Doğan SB, Dede FO, Ballı U, et al. - In the present study, the researchers sought to examine changes in the levels and relative ratios of interleukin-34 (IL-34), osteoprotegerin (OPG), and receptor activator of nuclear factor -kB ligand (RANKL) in the gingival crevicular fluid (GCF) of patients with periodontitis before and after non-surgical periodontal treatment (NSPT). There were 20 healthy participants (CTRL), 20 patients with stage 3-grade B periodontitis, and 20 patients with stage 3-grade C periodontitis. GCF IL-34 levels were high in periodontitis patients and decreased after NSPT, and it had a positive correlation with RANKL/OPG ratio levels, clinical attachment level, and gingival index. Determining IL-34 levels in GCF in conjunction with the RANKL/OPG ratio may thus be useful in identifying high-risk individuals with periodontitis.