Salivary Melatonin Change in Oral Lichen Planus Patients: A Pilot Study

Objective: Melatonin, a chronobiotic hormone, exerts a variety of biological functions. Very few studies of melatonin in the human oral mucosal tissues and oral diseases under chronic inflammation have been reported. This study aimed to investigate and assess the salivary melatonin levels in oral lichen planus (OLP), a chronic inflammatory disease affecting the oral mucosal surfaces and presenting with varied oral symptoms and clinical presentations. Methods: The study included 60 patients divided into four groups: healthy controls (15), periodontitis (15), keratotic oral lichen planus (K-OLP; 15), and non-keratotic oral lichen planus (NK-OLP; 15). Pocket depth and interdental clinical attachment loss were measured in all the patients. Unstimulated saliva samples were collected, centrifuged, and analyzed for melatonin using an enzyme-linked immunosorbent assay (ELISA) kit for all patients. Results: Salivary flow rate and salivary melatonin level consistently decreased from healthy controls to periodontitis, K-OLP, and NK-OLP. The salivary melatonin difference was more between controls and NK-OLP (p<0.05). Periodontitis patients showed more difference in pocket depth and interdental clinical attachment loss than other groups. Conclusions: Decreased salivary flow and melatonin levels in OLP patients imply that salivary melatonin cytoprotective action in chronic inflammation-generated oxidative stress is interrupted. Hence, such alteration can affect the oral mucosa of OLP patients and contribute to various clinical and oral symptoms.