Comparative Evaluation On The Effect Of The Shaping Ability With Different Nickel-Titanium Instruments By Micro-CT

Objective: To compare the forming effects of three different nickel-titanium machine tools on severely curved root canals,and provide reference for clinical selection of nickel-titanium instruments.Methods: Thirty-seven mandibular first molars with independent near-cheek and proximal tongue canals and 25°-35° curvature were collected.The selected samples were randomly divided into three groups: ProTaper Next group,Twisted File Adaptive.Group,Reciproc group.The preoperative images of each group of samples were taken by micro-CT with a resolution of 20 ?m,and then the root canal preparation was performed according to the group using the corresponding nickel-titanium instruments.The preparation method was performed by the crown-down method,and the three groups were used in the preparation process.The 17% EDTA and 3% sodium hypochlorite solution were alternately washed,and the root canal was dried after preparation,and then the postoperative images were taken by micro-CT.The scanned data was imported into the 3D image processing software for 3D reconstruction,and the morphological parameters before and after the root canal preparation were analyzed.The statistical method used the one-way ANOVA and Tukey test in SPSS20.0 software to analyze the following data:(1)the average root canal deviation degree and axial center rate of the three groups of samples at 1 mm,3 mm,5 mm,and 7 mm from the apical foramen Size;(2)tip 3mm,root diameter tube cross-section maximum diameter to minimum diameter ratio(RDR)and root canal cross-sectional area ratio(RA);(3)tube before and after volume and surface area change.Results:(1)Compared with ProTaper Next and Twisted File Adaptive,the average deviation of Reciproc from 5mm from the apical foramen was greater,and the difference was statistically significant(P<0.05).(2)The rootcanal enlargement of Reciproc group was more obvious at 3 mm from the apical foramen.Compared with the other two groups,the difference of RA values was statistically different(P < 0.05).(3)There was no significant difference in volume and surface area between the ProTaper Next and Twisted File Adaptive groups(P > 0.05).The Reciproc group had the highest mass of teeth removed,and the average root canal volume and surface area increased more significantly.The difference was statistically significant(P<0.05).Conclusion: The three systems can effectively prepare the root canal to the full working length.The continuous rotation of the ProTaper Next and the adaptive system Twisted File Adaptive produces less canal transportation,which can better maintain the original root canal anatomy of the severely curved root canal,has significant application value.Reciproc has strong cutting efficiency and should be used cautiously in the clinical use of severely curved root canals.