| Objective:Through comparative the removal ability of smear layer and the influence on microleakage of two types of ultrasonic working tips,to provide experimental data for clinical popularization and application of smooth working tips and provide basis and suggestions for further improvement of working tips.Methods:(1)Tooth collection: collecting 120 mandibular single canal premolars due to orthodontic subtraction with no caries on the root surface,complete apical development and the root canal curvature < 10°.(2)Grouping: 120 sample teeth were divided into smooth file group(group A),K-file group(group B)and syringe group(group C)according to different instruments in root canal preparation,with 40 teeth in each group;After root canal preparation,they were divided into scanning electron microscope group(A1,B1,C1)and microleakage group(A2,B2,C2)according to different methods deal with samples,with 20 samples in each group.(3)Sample processing : the sample teeth of the scanning electron microscope group are cutting off the crown from the enamel cementum boundary,split vertically,then dehydrated in gradient,dried,sprayed with gold,and observed under the scanning electron microscope;After the sample teeth in microleakage group dried the root canal,the hot gutta-percha was tightly filled with vertical pressure method,then stained and the stained sample was treated transparently and observed under a stereomicroscope.(4)Statistical methods: SPSS 20.0 software wasused for statistical description and statistical analysis.The experimental data of each group were description with(`x±s),One-way ANOVA was in progress,and T test was used for comparison between each two sample.The difference was statistically significant with P < 0.05.Results:1.The statistical results of scanning electron microscope group showed that the removal effect of group A1 and group B1 on the 1/3 of root tip was significantly better than that of group C1(P < 0.01),but there was no statistical difference between group A1 and group B1.The removal effect of group A1 on the middle 1/3 of root is better than that of group C1(P < 0.05),while there is no statistical difference between group B1 and group C1(P > 0.05).But there is no statistical difference between group A1 and group B1(P > 0.05).The removal effect of smear layer on the coronal of root of the three groups was not statistically significant(P > 0.05).On the other hand,there was no significant difference between the middle and coronal part of root canals in each group(P > 0.05).However,compared with the tip 1/3 of root,the removal effect of the middle and top 1/3 of root is more significant(P < 0.05)2.The experimental results of microleakage showed that microleakage occurred in different degrees in all three groups.The staining lengths of each group were group A2(1.51±0.77)mm,group B2(1.79±0.78)mm and group C2(2.72±1.49)mm;and the comparison between groups showed that group A2 and group B2 were significantly smaller than group C2(P < 0.05).Although group A2 was the shortst,there was no significant difference compared with group B2(P > 0.05).Conclusion:Under scanning electron microscope of root canal after ultrasonic irrigation,it can be observed that the removal ability of smear layer is better than that of syringe group,and the staining length in microleakage is obviously shorter than that of syringe group,and the two experimental results are consistent.However,the use of different working tips has no significant effect on the removal of smear layer in different areas of the root canal.And the use of different working tips has no significant effect on microleakage,although the microleakage length of the smooth tip is the smallest.Therefore,both types of working tips can be used clinically. |
PDF Full Text Request