Regenerative Endodontic Therapy Using Platelet-Rich Plasma (PRP) and Amelogenin for the Treatment of Non-vital Immature Permanent Teeth with Apical Periodontitis: An Animal Study

Background: Platelet-rich plasma (PRR) was proposed to serve as a possible scaffold model for regenerative endodontic therapies. However, its treatment outcomes are still controversial. Amelogenin protein has been shown to induce stem cell proliferation and differentiation. Thus, the aim of this study was to investigate whether the addition of amelogenin to PRP in non-vital immature permanent teeth with apical periodontitis can improve their treatment outcomes. Methods: Root canals of both maxillary and mandibular premolars in 8 mongrel dogs (n= 128) were instrumented and left open. After 14 days, in a second surgical procedure, canals were cleaned, irrigated, and treated with PRP (n=64) and PRP + amelogenin (n=64). After 1 and 3 months, animals were killed, and treated teeth were evaluated for histological and immune detection for nestin markers. Results: After 1 and 3 months post-surgery, PRP-treated canals showed full closure of opened apexes but minimal cementum, periodontal ligament (PDL), and bone regeneration. Importantly, no pulp regeneration was recognized. In contrast, PRP + amelogenin-treated canals at 1 and 3 months showed full closure of opened apexes, significant deposition of cementum, bone, regeneration of PDL, and pulp-like tissue regeneration compared to PRP-treated groups (p<0.001). By the 3-month period, full regeneration of all the lost dental-pulp complex tissues was seen, including vascular pulp-like tissue. Conclusions: PRP alone did not achieve the desired treatment outcomes, but after addition of amelogenin protein, it induced pulpal regeneration and regenerated the whole attachment apparatus. This combination could serve as a novel approach for regenerative endodontic therapy in non-vital immature permanent teeth with apical periodontitis. However, additional research is warranted to further evaluate the effect of such a combination in different animal settings before administrating this approach in clinical cases.