| Objective:(1)Establish a model of the smear layer of the root canal in vitro;(2)3%sodium hypochlorite was used for initial irrigation during root canal preparation.Compared with the different final irrigation after root canal preparation,3%sodium hypochlorite irrigation alone,3%sodium hypochlorite combined with EDTA irrigation,and 3%sodium hypochlorite combined with Er:YAG laser activation irrigation were used.The effect of removing the smear layer in the root canal,hoping to provide a theoretical basis for the clinic.Methods:Experiment 1:In vitro by imitating the process of root canal preparation,the motorized ProTaper nickel-titanium file was used to prepare the isolated teeth to establish a model of the root canal smear layer.The details are as follows:8 qualified human premolar teeth were removed about 15mm from the tip of the tooth,and Pull out the dental pulp.Use the motorized ProTaper nickeltitanium file to prepare root canals for 4 of the teeth,and each experimental sample was prepared to F3.During the root canal preparation,the instrument was rinsed with 2ml 3%sodium hypochlorite solution each time the instrument was changed,The remaining 4 teeth will not be treated after removing the crown.After the relevant treatment,observe under the scanning electron microscope,the result shows that the smear layer model is successfully established.Experiment 2:40 human premolar teeth were obtained on the basis of experiment 1,After the canal preparation were completed,the samples were divided into four groups A,B,C and D according to the different final treatment:Group A:5ml 0.9%normal saline for 60S(negative control);Group B:5ml 3%sodium hypochlorite solution for 60S;Group C:5ml 17%EDTA solution for 60S;Group D:Place the Er:YAG laser fiber head at the root canal orifice and irradiate it for 30s,Irradiate for another 30s after an interval of 10 seconds and continuously inject 3%sodium hypochlorite solution(total 5ml)into the root canal during irradiation.After washing,the root canals were dried with moisture absorbent paper tip.Then use the same method to observe the remove of the smear layer at 1/3 of the root tip,1/3 of the root tip and 1/3 of the root crown of the experimental samples by scanning electron microscope.refer to Hulsmann's smear layer classification standard to score it,Finally,these experimental data was analyzed and processed by using statistical software SPSS 22.0.Results:1.The root canal smear layer model was successfully established,and the results showed that a thick smear layer can be seen in the root canal wall of the experimental sample for in vitro root canal preparation;2.The smear layer scoring results showed that:the Er:YAG laser group had the best smear layer removal effect compared with the sodium hypochlorite group and the EDTA group(the average score was the smallest),and the difference was statistically significant(P<0.05);3.the effect of removing smear layer on the crown 1/3 of root in the sodium hypochlorite group and the crown 1/3 of root and the middle 1/3 of root in the EDTA group was acceptable(the average score was less than 3 points),and in the remaining sections of the two groups,The effect of removing smear layer is poor(the average score is more than 3 points),the difference is statistically significant(P<0.05).4.in the root canals that have undergone the same treatment,the removal of the smear layer in the four groups are as follows:crown 1/3 of root>middle 1/3 of root>tip 1/3 of root,the difference was statistically significant(P<0.05).Conclusion:1.When Er:YAG laser combine with 3%sodium hypochlorite to remove smear layer,its effect on crown 1/3 of root,middle 1/3 of root and tip 1/3 of root are better than when 3%sodium hypochlorite combine with 17%EDTA.The combined use of 3%sodium hypochlorite and 17%EDTA is better than 3%sodium hypochlorite alone.And the effect of normal saline to remove the smear layer is the worst.2.In the crown 1/3 of root,the effect of 3%sodium hypochlorite washing alone and the combined washing of 3%sodium hypochlorite and 17%EDTA to remove the smear layer is acceptable.3.In the root canal after the same treatment,1/3 of the root crown had the best removal effect,and the root tip 1/3 had the worst effect. |
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