Cryopreservation of human teeth for future organization of a tooth bank--a preliminary study

This study was aimed at evaluating whether cryopreserved teeth can be used for future transplantation by examining the viability and differentiation capability of periodontal ligament (PDL) cells and measuring the hardness of dental hard tissue. Fifty-four teeth were divided into two groups, control and frozen teeth. A MTT assay and a TUNEL assay were performed for the examination of the viability and apoptotic death of PDL cells. Immunohistochemical staining for alkaline phosphatase was performed to observe whether the differentiation capability of PDL cells was maintained by the freezing and thawing procedure. Hardness was measured to detect whether dental hard tissue was affected by the freezing conditions. The MTT and TUNEL assays showed no significant difference in the viability of PDL cells between the two groups. The differentiation capability of PDL cells was maintained in frozen teeth as evidenced by alkaline phosphatase staining. The hardness of frozen teeth was not changed, but a longitudinal fracture was found in 25% of the frozen group. The viability and differentiation capability of PDL cells were maintained in a frozen environment; however, it is thought that a new cryopreservation method preventing fracture of dental hard tissue should be developed for clinical application.