Clinical, radiological and histological diagnoses of periapical periodontitis spreading to the adjacent tooth: A case of endodontic failure

Aims: This article describes the apical infection in endodontically treated tooth 4.5 that spread to adjacent tooth 4.4. Case Report: A 52-year-old woman was referred for the presence of radiolucency extending from tooth 4.5 and mental foramen. Spontaneous symptoms were present. Tooth 4.5 showed poor-quality endodontics. The vitality of tooth 4.4 was negative, even though no mechanical trauma had been reported, nor was caries present. Both teeth were sensitive to percussion. Endodontic re-treatment of 4.5 and endodontic treatment of 4.4 were performed in a single visit. A large amount of endodontic sealer squeezed mesially from the root of tooth 4.5, where a partial horizontal root fracture was hypothesized. 6-, 12-, and 18-month radiographic follow-ups, by both periapical and cone-beam computed tomography (CBCT) analyses, showed incomplete osseous healing. CBCT excluded root fracture on 4.5. Local symptoms were still present. Clinical and radiological conditions led to extractions, and a cystic lesion was enucleated for histopathologic analyses. Histopathologic diagnosis was a periapical cyst. The supposed partial horizontal root fracture of 4.5 was actually a large lateral canal. Although the root canal treatments followed high standards in terms of quality, a persistent chronic infection developed histologically. The cystic lesion was one consistent reason for the unsuccessful healing of 4.5.