An experimental study on periodontal regeneration after subcutaneous transplantation of rat molar with and without cryopreservation: An in vivo study

This study analysed the effects of cryopreservation on periodontal regeneration of autotransplanted rat molars. First and second maxillary molars (n = 92) of 24 four-week-old Wistar rats were gently extracted and autotransplanted into the abdominal tissue immediately (control group n = 44) or after cryopreservation in liquid nitrogen for 7 days (experimental group n = 48). At 1, 2, 4 and 10 weeks after transplantation, the transplanted molars were excised and regeneration of the periodontal tissues was analysed on histological sections stained with routine H&E and Goldner method. Different tissue responses were scored on a tooth basis: inflammation, regeneration of the periodontal ligament, resorption/apposition of cementum, and alveolar bone formation. Sixty-two teeth were available for histological evaluation, including 30 experimental and 32 control samples. One week after transplantation, both control and test teeth were surrounded by granulation tissue and some areas of root resorption could be seen. After 2 weeks, signs of regeneration of the periodontal ligament, cementum apposition, and new bone formation roughly coincided in both groups, however markedly retarded in the experimental group. After 4 weeks, regeneration progressed equally in both groups, presenting fewer areas of cementum apposition in experimental samples. Finally, 10 weeks after baseline transplantation, no significant differences between both groups could be observed. Cryopreservation followed by autotransplantation of extracted teeth in rats appears to have minimal detrimental effects on regeneration of periodontal tissues after integration periods of 1-10 weeks. However, the present findings indicated that the regeneration process in general is retarded for cryopreserved teeth, as compared to their immediately transplanted homologues.