Oral orthodontic force real-time calculation method

Abstract

The application discloses a kind of orthodontic force real-time calculation methods.The method comprises: based on the three-dimensional geometric model of tooth, periodontal membrane, alveolar bone, corresponding grid model is obtained by grid division, the grid model includes multiple grid units;The mass matrix of grid unit node is calculated, and the dynamic equation of grid unit node is established, which represents the relationship between the mass matrix and the elastic force suffered by the grid unit node;Using the measured tooth displacement information, the deformation information of tooth, periodontal membrane and alveolar bone is obtained by solving the dynamic equation;According to the deformation information of tooth, periodontal membrane and alveolar bone, orthodontic force is calculated.The application can realize accurate, efficient orthodontic force real-time calculation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oral diagnosis and treatment, more particularly, to an oral orthodontic force real-time calculation method. BACKGROUND

[0002] Orthodontic force calculation is the basis for achieving precise oral orthodontic diagnosis and treatment. In particular, in the context of archwire appliance loading operations, by obtaining the orthodontic force size in real time, it can provide assistance and basis for precise loading by doctors.

[0003] In oral orthodontic diagnosis and treatment, the orthodontic force size and tooth movement after archwire appliance loading can be calculated / simulated, so as to better develop treatment plans and improve treatment effects. For example, in the treatment planning stage, the three-dimensional influence of the oral cavity and teeth can be obtained through CBCT (cone beam CT), oral scanning, etc., and the three-dimensional model of the teeth, periodontal membrane and alveolar bone can be obtained through segmentation and reconstruction. Doctors develop preliminary orthodontic treatment plans based on experience. Based on the above-mentioned three-dimensional model, the process of orthodontic force and tooth movement after archwire appliance loading is simulated by means of finite element method. Doctors adjust / optimize the final treatment plan according to the simulation results. The above process can be realized by means of finite element software such as Ansys. After determining the treatment plan, the doctor implements the archwire appliance loading operation. In existing oral diagnosis and treatment, doctors manually complete the operation of bracket sticking and archwire loading, and estimate tooth displacement and orthodontic force size based on experience. In precise oral diagnosis and treatment, especially in the process of precise appliance loading, the precise real-time calculation of orthodontic force (rather than relying solely on experience) can help doctors to accurately complete the loading operation, which can effectively improve the diagnosis and treatment effect and shorten the treatment cycle.

[0004] In the prior art, the orthodontic force simulation calculation method based on the finite element method usually uses the three-dimensional model of the teeth, periodontal membrane and alveolar bone to establish an orthodontic force simulation method, and calculates the orthodontic force size by inputting the tooth movement distance. However, this method has low calculation efficiency and cannot meet the real-time requirements of orthodontic force calculation for archwire appliance loading operation assistance. SUMMARY

[0005] The purpose of the present application is to overcome the defects of the prior art and provide an oral orthodontic force real-time calculation method. The method comprises the following steps:

[0006] Based on the three-dimensional geometric model of the teeth, periodontal membrane and alveolar bone, a corresponding grid model is obtained through grid division, and the grid model comprises a plurality of grid units;

[0007] The mass matrix of the grid unit node is calculated, and the dynamic equation of the grid unit node is established, which represents the relationship between the mass matrix and the elastic force acting on the grid unit node;

[0008] With the measured tooth displacement information, deformation information of the tooth, periodontal membrane and alveolar bone is obtained by solving the dynamic equation;

[0009] According to the deformation information of the tooth, periodontal membrane and alveolar bone, orthodontic force is calculated.

[0010] Compared with the prior art, the advantage of the present application is that the real-time calculation method of the orthodontic force in the oral cavity based on the "mass point-tensor" model is first proposed, which can realize accurate and more efficient real-time calculation of the orthodontic force compared with the existing finite element method, thereby improving the effect of oral orthodontic diagnosis and treatment.

[0011] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0012] The accompanying drawings incorporated in and forming a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the application.

[0013] Figure 1 is a flowchart of the real-time calculation method of the orthodontic force in the oral cavity according to an embodiment of the present application;

[0014] Figure 2 is a process schematic diagram of the real-time calculation method of the orthodontic force in the oral cavity according to an embodiment of the present application;

[0015] Figure 3 is a schematic diagram of tooth movement and orthodontic force in the oral cavity according to an embodiment of the present application;

[0016] Figure 4 is a schematic diagram of deformation and elastic force of a mesh element according to an embodiment of the present application. DETAILED DESCRIPTION

[0017] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. Note that the relative arrangement, numerical expressions and numerical values of the components and steps set forth in these embodiments are not limiting to the scope of the present application unless otherwise specifically stated.

[0018] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way limiting to the scope of the application or its applications or uses.

[0019] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein, but should be considered as part of the specification, where appropriate.

[0020] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments can have different values.

[0021] It should be noted that like reference numerals and letters refer to like items throughout the attached drawings, and once an item is defined in one drawing, it is not necessary to discuss it further in subsequent drawings.

[0022] The present application provides a real-time calculation method of orthodontic force based on a "mass-tensor" model. First, a mesh model is obtained by dividing a three-dimensional model of teeth, periodontal ligament and alveolar bone. Then, the elastic force of the mesh nodes is calculated based on the "mass-tensor" model after the displacement of the teeth is given. Next, the deformation of the teeth, periodontal ligament and alveolar bone is calculated by a time integration method. Finally, the orthodontic force is calculated according to the mesh deformation of the model, and the real-time calculation of the orthodontic force is realized.

[0023] Specifically, in combination with the method shown in Figure 1 and 2 The provided real-time calculation method of orthodontic force includes the following steps:

[0024] Step S110, based on the three-dimensional geometric model of teeth, periodontal ligament and alveolar bone, a mesh element model of teeth, periodontal ligament and alveolar bone is obtained by mesh division.

[0025] For example, based on the patient's oral CBCT image data, the teeth, periodontal ligament and alveolar bone are segmented and reconstructed to obtain the three-dimensional geometric model of the teeth, periodontal ligament and alveolar bone. The mesh model of the teeth, periodontal ligament and alveolar bone is obtained by mesh division of the three-dimensional geometric model.

[0026] The mesh model contains a plurality of mesh elements, which can reflect the positional relationship between the teeth, periodontal ligament and alveolar bone. Each mesh element can be in the form of a polyhedron. For the sake of clarity, the following will be described by taking a tetrahedral mesh element as an example, referring to Figure 4 As shown in the figure, a tetrahedral mesh element can be characterized by four mesh nodes.

[0027] Step S120, the mass of the mesh node is calculated.

[0028] In one embodiment, calculating the mass of the mesh node includes: traversing all the mesh elements, calculating the mass of the mesh element, and averaging / accumulating it to the nodes of the mesh element.

[0029] Step S130, the dynamic equation of the mesh node is established based on the mass of the mesh node.

[0030] Specifically, let the position of the grid node be x, the mass matrix be M, and the elastic force acting on the grid node be f. Then the dynamic equation of the grid node is:

[0031]

[0032] The position x of the grid node at time t+1 is calculated using the implicit time integration method. t+1 for:

[0033] x t+1 =x t +Δtv t+1 v t+1 =v t +ΔtM -1 f(x t+1 (2)

[0034] Where v is the velocity of the grid node. Let v represent the second derivative of x. t+1 v is the velocity of the grid node at time t+1, Δt is the time difference between time t and time t+1, and v t It is the velocity of the grid node at time t, x t It represents the position of the grid node at time t.

[0035] Step S140: Set the tooth movement distance.

[0036] See Figure 3 As shown, in orthodontics, an archwire appliance is used to apply a certain displacement to the teeth, causing corresponding deformations in the teeth, periodontal ligament, and alveolar bone, and generating orthodontic forces. In practice, the loading operation of the archwire appliance can be captured in real time using cameras or other means, and the tooth movement distance can be measured. The displacement of the corresponding tooth mesh nodes is set as the measured value.

[0037] Step S150: Solve the dynamic equations.

[0038] Solving the above dynamic equations yields the positions of the grid nodes at time t+1, which represent the deformations of the teeth, periodontal ligament, and alveolar bone.

[0039] Step S160: Calculate the deformation of the teeth, periodontal ligament, and alveolar bone, and output the elastic force generated by the deformation as the orthodontic force.

[0040] In step S160, the magnitude of the orthodontic force is calculated by measuring the displacement of the mesh nodes of the teeth, alveolar bone, and periodontal ligament, and the calculated value is output.

[0041] like Figure 4As shown, taking one grid unit in the grid model as an example, which is a tetrahedron unit. After the tetrahedron unit grid is deformed, the grid nodes generate corresponding elastic force f. The orthodontic force calculation process is as follows:

[0042] Let X (X, Y, Z) and x (x, y, z) be the initial position and the deformed position of the grid node respectively. For any tetrahedron unit, the initial positions of its nodes are X1, X2, X3 and X4, and thus the related matrix of the initial positions can be obtained as follows:

[0043]

[0044] The deformed positions of the nodes are x1, x2, x3 and x4, and thus the position matrix of the deformed nodes can be obtained as follows:

[0045]

[0046] Then the deformation gradient in the tetrahedron unit can be calculated as:

[0047]

[0048] The strain energy in the tetrahedron unit is:

[0049] W (x, X) = V·Ψ (F) (6)

[0050] Wherein, V is the volume of the tetrahedron unit, and Ψ (F) is the material strain energy density function. Then the elastic force generated after the deformation of the tetrahedron unit, that is, the orthodontic force, can be calculated as:

[0051]

[0052] In summary, the present application proposes an orthodontic force calculation method based on the "particle-tensor" model, which solves the problem of low calculation efficiency of the traditional finite element method. It has been verified that the present application can effectively improve the calculation efficiency of the orthodontic force.

[0053] The present application can be a system, a method and / or a computer program product. The computer program product can include a computer readable storage medium having computer readable program instructions loaded thereon for causing a processor to implement various aspects of the present application.

[0054] Computer readable storage media can be tangible storage media which can retain and store instructions for use by an instruction execution device. Computer readable storage media can be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer readable storage media include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

[0055] Computer readable program instructions described herein can be downloaded to respective computing / processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network can comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing / processing device.

[0056] Computer readable program instructions for carrying out operations of the present application can be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate array (FPGA), or programmable logic array (PLA) can execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present application.

[0057] The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0058] These computer readable program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer readable program instructions can also be stored in a computer readable storage medium that can include random access memory (RAM), read only memory (ROM), electrically erasable programmable read only memory (EEPROM), flash memory or nonvolatile memory, or a suitable combination of the different types of computer readable storage media. The computer readable program instructions can also be downloaded to a computer, other programmable data processing apparatus, or other device from a computer readable storage medium or to an external computer or external storage device via a data signal that can be transmitted for example via a wired medium or a wireless medium such as the Internet or Wireless Application Protocol (WAP) signaling.

[0059] The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus or other device to produce a computer implemented process such that the instructions which execute on the computer, other programmable data processing apparatus, or other device implement the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0060] The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus or other device to produce a computer implemented process such that the instructions which execute on the computer, other programmable data processing apparatus, or other device implement the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0061] Embodiments of the present application have been described above, and the description is intended to be illustrative, and not restrictive, of the disclosed embodiments. Many modifications and variations of the described embodiments are possible, and all such modifications and variations are intended to be within the scope of the described embodiments. The description used herein is intended to best explain the principles of the embodiments, the practical application, and the best mode of the present application, to make this disclosure understood in the art. The scope of the present application is defined by the appended claims.

Claims

1. A method for real-time calculation of orthodontic force, comprising the steps of: based on a three-dimensional geometric model of teeth, periodontal ligament and alveolar bone, a corresponding mesh model is obtained by meshing, the mesh model comprising a plurality of mesh elements; calculating the mass matrix of the mesh element nodes and establishing the dynamic equation of the mesh element nodes, the dynamic equation representing the relationship between the mass matrix and the elastic force acting on the mesh element nodes; obtaining the deformation information of the teeth, periodontal ligament and alveolar bone by solving the dynamic equation using the measured tooth displacement information; calculating the orthodontic force according to the deformation information of the teeth, periodontal ligament and alveolar bone; wherein the dynamic equation is expressed as: wherein, x is the position of the grid element node, M is the mass matrix of the grid element, f is the elastic force experienced by the grid element node, denotes x the second derivative of wherein the dynamic equation is solved according to the following steps: Based on the implicit time integration, the position of the grid cell node at time instant t+1 is calculated as t +1 x t+1 is expressed as: wherein, is the velocity of the grid cell node at time t +1, is the velocity of the grid cell node at time t is the time difference from time t +1, is the velocity of the grid cell node at time t +1, is the position of the grid cell node at time t +1. wherein the mesh element is a tetrahedral element, and the elastic force generated after the deformation of the tetrahedral element is calculated according to the following steps: calculating the initial position matrix of the tetrahedral element nodes: calculating the position matrix of the tetrahedral element nodes after deformation: wherein, with and represent the initial position and the deformed position of the tetrahedron unit, respectively, X 1, X 2, X 3, X 4 represent the initial position of the tetrahedron unit node, , , , represent the deformed position of the tetrahedron unit node; calculating the deformation gradient within the tetrahedral element: ； calculating the strain energy within the tetrahedral element: calculating the elastic force generated after the deformation of the tetrahedral element as the orthodontic force, expressed as: where V is the volume of the tetrahedron, is the material strain energy density function.

2. The method of claim 1, wherein, the mesh model is obtained according to the following steps: segmenting and reconstructing the teeth, periodontal ligament and alveolar bone to obtain a three-dimensional geometric model of the teeth, periodontal ligament and alveolar bone; meshing the three-dimensional geometric model to obtain a mesh model of the teeth, periodontal ligament and alveolar bone.

3. The method of claim 1, wherein, The mass matrix of the mesh element nodes is obtained by traversing all mesh elements, calculating the mass of the mesh elements, and distributing it evenly to the nodes of each mesh element.

4. The method of claim 1, wherein, The tooth displacement information is obtained by real-time acquisition of the archwire appliance loading operation image and measurement of the tooth movement distance through a camera.

5. The method of claim 1, wherein, The three-dimensional geometric model is based on patient oral CBCT image data, and is obtained by segmenting and reconstructing the teeth, periodontal ligament and alveolar bone.

6. A computer readable storage medium having stored thereon a computer program, wherein, The computer program, when executed by a processor, implements the steps of the method according to any one of claims 1 to 5.

7. A computer device comprising a memory and a processor, having stored on the memory a computer program capable of running on the processor, characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 5.

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