An histological study of the effects of extra-corporeal time on murine dental isografts

Mature, fully-erupted mandibular third molars, from male C57B1 mice aged 80–100 days, were transplanted under the renal capsule and into the tibial medulla in isologous male C57B1 mice. Before transplantation, the teeth were incubated in a humid environment at 25 °C for 30 or 60 min, or were immediately transplanted to the host site. Histologically after 30 days, the immediate transplants had vital pulp-like tissue within their pulp chambers, with deposition of irregular reparative dentine. Whereas there was no root resorption in the renal subcapsular grafts, the tibial grafts were ankylosed in small areas and were surrounded by a proliferative bony reaction. Teeth transplanted after 30 min extra-corporeal incubation produced a similar reaction, though more ankylosis was evident in the tibial site. Teeth incubated for 60 min contained no recognizable pulp-like tissue in either site. In the tibia, transplants were often markedly resorbed and ankylosed, with replacement of the pulp tissue by bone marrow and new bone. Pulp degeneration, necrosis of cementum, resorption and ankylosis occurred frequently after an extra-corporeal period of more than 30 min.