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Objective: The aim of this study was to perform a histomorphometric evaluation of the repair process in rat teeth replanted after root canals were filled with calcium hydroxide (CH) and mineral trioxide aggregate (MTA)., Design: Upper right incisors were extracted from 30 rats divided into three groups (n=10). The teeth were stored dry for 60min, after which the pulp and periodontal ligament (PDL) were removed and immersed in acidulated-phosphate sodium fluoride solution. In Group I, the root canals were filled with saline; in Group II, they were filled with CH; and in Group III, they were filled with CH, and the foramen was sealed with an MTA plug. The teeth were replanted, and the animals were sacrificed after 60 days. The sections with teeth were removed for histological preparation (haematoxylin and eosin, H&E). The characteristics of the PDL, cementum, dentine, and alveolar bone, as well as the occurrence of inflammatory and replacement root resorption and apical sealing, were subjected to histological and morphometric analysis (P<0.05)., Results: Group I was the most affected by root resorption (mean=67.05%). In Groups II and III, the resorption averaged 42.2% and 11.7%, respectively. Group III was less affected by inflammatory resorption and presented more areas of apical sealing by mineralized tissue (P<0.05)., Conclusion: An apical MTA plug improved the repair of the replanted tooth by decreasing surface resorption and repairing mineralized tissue in the periapical region., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Clinical experience has shown that most avulsed teeth are replanted after a long extra-alveolar time and dry or inadequate wet storage, causing necrosis of periodontal ligament cells. This condition invariably leads to development of external root resorption, leaving the filling material in contact with the periapical connective tissues. In this study, the periapical tissue reactions to calcium hydroxide (CH) and mineral trioxide aggregate (MTA) were evaluated after occurrence of external root resorption as an expected sequela of delayed tooth replantation. Twenty male Wistar rats (Rattus norvegicus, albinus) had their right upper incisor extracted and maintained in dry storage for 60 min. Then, the dental papilla, enamel organ, pulp tissue, and periodontal ligament were removed, and the teeth were immersed in a 2% acidulated phosphate sodium fluoride solution, pH 5.5, for 10 min. The teeth were randomly assigned into two groups (n = 10), in which the canals were filled with either a CH and saline paste (CH group) or MTA (MTA group). The sockets were irrigated with saline, and the teeth were replanted. After 80 days, it was possible to observe large areas of replacement root resorption and some areas of inflammatory root resorption in both groups. More severe inflammatory tissue reaction was observed in contact with calcium hydroxide compared with the mineral trioxide aggregate. New bone formation was more intense at the bottom of the socket in the MTA group. In conclusion, as far as periapical tissue compatibility is concerned, intracanal MTA can be considered as a viable option for root canal filling in delayed tooth replantation, in which external root resorption is an expected sequela., (© 2011 John Wiley & Sons A/S.)