Objective: To assess the radiographic quality of root canal fillings performed by residents from the third and fourth cohorts of the Postgraduate Program in Endodontics at Universidad de Los Hemisferios between October 2024 and April 2026. Materials and methods: This observational, retrospective, cross-sectional study included descriptive analyses and an exploratory analytical component. We analyzed 680 root canal records from 398 digital periapical radiographs of primary endodontic treatments. The principal investigator performed the initial classification, and an endodontist independently assessed the records to determine interobserver agreement. We evaluated the technical quality of root canal fillings by length, density, and taper, and classified them as adequate or inadequate. Statistical analyses included frequency distributions, chi-square tests, Cramér’s V, Cohen’s kappa, and Gwet’s AC1 for taper. 

Results: Overall technical quality was adequate in 575 root canals (84.6%). Filling length was adequate in 86.9% of canals, filling density was homogeneous in 97.6%, and taper was adequate in 98.5%. Filling material extending beyond the apex was observed in 12.5% of canals, gutta-percha extrusion in 0.9%, and sealer extrusion (“sealer puff”) in 11.8%. The exploratory analysis identified a weak association between tooth group and overall filling quality (χ² (5) = 11.354; p = 0.045; Cramér’s V = 0.129; 95% CI: 0.078–0.232). Interobserver agreement for overall filling quality was substantial (κ = 0.763; 95% CI: 0.692–0.834).

Conclusions: The overall radiographic quality of root canal fillings was favorable. Filling length was the main parameter requiring improvement. These findings should be interpreted in light of the retrospective design and the potential dependence among root canals belonging to the same tooth, patient, or resident.