Perforating external root resorption with periodontal-derived osseous ingrowth: a radiographic mimic of internal replacement resorption.

OBJECTIVE

Intraradicular mixed radiolucent and radiopaque changes within the root canal space are often diagnosed as internal replacement resorption. However, radiographs alone cannot confirm tissue origin or periodontal-endodontic communication. This study examined whether perforating external root resorption can establish a trans-radicular portal, permit periodontal-derived osseous ingrowth, and produce a radiographic mimic of internal replacement resorption.

METHODS

This observational clinico-radiographic and histomorphological correlation study analysed 97 extracted permanent teeth in two cohorts: 44 carious teeth with pulpal infection and intraradicular resorption, and 53 anterior teeth with dental trauma. Assessment was performed with periapical radiographs and cone beam computed tomography (CBCT). Extracted teeth underwent serial sectioning and light microscopy, with bacterial staining when required.

RESULTS

In the caries cohort, intraradicular resorption occurred in an infected, inflamed environment. Two teeth showed progressive internal inflammatory resorption with bacteria in dentinal tubules and necrotic tissue at the resorptive interface. No organised lamellar bone was identified in the canal space. In the trauma cohort, pulp canal obliteration was frequent. Four teeth showed a mixed radiolucent-radiopaque intraradicular pattern that radiographically mimicked internal replacement resorption. Serial CBCT and histology demonstrated a full-thickness portal linking the periodontal and endodontic compartments. Trabecular lamellar bone and marrow-like spaces were identified within the canal. Bacteria were absent in these cases.

CONCLUSIONS

Some trauma-associated lesions diagnosed radiographically as internal replacement resorption are better interpreted as perforating external root resorption with periodontal-derived osseous ingrowth. Diagnosis, prognosis, and treatment planning should prioritise detection of trans-radicular communication using serial CBCT interpretation.

CLINICAL SIGNIFICANCE: Trauma-related lesions that resemble internal replacement resorption may instead represent perforating external root resorption with periodontal-derived bone ingrowth. Careful serial CBCT review is therefore essential to identify trans-radicular communication, avoid misdiagnosis, refine prognosis, and guide management.