Spatiotemporal quantification of gingival crevicular fluid NLRP3 expression during non-surgical endodontic management of pulp necrosis with symptomatic apical periodontitis: A prospective case-control analysis

Objective: To evaluate gingival crevicular fluid (GCF) NOD-like receptor protein 3 (NLRP3) levels in pulp necrosis (PN) with symptomatic apical periodontitis (SAP) before and after non-surgical endodontic therapy (NSET) and compare them with periodontally healthy controls. Methods: GCF samples were collected from healthy controls (n = 30) and patients with PN and SAP (n = 30) at baseline and one-week following standardized two-visit NSET. Sampling was performed at three sites per patient: the involved tooth, contralateral and adjacent teeth. NLRP3 concentrations were quantified using enzyme-linked immunosorbent assay. Data distribution and variance assumptions were verified using Anderson-Darling and Levene's tests. Between-group and between-site differences were evaluated using unpaired t-tests and analysis of covariance, with longitudinal and clustered observations modelled using linear mixed-effects analysis. Diagnostic performance was examined using receiver operating characteristic (ROC) analysis. Results: Baseline NLRP3 concentrations were significantly higher at involved sites than in controls (adjusted mean difference 3.97 ng/mL; 95% CI 3.82-4.12; p < 0.05), and were also elevated at adjacent sites (1.11 ng/mL; 95% CI 0.98-1.24; p < 0.05). One week after NSET, a significant reduction was observed at involved sites (0.32 ng/mL; 95% CI 0.17-0.47; p < 0.05). Significant differences were detected across the three sampled locations (adjusted mean differences 2.93, 4.01, and 1.08 ng/mL). ROC analysis indicated excellent discriminatory ability (AUC = 1.0), with an optimal baseline threshold >2 ng/mL. Conclusions: Within the limitations of this exploratory clinical study, GCF NLRP3 levels were elevated in PN with SAP and decreased following NSET, supporting its potential role as a candidate inflammatory biomarker.