title: Evaluation of facial hard and soft tissue asymmetry using cone-beam computed tomography.
abstract: BACKGROUND
  The purposes of this study were to (1) evaluate facial asymmetry 3 dimensionally using cone-beam computed tomography (CBCT) and (2) compare the right and left facial hard and soft tissues volumetrically and their interferences on each other.
  
  
  METHODS
  The CBCT data of 49 asymmetric (soft tissue menton deviation, ≥4 mm; distance from the facial midline) (mean age, 19.9 ± 5.6 years) and 39 symmetric patients (soft tissue menton deviation, <4 mm) (mean age, 17.8 ± 5.5 years) were exported to the MIMICS software program (version 13.0; Materialise, Leuven, Belgium). Linear, surface distance, angular, volumetric, and surface area measurements were performed 3 dimensionally to assess and compare intragroup and intergroup differences.
  
  
  RESULTS
  In the asymmetry group, linear measurements such as ramus height, mandibular effective and corpus length, and absolute mandibular volumetric measurements were significantly decreased (P <0.001), whereas facial mandibular, and soft and hard tissue volumetric measurements made on 3-dimensional images, and linear measurements on 2-dimensional images were increased (P <0.001) on the deviation side.
  
  
  CONCLUSIONS
  Facial hard and soft tissue asymmetries can be precisely quantified using CBCT. However, especially in the gonial region where the surface topography shows alterations caused by asymmetry, many anatomic landmarks should be chosen for the assessment of asymmetry. At the gonial level, the compensation of the soft tissues for the hard tissues was found on 2-dimensional images; nevertheless, 3-dimensional right and left volumetric soft tissue evaluations provide evidence for asymmetry.
authors.affiliation: Teaching assistant, Department of Orthodontics, Faculty of Dentistry, Yeditepe University, Istanbul, Turkey. Electronic address: drburcunur@gmail.com.
authors.forename: Rahime Burcu
authors.initials: RB
authors.lastname: Nur
authors.affiliation: Associate professor, Department of Orthodontics, Faculty of Dentistry, Yeditepe University, Istanbul, Turkey.
authors.forename: Derya Germeç
authors.initials: DG
authors.lastname: Çakan
authors.affiliation: Professor; private practice, Istanbul, Turkey.
authors.forename: Tülin
authors.initials: T
authors.lastname: Arun
mesh_terms: D000293:Adolescent; D000328:Adult; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D002508:Cephalometry / Q000379:methods; D002648:Child; D002680:Chin / Q000000981:diagnostic imaging; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D003724:Dental Arch / Q000000981:diagnostic imaging; D005145:Face / Q000000981:diagnostic imaging*; D005146:Facial Asymmetry / Q000000981:diagnostic imaging*; D005147:Facial Bones / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008334:Mandible / Q000000981:diagnostic imaging; D008437:Maxilla / Q000000981:diagnostic imaging; D009295:Nasal Bone / Q000000981:diagnostic imaging; D009929:Organ Size; D012658:Sella Turcica / Q000000981:diagnostic imaging; D055815:Young Adult