Cone-beam Computed Tomography For Evaluation Of Shaping Ability In Moderate Curved Root Canal Prepared By Four Nickel-titanium Rotary Systems

Objective:In order to provide experimental basis for clinical application,MSolo File,ProTaper,WaveOne and Twisted File Adaptive(TFA)were used to evaluate the shaping ability of the moderate curved root canals by means of CBCT.Methods:44 premolars or molars extracted from our hospital due to orthodontic or periodontal diseases were collected.The surface stones and periodontal soft tissue were removed by ultrasonic cleaner,and then stored in normal saline at 4?for reserve.All of the root canals were randomly divided into four experimental groups containing 11 teeth each,based on rotary system used.Group-A:ProTaper files,Group-B:WaveOne files,Group-C:TFA files and Group-D:MSolo File files.The canals were irrigated with 2.5%sodium hypochlorite 2 mL and 17%EDTA 2 mL between each file size,and were lubricated with 17%EDTA.Each instrument was only used 5 times.Pre and post instrumentation CBCT images were obtained to record the 3D data of seven loci(canal transportation?centring ability?cross-sectional area).The preparation time?instrument fracture and deformation?the straightening of root canal curvature?canal transportation?centring ability and the changes of cross-sectional area were recorded and analyzed.Results:1.No files were fractured and deformed in the four groups2.Preparation timeThe preparation time of A,B,C,D groups were(379.0±42.9),(122.7±36.5),(215.4±48.9)and(91.1±33.1)s.There were significant differences in preparation time among the four groups(P<0.001).There was no significant difference between group B and group D(P>0.05),but there was significant difference between the other two groups(P<0.001).It is suggested that the preparation efficiency of group B and group D is higher than that of group A and group C.3.The straightening of root canal curvatureThe straightening of root canal curvature of A,B,C,D groups were(3.82±1.83)?(3.73±1.27)?(1.36±0.50)and(2.36±0.50)°.There were significant differences in the straightening of root canal curvature among the four groups(P<0.001).There was no significant difference between group A and group B?group C and group D(P>0.05),but there was significant difference between the other two groups(P<0.05).It is suggested that the degree of root canal straightening in group C and group D is less than that in group A and group B.4.Canal transportationThere was no significant difference in canal transportation among the four groups(P>0.05).5.Centring abilityThere was no significant difference in centring ability in bucco-lingual plane among the four groups(P>0.05).The centring ability in mesial-distal section of A,B,C,D groups were(0.42±0.07)?(0.53±0.08)?(0.74±0.12)and(0.64±0.12).There was significant difference in centring ability in mesial-distal section among the four groups(P<0.05).It is suggested that group C and D have better central localization ability.6.The changes of cross-sectional areaThe increase of cross-sectional area of A,B,C,D groups were(0.63±0.25)?(0.61±0.30)?(0.33±0.12)and(0.40±0.18)mm~2.The cross-sectional area of root canal increased significantly in the four groups(P<0.05).There was no significant difference between group A and group B?group C and group D(P>0.05),but there was significant difference between the other two groups(P<0.05).It is suggested that the increase of cross-sectional area in group C and group D is less than that in group A and group B.Conclusion:These four Ni-Ti instruments can maintain the original shape of moderate curved root canal better,produce smaller canal transportation.MSolo File file with higher preparation efficiency and less dentin cutting capacity,and have better curved root canal shaping ability.