阅读说明：本技术 一种应用于根管预备的变截面镍钛根管锉的设计方法及系统与制备 (Design method and system and preparation of variable cross-section nickel-titanium root canal file applied to root canal preparation ) 是由 王黎明 郭伟豪 李文祥 李剑峰 李方义 于 2020-07-09 设计创作，主要内容包括：本发明涉及一种应用于根管预备的变截面镍钛根管锉的设计方法,属于医疗器械制造领域,包括：对镍钛锉的整体结构进行离散化处理；对每个所述的切削微元进行二维单元刀具锉削力建模；建立了根管预备过程三维锉削力模型,获得镍钛锉各微元截面的最优参数；对各切削单元进行组装,对各截面几何参数进行二次调整。本发明通过对镍钛锉器械的离散化处理,借助于金属切削、磨削相关思路,利用微分几何,生物力学、牙体牙髓等多学科知识,对每一单元结构及整体结构进行参数优化,提高了镍钛锉器械的在使用过程中发生器械分离的问题,同时可以获得较高的镍钛锉器械抗扭转断裂能力,进而提高根管预备过程的效率和质量。(The invention relates to a design method of a variable cross-section nickel-titanium root canal file applied to root canal preparation, belonging to the field of medical instrument manufacture and comprising the following steps: discretizing the overall structure of the nickel-titanium file; performing two-dimensional unit tool filing force modeling on each cutting infinitesimal; establishing a three-dimensional filing force model in the root canal preparation process to obtain the optimal parameters of each infinitesimal section of the nickel-titanium file; and assembling each cutting unit, and performing secondary adjustment on geometric parameters of each section. According to the invention, through discretization treatment of the nickel-titanium file instrument, with the help of related ideas of metal cutting and grinding, and by utilizing multidisciplinary knowledge of differential geometry, biomechanics, dental pulp and the like, parameter optimization is carried out on each unit structure and the whole structure, so that the problem of instrument separation of the nickel-titanium file instrument in the use process is improved, and meanwhile, higher torsion fracture resistance of the nickel-titanium file instrument can be obtained, thereby improving the efficiency and quality of the root canal preparation process.)

1. A design method of a variable cross-section nickel titanium root canal file applied to root canal preparation is characterized by comprising the following steps:

discretizing the integral structure of the nickel-titanium file to obtain discrete complete structure;

performing two-dimensional unit tool filing force modeling on each cutting infinitesimal;

establishing a three-dimensional filing force model in the root canal preparation process by taking the minimum resultant force of the filing force as an optimization target to obtain the optimal parameters of each infinitesimal section of the nickel-titanium file;

and (3) assembling each cutting unit by taking the minimum integral torque as a target and geometric continuity as a constraint condition, and performing secondary adjustment on geometric parameters of each section to obtain the cutting tool.

2. The method of designing a variable cross-section nitinol root canal file for root canal preparation according to claim 1, wherein during the two-dimensional unit cutter filing, the model is as follows:

F_f＝μF_s+k·a_p·Δd (2)

k＝f₂(θ,L,V,H) (3)；

wherein theta is the angle of the knife tip, L is the width of the knife tip, F_sPositive pressure of the tool, a_pFor thickness of the filing layer, V is the filing speed of the tool, F_fMu is the friction coefficient, k is the filing coefficient, Δ d is the length of the edge line of the unit tool, and H is the material hardness.

3. The method of designing a variable cross-section nitinol root canal file for root canal preparation according to claim 1, wherein the three-dimensional filing force model of the root canal preparation process is as follows:

wherein m is the number of teeth of the cutting edge, beta is the helical angle of the cutter, alpha is the taper of the cutter, and delta d is the length of the infinitesimal cutting edge.

4. The method of claim 1, wherein the continuity test is performed on the adjacent cutter elements, and the geometric rate of change of the adjacent cutter elements is less than 5%, and if the geometric rate of change of the adjacent cutter elements exceeds 5%, the geometric parameters of the adjacent cutter elements are corrected according to the 5% rate of change.

5. A design system for a variable cross-section nickel titanium root canal file for root canal preparation, comprising:

the unit is used for discretizing the whole structure of the nickel-titanium file;

a unit for performing two-dimensional unit tool filing force modeling on each of the cutting elements;

a unit for establishing a three-dimensional filing force model of a root canal preparation process;

and the unit is used for assembling each cutting unit and secondarily adjusting each section geometric parameter.

6. The system for designing a variable cross-section nitinol root canal file for root canal preparation according to claim 5, wherein in the unit for two-dimensional unit tool filing force modeling of each of the cutting elements, the model is established as follows:

F_f＝μF_s+k·a_p·Δd (2)

k＝f₂(θ,L,V,H) (3)；

wherein theta is the angle of the knife tip, L is the width of the knife tip, F_sPositive pressure of the tool, a_pFor thickness of the filing layer, V is the filing speed of the tool, F_fMu is the friction coefficient, k is the filing coefficient, Δ d is the length of the edge line of the unit tool, and H is the material hardness.

7. The system for designing a variable cross-section nitinol root canal file for root canal preparation according to claim 5, wherein in the unit for establishing the three-dimensional filing force model of root canal preparation process, the three-dimensional filing force model of root canal preparation process is as follows:

wherein m is the number of teeth of the cutting edge, beta is the helical angle of the cutter, alpha is the taper of the cutter, and delta d is the length of the infinitesimal cutting edge.

8. The system for designing a nitinol variable cross-section file for root canal preparation according to claim 1, wherein the unit for assembling each cutting unit and making secondary adjustments to each section geometry parameter targets a minimum of overall torque and is constrained by geometric continuity.

9. The system of claim 8, wherein the continuity check is performed on adjacent cutter elements, with a constraint that the geometric rate of change of adjacent cutter elements is less than 5%, and if it exceeds 5%, the geometric parameters of adjacent elements are corrected at a rate of change of 5%.

10. A method of manufacturing a variable cross-section nitinol root canal file for root canal preparation, wherein the structure of the nitinol root canal file is designed according to the design method of any one of claims 1 to 4;

the nickel titanium root canal file is manufactured according to the design parameters.

Technical Field

The invention belongs to the field of medical instrument manufacturing, and particularly relates to a design method of a variable-section nickel-titanium root canal file applied to root canal preparation.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

The tooth root canal preparation is to remove pathological dentin and the like in the root canal by using the rotation and reciprocating motion of a special surgical instrument to form a smooth and conical root canal, and is one of key steps for treating endodontic diseases. The nickel-titanium file is a common and first equipment in the root canal preparation process, compared with the traditional stainless steel instrument, the nickel-titanium file has the functions of shape memory and superelasticity, has the advantages of less chip push-out apical pore and the like due to small deviation degree and working length loss in the root canal preparation process, and is widely applied to clinic in recent years.

The inventor finds that the nickel-titanium file has different contact states along different positions in the root canal, so that the nickel-titanium file is different in load, the nickel-titanium file is broken and falls off due to overlarge load, the root canal is blocked, and then the tooth tissue is irreversibly damaged, and the success rate of root canal preparation is influenced.

Disclosure of Invention

In order to overcome the problems, the invention provides a design method of a nickel titanium file instrument with a variable cross section. The invention solves the problem that the nickel titanium file instrument is easy to separate in the root canal preparation process. The existing nickel titanium file instrument has the problem that the cutting force is too large in the using process, so that the instrument is subjected to torsional fracture. In the invention, through discretization processing of a nickel-titanium file instrument, by means of related ideas of metal cutting and grinding, by utilizing multidisciplinary knowledge of differential geometry, biomechanics, dental pulp and the like, parameter optimization is carried out on each unit structure and the whole structure, a deformation, extrusion, torsion and filing load model in the working process of the nickel-titanium file is established, the internal association relation between the cutter structure and the filing force and torque is disclosed, and the influence rule of structures such as a helical angle, a cutter point shape, conicity and the like on the cutting force is researched. Can effectively avoid nickel titanium file apparatus take place the problem of apparatus separation in the use, can obtain higher nickel titanium file apparatus anti torsional fracture ability simultaneously, and then improve root canal preparation process's efficiency and quality.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

in a first aspect of the present invention, there is provided a method of designing a variable cross-section nitinol root canal file for root canal preparation, comprising:

discretizing the integral structure of the nickel-titanium file to obtain discrete complete structure;

performing two-dimensional unit tool filing force modeling on each cutting infinitesimal;

establishing a three-dimensional filing force model in the root canal preparation process by taking the minimum resultant force of the filing force as an optimization target to obtain the optimal parameters of each infinitesimal section of the nickel-titanium file;

and (3) assembling each cutting unit by taking the minimum integral torque as a target and geometric continuity as a constraint condition, and performing secondary adjustment on geometric parameters of each section to obtain the cutting tool.

The nickel-titanium file structure provided by the invention is designed based on a new theory, so that the current root canal treatment system can be perfected, and the theoretical support and the design method thereof in the root canal filing process can be perfected. Can effectively improve the filing power of the filing process, improve the fracture resistance of the file, improve the fatigue life and the cutting performance, and further improve the guiding capability, the efficiency and the quality of the root canal preparation.

In a second aspect of the present invention, there is provided a system for designing a variable cross-section nitinol root canal file for root canal preparation, comprising:

the unit is used for discretizing the whole structure of the nickel-titanium file;

a unit for performing two-dimensional unit tool filing force modeling on each of the cutting elements;

a unit for establishing a three-dimensional filing force model of a root canal preparation process;

and the unit is used for assembling each cutting unit and secondarily adjusting each section geometric parameter.

The design method of the secondary optimization of the nickel titanium file provided by the invention can be used for root canal preparation operations such as: the selection of the type of the nickel titanium file, the application of the filing torque and the like provide scientific and accurate data support, the experience of a doctor is simply depended on, and the clinical application background is obvious; on the basis, the optimal design method of the nickel titanium file structure based on the filing force, provided by the invention, disperses the cutters into a series of unit cutters, further optimizes the cutter parameters, improves the stress state and improves the reliability and cleaning capability of the nickel titanium file product.

In a third aspect of the present invention, there is provided a method of manufacturing a variable cross-section nickel titanium root canal file for root canal preparation, the method comprising designing a structure of the nickel titanium root canal file according to any of the above-mentioned design methods;

the nickel titanium root canal file is manufactured according to the design parameters.

Based on the design method of the nickel-titanium root canal file with the variable cross section, the whole anti-torsional fracture capability of the novel nickel-titanium file can be obviously improved, the root canal blockage phenomenon caused by fracture, falling off and the like in the operation process is avoided, and the usability and the safety in the operation process are improved.

The invention has the beneficial effects that:

(1) through the implementation of the structure optimization method, a novel variable cross-section nickel-titanium file instrument is formed. Based on the filing force model, the influence rule of the cutter geometric structure (spiral angle, cutter point width, cutter point angle and taper) on the cutting force load and the torque is researched, the cutter geometric structure, the cutting force and the torque map are drawn, and guidance is provided for cutter structure design and drilling machine torque selection in an operation.

(2) Compared with the design method of the nickel-titanium file, the design method of the nickel-titanium file provided by the invention can obviously improve the integral torsion fracture resistance of the novel nickel-titanium file, avoid root canal blockage caused by fracture, falling off and the like in the operation process and improve the usability and safety in the operation process.

(3) The nickel-titanium file structure provided by the invention is designed based on a new theory, so that the current root canal treatment system can be perfected, and the theoretical support and the design method thereof in the root canal filing process can be perfected. Can effectively improve the filing power of the filing process, improve the fracture resistance of the file, improve the fatigue life and the cutting performance, and further improve the guiding capability, the efficiency and the quality of the root canal preparation.

(4) The design method of the secondary optimization of the nickel titanium file provided by the invention can be used for root canal preparation operations such as: the selection of the type of the nickel titanium file, the application of the filing torque and the like provide scientific and accurate data support, the experience of a doctor is simply depended on, and the clinical application background is obvious; on the basis, the optimal design method of the nickel titanium file structure based on the filing force, provided by the invention, disperses the cutters into a series of unit cutters, further optimizes the cutter parameters, improves the stress state and improves the reliability and cleaning capability of the nickel titanium file product.

(5) The design method is simple, the cutter performance is obviously improved, the practicability is strong, and the popularization is easy.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a diagram of the discrete microminiaturization and analysis of a nickel titanium file according to example 1 of the present invention;

FIG. 2 is a drawing showing the modeling of the filing process of the unit nickel titanium file of the embodiment 1 of the present invention.

FIG. 3 is a simulation of the filing process of the nickel titanium file according to embodiment 1 of the present invention.

FIG. 4 is a flow chart of the design of the variable cross-section nickel titanium root canal file of the present invention.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

A design method of a variable cross-section nickel titanium file instrument comprises the following steps:

1) discretizing the integral structure of the existing nickel-titanium file, and discretizing the integral structure into cutting microelements;

2) based on the step 1), performing two-dimensional unit cutter filing force modeling on each cutting element;

3) based on the step 2), establishing a three-dimensional filing force model in the root canal preparation process by taking the minimum resultant force of the filing force as an optimization target, and obtaining the optimal parameters of each infinitesimal section of the nickel-titanium file;

4) assembling each cutting unit in the step 3) by taking the minimum integral torque as a target and geometric continuity as a constraint condition, and performing secondary adjustment on geometric parameters of each section;

further 1.1) as shown in fig. 1(a), the cutting process of the nickel titanium file in the root canal is dispersed into a plurality of micro-cutters;

further 1.2) in the filing process of the two-dimensional unit tool, as shown in FIG. 2, the parameters of the tool structure are the tool tip angle theta and the tool tip width L, and the unit tool is under a certain pressure F_sUnder the action of the medicine, the medicine is cut into the dentin material to a depth a_pThe tool has a filing speed V, and the tool is subjected to a reverse filing force F in the direction of the filing speed during the filing process_f. During filing, the depth of the filed layer a_pIn relation to the tip pressure, the tip angle and the hardness of the material, an expression formula as shown in formula (1) is proposed, in whichDelta d is the edge line length of the unit cutter, and H is the material hardness. Function relation f₁Obtained by finite element simulation and polynomial fitting.

The invention divides the filing force F into two parts: the friction force under the action of pressure and the force required for removing the material, wherein the friction force under the action of pressure can be obtained by the coulomb law, and the force required for removing the material is in a linear relation with the area of the filing layer. Therefore, the formula (2) is provided, wherein mu is the friction coefficient, k is the filing coefficient, and the formula (3) is provided according to the mechanical properties of the material, the structure of the cutter and the filing speed. Wherein the functional relationship f₂Obtained by finite element simulation and polynomial fitting.

F_f＝μF_s+k·a_p·Δd (2)

k＝f₂(θ,L,V,H) (3)

Further 1.3), determining the working state of each infinitesimal element at a certain moment through the geometric contact and motion states of the nickel-titanium file and the root canal, and establishing a filing model of the infinitesimal element shown in the figure 1 (b); for the cutting edge of the tool infinitesimal, the stress state of the cutting edge is calculated according to the geometric profile of the cutting edge, and the unit filing force can be geometrically decomposed in a spatial domain according to the edge shape of the tool, and the decomposition mode is shown in fig. 1 (c). And sequentially calculating the stress state and the spatial decomposition of each infinitesimal element to obtain the load distribution of the nickel-titanium file, and finally obtaining formulas (4) - (6), namely a three-dimensional filing force model in the root canal preparation process, by a unit synthesis method. Wherein, F_x,F_y,F_zThe stress along X, Y, Z axis is applied during the preparation of root canal.

Wherein m is the number of blade teeth; alpha is the cutter taper; beta is the cutter helix angle; i. n is a natural number greater than 0, and n is greater than i.

Further 1.4) adjacent cell continuity: in the unit-level optimization, the connection state between the units is not considered, and if the difference between the geometric structures of two adjacent units is too large, geometric singularities are caused, so that the comprehensive stress state of the tool is deteriorated (stress concentration). Therefore, continuity inspection is carried out on the adjacent cutter micro-elements, the constraint condition that the geometric change rate of the adjacent cutter micro-elements is less than 5%, and if the geometric change rate of the adjacent cutter micro-elements exceeds 5%, the geometric parameters of the adjacent micro-elements are corrected according to the 5% change rate. Analyzing the comprehensive stress of the cutter: testing that the cutter stress meets the cutter strength condition; analyzing the torque of the tool: the tool torque meets the fatigue life requirement, and the overall tool parameter, namely the helical angle, is optimized with the aim of minimum comprehensive torque.

The present invention is described in further detail below with reference to specific examples, which are intended to be illustrative of the invention and not limiting.