Evaluation of the Relationship Between Bruxism and Tryptophan Metabolites: A Case–Control Study

Background: Bruxism has garnered increasing attention in both clinical practice and scientific research, underscoring its significance for patient management and understanding of its pathophysiology. Objective: This study aims to investigate the potential relationship between tryptophan metabolites and bruxism. Methods: The patients were divided into bruxism and non-bruxism groups. The bruxism group was determined according to the bruxism and Diagnostic Criteria for Temporomandibular Disorders classifications. Patients who did not fit either classification were classified as a non-bruxism group. Demographic data of all patients, maximum clinical interincisal opening (IO), state and trait anxiety levels (STAI), perceived stress (PS) levels, Oral Health Impact Profile-14, and pain on palpation (PoP) were recorded. Laboratory findings included measurements of tryptophan and its metabolites. Results: A total of 97 participants volunteered; 49 had non-bruxism, and 48 had bruxism. There were no differences between the two groups in demographic findings. In clinical findings, a difference was found between the two groups in PS (p = 0.048), IO (p < 0.01), STAI-S (p < 0.01), and PoP (p < 0.01). Regarding laboratory findings, lower kynurenine levels (p < 0.01) and higher quinolinic acid levels (p < 0.01) were found in patients in the bruxism group. Conclusions: The findings suggest a possible role of TRP metabolites in the pathophysiology of bruxism. In particular, alterations in quinolinic acid and kynurenine may provide insight into the metabolic mechanisms involved. However, these results should be interpreted with caution, and further studies are warranted to confirm and expand upon these associations. Trial Registration: ClinicalTrials.gov identifier: NCT05760482.