Korean J Orthod.  2010 Jun;40(3):145-155. 10.4041/kjod.2010.40.3.145.

Three dimensional cone-beam CT study of upper airway change after mandibular setback surgery for skeletal Class III malocclusion patients

• Kim NR
• Kim YI
• Park SB
• Hwang DS

• KMID: 1459568
• DOI: http://doi.org/10.4041/kjod.2010.40.3.145

Abstract

OBJECTIVE
Lateral cephalometric radiographs have been the main form of resource for assessing two dimensional anteroposterior airway changes. The purpose of this study was to evaluate the three dimensional volumetric change in the upper airway space in Class III malocclusion patients who underwent mandibular setback surgery.
METHODS
Three dimensional cone-beam computed tomographs (CBCT) and their three dimensional reconstruction images were analyzed. The samples consisted of 20 adult patients (12 males and 8 females) who were diagnosed as skeletal Class III and underwent mandibular setback surgery. CBCTs were taken at 3 stages - Baseline (1.8 weeks before surgery), T1 (2.3 months after surgery), and T2 (1 year after surgery). Pharyngeal airway was separated according to the reference planes and reconstructed into the nasopharynx, the oropharynx and the hypopharynx. Measurements at Baseline, T1, and T2 were compared between groups.
RESULTS
The result showed the volume of the pharyngeal airway decreased significantly 2.3 months after surgery (p < 0.001) and the diminished airway did not recover after 1 year post-surgery. The oropharynx was the most decreased area.
CONCLUSIONS
These findings suggest that mandibular setback surgery causes both short-term and long-term decrease in the upper airway space.

Keyword

Cone-beam computed tomography; Orthognathic surgery; Pharyngeal airway

MeSH Terms

Adult
Cone-Beam Computed Tomography
Humans
Hypopharynx
Male
Malocclusion
Nasopharynx
Oropharynx
Orthognathic Surgery

Figure

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  Fig. 1 Three dimensional image and MPR (multiplanar projection reformat) overlay views of airways. A, Reference planes (PNS-Vp plane, CV1 plane, CV2 plane, CV4 plane); B, volumetric image at nasopharynx area; C, volumetric image at oropharynx area; D, volumetric image at hypopharynx area. PNS, Psterior nasal spine; Vp, the most posterior point of the ala of vomer; CV, cervical vertebrae.

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  Fig. 2 Measurement of mandibular position. Mandibular position was evaluated using anotomical B point at each time period.

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  Fig. 3 Mean pharyngeal volume change. Baseline, Before surgery; T1, 2.3 months after surgery; T2, 1 year after surgery.

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