title: Monitoring of typodont root movement via crown superimposition of single cone-beam computed tomography and consecutive intraoral scans.
abstract: BACKGROUND
  The purpose of this study was to develop a new methodology to visualize in 3 dimensions whole teeth, including the roots, at any moment during orthodontic treatment without the need for multiple cone-beam computed tomography (CBCT) scans.
  
  
  METHODS
  An extraoral typodont model was created using extracted teeth placed in a wax base. These teeth were arranged to represent a typical malocclusion. Initial records of the malocclusion, including CBCT and intraoral surface scans, were taken. Threshold segmentation of the CBCT was performed to generate a 3-dimensional virtual model. This model and the intraoral surface scan model were superimposed to generate a complete set of digital composite teeth composed of high-resolution surface scan crowns sutured to the CBCT roots. These composite teeth were individually isolated from their respective arches for single-tooth manipulations. Orthodontic treatment for the malocclusion typodont model was performed, and posttreatment intraoral surface scans before and after bracket removal were taken. A CBCT scan after bracket removal was also obtained. The isolated composite teeth were individually superimposed onto the posttreatment surface scan, creating the expected root position setup. To validate this setup, it was compared with the posttreatment CBCT scan, which showed the true positions of the roots. Color displacement maps were generated to confirm accurate crown superimpositions and to measure the discrepancies between the expected and the true root positions.
  
  
  RESULTS
  Color displacement maps through crown superimpositions showed differences between the expected and true root positions of 0.1678 ± 0.3178 mm for the maxillary teeth and 0.1140 ± 0.1587 mm for the mandibular teeth with brackets. Once the brackets were removed, differences of 0.1634 ± 0.3204 mm for the maxillary teeth and 0.0902 ± 0.2505 mm for the mandibular teeth were found.
  
  
  CONCLUSIONS
  A new reliable approach was demonstrated in an ex-vivo typdont model to have the potential to track the 3-dimensional positions of whole teeth including the roots, with only the initial CBCT scan and consecutive intraoral scans. Since the presence of brackets in the intraoral scan had a minimal influence in the analysis, this method can be applied at any stage of orthodontic treatment.
authors.affiliation: Dental student, School of Dentistry, University of California, Los Angeles, Calif.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lee
authors.affiliation: Biomedical and computer engineer and resident, Advanced Orthodontic Program, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, Calif.
authors.forename: John
authors.initials: J
authors.lastname: Pham
authors.affiliation: Resident, Department of Orthodontics and Dentofacial Orthopedics, University of Pittsburgh, Pittsburgh, Pa.
authors.forename: Michael
authors.initials: M
authors.lastname: Choy
authors.affiliation: Professor, Department of Orthodontics, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Andre
authors.initials: A
authors.lastname: Weissheimer
authors.affiliation: Clinical assistant professor, Advanced Orthodontic Program, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles.
authors.forename: Harry L
authors.initials: HL
authors.lastname: Dougherty
authors.affiliation: Associate professor and director, Advanced Orthodontic Program, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles.
authors.forename: Glenn T
authors.initials: GT
authors.lastname: Sameshima
authors.affiliation: Clinical assistant professor, Advanced Orthodontic Program, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, Calif. Electronic address: drhstong@yahoo.com.
authors.forename: Hongsheng
authors.initials: H
authors.lastname: Tong
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000379:methods*; D003724:Dental Arch / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008310:Malocclusion / Q000473:pathology / Q000628:therapy; D003765:Models, Dental; D015203:Reproducibility of Results; D012984:Software; D019228:Tooth Crown / Q000000981:diagnostic imaging / Q000473:pathology*; D014087:Tooth Movement Techniques / Q000379:methods*; D014092:Tooth Root / Q000000981:diagnostic imaging / Q000473:pathology*; D014584:User-Computer Interface