Effect of smoking on concentrations of RANKL and OPG in human gingival crevicular fluid.

Background and Objective: Smoking is one of the major risk factors for chronic periodontitis. However, the mechanisms involved in tissue degradation due to cigarette smoking are not clear. Receptor activator of nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) are a system of molecules that regulate bone resorption. The aim of this study was to compare the levels of soluble RANKL (sRANKL), OPG and their relative ratio in GCF among periodontitis patients with varying smoking histories. Material and Methods: GCF samples were collected from 149 periodontitis patients who were never smokers (n=58), former smokers (n=39) and current smokers (n=52). sRANKL and OPG concentrations in GCF were measured by enzyme-linked immunosorbent assays. Results: sRANKL, OPG and their relative ratio were not statistically significant among the never smokers, former smokers and current smokers. However, OPG was significantly reduced and subsequently the sRANKL:OPG ratio was significantly increased in the high pack-years group as compared with never smokers. The positive correlation between packyears and sRANKL:OPG ratio was statistically significant even after adjusting for age and current smoking status. Conclusion: Increased lifetime exposure to cigarette smoking above a minimum threshold suppresses OPG production and leads to increased sRANKL:OPG. This may partially explain increased bone loss in smoking-related periodontitis.Thesis (D.Clin.Dent.) - University of Adelaide, School of Dentistry, 200