Preliminary Study On Application Of Cryopreservation Technolgy In The Preservation Of Tooth

Objectives:Autogenous tooth transplantation is known as a surgical movement of donor tooth out of its socket to another one in the same individual.Our expectation is that donor tooth can restore the blood circulation and achieve revascularization of pulp.Compared to other dental prosthesis,autogenous tooth transplantation has advantages in being comfortable,economical and beautiful,with short course of treatment and less pain.Therefore this technique is considered as a alternative method to replace dental implant.However,autotransplantation is hard to be operated due to the difficulty in matching extraction time and transplantation time of donor tooth.Accordingly,it is urgent to find a long-time method to preserved the autogenous tooth.In recent years,the great development of biological cryopreservation technology has brought hope to the teeth preservation.This study aims to researching the influences of different cryoprotectant agents or freezing methods on biomechanical properties of dental tissues and viability of periodontal ligament cell(PDLC)in vitro,in order to lay a foundation for further experimental study and clinical application.Methods:(1)A total of 75 fresh teeth(the first premolar or second premolar)were collected and divided into five groups.Four experimental groups were cryopreserved by programmed freezer or rapid freezer in cryoprotectant with or without trehalose for 1 week.The control group were not given any treatment.(2)The presence/absence of crack on the enamel surface was observed of four experimental groups under the stereomicroscope before and after cryopreservation.(3)Compression strength and modulus of elasticity were measured in 5 tooth each group.Another 5 tooth each group were prepared the V type cavity and filled with risen,then micro-leakage at the edge of filling materials was measured by dye penetration test with 2%methylene blue solution after 500 temperature cycles.(4)PDL attached to the middle third on the roots of last 5 teeth each group was cut from the root surface using a scalpel knife.After digestion and centrifugation,the supernatant was abandoned and the rest fluid was stained by Trypan blue after washed in PBS.The living PDLCs were counted at high magnification and calculated the cell survival rate.Results:(1)There was no significant crack on the enamel surface of four groups under the stereomicroscope before and after freezing.(2)There were no obvious differences in dental compression strength,modulus of elasticity,micro leakage and survival rate of PDLCs between groups with different cooling methods and different cryoprotectants,even compared with the control group,But the survival rate of PDLCs in the group that using programmed freezer and cryoprotectant with trehalose was the highest.Conclusions:The present study shows that cryopreservation of teeth maintains the viability of PDLCs,and do not affect the hard tissue of tooth..These results suggest that using the programmed freezer in cryoprotectant with trehalose have minimum effect on the activity of periodontal ligament cells.