(PR117) Histological and Immunohistochemical Evaluation of the role of Dental Pulp and Pericanalar Resorption Resistant Sheet Layer in the Process of External Cervical Root Resorption

Objectives: External cervical root resorption (ECRR) is a pathological process involving the progressive loss of mineralized tooth structure. This resorption is regulated by proteins such as RANK, RANKL, and Osteoprotegerin (OPG), which influence its severity. The pulp space is often spared due to a thin, protective tissue layer known as the pericanalar resorption resistant sheet (PRRS). This study aims to elucidate the role of the vital pulp and characterize the ECRR process by examining human teeth affected by this condition. Histological and immunofluorescence analyses were performed on extracted healthy teeth (n=2) and teeth with ECRR (n=4). Before extraction, endodontic diagnosis tests were conducted to confirm pulpal vitality. After decalcification, samples were sectioned to 7-8 µm using a cryostat. An anti-OPG primary antibody was applied for immunofluorescence observation.

Results: Analyses highlighted the pulp’s critical role in resisting ECRR. OPG was detected in the pulp tissue and dentinal tubules within the PRRS, indicating that pulp cells secrete OPG in response to resorption. The PRRS appears to be regulated by osteoclastic activity through pulp signaling that modulates the RANKL/RANK/OPG pathway. Tissue remodeling was evident, with higher OPG secretion observed in resorbed teeth, especially near resorption sites.

Conclusion: This study underscores the pivotal role of the pulp in ECRR, emphasizing its protective functions and contributions to tissue remodeling. It provides valuable insights into the regulatory mechanisms governing resorption, particularly the interplay between pulp signaling and osteoclastic activity, thereby enhancing our understanding of ECRR's complex pathophysiology.