Korean J Orthod.  2019 May;49(3):170-180. 10.4041/kjod.2019.49.3.170.

Relationship between the maxillofacial skeletal pattern and the morphology of the mandibular symphysis: Structural equation modeling

• Ahn MS
• Shin SM
• Yamaguchi
• Maki K
• Wu TJ
• Ko CC
• Kim YI

• KMID: 2450226
• DOI: http://doi.org/10.4041/kjod.2019.49.3.170

Abstract

OBJECTIVE
The purpose of this study was to investigate the relationship between the facial skeletal patterns and the shape of the mandibular symphysis in adults with malocclusion by using a structural equation model (SEM).
METHODS
Ninety adults who had malocclusion and had records of facial skeletal measurements performed using cone-beam computed tomography were selected for this study. The skeletal measurements were classified into three groups (vertical, anteroposterior, and transverse). Cross-sectional images of the mandibular symphysis were analyzed using generalized Procrustes and principal component (PC) analyses. A SEM was constructed after the factors were extracted via factor analysis.
RESULTS
Two factors were extracted from the transverse, vertical, and anteroposterior skeletal measurements. Latent variables were extracted for each factor. PC1, PC2, and PC3 were selected to analyze the variations of the mandibular symphyseal shape. The SEM was constructed using the skeletal variables, PCs, and latent variables. The SEM showed that the vertical latent variable exerted the most influence on the mandibular symphyseal shape.
CONCLUSIONS
The relationship between the skeletal pattern and the mandibular symphysis was analyzed using a SEM, which showed that the vertical facial skeletal pattern had the highest effect on the shape of the mandibular symphysis.

Keyword

Structural equation model; Morphology of mandibular symphysis; Facial skeletal pattern

MeSH Terms

Adult
Cone-Beam Computed Tomography
Humans
Malocclusion

Figure

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  Figure 1 Obtaining the landmarks for the mandibular symphysis cross-sectional images. The outline of the mandibular symphysis is considered for the external (A) and internal (B) cortices. Two landmarks (yellow) and 21 semi-landmarks (red) are positioned along the outline of the mandibular cortex.

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  Figure 2 Principal component (PC) analysis of the internal cortices of the mandibular symphysis. M, Mean; SD, standard deviation.

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  Figure 3 Principal component (PC) analysis of the external cortices of the mandibular symphysis. M, Mean; SD, standard deviation.

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  Figure 4 Structural equation model of the skeletal factors and mandibular cortices of the symphysis. The double and dotted arrows show the relationship of the vertical, horizontal, and anteroposterior latent variables. PC, Principal component.

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