Comparison Of Shaping Ability Of Five Mechanical Nickel-Titanium Instruments In Severely Curved Root Canals

Objective:By preparing resin simulated root canals,this study compared the shaping ability of five types of nickel-titanium instruments for preparing severely curved root canals,in order to provide an experimental basis for their clinical application.Methods:Fifty resin simulated root canals of 40° were randomly divided into five groups(n=10),and were used in sequence,including Pro Taper Universal(group PTU)Pro Taper Gold(group PTG),Reciproc Blue(group RB),One Curve(group OC)and Rotate(group R),the preparation time of each group and the deformation and separation of the instrument were recorded.Using a visual,uniform,and standardized method,we took ink-stained images before and after the resin root canal preparation,and then they were superimposed using Adobe Photoshop.The changes of the canal transportation,centering ability and the curvature angle were measured and at the level of 10 observation points.The data were processed by SPSS 22.0 software,and the shaping effects of five different mechanical nickel-titanium instruments were compared.Results:1.The longest preparation time was(83.02±2.11)s in the PTU group,and the shortest was(31.06±1.34)s in the RB group.The difference of preparation time was statistically significant among the five groups(P<0.05).2.During the whole experiment,there was no deformation and separation of the five mechanical nickel titanium instruments.3.The change of curvature of five mechanical nickel titanium instruments before and after root canal preparation: The change of root canal curvature in OC group was significantly less than that in PTU group(P<0.05);the changes of root canal curvature in group R were significantly lower than those in PTU,PTG,and RB groups(P<0.05);there is no statistically significant difference between other groups(P>0.05).4.The shaping effects of five mechanical nickel titanium instruments at each point of the root canal: At 1,2,3 and 8 mm from the apical foramen,the canal transportation of group PTU was significantly larger than that of the other groups,and the difference was statistically significant(P<0.05);at 4 and 5 mm from the apical foramen,the canal transportation of groups PTG,OC and R was smaller than that of the other groups,and the difference was statistically significant(P<0.05);at 6 and 7 mm from the apical foramen,the canal transportation of groups OC and R was smaller than that of the other groups,and the difference was statistically significant(P<0.05).Conclusions:1.Five nickel-titanium instruments can prepare curved root canals quickly,efficiently and safely,and can keep the original shape of severely curved root canals.2.In the apical part,compared with Pro Taper Universal,the other four instruments have shown superior centering ability;in the curved part of root canal,the centering ability of Pro Taper Gold,One Curve and Rotate was relatively superior than the other two instruments;at the 6 and 7 mm level of the root canal crown,the centering ability of One Curve and Rotate was relatively better than the other three instruments.