the M3s are present.
authors.affiliation: Assistant Professor, Department of Advanced General Dentistry, Dental Hospital, Dankook University, Cheonan, South Korea.
authors.forename: Tae-Min
authors.initials: TM
authors.lastname: You
authors.affiliation: Resident, Department of Advanced General Dentistry, Dental Hospital, Yonsei University, Seoul, South Korea.
authors.forename: Bo Hyun
authors.initials: BH
authors.lastname: Ban
authors.affiliation: Researcher, Department of Advanced General Dentistry, Dental Hospital, Yonsei University, Seoul, South Korea.
authors.forename: Jin-Sun
authors.initials: JS
authors.lastname: Jeong
authors.affiliation: Researcher, Department of Advanced General Dentistry, Dental Hospital, Yonsei University, Seoul, South Korea.
authors.forename: Jisun
authors.initials: J
authors.lastname: Huh
authors.affiliation: Clinical Assistant Professor, Department of Advanced General Dentistry, Dental Hospital, Dankook University, Cheonan, South Korea.
authors.forename: Re-Mee
authors.initials: RM
authors.lastname: Doh
authors.affiliation: Associate Professor, Department of Advanced General Dentistry, Dental Hospital, Yonsei University, Seoul, South Korea. Electronic address: wonse@yuhs.ac.
authors.forename: Wonse
authors.initials: W
authors.lastname: Park
mesh_terms: D001641:Bicuspid / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008963:Molar / Q000000981:diagnostic imaging / Q000502:physiology*; D008964:Molar, Third / Q000000981:diagnostic imaging / Q000502:physiology*; D009971:Orthodontics, Corrective; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D014081:Tooth Extraction