Evaluation Of The Effectiveness Of Two Kinds Of Nickel Titanium Instruments For Gutta-percha Removal

Objective Root canal retreatment is a more conservative way to resolve the failure of root canal treatment.With the development of modern root canal retreatment instruments and equipment,the success rate of root canal retreatment has been improved.which provides a guarantee for the preservation of teeth.Pro Taper Universal and K3 is currently used nickel-titanium rotary instruments.This study aims to further explore the comparison with the two kinds of nickel-titanium instruments for comprehensive effect of root canal retreatment differences,so as to guide the clinical application.Methods In this study,the root canals of 60 human single-rooted premolars were prepared.The specimens in each group were randomly divided into two subgroups.Pro Taper Universal were used in groups P while K3 were used in groups K.The samples were decoronated by means of a diamond disc to leave a 16 mm root section.The root canals were prepared using step-back technique with K-files.The canals were enlarged up to a 25# file as the master apical file and flared to 40# file by reducing 1 mm for each successive instrument.During preparation,each canal was irrigated after each instrument.The roots were filled with gutta-percha and sealeranal orifices were temporarily sealed.Taken X ray photograph.Then the roots were incubated for 2 weeks at 37oC and 100%humidity.The specimens in each group(groups P and groups K)were retreated as standard.Taken X ray photograph.All operations were performed by the same physician.The photographs were analyzed using Auto CAD software.Also,the total time required and instruments damage for gutta-percha removal was calculated by a chronometer.The volume of filling materials inside the canal was calculated before and after retreatment.The percentage of filling material and the total time on canal walls was analyzed using the independent t-test.Results Both Pro Taper Universal and K3 used in this study left some filling materials inside the root canals.The buccolingual directions root canal filling material removal rate in P group and K group was(90.8±2.8)% and(90.2±4.4)%.The mesiodistal directions root canal filling material removal rate in P group and K group was(91.5±3.8)%and(91.2±2.6)%.The residual rate of total time in P group and K group was(308.1±15.6)s and(316.4±22.7)s.There was no statistical differences between two nickel-titanium instruments regarding the removal of gutta-percha filling material and total time(p >0.05).P group of 1 D3,1 F2 slight deformation,K group of 1 0.06 taper instruments slightly deformed.There was no case of instrument separation.There was no step,root canal blockage and root canal perforation in the root canal retreatment.Conclusions Both Pro Taper Universal and K3 used in this study removed most of the root canal filling.There was no statistical differences between two nickel-titanium instruments regarding the removal of gutta-percha filling material and total time.In order to prevent the occurrence of fracture,the frequency of use of the instrument should be paid attention to.