The Experimental Study Of The Influence Of Extracted Teeth Storage Methods And Smear Layer On The Apical Microleakage

Objectives 1 Compare the influence of different storage methods and storage time on root tip penetration in vitro, in order to get storage methods which are similar to the experimental results of the fresh extracted teeth. 2 Compare the influence of apical leakage whether remove the smear layer or not when use different retrograde filling materials.Methods 1 55 collected single canal fresh extracted teeth were randomly divided into different experimental groups: 1) The experemental group: we use four different storage methods(10 counts in each group): 4℃distilled water,4℃10%formaldehyde solution,4℃2% Benjamin chlorine solution and stored at-20℃freezer. 2) The control group(5counts): Fresh extracted teeth(within 30 minutes for the experiment). 3) Positive control and negative control group(each group 5): In the first 30 days and 60 days, five randomly selected samples from the experimental group were used in the experiment. After conventional root canal preparation of all the samples, we take the cold lateral compaction technique to fill the root canals, and make retropreparations after the apical resection. All samples were root-end filled with GIC, remove the root canal fillings of the upper section, and the root surface were coated with two layers of nail polish, and use the Incubator to dry the samples. The samples are placed in the detecting microleakage model. Detect the concentration of glucose which is leaked from the crown to the root direction in the first 1,2,4,7,10,15,20 and 30 days.2 After conventional root canal preparation of 130 collected single canal teeth, we take the cold lateral compaction technique to fill the root canals, and make retropreparations after the apical resection. All the samples were randomly divided into experimental groups and control groups(65 in each group).Experimental group: 17% EDTA+1%chlorine Benjamin swished root canal. Control group: swished with 5m L saline canal.5 teeth were randomly selected from the experimental group and the control group to be scanned in scanning electron microscope. The remaining 60 groups were divided into three groups. They were root-end filled with the MTA, GIC and amalgam. The root canal filling material of upper section were removed, and the root surface were coated with two layers of nail polish, use the Incubator to dry the samples. The samples are placed in the detecting microleakagemodel. Detect the concentration of glucose which is leaked from the coronal to the root direction in the first 1,2,4,7,10,15,20 and 30 days.Results 1 In the first days latex tube liquid drops significantly in positive control group; In the negative control group did not detect glucose during the period of observation. Different degrees of leakage are detected at each time in the experimental groups and the control groups.There is no significant differences in the concentration of the leaked glucose between the 30 days and 60 days(P>0.05).Among all the experimental groups, the concentration of the leaked glucose which is stored in the-20℃freezer is the least, it’s statistically different compared with the other experimental groups(P<0.05).There is no statistical difference between the-20℃freezer storage and the control group(fresh tooth).2 Glucose can be detected in the experimental group and control group at all time. With or without the smear layer, the concentration of the leaked glucose of MTA is the least compared with GIC and amalgam. And the amalgam is the most. The difference was statistically significant(P<0.05). When retrograde filling using the MTA and GIC without the smear layer, the concentration of glucose is smaller.This difference was statistically significant(P<0.05); When use the amalgam, There was no significant difference in the concentration of glucose with or without the smear layer(P>0.05).Conclusions 1 The storage time of extracted teeth do not influence the root tip penetration.We get the similar results from the fresh extracted teeth and teeth which are stored in the-20℃freezer.2 MTA for retrograde filling caused significantly lower microleakage than GIC and amalgam. When using MTA and GIC, it is better to remove the smear layer for apical sealing. But when using the amalgam, whether to remove or to remain the smear layer did not make a difference to improve the apical closure.