Coronal Microleakage Of Zinc Oxide Eugenol With Different Proportions Of Powder And Liquid:An In Vitro Study

Objectives:By study in-vitro,to compare the situation of the marginal integrity and micro-leakage among the groups which were treated by the Zinc Oxied Eugenol(ZOE)of different powder-liquid ratio and a commercial material(Caviton,GC)after they were restored for 3 days,7 days and 14 days.The materials have similar hardness before application.Through the study,we try to find the optimal powder-liquid ratio of ZOE,and offer the experimental finding to improve the use effect of temporary restorative materials in community based hospitals.Methods:99 premolars and molars were collected,the roots of which were cut off.The crowns were split from mesial side to distal side.Type-I cavities were prepared on the buccal and lingual pieces.Totally 198 samples were prepared.According to ISO 7619:1986,tested by Shore durometer,the hardness of Caviton(GC)of F group was 13HC.This result was taken as reference.According to ISO 3107:2011,five groups of ZOE with different powder-liquid ratios ZOE:A:3.5g:1.0ml,B:4.0g:1.0ml,C:4.5g:1.0ml,D:5.0g:1.0ml,E:5.5g:1.0ml were prepared and stored for a while.When the hardness of five groups was close to 13HC(range from 11.5-14.5HC),the materials were applied to seal the prepared cavities.The samples were stored in the environment which mimic the oral cavity and subjected to temperature cycle(in water bath of 0-5? and 50-55?,15 seconds/cycle.).After the cavities were temporarily sealed for 3 days,7 days and 14 days,samples in each group were selected randomly on each time point(11samples/time).Each time,One sample is observed by SEM,the other 10 samples were immersed in 1%methylthionine chloride for 30 minutes.Stereomicroscope was used to observe the microleakage.The results were statistically analyzed by Kruskal-Wallis H test and Mann-Whitney rank-sum test.Results:SEM result:Obvious cracks appeared in five groups of ZOE,Caviton(GC)in F group was tightly combined with tooth and there was no obvious crack.Stereoscopic microscope result:When five groups of ZOE were applied in cavitieds for 3 days,7 days and 14 days,the difference of micro-leakage among groups has no statistical significant(P>0.0033).But compared with Caviton(GC)group,There was statistical significant(P<0.0033).Conclusions:The study shows that the ZOE of different powder-liquid ratios have similar hardness before application,have no statistical significant in micro-leakage and marginal integrity.Micro-leakage between the material and the tooth occurred in each group.The commercial material(Caviton,GC)has less micro-leakage than ZOE(P<0.0033).ZOE,which powder-liquid ratio is 4.5g:1.0ml,is easy to prepare,the powder and liquid can be well mixed,the homogeneity is also suitable for clinical use.