Comparison Of The Apical Debris Extrusion Among Three NiTi Files During Preparation In Curved Root Canals

Objective The aim of the experiment is to compare the amount of apical debris extrusion during root canal preparation in curve root canal of three engine-driven root canal treatment instruments--M3-L,M3 pro and Hyflex-EDM.And also to evaluate the influence of different usage on the amount of apical debris extrusion.Methods 45 root canal models with curvature of 30 degree were chose and the working length of them were calculated using microscope.In detail,put the ISO 15#k file into the root canal and clear it.Keep the motion until the tip of the k file can be seen from the apical foramen.Take out the k file and measure the length of it.The length is used as working length.The operation made all the diameter of the root canals be the same.Then,the models were numbered and randomly divided into 3 groups according to the random number table(n=15).The groups are M3-L group,Hyflex-EDM group and M3 pro group.And there are five subgroups which consists of 3 samples of each in every group,the subgroups are divided according to the times used in each instrument(1,2,3,4,5 times).1.preparation and irrigation of root canal The all process obeyed the manufacturer's instruction of each instrument strictly.And the apical diameter after preparation of all the groups were 0.25mm(the red one of M3-L,ISO 25#08 of Hyflex-EDM,ISO 25#06 of M3pro).Put the flushing needle at the length which is 3mm shorter than the working length.There shouldn't be any forcing strength during the irrigation.And move the flushing needle up and down during all the process of irrigation.The speed of the irrigation is 2m L/min.2.collection and weighing of debris Firstly,weigh the weight of EP tube with cover using the Precision electronic scale(m)and recorded it.And then parcel the model with rubber dam to isolate water and shelter the downside of the model from the operator.Then put the model and rubber dam into the EP tube until the 4mm coronal side of the model is keepedoutside and the most side of the model hanging in the tube.Put some cotton balls on the juncture of model and rubber dam to absorb the fluid flushing from the coronal side.Take out the model and the rubber dam from the EP tube after the preparation of the root canal and remove the rubber dam.Using 1.5m L purified water to wash the apical side of the model to push the debris which attached to the model into the EP tube.Then open the EP tube and put it into an oven with 50 degree centigrade for 7 days to evaporate the water in the EP tube completely.And then weigh the EP tube again(m1).All the weighing data were exacted to 10-5g.The weight of the debris extruded from the apical foramen= m1-m 3.record preparation time Record the preparation time during the process of root canal preparation.Because of big differences on the time of irrigation and change instruments,we only record the time that the instrument were working in the root canal.4.statistical analysis SPSS 23.0 was used for data input and analysis.The data which conformed to normal distribution were expressed with mean ± standard deviation(x±s).ANOVA was used to compare the overall means of the amount of apical debris of each group.LSD-t test was used to compare every 2 groups.P<0.05 was considered statistically significant.Results 1.fracture of the instrument and apical transportation of the model There were only 1 instrument which broke of during the test and it happened in M3 pro group in which the instrumrnt has been used for 3 root canals.And there were 4 models which transported from the original apical foramen of the root canal obviously in M3-L group.The apical transportation didn't happpen in the other 2 groups.2.the preparaion time of each group The preparation time of M3-L group and Hyflex-EDM group were less than the one in M3 pro group.There were no obvious difference between M3-L group andHyflex-EDM group.3.the amount of the apical debris extrusion in each group The amount of the apical debris extrusion of M3-L group and Hyflex-EDM group were less than the one in M3 pro group and the data were statistically significant(p<0.01).And there were no obvious difference between M3-L group and Hyflex-EDM group.3.the amount of the apical debris extrusion of the instruments which were used for different times in each group.There were no obvious differences when compared the times(1-5 times)used by the instruments in each group.Conclusion 1.M3 pro and Hyflex-EDM are more prone to keep the original shape of the root canal in curved root canal preparation compared to M3-L.2.The amount of the apical debris extrusion of M3-L group and Hyflex-EDM group were less than the one in M3 pro group.3.There were no obvious difference on the amount of the apical debris extrusion between M3-L group and Hyflex-EDM group.4.There were no obvious differences when compared the times(1-5 times)used by the instruments in each group.5.The preparation time of M3-L group and Hyflex-EDM group were less than the one in M3 pro group.6.There were no obvious difference on preparation time between M3-L group and Hyflex-EDM group.