[Associations between salivary melatonin and periodontal disease: a systematic review and meta-analysis].

THE AIMS OF THE STUDY: To perform systematic search, qualitative and quantitative synthesis of the scientific evidence on the associations between melatonin levels in saliva in patients with periodontitis and healthy individuals. MATERIAL AND METHODS: In accordance with the PRISMA-2020 guidelines, we conducted a systematic search of scientific publications in Russian and English using PubMed and eLibrary.Ru sources. A total of 252 papers were identified. Finally, 20 studies were included in qualitative synthesis. Meta-analysis was performed using the random effects model with Cohen's d as the effect size measure. RESULTS: Twenty selected articles were published between 2003 and 2023. In 10% of the papers, patients with periodontitis had higher concentrations of melatonin in saliva compared to healthy individuals. However, most of the studies reported the opposite. According to the results of the meta-analysis, the melatonin level in individuals with periodontitis was lower than in healthy subjects: the overall effect was -1.90 (95% CI: -3.47; -0.34). High level of heterogeneity was noted (I(2)=96.5%). CONCLUSIONS: The results suggest that lower concentrations of salivary melatonin were associated with periodontitis. However, high variability of concentrations of melatonin in saliva and heterogeneity of the effects across individual studies warrant further research using larger samples.