Korean J Orthod.  2014 Mar;44(2):62-68. 10.4041/kjod.2014.44.2.62.

Three-dimensional symmetry and parallelism of the skeletal and soft-tissue poria in patients with facial asymmetry

  • 1Department of Orthodontics, School of Dentistry, Dankook University, Cheonan, Korea. saegum@naver.com


The purpose of this study was to examine the symmetry and parallelism of the skeletal and soft-tissue poria by three-dimensional (3D) computed tomographic (CT) imaging.
The locations of the bilateral skeletal and soft-tissue poria in 29 patients with facial asymmetry (asymmetric group) and 29 patients without facial asymmetry (symmetric group) were measured in 3D reconstructed models of CT images by using a 3D coordinate system. The mean intergroup differences in the anteroposterior and vertical angular deviations of the poria and their anteroposterior and vertical parallelism were statistically analyzed.
The symmetric and asymmetric groups showed significant anteroposterior angular differences in both the skeletal and the soft-tissue poria (p = 0.007 and 0.037, respectively; Mann-Whitney U-test). No significant differences in the anteroposterior and vertical parallelism of the poria were noted (p < or = 0.05; Wilcoxon signed-rank test).
In general, the skeletal poria are parallel to the soft-tissue poria. However, patients with facial asymmetry tend to have asymmetric poria.


Computed tomography; Soft tissue; Anatomy; Facial asymmetry; Porion; Parallelism

MeSH Terms

Facial Asymmetry*


  • Figure 1 Parallelism of the skeletal and soft-tissue poria. A, Vertical parallelism; B, anteroposterior parallelism.

  • Figure 2 The three-dimensional (3D) reconstructed model. A, 3D reconstruction of computed tomographic images; B, 3D coordinate system.

  • Figure 3 Measurement of the angular deviations. A, Anteroposterior deviation (θ1); B, vertical deviation (θ2).a, l x coordinate of left porion - x coordinate of right porion l; b, l z coordinate of left porion - z coordinate of right porion l; c, l y coordinate of left porion - y coordinate of right porion l.

  • Figure 4 Receiver operating characteristic (ROC) curves of θsk1 and θsof1. a, cutoff section of θsk1; b, cutoff section of θsof1.

  • Figure 5 Conversion of angular deviation into linear deviation. A, For the skeletal poria; B, for the soft-tissue poria.

Cited by  1 articles

Cone-beam computed tomography based evaluation of rotational patterns of dentofacial structures in skeletal Class III deformity with mandibular asymmetry
Hyeong-Seok Ryu, Ki-Yong An, Kyung-Hwa Kang
Korean J Orthod. 2015;45(4):153-163.    doi: 10.4041/kjod.2015.45.4.153.


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