Potential of Salivary IL-36γ, IL-38, and RANKL in Differentiating Periodontal Health from Periodontitis

Objective: To evaluate the diagnostic potential of combined salivary biomarkers RANKL, IL-36γ, and IL-38 in distinguishing individuals with generalized unstable periodontitis from those with a healthy periodontium, by analyzing their concentrations and correlation with clinical periodontal parameters. Material and Methods: A total of 120 participants were included in this case-control study, comprising 90 subjects with generalized unstable periodontitis and 30 periodontally healthy controls. Clinical periodontal measurements, PI, PPD, CAL, and BOP, were recorded. Before data collection, inter- and intra-examiner calibration were performed on five subjects each, using kappa and intraclass correlation coefficients to ensure measurement reliability (>70% for BOP and >90% for PPD and CAL). Unstimulated saliva samples were collected, preserved in antiprotease solution, and stored on ice, then frozen for laboratory analysis. Salivary concentrations of RANKL, IL-36γ, and IL-38 were measured using ELISA kits. Data analysis included comparison between groups, correlation with clinical parameters, and diagnostic evaluation through sensitivity, specificity, and AUC analysis. Data were analyzed using SPSS v29 and GraphPad Prism v9. Normality was assessed using the Shapiro-Wilk test. Parametric tests (ANOVA, t-test) and non-parametric tests (Kruskal-Wallis, Mann-Whitney) were applied as appropriate. Correlations were evaluated using Spearman’s test. Diagnostic accuracy was assessed through ROC curve analysis and AUC values, with statistical significance set at p < 0.05. Results: RANKL and IL-36γ salivary levels in periodontitis were significantly increased compared to healthy controls, while IL-38 levels were significantly reduced (p < 0.001). RANKL peaked in stage III, while IL-36γ was highest in stage IV. Conversely, IL-38 was consistently lower in both disease stages. Only IL-36γ with CAL correlation was a significant positive, while other clinical correlations were not statistically significant different. ROC analysis demonstrated excellent diagnostic accuracy for all three biomarkers in differentiating periodontal health from disease, with AUC values of 0.944 (RANKL), 0.982 (IL-36γ), and 0.960 (IL-38), along with high sensitivity and specificity. Conclusion: Salivary levels of RANKL, IL-36γ, and IL-38 demonstrated strong potential as non-invasive biomarkers for distinguishing generalized unstable periodontitis from periodontal health. Their diagnostic accuracy supports their utility in early detection and monitoring, although they showed limited ability to differentiate between periodontitis severity stages.