A Comparative Study On Several Calcium Hydroxide Paste Placement And Removal Techniques In S-shaped Root Canals

Background and Objective:Calcium hydroxide is the first choice in clinical root canal disinfection,which plays a role through antibacterial activity,diffusion and biological activity.The antibacterial activity of calcium hydroxide is mainly reflected in the direct killing of contact bacteria.Calcium hydroxide paste should be placed deeply and densely in the whole root canal during the clinic sealing period.The residual calcium hydroxide on the root canal wall will affect the quality of root canal therapy,so it is necessary to remove calcium hydroxide from the root canal before root canal filling.The placement and removal efficiency of calcium hydroxide paste is affected by the type of root canal to some extent,but the related research of S-shaped root canal has not been reported.Therefore,the purpose of this study is to compare the application effects of 4 calcium hydroxide paste placement technology and 5 calcium hydroxide paste removal technology in S-shaped root canals.Materials and Methods:Eighty S-shaped resin simulated root canals were prepared to F2 with ProTaper machine Ni-Ti instruments.According to the placement method of calcium hydroxide paste,the samples was randomly divided into four groups(n=20):counterclockwise rotation introduction with manual K file group(K file group),ProGlider counterclockwise rotation introduction group(PG group),calcium hydroxide paste injection group with syringe(injection group)and Lentulo introduction group(LEN group).The density and length of calcium hydroxide paste were evaluated by X-ray analysis.The differences of placement length and density between groups were compared by Kruskal-Wallis test,and pairwise comparison was made by Mann-Whitney test.Set the significance level to 5%(P<0.05).Another 80 S-shaped resin simulated root canals were prepared to F2 with ProTaper Gold machine Ni-Ti instruments.According to the removal method of calcium hydroxide paste,the samples were randomly divided into 5 groups(n=16):PIPS laser irrigation group(PIPS group),EDDY irrigation group(EDDY group),passive ultrasonic irrigation group(PUI group),XP-endo Finisher irrigation group(XPF group)and Syringe irrigation group(SNI group).The residual area of calcium hydroxide paste in root canals after removal was evaluated by X-ray analysis.The differences between groups were compared by Kruskal-Wallis test and pairwise comparison by Mann-Whitney test.Set the significance level to 5%(P<0.05).Result:The results of calcium hydroxide paste placement experiment showed that the mean scores of calcium hydroxide paste placed on the apical of the four groups were as follows:PG group<injection group<K file group<LEN group,but there was no significant difference between groups(P>0.05).In terms of the placement density of calcium hydroxide paste,the mean scores of the root curved part of the root canal was in the following order:PG group<injection group<LEN group<K file group,and there was no significant difference among the four groups(P>0.05).In the crown curved part of the root canal,the average score was in the following order:PG group<LEN group<inj ection group<K file group.There was significant difference among the four groups(P<0.05).The density in PG group was significantly higher than that in K file group(P<0.05).There was no significant difference among other groups(P>0.05).In the straight part of root canal,the mean scores were as follows:PG group<LEN group<K file group<injection group,and there was significant difference among the four groups(P<0.05).The density in PG group was significantly higher than that in injection group and K file group(P<0.05).There was no significant difference between the other two groups(P>0.05).The results of calcium hydroxide paste removal experiment showed that in the crown curved and straight part of the root canal,there was no residual calcium hydroxide paste in the five experimental groups,and the score was 0.In the root curved part of the root canal,the mean scores of calcium hydroxide paste residues in the five groups were as follows:PUI group<EDDY group<PIPS group<XPF group<SNI group.The residual amount of calcium hydroxide paste in PUI group,EDDY group,PIPS group and XPF group was significantly lower than that in SNI group(P<0.05),but there was no significant difference between the other two groups(P>0.05).Conclusions:In S-shaped root canals,the use of ProGlider counterclockwise rotation technology,Lentulo technology and injection technology to place calcium hydroxide is better,in which ProGlider counterclockwise rotation technology is a feasible placement technology,which is recommended to be used in clinical work.In S-shaped root canals,the calcium hydroxide removaling effect of PIPS laser irrigation,EDDY irrigation,PUI and XP-endo Finisher irrigation is significantly better than that of Syringe irrigation.