Associations between mandibular symphysis form and craniofacial structures

Objectives

This study aimed to (1) analyze the relationships between mandibular symphysis characteristics (height, prominence, inclination, concavity, and convexity) and facial pattern, skeletal class, lower incisor position, and sex, and (2) determine the associations between the symphysis soft tissue dimensions and the underlying osseous structures.

Methods

Cone-beam computed tomography (CBCT) images were selected for 385 patients (206 women and 179 men). The patients were classified according to their skeletal class and vertical pattern. The lower incisor inclination (IMPA) was recorded. Twelve measurements were taken for each mandibular symphysis using Invivo5 software (Anatomage, San Jose, CA, USA).

Results

Symphyseal measurements were larger in males than in females. Skeletal Class II and III hyperdivergent patients showed the highest symphysis height values. Hypodivergent individuals showed lower symphysis convexity angles. Concavity of the symphysis was greater for Class II hyperdivergent patients. Lower incisor inclination showed a positive correlation with symphysis concavity and inclination. Moderate and weak correlations were found between hard tissue and soft tissue parameters.

Conclusions

Only a few characteristics of symphysis morphology depend on sex, incisor position, skeletal class, and vertical pattern. More significant relationships are found when the vertical pattern and skeletal class are analyzed in combination. The shape of the symphysis soft tissue is not directly correlated with the underlying skeletal structures.