Preliminary Study On Effect Of Different Ultrasonic Irrigation Combined Liquids On Root Canal

Objective: In this experiment,the root canals were subjected to root canal ultrasonic irrigation at the same temperature and at the same time with different root canal irrigation combined liquid in clinically.After the irrigation,observed and compared the effects of microhardness and dentin smear layer changes in root canals.It provides experimental basis for clinical root canal therapy and further study of root canal irrigation,thereby reducing the generation of vertical root fractures and effectively reducing the occurrence of microleakage,in order to improve the success rate of root canal therapy.Subjects and methods: 80 fresh maxillary anterior teeth removed due to periodontal disease were selected.The roots were required to be intact and have no cracks,no sputum,no root canal therapy,and complete apical foramen.Remove the calculus around the root and remove the soft tissue around the root.After thorough cleaning,immerse in normal saline and place in a refrigerator at 4°C.Samples were conventionally extirpated the dental pulp with hand-pulled instrument in each group.The root canal was then dredged with a manual No.15 K file.After observing the K file reached the apical foramen,the manual K file was removed from the root canal.The working length was measured as length minus 1mm.The Mtwo mechanical root canal preparations 10/.04,15/.05,20/.06,25/.06 were used to prepare the root canal of each tooth,and each instrument was prepared for the root canal to work length.The rotation speed was 280-.300 rev / min.The root canal was flushed with a injection syringe containing 5 ml of distilled water after each instrument was changed.After the root canal was mechanically prepared by Mtwo,the ultrasonic treatment instrument was adjusted to the 4th gear.After the working length of the root canal was retreated approximately 3 ?,the 15# ultrasonic file was inserted.When the root canal was ultrasonically swept,the ultrasonic file was not required to touch the root canal wall,not to lift or ring action.Four groups of isolated teeth were rinsed with different flushing fluid at the same time.Group A was ultrasonically irrigated with combination of MTAD and 3% Na Cl O for 3 min.Group B was ultrasonically irrigated with combination of 17% EDTA and 3% Na Cl O for 3 min.Group C was ultrasonically irrigated with combination of 2% CHX and 3% H2O2 for 3 min.The group D was ultrasonically irrigated with distilled water(negative control group)for 3 min.After ultrasonic irrigation,2 ml saline was injected into the root canal to prevent the continuous action of the flushing fluid.The irrigated root canal was dried with paper spills and the root canal was temporarily sealed with a small cotton ball to prevent the entry of debris.The tooth roots randomly selected from 40 anterior teeth were first cut from the margin of the neck to the apex and perpendicular to the macroaxis,dividing into 1/3 of the root neck,1/3 of the root,and 1/3 of the apex averagely.Each segment was about 3 to 5 ?.Then,they were slit along the longitudinal grooves,embedded in epoxy resin,and then sanded with #800,#1500,and #2000 metallographic sandpaper respectively,and polished with the rubber wheel.Each specimen was placed upside-down on the stage of the HMV-G20 Microhardness Tester.Three points were measured on the dentin,and each point was examined the microhardness value under an applied force of 150 g for 30 s.The microhardness value is taken as the the sample average value at the three-point,and the result is expressed by the numerical value plus HV.Another 40 anterior teeth were slit along the longitudinal grooves and placed in 2.5% glutaric acid solution fixed for 24 hours.After fixation,they were soaked in sterile distilled water and then placed in 25% alcohol,75% alcohol,90% alcohol,95% alcohol and anhydrous ethanol in order were dehydrated stepwise for 15 minutes to make samples and spray gold.The dentinal tubules' smear layer were observed and analyzed under the scanning electron microscopy.Results:1.The microhardness of root canal was observed and compared.The results showed that the microhardness of 3% Na Cl O and 17% EDTA was significantly lower than that of other groups(P<0.05).The microhardness of 3% Na Cl O and MTAD irrigation liquid and 3% H2O2 and CHX irrigation liquid were significantly lower than that of the distilled water group.The difference was significant(P<0.05).The microhardness of 3% Na Cl O and MTAD irrigation fluid were lower than 3%H2O2+2%CHX,but there was no significant difference between these(P>0.05).2.By observing and comparing the conditions of the smear layer and debris of the root canal,the results showed that the 3% Na Cl O and 17% EDTA irrigation fluids and 3% Na Cl O and MTAD irrigation fluids to remove the smear layer was better,and the difference between the distilled water group was significant(P<0.05),3% Na Cl O and 17% EDTA irrigation fluids had no significant difference with 3% Na Cl O and MTAD irrigation fluids(P>0.05).The smear layer removal of 3% Na Cl O and 17% EDTA irrigation fluids and 3% Na Cl O and MTAD was better than 3% H2O2 and CHX irrigation fluids,the difference was significant(P<0.05),the effect of removing the smear layer by 3%H2O2 and CHX irrigation fluids was better than distilled water,and there was no significant difference between these(P>0.05).Conclusion:1.3% Na Cl O and MTAD irrigation liquids and 3%H2O2 and 2%CHX irrigation liquids had less effect on the microhardness of the root canal compared with 17% EDTA and 3% Na Cl O irrigation liquids solution.2.3% Na Cl O and MTAD irrigation liquids and 17% EDTA and 3% Na Cl O irrigation fluids remove the smear layer better than others.3.MTAD and 3% Na Cl O irrigation liquids is a good root canal flushing fluid.