Internal Resorption: A Retrospective Cone-Beam Computed Tomography Analysis of 50 Cases With Outcome Assessment

Internal resorption is a rare condition that may complicate endodontic treatment and tooth retention strategies. There is a lack of information in the literature on the nature of these lesions, as well as prognosis after treatment. The aims of this study were to determine which factors may be associated with treatment outcomes, and to identify and characterise clinical and radiographic features of internal resorption lesions.

A retrospective chart review was conducted to identify cases of internal resorption at the Tufts University School of Dental Medicine Postgraduate Endodontic Clinic between the years of 2010 and 2025. All cases of internal resorption were required to have a periapical radiograph and cone-beam computed tomography (CBCT) scan of the tooth in question. Lesion characteristics were independently judged by two calibrated board-certified endodontists. Inter-observer agreement was calculated using kappa statistics, weighted kappa statistics, and intraclass correlation coefficients. One-, five-, and seven-year outcomes were determined. Statistical analysis was performed to assess associations using Fisher's exact test. No funding was provided for this study.

Fifty internal resorption cases were identified. 98% were classified as internal inflammatory resorption and 2% as internal replacement resorption. Lesions were most frequent in first molars and maxillary central incisors. Perforation was present in 36% of cases. Twenty-six teeth had ≥ 1-year of follow-up; survival and success rates were 88% and 83.3%, respectively. Teeth with a pulpal diagnosis of 'normal pulp' (p = 0.003) or periapical diagnosis of 'normal apical tissues' (p = 0.031), as well as those in female patients (p = 0.032), were significantly more likely to fail at 1 year. No significant association was found between perforation and treatment outcome. Inter-observer agreement was high across all lesion parameters.

Internal resorption lesions can be successfully treated with contemporary endodontic techniques. Increased risk of failure may be found in teeth with a vital pulp and absence of periapical signs or symptoms of disease due to their capacity for continued growth, or those found in female patients. Traumatised teeth are more likely to present with lesions in the middle third. Future prospective studies with larger samples will further refine treatment strategies and identify prognostic indicators.