cryopreservation periodontal tissue. METHODS:Periodontal tissue was scraped from healthy human teeth and divided them into three equal parts:fresh group, harvesting periodontal ligament stem cel s from fresh tissue;5%dimethyl sulfoxide group, 5%dimethyl sulfoxide added into the cryopreservation system;10%dimethyl sulfoxide group, 10%dimethyl sulfoxide added into the cryopreservation system. One month later, periodontal ligament stem cel s were extracted from the cryopreserved periodontal ligament from the latter two groups. RESULTS AND CONCLUSION:In the time that cel s swam out of tissue mass and cel harvest amount, the 5%dimethyl sulfoxide group was inferior to the fresh group but better than the 10%dimethyl sulfoxide group (P<0.05). No differences were found among the three groups in the fol owing aspects (P>0.05):colony formation rate of passage 1 periodontal ligament stem cel s, cel survival rate, proliferation ability of passage 3 periodontal ligament stem cel s, cel growth curve and surface marker expression of periodontal ligament stem cel s. The results suggest that the 5%dimethyl sulfoxide added cryopreserved system for periodontal ligament tissue cannot only shorten the time of periodontal ligament stem cel s amplification in vitro, ensure cel harvest and maintain basic cel ular biological characteristics, but also reduce the total amount of the dimethyl sulfoxide and the direct damage to the cel s caused by repeatedly frozen cel s, thereby providing a more secure guarantee for the future implementation of clinical transplantation therapy. So, the 5%dimethyl sulfoxide added cryopreserved system may be the new selection for donor tissue storage.