Analysis Of The Effect Of Eccentricity On The Performance Of NiTi Instruments For Root Canal Instrumentation

Root canal therapy is the main treatment of pulp disease and periapical disease,including procedures such as pulping,root canal preparation,root canal disinfection,and root canal filling.Root canal preparation is the most important part of root canal treatment.The instrument used was Instruments For Root Canal Instrumentation(IRCI).Due to the super-elastic properties of nickel-titanium alloy materials,the IRCI made of material has excellent flexibility.Compared with traditional stainless steel IRCI,nickel-titanium IRCI has higher preparation efficiency and fewer complications.However,nickel-titanium IRCI often instrument fracture when there is no obvious permanent deformation of the instrument.In order to avoid the instrument fracture,various Designed IRCI have come out one after another.The eccentric structure design is intended to reduce the stress and the instrument fracture in the root canal by reducing the contact between the instrument and the root canal wall and increasing the chip removal space.Since there are few studies on the influence of eccentric design on the mechanical properties of IRCI,this paper explores the methods to reduce the breakage of the device by studying the effects of different eccentric forms on the chip space,mechanical properties and fatigue life of NiTi IRCI.First,the parametric equation of the equiangular IRCI helix is derived,and the Pro/ E software is used to establish an IRCI three-dimensional geometric model with variable cross-sectional area eccentricity,variable theoretical taper eccentricity and variable actual taper eccentricity.Analyze the influence of three eccentric forms on IRCI chip space.The results show that the chip space of IRCI increases with the increase of eccentricity;for the chip removal rate of variable cross-sectional area eccentric instruments,the larger the cross-sectional area,the better the chip space improvement effect;the same cross-sectional shape,different eccentricity The order of improving the chip space of the form IRCI from high to low is: variable theoreticaltaper type eccentricity> variable cross-sectional area type eccentricity> variable actual taper type eccentricity.Then,based on the finite element theory and the superelastic mechanical behavior of the nickel-titanium alloy material,the effects of three eccentric forms on the bending properties and torsional properties of the NiTi IRCI were analyzed by the abaqus finite element software.The results show that the maximum stress,bending stiffness and torsional stiffness of NiTi IRCI decrease with the increase of eccentricity;the three eccentric forms have little effect on the stress of NiTi IRCI,but have a greater influence on its bending stiffness and torsional stiffness.The effect of variable cross-sectional area eccentricity on the NiTi IRCI has little to do with the cross-sectional shape.The same cross-sectional shape,different eccentric forms have different degrees of influence on the bending stiffness and torsional stiffness of Ni Ti IRCI.The degree of influence on the bending stiffness from high to low is: variable theoretical taper type eccentricity>variable cross-sectional area type eccentricity> variable actual taper Eccentricity;the order of influence on torsional stiffness from high to low is: variable cross-sectional area eccentricity> variable theoretical taper type eccentricity> variable actual taper type eccentricity.Finally,based on the load spectrum required for fatigue analysis generated by the bending finite element simulation results,the fatigue properties of the nickel-titanium alloy material are given,and the fatigue fatigue analysis of the NiTi IRCI is performed using fe-safe software to obtain three kinds of eccentric forms the fatigue life of NiTi IRCI.The results show that the variable theoretical taper eccentricity has the best effect,the variable cross-sectional area eccentricity is the second,and the actual taper eccentricity is the worst.The minimum life first appeared at the cutting edge of the NiTi IRCI,and the number of bending cycles obtained within the analysis was within a reasonable range of the number of NiTi IRCI bending fatigue tests.NiTi IRCI is designed to provide a reference for estimating its service life.This paper analyzes the effects of three eccentric forms on the chip space,bending performance,torsional performance and fatigue life of NiTi IRCI.Based on the ideal NiTi IRCI mechanical properties,it has small bending stiffness,large torsional stiffness,and long bending fatigue life.Therefore,it is recommended to use variable theoretical taper eccentricity to improve NiTi IRCI.In the product development stage,understanding the performance of the eccentric Ni Ti IRCI and optimizing the design scheme on this basis can shorten the development cycle and reduce the cost of research and development,and it is expected to develop devices with a low breaking rate.