The goal of this observational study is to evaluate salivary biomarkers and perceived stress in adults with bruxism compared with healthy individuals. The study aims to determine whether salivary cortisol, immunoglobulin A (IgA), free kappa light chain (FLC-κ), free lambda light chain (FLC-λ), total free light chains, and perceived stress levels differ between individuals with bruxism and healthy controls. The main questions it aims to answer are:

• Do salivary cortisol, IgA, FLC-κ, FLC-λ, and total free light chain levels differ between individuals with bruxism and healthy controls?
• Is perceived stress associated with changes in salivary biomarkers in individuals with bruxism? Researchers will compare participants with bruxism and healthy control participants to evaluate differences in salivary biomarker levels and perceived stress.

Participants will:

• undergo a clinical examination for the diagnosis of bruxism or confirmation of healthy status;
• complete the Perceived Stress Scale (PSS-14) questionnaire;
• provide an unstimulated saliva sample for laboratory analysis of cortisol, IgA, free kappa light chain, free lambda light chain, and total free light chains.

Bruxism is a repetitive jaw-muscle activity characterized by clenching or grinding of the teeth and/or bracing or thrusting of the mandible during sleep or wakefulness. Increasing evidence suggests that psychological stress and neuroendocrine mechanisms may contribute to the development and progression of bruxism. Salivary biomarkers provide a non-invasive approach for evaluating physiological responses related to stress, immune function, and inflammation.

The purpose of this observational case-control study is to investigate whether salivary cortisol, immunoglobulin A (IgA), free kappa light chain (FLC-κ), free lambda light chain (FLC-λ), total free light chains, and perceived stress differ between individuals with bruxism and healthy controls. The study also aims to evaluate the relationship between perceived stress and salivary biomarker levels in individuals with bruxism.

Participants diagnosed with bruxism healthy control participants will undergo a standardized clinical examination. Perceived stress will be assessed using the Perceived Stress Scale (PSS-14). Unstimulated whole saliva samples will be collected under standardized conditions and analyzed for cortisol, IgA, free kappa light chain, free lambda light chain, and total free light chain concentrations using validated laboratory methods.

The results of this study are anticipated to enhance the understanding of the biological mechanisms involved in bruxism and to determine if salivary biomarkers can be used as objective markers of stress-related changes in bruxism patients.

Inclusion Criteria:

• Adults aged 25 to 50 years.
• Systemically healthy individuals.
• Presence of no more than four-unit fixed partial dentures.
• Absence of clinical signs of oral inflammation.
• Good oral hygiene.
• Individuals diagnosed with bruxism according to the study diagnostic criteria (bruxism group) or healthy volunteers without signs or symptoms of bruxism (control group).
• Ability and willingness to provide written informed consent.

Exclusion Criteria:

• Use of medications that may affect the nervous system or salivary gland function (e.g., benzodiazepines, antidepressants).
• Psychiatric disorders.
• Epilepsy.
• Diabetes mellitus or other pancreatic diseases.
• Current corticosteroid therapy.
• Cushing syndrome or Addison disease.
• Pregnancy.
• Current smoking.
• Alcohol or substance abuse.
• History of facial trauma.
• Rheumatic muscle or joint disorders.
• Degenerative joint disease.
• Migraine.
• Use of medications affecting sleep or motor activity.
• Recent history of occlusal splint therapy.
• Salivary gland disorders, including Sjögren syndrome or autoimmune sialadenitis.

The study population consisted of adults with clinically diagnosed bruxism and age- and sex-matched healthy control participants recruited from the Faculty of Dentistry. All participants underwent clinical examination, completed the Perceived Stress Scale (PSS-14), and provided unstimulated saliva samples for biomarker analysis.