Periodontal Tissue Engineering After Tooth Replantation Luciana Reichert da Silva Assunc xa ˜o,* Renato Colenci, † Caril Constante Ferreira do-Amaral, ‡ Celso Koogi Sonoda, § Suely Regina Mogami Bomfim, i Roberta Okamoto, § Marjorie de Assis Golim, ¶ Elenice Deffune, † Ce ´ lio Percinoto, # and Sandra Helena Penha de Oliveira ‡ Background: Blood-derived products, platelet-poor plasma (PPP) and platelet-rich plasma (PRP), constitute an approach in the enhancement of tissue healing. PRP has also been used as a scaffold for bone marrow stem cells in tissue engineering. This study evaluates the effect of PPP, calcium chloride–acti- vated PRP (PRP/Ca), calcium chloride– and thrombin-activated PRP (PRP/Thr/Ca), and bone marrow mononuclear cells and PRP/Ca (BMMCs/PRP/Ca) on the healing of replanted dog teeth. Methods: After 30 minutes of extraction, teeth were replanted with 1) no material (control); 2) PPP; 3) PRP/Ca; 4) PRP/Thr/Ca; or 5) BMMCs/PRP/Ca. Histologic, histomorphometric, and immunohistochemical analysis was assessed 120 days after replantation. Data from histomorphometric analysis were ana- lyzed statistically (analysis of variance, Tukey; P <0.05). Quan- titative immunohistochemical analysis was analyzed by Kruskal-Wallis and Dunn post hoc test (P <0.05). Results: Flow cytometry analysis showed 55.98% of CD34 + and 32.67% of CD90/Thy-1 for BMMCs sample. BMMCs/PRP/ Ca presented the largest areas of replacement resorption char- acterized by osseous ingrowth into cementum (P <0.05), with intense immunomarcation for tartrate-resistant acid phospha- tase. The PRP/Ca group also showed areas of replacement re- sorption with significant immunomarcation for osteopontin. PRP/Thr/Ca presented no replacement resorption. PPP showed areas of inflammatory resorption, with immunomarcation for tartrate-resistant acid phosphatase. Conclusions: The results suggest that platelets activated with thrombin play an important role in the healing of tissues after tooth replantation. Additional studies are necessary to test other materials, because PRP/Ca did not present an appropriate scaf- fold for undifferentiated cells in the treatment of avulsed teeth. J Periodontol 2011;82:758-766. KEY WORDS Bone marrow; platelet-rich plasma; stem cells; tissue engineering; tooth replantation. D ental avulsion is a complex injury that results in the loss of continu- ity of multiple tissue compart- ments. Repair with a normal periodontal ligament (PDL) after tooth replantation is difficult to achieve in clinical situations, because the injury results in a minimum lesion in the internal layer of the PDL. 1 Researchers have recommended the use of substances for root surface treatment before replantation. 2-4 Although some of these therapies reduced root resorp- tion, regeneration of the PDL was not successful. 2 Reinsertion of connective tissue into the root surface after tooth replantation depends on sequential healing events. A blood clot is formed between the two parts of the ruptured PDL immediately after replantation. Fibrinogen is con- verted into fibrin during coagulation. 5 Fibrin contributes to improved wound healing by linking with fibronectin and stimulating fibroblast migration and an- giogenesis. 6 Wound healing is controlled and regulated by biologically active substances known as growth factors (GFs). 7 These biologic mediators are capable of regulating cellular events, in- cluding cell proliferation, differentiation, and extracellular matrix synthesis. 8 Plasmatic fractions, platelet-rich plasma (PRP), and platelet-poor plasma (PPP) constitute an interesting approach for enhancing tissue healing because they can regenerate bone, 9 cartilage, 10 ten- don, 11 and periodontal tissues. 12 PRP * School of Dentistry, Federal University of Para ´ , UFPA, Para ´ , Brazil. † Laboratory of Cellular Engineering, Botucatu Blood Center, Faculty of Medicine, UNESP- University Estadual Paulista, Sa ˜o Paulo, Brazil. ‡ Department of Basic Sciences, School of Dentistry, UNESP-University Estadual Paulista. § Department of Surgery and Integrated Clinics, School of Dentistry, UNESP-University Estadual Paulista. i Department of Clinic and Surgery and Animal Reproduction, Veterinary Medicine Course, School of Dentistry, UNESP-University Estadual Paulista. ¶ Laboratory of Flow Cytometry, Botucatu Blood Center, Faculty of Medicine, UNESP- University Estadual Paulista. # Department of Pediatric Dentistry, School of Dentistry, UNESP-University Estadual Paulista. doi: 10.1902/jop.2010.100448 Volume 82 • Number 5 758