Effect of the Periapical "Inflammatory Plug" on Dental Pulp Regeneration: A Histologic In Vivo Study

Introduction: In the current study, we investigate the effect of the inflammation occupying the apical foramen - a phenomenon we refer to as "inflammatory plug" - on the regenerative potential of a root canal therapy. Methods: We performed root canal treatment (RCT) in 12 canine root canals while aseptically instrumenting the apex to a 0.5-mm-wide foramen and obturating the canals with the following materials: collagen sponge, platelet-rich fibrin, and blood clot (no material introduced). Results: We were successful in maintaining the integrity of the periapical tissue in 8 of 12 RCTs. Injury to the periapical tissue occurred during the remaining 4 RCTs, which initiated inflammation accompanied by bone and dentin resorption. Our histologic analyses showed that the resulting inflammatory plug contained abundant M1 macrophages and was associated with an absence of intracanal cellular infiltration. On the contrary, noninflamed samples showed signs of repair, as indicated by the migration of periapical cells throughout the root canal. Conclusions: We conclude that controlling periapical inflammation is key while attempting to achieve dental pulp regeneration.