Bruxism and Stress: Ultrasonographic Masseter Muscle Assessment and Salivary Melatonin-Cortisol Dynamics

Bruxism is a parafunctional activity characterised by teeth grinding or clenching, often associated with stress and neurophysiological factors. Its aetiology is multifactorial, with recent studies emphasising neurotransmitters and hormonal imbalances, particularly melatonin and cortisol. This study assesses masseter muscle thickness using ultrasonography and examines the relationship between salivary melatonin and cortisol levels in bruxism.

This study aimed to evaluate the ultrasonographic characteristics of the masseter muscle in individuals with bruxism and investigate the association between salivary melatonin and cortisol levels.

This cross-sectional study included 80 participants (38 bruxists, 42 controls), aged 20-25 years. Bruxism was diagnosed through clinical examination and self-reported questionnaires. Masseter muscle thickness was measured via ultrasonography in relaxed and contracted states. Salivary melatonin and cortisol levels were analysed using enzyme-linked immunosorbent assay (ELISA). Group comparisons were conducted using independent t-tests and ANOVA, with correlation analyses using Pearson's tests.

Salivary melatonin levels showed no significant difference between groups (p = 0.067), while salivary cortisol levels were significantly higher in the bruxism group (p = 0.001). No significant differences in masseter muscle thickness were observed in either state (p > 0.05). A weak but significant positive correlation existed between melatonin and cortisol levels (p < 0.05).

Although not statistically significant, melatonin levels tended to be higher in bruxist patients, possibly due to a negative feedback mechanism to prevent the side effects of cortisol such as oxidative stress or a balancing process of these hormones by cytokines involved such as IL-1β.