title: [Study of radiographic method of increasing vertical angle for identifying double root in maxillary premolar with cone-beam CT].
abstract: OBJECTIVE
  To explore the feasibility of radiography method of increasing vertical angle for identifying double root in maxillary premolar with cone-beam computed tomography(CBCT).
  
  
  METHODS
  Thirty-one patients with 109 maxillary premolars who needed CT scan for maxillary teeth were selected and scanned by CBCT. The interested region was chosen to reconstruct the image of maxillary premolar at axial, coronal and sagittal section. The actual diameter of root in maxillary premolar and the projection diameter at the center vertical angle of 45° and horizontal angle of 38.5° were measured with CBCT. The data was analyzed with SPSS12.0 software package for Student's t test.
  
  
  RESULTS
  There were no significant differences between the actual diameter of double root tip which was (3.74±0.22)mm and projection diameter which was (3.69±0.16)mm of maxillary premolar at the central vertical angle of 45° and horizontal angle of 38.5° with CBCT (P>0.05); There were also no significant difference between the actual diameter of middle 1/3 section of buccal-lingual diameter (7.87±0.66)mm and projection diameter (7.95±0.52)mm of maxillary premolar at the center vertical angle of 45° and horizontal angle of 38.5° with CBCT (P>0.05).
  
  
  CONCLUSIONS
  CBCT can provide an evidence for radiographic method of increasing vertical angle for identifying double root of maxillary premolar.
authors.affiliation: Department of Stomatology, Chinese PLA General Hospital, Beijing, China. JH1225@163.com
authors.forename: Hua
authors.initials: H
authors.lastname: Jiang
authors.forename: Xiao-wei
authors.initials: XW
authors.lastname: Shi
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
authors.forename: Zhan-ping
authors.initials: ZP
authors.lastname: Shi
authors.forename: Hui
authors.initials: H
authors.lastname: Zhou
authors.forename: Zhao-wu
authors.initials: ZW
authors.lastname: Wang
mesh_terms: D001641:Bicuspid; D054893:Cone-Beam Computed Tomography; D006801:Humans; D014070:Tooth; D014092:Tooth Root