Korean J Orthod.  2020 Mar;50(2):129-135. 10.4041/kjod.2020.50.2.129.

Immediate effects of mandibular posterior displacement on the pharyngeal airway space: A preliminary study

• Choi Y
• Kim YI
• Kim SS
• Park SB
• Son WS
• Kim SH

• KMID: 2471873
• DOI: http://doi.org/10.4041/kjod.2020.50.2.129

Abstract

OBJECTIVE
This study aimed to evaluate the immediate effects of mandibular posterior displacement on the pharyngeal airway space (PAS) by using cephalometric evaluations and to investigate how the surrounding structures are schematically involved.
METHODS
In this retrospective study, 38 subjects with functional Class III malocclusion and two lateral cephalograms were selected. The first lateral cephalogram was taken with the mandible in the habitual occlusal position, and the second in anterior edge-to-edge bite. Paired t-test was used to analyze changes in the PAS, hyoid bone, tongue, and soft palate, followed by mandibular posterior displacement. Pearson's correlation analysis was used to determine the relationship between the amount of mandibular posterior displacement and other variables.
RESULTS
A statistically significant decrease was observed in the PAS following mandibular posterior displacement. Along with mandibular posterior displacement, the tongue decreased in length (p < 0.001) and increased in height (p < 0.05), while the soft palate increased in length, decreased in thickness, and was posteriorly displaced (p < 0.001). The hyoid bone was also posteriorly displaced (p < 0.05). There was no correlation between the amount of mandibular posterior displacement and the measured variables.
CONCLUSIONS
The PAS showed a statistically significant decrease following mandibular posterior displacement, which was a consequence of retraction of the surrounding structures. However, there were individual variances between the amount of mandibular posterior displacement and the measured variables.

Keyword

Lateral cephalogram; Airway; Mandibular posterior displacement

MeSH Terms

Hyoid Bone
Malocclusion
Mandible
Palate, Soft
Retrospective Studies
Tongue

Figure

• 

  Figure 1 Two lateral cephalograms. A, In the habitual occlusal position. B, In the anterior edge-to-edge bite.

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  Figure 2 Cephalometric landmarks.S, Sella; N, nasion; Po, porion; Or, orbitale; PNS, posterior nasal spine; ANS, anterior nasal spine; A, point A; B, point B; Go, gonion; Me, menton.See Table 2 for definitions of the other landmarks.

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  Figure 3 Changes in the pharyngeal airway space after mandibular posterior displacement.NS, Not significant.*p < 0.05, ***p < 0.001.

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  Figure 4 Changes in the surrounding structures after mandibular posterior displacement. Gray arrow, Changes in the mandible; Black arrows, changes in the tongue, soft palate, and hyoid bone.

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