Consistency in staging, grading, and extent of periodontitis diagnosis: A cross-sectional online-based assessment among Indonesian periodontics specialist students.

Periodontitis remains a significant global health burden, and its accurate diagnosis is critical for effective management. The 2018 classification system for periodontitis introduces staging, grading, and extent parameters to enhance diagnostic consistency, but its application among trainees remains underexplored. This study evaluates the consistency of staging, grading, and extent diagnosis of periodontitis among Indonesian periodontics specialist students using the 2018 classification system, highlighting challenges and variability in interpretation. A total of 41 students across different training levels participated in the study, classifying 5 clinical cases based on comprehensive diagnostic materials, including radiographs, periodontal charts, and medical histories. Diagnostic concordance with gold-standard diagnoses was assessed and using Fleiss Kappa for inter-reliability analysis. Agreement rates were 56.10% for staging (Fleiss' Kappa = 0.170, 95% CI: 0.145-0.196), 76.10% for grading (Kappa = 0.210, 95% CI: 0.185-0.235), and 74.15%. for extent (Kappa = 0.168, 95% CI: 0.144-0.192). Overestimation of severity occurred in 35.12% of staging decisions, while 20.93% of cases were underestimated in grading. Diagnostic variability was greatest in borderline cases. Indonesian periodontics specialist students demonstrated fair consistency in grading but poor agreement in staging and extent compared with expert consensus. These findings highlight the need for enhanced calibration exercises and curriculum reform to improve diagnostic reliability. Multi-institutional studies with larger cohorts are recommended to further validate these findings.