Structural optimization design method of pseudo composite multi-layer appliance based on finite element analysis

Abstract

The present invention relates to a method for optimizing the structure of a pseudo composite multi-layer appliance based on finite element analysis, including: a finite element geometric modeling module for geometrically modeling a plurality of pseudo composite multi-layer appliances of different structures; a finite element physical modeling module for setting the interlayer interface friction coefficient of each pseudo composite multi-layer appliance; a finite element calculation module for calculating the stress and displacement of different layers of materials of each pseudo composite multi-layer appliance of different structures; and a result analysis and evaluation module for analyzing and evaluating the stress and displacement of different layers of materials of each pseudo composite multi-layer appliance to obtain the structure of the pseudo composite multi-layer appliance after optimized design. The advantages are: the method is scientific, intuitive and convenient, improves the correction effect, avoids the high cost and long cycle problems of the prior art, and has high practical value, and is worthy of large-scale promotion and application.

Description

Technical Field

[0001] The invention relates to an optimization design method, and in particular to an optimization design method for a pseudo composite multi-layer orthodontic appliance structure based on finite element analysis. Background Art

[0002] In recent years, invisible orthodontic technology has developed rapidly. Invisible orthodontic technology is that patients wear invisible braces of different shapes. The invisible braces rely on slight elastic deformation force to gradually move the patient's teeth according to the technician's correction plan, thereby ultimately achieving orthodontic treatment of the patient's teeth.

[0003] Invisible orthodontic appliances are formed by hot pressing dental films on a laminating machine. Dental films are divided into single-layer dental films and multi-layer dental films. Invisible orthodontic appliances are also divided into single-layer invisible orthodontic appliances and multi-layer invisible orthodontic appliances. The stress relaxation rates of multi-layer dental films and multi-layer invisible appliances are lower than those of single-layer dental films and single-layer invisible appliances. They are high-end medical consumables in the invisible correction industry. Multi-layer dental films are generally prepared by multi-layer co-extrusion equipment, that is, a single-layer dental film is first extruded, and then a co-extrusion equipment is used to obtain an integrated multi-layer dental film. However, this multi-layer co-extrusion equipment is expensive to produce, which is too expensive for general invisible orthodontic manufacturers.

[0004] In order to reduce costs, a Chinese invention patent with application number CN202310979472.5 (application publication number CN116849845A) discloses a low-cost multi-layer dental film and appliance and a manufacturing method thereof. Although the patent is directly made on an existing laminating machine by stacking two or more single-layer dental films, it eliminates the expensive multi-layer co-extrusion equipment production and processing costs, and the cost is low; however, this pseudo-composite multi-layer appliance will have inter-layer sliding displacement in some complex correction schemes, thereby affecting the correction effect, so it is urgent to optimize the structure of the pseudo-composite multi-layer appliance; however, due to the complex nonlinear characteristics of the multi-layer appliance structure, there is a lack of theoretical design methods in the structural optimization design, so the existing technology often uses experience and trial and error methods, which are costly and long. For this reason, further improvements to the existing technology are needed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a structural optimization design method of a pseudo composite multi-layer orthodontic appliance based on finite element analysis, which can improve the correction effect, in view of the above-mentioned prior art.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a method for optimizing the structure of a pseudo composite multi-layer appliance based on finite element analysis, which is characterized by comprising:

[0007] A finite element geometric modeling module is used to perform geometric modeling on multiple pseudo composite multi-layer appliances with different structures and construct finite element geometric models of multiple pseudo composite multi-layer appliances;

[0008] A finite element physical modeling module, connected to the output end of the finite element geometric modeling module, is used to set the interlayer interface friction coefficient of each pseudo composite multi-layer appliance;

[0009] A finite element calculation module, connected to the output end of the finite element physical modeling module, for calculating the stress and displacement of different layers of materials of each pseudo composite multi-layer appliance with different structures; and

[0010] The result analysis and evaluation module is connected to the output end of the finite element calculation module and is used to analyze and evaluate the stress and displacement of different layers of materials of each pseudo-composite multi-layer appliance to obtain the pseudo-composite multi-layer appliance structure after optimized design.

[0011] Preferably, each pseudo-composite multi-layer appliance has three layers.

[0012] Preferably, the geometric modeling process of the finite element geometric modeling module is:

[0013] Obtain the original DICOM data of the patient's teeth and the entire jaw, and process the original DICOM data to obtain the STL data of the teeth and the entire jaw;

[0014] Process the STL data of teeth and the entire jaw to obtain the periodontal ligament STL data;

[0015] Perform Boolean subtraction operation on the whole jaw and teeth to obtain the socket structure jaw; and perform Boolean subtraction operation on the socket structure jaw and periodontal membrane to obtain alveolar bone STL data;

[0016] Draw a retention structure of a certain shape and store it as STL data. In a specific software, select a tooth of a suitable size as the gum. Use the copy and move functions to fill the gap between the teeth. At the same time, import a retention structure of a certain shape at a specific tooth position. Move the corresponding teeth according to the simulated correction plan. Then perform Boolean operations on all teeth, gums and retention structures to form a whole. Use the curve drawing function to draw an appliance shape curve on the whole.

[0017] After converting the shape curve of the appliance into a boundary line, select the surface S surrounded by the shape curve of the appliance, and perform N1 mm shelling on the selected surface S to obtain the STL data of the M1 appliance; perform N2 mm shelling on the selected surface S to obtain the STL data of the M2 appliance; perform N3 mm shelling on the selected surface S to obtain the STL data of the M3 appliance, where N1, N2 and N3 are all constants, and N1>N2>N3;

[0018] The STL data of the M1 appliance and the STL data of the M2 appliance are subjected to Boolean subtraction and mesh optimization and denoising to obtain the STL data of the outer layer of the pseudo composite multi-layer appliance;

[0019] The STL data of the M2 appliance and the STL data of the M3 appliance are subjected to Boolean subtraction and mesh optimization and denoising to obtain the STL data of the middle layer of the pseudo composite multi-layer appliance;

[0020] The STL data of the M3 appliance was mesh optimized and denoised to obtain the STL data of the inner layer of the pseudo composite multi-layer appliance.

[0021] The STL data of the outer layer appliance of the pseudo composite multi-layer appliance, the STL data of the middle layer appliance of the pseudo composite multi-layer appliance and the STL data of the inner layer appliance of the pseudo composite multi-layer appliance are respectively converted into SAT format data, that is, the finite element geometric model of the outer layer appliance of the pseudo composite multi-layer appliance, the finite element geometric model of the middle layer appliance of the pseudo composite multi-layer appliance and the finite element geometric model of the inner layer appliance of the pseudo composite multi-layer appliance are obtained.

[0022] Preferably, the finite element geometric modeling module also includes geometric modeling of the dentition, periodontal membrane and alveolar bone respectively.

[0023] Preferably, the finite element geometric modeling module also includes the geometric modeling process of the dentition, periodontal membrane and alveolar bone, specifically:

[0024] The STL data of teeth, the STL data of periodontal ligament and the STL data of alveolar bone are obtained, and the STL data of teeth, the STL data of periodontal ligament and the STL data of alveolar bone are converted into SAT format data respectively, that is, the finite element geometric model of teeth, the finite element geometric model of periodontal ligament and the finite element geometric model of alveolar bone are obtained.

[0025] Preferably, the specific modeling process of the finite element physical modeling module is:

[0026] Import the finite element geometric model of teeth, the finite element geometric model of periodontal membrane, the finite element geometric model of alveolar bone, the finite element geometric model of the outer appliance of the pseudo-composite multi-layer appliance, the finite element geometric model of the middle appliance of the pseudo-composite multi-layer appliance, and the finite element geometric model of the inner appliance of the pseudo-composite multi-layer appliance into the finite element software;

[0027] In the finite element software, the material constitutive parameters of the teeth, periodontal ligament and alveolar bone, the outer appliance of the pseudo composite multi-layer appliance, the middle appliance of the pseudo composite multi-layer appliance and the inner appliance of the pseudo composite multi-layer appliance are assigned respectively;

[0028] The teeth, the inner side of the periodontal ligament, the outer side of the periodontal ligament and the alveolar bone are set as binding constraints; the teeth and the inner layer of the pseudo-composite multi-layer appliance, the inner layer of the pseudo-composite multi-layer appliance and the middle layer of the pseudo-composite multi-layer appliance, the middle layer of the pseudo-composite multi-layer appliance and the outer layer of the pseudo-composite multi-layer appliance are set to be in contact, and the contact friction coefficient is simulated by a penalty function. The different interlayer friction coefficients of the pseudo-composite multi-layer appliance correspond to the roughness structure design between different layers; the alveolar bone is completely fixed and the rest are free constraints; the mesh is divided by tetrahedral meshing.

[0029] Preferably, the finite element calculation module adopts a general static program.

[0030] Preferably, the specific evaluation process of the result analysis and evaluation module is as follows:

[0031] If the maximum stress of different layers of materials of the pseudo-composite multi-layer orthodontic appliance is greater than the first predetermined threshold, or the displacement of different adjacent layers of the pseudo-composite multi-layer orthodontic appliance is greater than the second predetermined threshold, it means that the structure of the pseudo-composite multi-layer orthodontic appliance is not suitable in the simulated correction plan, and it is necessary to adjust the position of the retention structure, the shape of the retention structure and the friction coefficient between the layers of the pseudo-composite multi-layer orthodontic appliance until the maximum stress of different layers of materials of the pseudo-composite multi-layer orthodontic appliance is less than the first predetermined threshold and the displacement data of different adjacent layers of the pseudo-composite multi-layer orthodontic appliance is less than the second predetermined threshold, then the pseudo-composite multi-layer orthodontic appliance structure after optimized design is obtained.

[0032] Compared with the prior art, the advantages of the present invention are: by performing finite element geometric modeling on pseudo composite multilayer appliances of different structures, and setting the interlayer interface friction coefficient of each pseudo composite multilayer appliance, the stress and displacement of different layers of materials of the pseudo composite multilayer appliance are finally calculated, and the stress and displacement of different layers of materials are used to judge the structural performance of the pseudo composite multilayer appliance, thereby completing the structural optimization design of structural parameters such as the retention structure shape, retention structure position and interlayer roughness of the pseudo composite multilayer appliance. Therefore, this method is scientific, intuitive and convenient, improves the correction effect, avoids the high cost and long cycle problems of the prior art, and has high practical value, and is worthy of large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of a method for optimizing the structure of a pseudo composite multi-layer appliance based on finite element analysis in an embodiment of the present invention;

[0034] Figure 2 Schematic diagram of alveolar bone, gum, tooth and cylindrical retention structure in an embodiment of the present invention;

[0035] Figure 3 Schematic diagram of alveolar bone, gum, tooth and square column retention structure in an embodiment of the present invention;

[0036] Figure 4 Schematic diagram of a pseudo composite multi-layer appliance in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below with reference to the accompanying drawings.

[0038] like Figure 1 As shown, the method for optimizing the structure of a pseudo-composite multi-layer appliance based on finite element analysis in this embodiment includes a finite element geometric modeling module, a finite element physical modeling module, a finite element calculation module, and a result analysis and judgment module that are sequentially connected. The finite element geometric modeling module is used to perform geometric modeling on multiple pseudo-composite multi-layer appliances of different structures, and construct finite element geometric models of multiple pseudo-composite multi-layer appliances; the finite element physical modeling module is used to set the interlayer interface friction coefficient of each pseudo-composite multi-layer appliance; the finite element calculation module is used to calculate the stress and displacement of different layers of materials of each pseudo-composite multi-layer appliance of different structures; the result analysis and judgment module is used to analyze and judge the stress and displacement of different layers of materials of each pseudo-composite multi-layer appliance, and obtain the structure of the pseudo-composite multi-layer appliance after optimized design. The finite element calculation module in this embodiment adopts a general static program.

[0039] like Figure 4 As shown, in this embodiment, each pseudo composite multi-layer appliance has three layers. Figure 4 The left picture in the figure is a partial enlarged picture of the pseudo composite multi-layer appliance in the right picture; the geometric modeling process of the finite element geometric modeling module is:

[0040] Obtain the original DICOM data of the patient's teeth and the entire jaw, and process the original DICOM data to obtain the STL data of the teeth and the entire jaw;

[0041] Process the STL data of teeth and the entire jaw to obtain the periodontal ligament STL data;

[0042] Perform Boolean subtraction operation on the whole jaw and teeth to obtain the socket structure jaw; and perform Boolean subtraction operation on the socket structure jaw and periodontal membrane to obtain alveolar bone STL data;

[0043] Draw a retention structure of a certain shape and store it as STL data. In a specific software, select a tooth of a suitable size as the gum. Use the copy and move functions to fill the gap between the teeth. At the same time, import a retention structure of a certain shape at a specific tooth position. Move the corresponding teeth according to the simulated correction plan. Then perform Boolean operations on all teeth, gums and retention structures to form a whole. Use the curve drawing function to draw an appliance shape curve on the whole.

[0044] After converting the shape curve of the appliance into a boundary line, select the surface S surrounded by the shape curve of the appliance, and perform N1 mm shelling on the selected surface S to obtain the STL data of the M1 appliance; perform N2 mm shelling on the selected surface S to obtain the STL data of the M2 appliance; perform N3 mm shelling on the selected surface S to obtain the STL data of the M3 appliance, where N1, N2 and N3 are all constants, and N1>N2>N3;

[0045] The STL data of the M1 appliance and the STL data of the M2 appliance are subjected to Boolean subtraction and mesh optimization and denoising to obtain the STL data of the outer layer of the pseudo composite multi-layer appliance;

[0046] The STL data of the M2 appliance and the STL data of the M3 appliance are subjected to Boolean subtraction and mesh optimization and denoising to obtain the STL data of the middle layer of the pseudo composite multi-layer appliance;

[0047] The STL data of the M3 appliance was mesh optimized and denoised to obtain the STL data of the inner layer of the pseudo composite multi-layer appliance.

[0048] The STL data of the outer layer appliance of the pseudo composite multi-layer appliance, the STL data of the middle layer appliance of the pseudo composite multi-layer appliance and the STL data of the inner layer appliance of the pseudo composite multi-layer appliance are respectively converted into SAT format data, that is, the finite element geometric model of the outer layer appliance of the pseudo composite multi-layer appliance, the finite element geometric model of the middle layer appliance of the pseudo composite multi-layer appliance and the finite element geometric model of the inner layer appliance of the pseudo composite multi-layer appliance are obtained.

[0049] In this embodiment, an oral scanning device is used to obtain the original DICOM data of the patient's teeth and the entire jaw, and the original DICOM data of the patient's teeth and the entire jaw are imported into the Mimics software for image cutting and adjustment of the upper and lower thresholds to obtain the STL data of the teeth and the entire jaw; the above-mentioned Mimics software is a medical image processing software in the prior art.

[0050] In this embodiment, the STL data of the teeth and the whole jaw are imported into Geomagic Studio reverse engineering software, the teeth are shelled and Boolean intersection operation is performed with the whole jaw to obtain the periodontal ligament STL data. The above-mentioned Geomagic Studio reverse engineering software is an existing software that can automatically generate an accurate digital model based on any physical parts by scanning point clouds.

[0051] In this embodiment, a retaining structure of a certain shape is drawn in Creo software, which is a three-dimensional software in the prior art, and the specific software is Geomagic Studio software; Figure 2 As shown, the retaining structure is cylindrical; Figure 3 As shown, the retaining structure is a square column; Figure 2 and Figure 3 As shown, the alveolar bone is labeled 1, the cylindrical retention structure is labeled 2, the gum is labeled 3, the tooth is labeled 4, and the square column retention structure is labeled 5.

[0052] In this embodiment, the outer layer STL data of the pseudo composite multi-layer appliance, the middle layer STL data of the pseudo composite multi-layer appliance, and the inner layer STL data of the pseudo composite multi-layer appliance can be respectively imported into the Rhinoceros software, and converted into SAT format data by the Rhinoceros software. The Rhinoceros software is a 3D modeling software based on NURBS* in the prior art, which can create, edit, analyze and translate NURBS, and simulate with basic mathematical 2D graphics such as straight lines, arcs, circles, squares, etc.

[0053] Of course, the finite element geometric modeling module also includes geometric modeling of the dentition, periodontal ligament and alveolar bone respectively; the finite element geometric modeling module also includes the geometric modeling process of the dentition, periodontal ligament and alveolar bone, specifically: obtaining the STL data of the teeth, the STL data of the periodontal ligament and the STL data of the alveolar bone, and converting the STL data of the teeth, the STL data of the periodontal ligament and the STL data of the alveolar bone into SAT format data respectively, that is, obtaining the finite element geometric model of the teeth, the finite element geometric model of the periodontal ligament and the finite element geometric model of the alveolar bone. In this embodiment, Rhinoceros software is also used to convert the STL data into SAT format data.

[0054] The specific modeling process of the finite element physical modeling module is as follows:

[0055] Import the finite element geometric model of teeth, the finite element geometric model of periodontal membrane, the finite element geometric model of alveolar bone, the finite element geometric model of the outer appliance of the pseudo-composite multi-layer appliance, the finite element geometric model of the middle appliance of the pseudo-composite multi-layer appliance, and the finite element geometric model of the inner appliance of the pseudo-composite multi-layer appliance into the finite element software;

[0056] In the finite element software, the material constitutive parameters of the teeth, periodontal membrane and alveolar bone, the outer appliance of the pseudo composite multi-layer appliance, the middle appliance of the pseudo composite multi-layer appliance and the inner appliance of the pseudo composite multi-layer appliance are assigned respectively; the material constitutive parameters of the teeth, periodontal membrane and alveolar bone in this embodiment are prior art and will not be elaborated here; and the material constitutive parameters of the outer appliance of the pseudo composite multi-layer appliance, the middle appliance of the pseudo composite multi-layer appliance and the inner appliance of the pseudo composite multi-layer appliance are assigned according to the designed elastic modulus and Poisson's ratio, and the material constitutive parameters of the present invention use the linear elastic constitutive equation;

[0057] The teeth, the inner side of the periodontal ligament, the outer side of the periodontal ligament and the alveolar bone are set as binding constraints; the teeth and the inner layer of the pseudo-composite multi-layer appliance, the inner layer of the pseudo-composite multi-layer appliance and the middle layer of the pseudo-composite multi-layer appliance, the middle layer of the pseudo-composite multi-layer appliance and the outer layer of the pseudo-composite multi-layer appliance are set to be in contact, and the contact friction coefficient is simulated by a penalty function. The different interlayer friction coefficients of the pseudo-composite multi-layer appliance correspond to the roughness structure design between different layers; the alveolar bone is completely fixed and the rest are free constraints; the mesh is divided by tetrahedral meshing.

[0058] The specific evaluation process of the result analysis and evaluation module is as follows: if the maximum stress of different layers of materials of the pseudo composite multi-layer appliance is greater than the first predetermined threshold, or the displacement of different adjacent layers of the pseudo composite multi-layer appliance is greater than the second predetermined threshold, it means that the structure of the pseudo composite multi-layer appliance is not suitable in the simulated correction scheme, and the position of the retention structure, the shape of the retention structure and the interlayer friction coefficient of the pseudo composite multi-layer appliance need to be adjusted until the maximum stress of different layers of materials of the pseudo composite multi-layer appliance is less than the first predetermined threshold and the displacement data of different adjacent layers of the pseudo composite multi-layer appliance is less than the second predetermined threshold, then the optimized pseudo composite multi-layer appliance structure is obtained. In this embodiment, the value range of the first predetermined threshold is 200-400MPa, and the value range of the second predetermined threshold is 0.1-0.5mm; according to different correction situations, the first predetermined threshold and the second predetermined threshold can be changed. In this embodiment, the friction coefficient of different interlayer roughness structures can be measured by experiment before finite element analysis, so that the corresponding interlayer roughness structure can be known after obtaining a suitable friction coefficient in finite element analysis.

[0059] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A structural optimization design method for pseudo composite multi-layer orthodontic appliances based on finite element analysis, characterized in that include: A finite element geometric modeling module is used to perform geometric modeling on multiple pseudo composite multi-layer appliances with different structures and construct finite element geometric models of multiple pseudo composite multi-layer appliances; Each pseudo-composite multi-layer appliance has three layers, and constructing the finite element geometric models of multiple pseudo-composite multi-layer appliances specifically includes: constructing the finite element geometric model of the outer layer appliance of the pseudo-composite multi-layer appliance, the finite element geometric model of the middle layer appliance of the pseudo-composite multi-layer appliance, and the finite element geometric model of the inner layer appliance of the pseudo-composite multi-layer appliance; The finite element geometric modeling module also includes geometric modeling of the dentition, periodontal ligament and alveolar bone respectively; A finite element physical modeling module, connected to the output end of the finite element geometric modeling module, is used to set the interlayer interface friction coefficient of each pseudo composite multi-layer appliance; The specific modeling process of the finite element physical modeling module is as follows: Import the finite element geometric model of teeth, the finite element geometric model of periodontal membrane, the finite element geometric model of alveolar bone, the finite element geometric model of the outer appliance of the pseudo-composite multi-layer appliance, the finite element geometric model of the middle appliance of the pseudo-composite multi-layer appliance, and the finite element geometric model of the inner appliance of the pseudo-composite multi-layer appliance into the finite element software; In the finite element software, the material constitutive parameters of the teeth, periodontal ligament and alveolar bone, the outer appliance of the pseudo composite multi-layer appliance, the middle appliance of the pseudo composite multi-layer appliance and the inner appliance of the pseudo composite multi-layer appliance are assigned respectively; The teeth, the inner side of the periodontal ligament, the outer side of the periodontal ligament and the alveolar bone are set as binding constraints; the teeth and the inner appliance of the pseudo-composite multi-layer appliance, the inner appliance of the pseudo-composite multi-layer appliance and the middle appliance of the pseudo-composite multi-layer appliance, the middle appliance of the pseudo-composite multi-layer appliance and the outer appliance of the pseudo-composite multi-layer appliance are set to be in contact, and the contact friction coefficient is simulated by a penalty function. The different inter-layer friction coefficients of the pseudo-composite multi-layer appliance correspond to the roughness structure design of different layers; the alveolar bone is completely fixedly constrained, and the rest are free constraints; the mesh is divided by tetrahedral mesh; A finite element calculation module, connected to the output end of the finite element physical modeling module, is used to calculate the stress and displacement of different layers of materials of each pseudo composite multi-layer appliance with different structures; as well as The result analysis and evaluation module is connected to the output end of the finite element calculation module and is used to analyze and evaluate the stress and displacement of different layers of materials of each pseudo-composite multi-layer appliance to obtain the pseudo-composite multi-layer appliance structure after optimized design.

2. The method for optimizing the structure of a pseudo composite multi-layer appliance according to claim 1, characterized in that: The geometric modeling process of the finite element geometric modeling module is as follows: Obtain the original DICOM data of the patient's teeth and the entire jaw, and process the original DICOM data to obtain the STL data of the teeth and the entire jaw; Process the STL data of teeth and the entire jaw to obtain the periodontal ligament STL data; Perform Boolean subtraction operation on the whole jaw and teeth to obtain the socket structure jaw; and perform Boolean subtraction operation on the socket structure jaw and periodontal membrane to obtain alveolar bone STL data; Draw a retention structure of a certain shape and store it as STL data. In a specific software, select a tooth of a suitable size as the gum. Use the copy and move functions to fill the gap between the teeth. At the same time, import a retention structure of a certain shape at a specific tooth position. Move the corresponding teeth according to the simulated correction plan. Then perform Boolean operations on all teeth, gums and retention structures to form a whole. Use the curve drawing function to draw an appliance shape curve on the whole. After converting the shape curve of the appliance into a boundary line, select the surface S surrounded by the shape curve of the appliance, and perform N1 mm shelling on the selected surface S to obtain the STL data of the M1 appliance; perform N2 mm shelling on the selected surface S to obtain the STL data of the M2 appliance; perform N3 mm shelling on the selected surface S to obtain the STL data of the M3 appliance, where N1, N2 and N3 are all constants, and N1>N2>N3; The STL data of the M1 appliance and the STL data of the M2 appliance are subjected to Boolean subtraction and mesh optimization and denoising to obtain the STL data of the outer layer of the pseudo composite multi-layer appliance; The STL data of the M2 appliance and the STL data of the M3 appliance are subjected to Boolean subtraction and mesh optimization and denoising to obtain the STL data of the middle layer of the pseudo composite multi-layer appliance; The STL data of the M3 appliance was mesh optimized and denoised to obtain the STL data of the inner layer of the pseudo composite multi-layer appliance. The STL data of the outer layer appliance of the pseudo composite multi-layer appliance, the STL data of the middle layer appliance of the pseudo composite multi-layer appliance and the STL data of the inner layer appliance of the pseudo composite multi-layer appliance are respectively converted into SAT format data, that is, the finite element geometric model of the outer layer appliance of the pseudo composite multi-layer appliance, the finite element geometric model of the middle layer appliance of the pseudo composite multi-layer appliance and the finite element geometric model of the inner layer appliance of the pseudo composite multi-layer appliance are obtained.

3. The method for optimizing the structure of a pseudo composite multi-layer appliance according to claim 1, characterized in that: The finite element geometric modeling module also includes the geometric modeling process of the dentition, periodontal membrane and alveolar bone, specifically: The STL data of teeth, the STL data of periodontal ligament and the STL data of alveolar bone are obtained, and the STL data of teeth, the STL data of periodontal ligament and the STL data of alveolar bone are converted into SAT format data respectively, that is, the finite element geometric model of teeth, the finite element geometric model of periodontal ligament and the finite element geometric model of alveolar bone are obtained.

4. The method for optimizing the structure of a pseudo composite multi-layer appliance according to any one of claims 1 to 3, characterized in that: The finite element calculation module adopts a general static program.

5. The method for optimizing the structure of a pseudo composite multi-layer appliance according to claim 1, characterized in that: The specific evaluation process of the result analysis and evaluation module is as follows: If the maximum stress of different layers of materials of the pseudo-composite multi-layer orthodontic appliance is greater than the first predetermined threshold, or the displacement of different adjacent layers of the pseudo-composite multi-layer orthodontic appliance is greater than the second predetermined threshold, it means that the structure of the pseudo-composite multi-layer orthodontic appliance is not suitable in the simulated correction plan, and it is necessary to adjust the position of the retention structure, the shape of the retention structure and the friction coefficient between the layers of the pseudo-composite multi-layer orthodontic appliance until the maximum stress of different layers of materials of the pseudo-composite multi-layer orthodontic appliance is less than the first predetermined threshold and the displacement data of different adjacent layers of the pseudo-composite multi-layer orthodontic appliance is less than the second predetermined threshold, then the pseudo-composite multi-layer orthodontic appliance structure after optimized design is obtained.

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