title: A new method to measure mesiodistal angulation and faciolingual inclination of each whole tooth with volumetric cone-beam computed tomography images.
abstract: BACKGROUND
  The purpose of this study was to develop a methodology to measure the mesiodistal angulation and the faciolingual inclination of each whole tooth (including the root) by using 3-dimensional volumetric images generated from cone-beam computed tomography scans.
  
  
  METHODS
  A plastic typodont with 28 teeth in ideal occlusion was fixed in position in a dry human skull. Stainless steel balls were fixed to the occlusal centers of the crowns and to the apices or bifurcation or trifurcation centers of the roots. Cone-beam computed tomography images were taken and rendered in Dolphin 3D (Dolphin, Chatsworth, Calif). The University of Southern California root vector analysis program was developed and customized to digitize the crown and root centers that define the long axis of each whole tooth. Special algorithms were used to automatically calculate the mesiodistal angulation and the faciolingual inclination of each whole tooth. Angulation measurements repeated 5 times by using this new method were compared with the true values from the coordinate measuring machine measurements. Next, the root points of 8 selected typodont teeth were modified to generate known angulation and inclination values, and 5-time repeated measurements of these teeth were compared with the known values.
  
  
  RESULTS
  Intraclass correlation coefficients for the repeated mesiodistal angulation and faciolingual inclination measurements were close to 1. Comparisons between our 5-time repeated angulation measurements and the coordinate measuring machine's true angulation values showed 5 teeth with statistically significant differences. However, only the maxillary right lateral incisor showed a mean difference that might exceed 2.5° for clinical significance. Comparisons between the 5-repeated measurements of 8 teeth with known mesiodistal angulation and faciolingual inclination values showed no statistically significant differences between the measured and the known values, and no measurement had a 95% confidence interval beyond 1°.
  
  
  CONCLUSIONS
  We have developed the novel University of Southern California root vector analysis program to accurately measure each whole tooth mesiodistal angulation and faciolingual inclination, in a clinically significant level, directly from the cone-beam computed tomography volumetric images.
authors: Advanced Orthodontic Program, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA. drhstong@yahoo.com
authors: Hongsheng
authors: H
authors: Tong
authors: Reyes
authors: R
authors: Enciso
authors: Dana
authors: D
authors: Van Elslande
authors: Paul W
authors: PW
authors: Major
authors: Glenn T
authors: GT
authors: Sameshima
mesh_terms: D000465:Algorithms; D054893:Cone-Beam Computed Tomography / Q000379:methods* / Q000592:standards; D057918:Fiducial Markers; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000592:standards; D021621:Imaging, Three-Dimensional / Q000379:methods* / Q000592:standards; D003765:Models, Dental; D009811:Odontometry / Q000379:methods* / Q000592:standards; D012984:Software / Q000592:standards; D014070:Tooth / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D019227:Tooth Apex / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D019228:Tooth Crown / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014092:Tooth Root / Q000033:anatomy & histology / Q000000981:diagnostic imaging