Comparison of RANKL and osteoprotegerin levels in the gingival crevicular fluid of young cigarette- and waterpipe-smokers and individuals using electronic nicotine delivery systems

Objective: The aim of the present observational case-control study was to compare the levels of Receptor activator of NF-kappa B ligand (RANKL) and osteoprotegerin (OPG) in the gingival crevicular fluid (GCF) of cigarette- and waterpipe-smokers and electronic-nicotine-delivery-systems (ENDS)-users. Methods: Demographic data was collected using a questionnaire. Clinical periodontal parameters (plaque index [PI], bleeding on probing [BOP], probing depth [PD] and clinical attachment loss [CAL]) were measured; and GCF samples were collected from the deepest periodontal pocket of the mandibular right first molar. The GCF volume was determined and levels of RANKL and OPG were determined. Group comparisons were performed and P < 0.05 was considered statistically significant. Results: One hundred and twenty male individuals (30 cigarette-smokers, 30 waterpipe users, 30 ENDS-users and 30 non-smokers) were included. Scores of PI (P < 0.01) and PD (P < 0.01) were significantly higher among cigarette- and waterpipe smokers, and ENDS-users than non-smokers. The GCF volume was significantly higher among cigarette- (0.92 +/- 0.05 mu l) (P < 0.01) and waterpipe-smokers (0.66 +/- 0.08111) (P < 0.001) and ENDS-users (0.62 +/- 0.03 mu l) (P < 0.01) than non-smokers (0.21 +/- 0.007 mu l). The GCF RANKL levels were significantly higher among cigarette- (14.9 +/- 8.2 pg/ml) (P < 0.001) and waterpipe-smokers (12.6 +/- 8.8 pg/ ml) (P < 0.01) and ENDS-users (11.5 +/- 8.4 pg/ml) (P < 0.01) than non-smokers (3.5 +/- 0.7 pg/ml). The GCF OPG levels were significantly higher among cigarette- (95.9 +/- 7.2 pg/ml) (P < 0.001) and waterpipe-smokers (86.6 +/- 5.8 pg/ml) (P < 0.01) and ENDS-users (77.5 +/- 3.4 pg/ml) (P < 0.05) than non-smokers (21.5 +/- 10.7 pg/ml). There was no significant difference in GCF RANKL and OPG levels among cigarette- and waterpipe smokers, ENDS users. Conclusion: Cigarette- and waterpipe smoking and ENDS usage is associated with an increased expression of RANKL and OPG in the GCF.