TNFSF11 and major depressive disorder: This study aimed to evaluate salivary concentrations of Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL) and Osteoprotegerin (OPG)-key regulators of osteoclast activity and periodontal bone resorption-in patients with periodontitis and depression.<h4>Materials and methods</h4>In this cross-sectional study, 80 patients from Shahid Beheshti University Dental School were categorized into four groups based on the presence or absence of periodontitis and depression.