title: Three-dimensional cone-beam computed tomography for assessment of mandibular changes after orthognathic surgery.
abstract: BACKGROUND
  The purpose of this study was to assess alterations in the 3-dimensional (3D) position of the mandibular rami and condyles in patients receiving either maxillary advancement and mandibular setback or maxillary surgery only.
  
  
  METHODS
  High-resolution cone-beam computed tomography scans were taken of 21 patients before and after orthognathic surgery. Ten patients with various malocclusions underwent maxillary surgery only, and 11 Class III patients received maxillary advancement and mandibular setback. Presurgery and postsurgery 3D models were registered on the surface of the cranial base. A new tool was used for graphical overlay and 3D display with color maps to visually assess the locations and to quantify positional changes in the posterior border of the mandibular rami and condyles between superimposed models.
  
  
  RESULTS
  The average displacements in condylar position were small--0.77 mm (SD, 0.12 mm) and 0.70 mm (SD, 0.08 mm)--for 2-jaw and 1-jaw surgeries, respectively (not significant, P >.05). All 2-jaw surgery patients had backward rotational displacements of the mandibular rami (mean, 1.98 mm; SD, 1.03 mm), with a maximum surface distance change of > or =2 mm in 8 of 11 subjects. For the 1-jaw surgery, all subjects had small backward rotational displacements of the mandibular rami (mean, 0.78 mm; SD, 0.25 mm), with only 1 subject having a maximum surface distance change > or =2 mm. The difference in mean backward rotational displacement was statistically significant (P <.01).
  
  
  CONCLUSIONS
  The visualization of 3D model superimposition clearly identified the location, magnitude, and direction of mandibular displacement. The 3D imaging allowed quantification of vertical, transverse, and anteroposterior ramus displacement that accompanied mandibular, but not maxillary only, surgery.
authors.affiliation: Department of Orthodontics, School of Dentistry, University of North Carolina, Chapel Hill, NC 27599-7450, USA. cevidanl@dentistry.unc.edu
authors.forename: Lucia H S
authors.initials: LH
authors.lastname: Cevidanes
authors.forename: L'Tanya J
authors.initials: LJ
authors.lastname: Bailey
authors.forename: Scott F
authors.initials: SF
authors.lastname: Tucker
authors.forename: Martin A
authors.initials: MA
authors.lastname: Styner
authors.forename: Andre
authors.initials: A
authors.lastname: Mol
authors.forename: Ceib L
authors.initials: CL
authors.lastname: Phillips
authors.forename: William R
authors.initials: WR
authors.lastname: Proffit
authors.forename: Timothy
authors.initials: T
authors.lastname: Turvey
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008313:Malocclusion, Angle Class III / Q000601:surgery; D008334:Mandible / Q000000981:diagnostic imaging* / Q000601:surgery; D008335:Mandibular Condyle / Q000000981:diagnostic imaging; D008437:Maxilla / Q000601:surgery; D011184:Postoperative Period; D014057:Tomography, X-Ray Computed / Q000379:methods*