title: 3D Mandibular Superimposition: Comparison of Regions of Reference for Voxel-Based Registration.
abstract: BACKGROUND
  The aim was to evaluate three regions of reference (Björk, Modified Björk and mandibular Body) for mandibular registration testing them in a patients' CBCT sample.
  
  
  METHODS
  Mandibular 3D volumetric label maps were built from CBCTs taken before (T1) and after treatment (T2) in a sample of 16 growing subjects and labeled with eight landmarks. Registrations of T1 and T2 images relative to the different regions of reference were performed, and 3D surface models were generated. Seven mandibular dimensions were measured separately for each time-point (T1 and T2) in relation to a stable reference structure (lingual cortical of symphysis), and the T2-T1 differences were calculated. These differences were compared to differences measured between the superimposed T2 (generated from different regions of reference: Björk, Modified Björk and Mandibular Body) over T1 surface models. ICC and the Bland-Altman method tested the agreement of the changes obtained by nonsuperimposition measurements from the patients' sample, and changes between the overlapped surfaces after registration using the different regions of reference.
  
  
  RESULTS
  The Björk region of reference (or mask) did work properly only in 2 of 16 patients. Evaluating the two other masks (Modified Björk and Mandibular body) on patients' scans registration, the concordance and agreement of the changes obtained from superimpositions (registered T2 over T1) compared to results obtained from non superimposed T1 and T2 separately, indicated that Mandibular Body mask displayed more consistent results.
  
  
  CONCLUSIONS
  The mandibular body mask (mandible without teeth, alveolar bone, rami and condyles) is a reliable reference for 3D regional registration.
authors.affiliation: School of Dentistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Antonio Carlos de Oliveira
authors.initials: AC
authors.lastname: Ruellas
authors.affiliation: Bauru Dental School, University of São Paulo, Bauru, Brazil.
authors.forename: Marilia Sayako
authors.initials: MS
authors.lastname: Yatabe
authors.affiliation: School of Dentistry, Pontifical Catholic University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Bernardo Quiroga
authors.initials: BQ
authors.lastname: Souki
authors.affiliation: School of Dentistry, University of Michigan, Ann Arbor, MI, United States of America.
authors.forename: Erika
authors.initials: E
authors.lastname: Benavides
authors.affiliation: School of Dentistry, University of North Carolina, Chapel Hill, NC, United States of America.
authors.forename: Tung
authors.initials: T
authors.lastname: Nguyen
authors.affiliation: Institute of Public Health Studies (IESC), Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
authors.forename: Ronir Raggio
authors.initials: RR
authors.lastname: Luiz
authors.affiliation: Bauru Dental School, University of São Paulo, Bauru, Brazil.|Department of Surgery and Translational Medicine, University of Florence, Florence, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Franchi
authors.affiliation: Bauru Dental School, University of São Paulo, Bauru, Brazil.
authors.forename: Lucia Helena Soares
authors.initials: LH
authors.lastname: Cevidanes
mesh_terms: D000293:Adolescent; D002648:Child; D054893:Cone-Beam Computed Tomography; D006801:Humans; D021621:Imaging, Three-Dimensional; D008334:Mandible / Q000000981:diagnostic imaging*; D008953:Models, Anatomic; D011861:Radiography, Dental; D012016:Reference Values