Cone-beam computed tomographic and histological investigation of regenerative endodontic procedure in an immature mandibular second premolar with chronic apical abscess

The aim of the present study was to investigate the tissue generated after regenerative endodontic procedure (REP) in the root canal space of an immature mandibular second premolar with pulp necrosis and chronic apical abscess using cone-beam computed tomographic (CBCT) and histological methods.REP was performed in an immature mandibular second premolar. At the 3-year follow up, CBCT scans were taken to evaluate the outcome of treatment. As the tooth was not restorable to function, it was extracted and processed for histological examination.CBCT showed a reduction in size of the periradicular radiolucency, with a marginal increase in root length. Apical closure and thickening of the root canal walls were apparent. Histologically, the root canal space was filled with minimally-inflamed fibrous connective tissue. Some cementum-like mineralized connective tissue was evident on the internal canal walls. The apical third showed cementum-like deposits at the apex and the outer canal walls, without dentin formation.The present study of a structurally-failed tooth with prior REP demonstrates that the tissue formed within the root canal space was fibrous connective tissue with cementum-like deposition in the canal space. No evidence of dentin- or pulp-like tissue was found.