# Magnetic Resonance Imaging of Submental and Masticatory Muscle Morphology and Its Relationship with Temporomandibular Joint Structures

## TL;DR

This study uses MRI and CT scans to show how the thickness of certain facial muscles is linked to jaw joint structures and issues like disc displacement.

## Contribution

The study identifies specific correlations between masticatory/submental muscle thickness and TMJ structures, suggesting a functional link.

## Key findings

- Right digastric and mylohyoid muscles correlated with disc–condyle position (p = 0.02 and p = 0.004).
- Left medial pterygoid and masseter muscles correlated with left condyle pathology (p = 0.02 and p = 0.014).
- Condylar flattening was most common, affecting 58% of right and 53% of left condyles.

## Abstract

Introduction: This study aimed to evaluate the submental and masticatory muscles in patients of different age groups using magnetic resonance imaging (MRI) and computed tomography (CT) methods, and investigate potential associations between muscle morphology, temporomandibular joint (TMJ) structures, and disc displacement. Materials and Methods: A total of 185 MRI scans were retrospectively analyzed to assess the thickness of the digastric, geniohyoid, mylohyoid, medial pterygoid, masseter, and lateral pterygoid muscles bilaterally. TMJ hard tissue changes were classified using computed tomography (CT). Correlations between muscle thickness and TMJ structures were analyzed using Pearson correlation coefficients, with statistical significance set at p < 0.05. Results: The study population included 110 females and 75 males, with a mean age of 50.08 ± 20.15 years. The largest age group was 51–75 years (41%), followed by 18–35 years (28%). Significant correlations were observed between muscle thickness and TMJ structures as follows: Right digastric muscle showed a significant association with right disc–condyle position (p = 0.02). Right mylohyoid muscle exhibited a strong correlation with right disc–condyle position (p = 0.004). Left medial pterygoid muscle was significantly correlated with left condyle pathology (p = 0.02). Left masseter muscle showed a significant correlation with left condyle pathology (p = 0.014). Condylar flattening was the most frequent pathology, observed in 58% of right condyles and 53% of left condyles. Disc displacement was present in 41% of right TMJs and 34% of left TMJs. Conclusions: This study highlights the important associations between masticatory and submental muscle morphology and TMJ structures, suggesting that muscle function may play a role in condylar positioning and disc alignment. These findings emphasize the need for comprehensive muscle evaluation in TMJ disorder (TMD) diagnosis and treatment planning.