Abstract
<title>Abstract</title> <p> Objective To investigate the factors influencing sealer overfilling during root canal treatment with the bioceramic sealer iRoot SP using the single-cone technique in teeth with apical periodontitis, thereby providing evidence-based clinical guidance. Methods This retrospective clinical study included 1,963 teeth with apical periodontitis that underwent root canal treatment with iRoot SP using the single-cone technique at the Stomatological Hospital of Xiamen Medical College between December 2019 and December 2024. Patients' clinical and radiographic data were recorded. Univariate analysis and a binary logistic regression model were employed to analyze the incidence and risk factors for sealer overfilling. Results A total of 1,963 teeth with apical periodontitis were included, with an overall overfilling rate of 49.3%. Multivariate logistic regression analysis revealed that operator inexperience (≤ 5 years of clinical working years) ( <italic>OR</italic> = 1.745, 95% <italic>CI</italic> : 1.389–2.193, <italic>P</italic> < 0.001), molar teeth( <italic>OR</italic> = 1.909, 95% <italic>CI</italic> : 1.511–2.412, <italic>P</italic> = 0.000), tooth mobility (Grade I: <italic>OR</italic> = 1.450, 95% <italic>CI</italic> : 1.142–1.843, <italic>P</italic> = 0.02), and a higher Periapical Index (PAI) score, with a clear dose-response gradient ( <italic>P</italic> for trend < 0.001), were independent risk factors for sealer overfilling. Conclusion When using the iRoot SP single-cone technique, sealer overfilling is significantly associated with operator experience, tooth type, tooth mobility, and severe preoperative periapical destruction (high PAI score). Clinicians should be aware of these risk factors—particularly molars, high PAI scores, and tooth mobility—and adopt risk-aware obturation protocols when using iRoot SP with the single-cone technique. </p>