Imaging Sci Dent.  2011 Sep;41(3):95-100. 10.5624/isd.2011.41.3.95.

Application of spherical coordinate system to facial asymmetry analysis in mandibular prognathism patients

• Yoon SJ
• Wang RF
• Hwang HS
• Kang BC
• Lee JS
• Palomo JM

• KMID: 1449953
• DOI: http://doi.org/10.5624/isd.2011.41.3.95

Abstract

PURPOSE
The purpose of this study was to compare asymmetric mandibular prognathism individuals with symmetric mandibular prognathism individuals using a new alternate spherical coordinate system.
MATERIALS AND METHODS
This study consisted of 47 computed tomographic images of patients with mandibular prognathism. The patients were classified into symmetric and asymmetric groups. Mandibular and ramal lines were analyzed using an alternate spherical coordinate system. The length as well as midsagittal and coronal inclination angle of the lines was obtained. The bilateral differences of the spherical coordinates of the facial lines were statistically analyzed in the groups.
RESULTS
There were significant differences between the groups in bilateral difference of the length and midsagittal inclination angle of the lines (p<0.05). The bilateral difference of the length and midsagittal inclination angle of the lines has significant correlation with chin deviation (p<0.05).
CONCLUSION
The new alternate spherical coordinate system was able to effectively evaluate facial lines. The bilateral difference of lengths and midsagittal inclination of the facial lines might contribute to the facial asymmetry in mandibular prognathism individuals.

Keyword

Prognathism; Face; Tomography, X-ray Computed; Quantitative Evaluation

MeSH Terms

Chin
Evaluation Studies as Topic
Facial Asymmetry
Humans
Prognathism
Tomography, X-Ray Computed

Figure

• 

  Fig. 1 A mandibular prognathism individual. Three orthogonal planes were established, and facial lines were identified. A. The chin deviation was 12.95°. The ramus lateral (RL) was identified with the most lateral points of condyle and of gonoin area. B. The longitude of the ramus (LR) was identified with the most superior point of condyle and the most inferior point of gonion area, and the ramus posterior (RP) with the most posterior points of condyle and gonion area. C. The mandibular body (MB) was identified with menton and the most posterior point of gonion area.

• 

  Fig. 2 A. An alternate spherical coordinate system (v, θ, φ) for 3D evaluation of the longitude of ramus (Cdsup-Goinf) as an example, where v is the length, θ the midsagittal inclination angle, φ the coronal inclination angle. B. This picture shows the alternate spherical coordinate system of the longitude of the ramus of the patient in Figure 1.

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