Korean J Orthod.  2010 Jun;40(3):134-144. 10.4041/kjod.2010.40.3.134.

Three dimensional analysis of the upper airway and facial morphology in children with Class II malocclusion using cone-beam computed tomography

• Hong JS
• Kim DS
• Oh KM
• Kim YJ
• Lee KH
• Park YH

• KMID: 1459567
• DOI: http://doi.org/10.4041/kjod.2010.40.3.134

Abstract

OBJECTIVE
The aim of this study was to evaluate the volumes and areas of the upper airways in children with Class II malocclusion, using three dimensional cone-beam computed tomography (CBCT) and to compare the volumetric and cross-sectional measurements and cephalometric variables to investigate possible relationships between the upper airway and facial morphology.
METHODS
CBCT scans were obtained from 37 subjects (17 boys and 20 girls; average age, 11.02 years). The upper airway volumes and areas were measured, and compared with cephalometric variables.
RESULTS
The area of the PNS-posterior plane (SPP) was significantly smaller in the Class II malocclusion group (p < 0.05). Also, the volumetric and cross-sectional measurements were lower in Class II than in Class I malocclusion groups, although the differences were not significant between the two groups (p > 0.05). The Class II malocclusion group showed significantly smaller values of PFH, mandibular body length, pog to N perp and showed larger values of FMA, ANB, and facial convexity than the Class I malocclusion group. The volume of the upper airway in front of PNS point (WN) showed negative correlation with ANB (p < 0.05).
CONCLUSIONS
The Class II malocclusion group had a narrower upper airway associated with a decreased posterior facial height and a divergent growth pattern than the Class I malocclusion group.

Keyword

Upper airway; CBCT; Class II malocclusion; Facial morphology

MeSH Terms

Child
Cone-Beam Computed Tomography
Humans
Malocclusion

Figure

• 

  Fig. 1 The three-dimensional image was reoriented, using the FH plane as its horizontal reference plane. The FH plane was constructed from the right and left porions (Po(R), Po(L)) and the right orbitale (Or(R)).

• 

  Fig. 2 Reference planes and the cross-sectional area measurements of the upper airway. Reference planes: A, ANS plane, the coronal plane passing through the anterior nasal spine (ANS); B, PNS plane, the coronal plane passing through the posterior nasal spine (PNS); C, PNS-posterior plane, the coronal plane passing through the point on the anterior pharyngeal wall extending from PNS (PNS-posterior); D, PNS-axial plane, the axial plane perpendicular to the coronal plane from PNS. The cross-sectional area measurements of these planes: the ANS plane area (SA), the PNS plane area (SP), the PNS-posterior plane area (SPP), the PNS-axial plane area (SPA).

• 

  Fig. 3 Upper airway volumetric measuremets. To isolate the space of the airway, the threshold value was set at a range of -1,024 to -300 Hounsfield units. The airway was sculpted to be isolated and divided into two parts by the PNS plane; the volume of the upper airway in front of PNS point (WN), the volume of the upper airway just behind of PNS point (WP). Volumetric measurements were carried out using InVivoDental software (Anatomage Inc., San Jose, CA, USA).

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  Fig. 4 Two-dimensional cephalometric images were derived from the three dimensional CT scans by creating an orthogonal projection with parallel rays.

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  Fig. 5 Cephalometric measurements used in this study. 1, A to N perp; 2, Pog to N perp; 3, facial convexity; 4, mandibular body length; 5, ANB; 6, gonial angle; 7, anterior facial height; 8, posterior facial height; 9, FMA; 10, Ba-SE-FMN.

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