Evaluating The Efficiency Of Different Irrigation Protocols On Removing Calcium Hydroxide In Root Canals

OBJECTIVE:As a intracanal medicament,Calcium hydroxide（Ca（OH）₂）is commonly used to disinfect the root canal clinically.Any Ca（OH）₂ residue on the dentin walls may affect the penetration of sealers into the dentin tubules,and the dentinal bond strength,and may increase apical leakage.A large number of scholars have got some achievements of the removal efficiency of Ca（OH）₂ combining different mechanics with different irrigation solutions.The aim of this study is to investigate the efficiency of removing Ca（OH）₂in vitro root canals by using three equipments:syringe,ultrasonic,and laser（semiconductor laser）combined with 0.9%saline,3%NaClO+17%EDTA,and MTAD.Besides that,the result can provide guidelines for clinical physicians.METHODS:A total of 45 freshly extracted single-rooted teeth were selected in this research.The tartar and periodontal ligament in the surface were removed.To ensure standardization,the crowns of the teeth were partially removed to achieve final roots with a length of13mm.Working length（WL）was determined by subtracting 1mm from this measurement anatomical apex.Each sample was shaped to F3 by the same operator using Protaper Universal rotary instruments.After that,the root canal was flushed with 5 ml of3%NaClO,5ml of 17%EDTA solution,and 10 ml of 0.9%saline,followed by a moisture absorbing tip to dry them.The Ca（OH）₂ paste resisted by X ray was placed into the root canal and homogenized with a screw conveyor so that the root canal was filled with Ca（OH）₂ in the WL,and then the cavity was sealed with a temporary sealing paste.The samples were stored in a 37°C constant temperature oven for one week.Subsequently,all samples were fixed and photographed for CBCT.The volume of the Ca（OH）₂ paste in the root canal was measured by using Mimics Research 19.0 software and recorded as V1.The samples were randomly divided into nine groups（n=5）according to different irrigation protocol for removing Ca（OH）₂:A1:syringe+0.9%saline;A2:syringe+3%NaClO+17%EDTA;A3:syringe+MTAD;B1:Ultrasonic+0.9%saline;B2:Ultrasonic+3%NaClO+17%EDTA;B3:Ultrasonic+MTAD;C1:Laser+0.9%saline;C2:Laser+3%NaClO+17%EDTA;C3:Laser+MTAD.The canals were irrigated with 5ml irrigation for 30sec.After washing,the root canal was dried and CBCT was immediately taken again.The volume of residual Ca（OH）₂ paste in the root canal was measured with Mimics Research 19.0 software.The volume was recorded as V2,and the efficiencyofCa（OH）₂removalintherootcanalwascalculatedas Pv=（V1-V2）/V1×100%.Each set of experimental data was imported into SPSS 22.0 software,and they were analyzed by factorial design analysis of variance（ANOVA）.α=0.05 was the test level and statistical significance was set at P<0.05.Results:There are interactions between different irrigating equipments and irrigating solutions（P=0.01）.When irrigating solution was fixed,there was a statistically significant difference in the individual effects of the irrigating equipments（P<0.001）;when the irrigating equipment was fixed,the difference in the individual effects of the irrigating solution was statistically significant（P<0.001）.When using syringes,ultrasonic and laser irrigation,the removing Ca（OH）₂ efficacy of 3%NaCl O+17%EDTA and MTAD was better than that of saline,and the difference was statistically significant（P<0.001）.When the syringe and ultrasonic were used,there was no significant difference in the removing efficacy of 3%NaClO+17%EDTA and MTAD（P>0.05）.When using lasers,the removing efficacy of MTAD was better than 3%NaClO+17%EDTA（P=0.042）.When saline and MTAD were used,the irrigating efficacy of ultrasonic and laser was superior to those of the syringe,and the laser irrigating efficacy was superior to ultrasonic（P<0.001）;when using 3%NaCl O+17%EDTA,the laser irrigating efficacy was better than the syringe and ultrasonic（P<0.001）,and there was no significant difference between the ultrasonic and the syringe（P>0.05）.Conclusion:1.Under the action of saline and MTAD,the application of semiconductor lasers and ultrasonic equipment is more effective to the removal of Ca（OH）₂ in the root canal than the conventional syringe,and the removal efficiency of the semiconductor laser is higher.Therefore,clinically we recommend semiconductor laser devices to remove Ca（OH）₂ in the root canal.2.Under the same flushing equipment,MTAD and 3%NaClO+17%EDTA irrigating solution can remove Ca（OH）₂ paste in root canal more effectively than 0.9%saline.When semiconductor lasers are used,MTAD removal efficiency is higher.