title: A new mandible-specific landmark reference system for three-dimensional cephalometry using cone-beam computed tomography.
abstract: To develop a novel 3D landmark reference system that is specific for mandibular midline cephalometric landmarks and to assess its repeatability and reproducibility.
  
  
  
  Cone-beam computed tomography (CBCT) scans (3D Accuitomo® 170) were performed on 26 dry human skulls. The CBCT data were exported into DICOM files and imported to Maxilim® software to create 3D surface models. Two observers identified five landmarks to create a specific mid-sagittal mandibular plane: two mandibular foramina, two molar landmarks and one interincisive landmark. On this mid-sagittal mandibular plane, four mandibular cephalometric landmarks were marked: Point B, Pogonion, Gnathion and Menton. All observations were repeated by the two observers after an interval of 4 weeks. The coordinates (x, y, z) of each landmark were exported, and statistical analyses were performed to evaluate inter- and intra-rater precision.
  
  
  
  The intra-observer median precision in locating all landmarks ranged between 0.17 and 0.61mm. The intra-observer repeatability was generally good with a precision under 1mm in more than 50 per cent. The overall median inter-observer precision was 0.26-2.30mm. The mandibular foramina showed the best inter-observer reproducibility. The general inter-observer reproducibility was moderate to good, except for Pogonion and Point B.
  
  
  
  Dry human skulls may not represent anatomical conditions found in living patients, thus the system should be validated using patients' data.
  
  
  
  The novel reference system offered good precision and generally good to moderate repeatability and reproducibility for mandibular midline cephalometric landmark identification in three dimensions. These findings will be useful for further improvement of 3D cephalometric systems.
authors.affiliation: *OIC, OMFS-IMPATH Research Group, Department of Imaging & Pathology, Faculty of Medicine, University of Leuven and Oral & Maxillofacial Surgery, University Hospitals Leuven, Belgium, p.pittayapat@gmail.com.|**Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Pisha
authors.initials: P
authors.lastname: Pittayapat
authors.affiliation: *OIC, OMFS-IMPATH Research Group, Department of Imaging & Pathology, Faculty of Medicine, University of Leuven and Oral & Maxillofacial Surgery, University Hospitals Leuven, Belgium.
authors.forename: Reinhilde
authors.initials: R
authors.lastname: Jacobs
authors.affiliation: *OIC, OMFS-IMPATH Research Group, Department of Imaging & Pathology, Faculty of Medicine, University of Leuven and Oral & Maxillofacial Surgery, University Hospitals Leuven, Belgium.|***Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Switzerland.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Bornstein
authors.affiliation: ****Service de chirurgie orthopédique et traumatologique, Centre Hospitalier Régional d'Orléans, Orléans cedex 2, France.
authors.forename: Guillaume A
authors.initials: GA
authors.lastname: Odri
authors.affiliation: *OIC, OMFS-IMPATH Research Group, Department of Imaging & Pathology, Faculty of Medicine, University of Leuven and Oral & Maxillofacial Surgery, University Hospitals Leuven, Belgium.
authors.forename: Min Sung
authors.initials: MS
authors.lastname: Kwon
authors.affiliation: *****Biomedical Research Institute, Laboratory of Morphology, Hasselt University, Campus Diepenbeek, Diepenbeek, Belgium.
authors.forename: Ivo
authors.initials: I
authors.lastname: Lambrichts
authors.affiliation: ******Orthodontics, Department of Oral Health Sciences, KU Leuven & Dentistry, University Hospitals Leuven, University of Leuven, Belgium, and.
authors.forename: Guy
authors.initials: G
authors.lastname: Willems
authors.affiliation: *OIC, OMFS-IMPATH Research Group, Department of Imaging & Pathology, Faculty of Medicine, University of Leuven and Oral & Maxillofacial Surgery, University Hospitals Leuven, Belgium.
authors.forename: Constantinus
authors.initials: C
authors.lastname: Politis
authors.affiliation: *******Department of Oral and Maxillofacial Surgery, Cliniques Universitaires Saint Luc, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Olszewski
mesh_terms: D059925:Anatomic Landmarks; D002508:Cephalometry / Q000379:methods*; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008334:Mandible / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D008963:Molar / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D015588:Observer Variation; D015203:Reproducibility of Results