title: [A cone-beam computed tomography study on crown-root morphology of maxillary anterior teeth in Class II, division 2 malocclusion].
abstract: OBJECTIVE
  To study crown-root morphology of maxillary anterior teeth in Class II, division 2 malocclusion using cone-beam CT (CBCT) combined with computer aided measurement technology to provide guidance for clinical treatment.
  
  
  METHODS
  The samples which consisted of 36 cases radiographed with CBCT techniques were selected and divided into two groups (18 each ) based on the type of malocclusion presented: Class II, division 2 group (group II 2) and Class I group (group I). The measurements of crown-root morphology including crown-root angle and surface-shaft angle were got by Multiple Planer Reconstruction of CBCT data uploaded into InvivoDental software 5.0. The data were processed with SPSS 20.0 software package and t test was employed for comparison of angular measurements.
  
  
  RESULTS
  In group I, crown-root angles of maxillary central incisor, maxillary lateral incisor and maxillary canines were 179.08° ± 3.31°, 176.55° ± 2.77° and 184.20° ± 2.51° respectively, surface-shaft angles were 21.00° ± 2.63°, 19.63° ±2 .35° and 19.36° ± 2.30° respectively. While in group II 2, crown-root angles of maxillary central incisor, maxillary lateral incisor and maxillary canines were 176.80° ± 2.62°, 174.13° ± 3.28° and 181.79° ± 2.88° respectively, surface-shaft angles were 23.20° ± 2.95°, 22.29° ± 2.19° and 20.61° ± 2.34° respectively. Compared with group I, significant statistical differences were observed with the exception of surface-shaft angle of maxillary incisor. There was significant difference in crown-root angle between group II 2 and 180°.
  
  
  CONCLUSIONS
  The maxillary anterior teeth in Class II, division 2 malocclusion exhibited significant crown-root morphology which would influence the torque after orthodontic treatment. Special attention should be paid to the position of maxillary anterior teeth roots during orthodontic treatment for Class II, division 2 malocclusion. The ideal position of tooth movement should be decided by the root rather than the location of the crowns.
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing 100081,China.
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing 100081,China.
authors.forename: Si-wei
authors.initials: SW
authors.lastname: Wang
authors.affiliation: Center of Digital Dentistry & National Engineering Laboratory for Digital and Material Technology of Stomatology, Peking University School and Hospital of Stomatology, Beijing 100081,China.
authors.forename: Yi-jiao
authors.initials: YJ
authors.lastname: Zhao
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing 100081,China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
mesh_terms: D054893:Cone-Beam Computed Tomography; D003442:Crowns; D003481:Cuspid; D006801:Humans; D007180:Incisor; D008310:Malocclusion; D008437:Maxilla; D014087:Tooth Movement Techniques; D014092:Tooth Root