Design and preparation method of personalized gradient thickness invisible appliance model

Abstract

The invention discloses a design and preparation method of a personalized gradient thickness invisible orthodontic appliance model, relates to the technical field of tooth orthodontics, and aims to overcome the defects that the thickness is uncontrollable and preset mechanical properties cannot be accurately realized when an invisible orthodontic appliance is manufactured by a traditional hot press molding process. The method comprises the following steps: firstly, reconstructing a personalized dental model containing tooth roots and bone tissues based on CBCT data of a patient; designing a plurality of gradient thickness appliance schemes; through finite element analysis and simulation, selecting an optimal scheme which is most favorable for realizing correction effects such as overall movement of teeth; and finally, integrally forming and manufacturing the selected appliance by adopting a direct 3D printing technology. The direct 3D printing ensures that the appliance can be manufactured in a high-precision and high-fidelity manner from a complex gradient thickness structure with thick gingiva and thin occlusal surface, so that the optimized mechanical property verified by simulation can accurately reproduce in a real object, the inherent defects of a hot-pressing film process are thoroughly overcome, and the accuracy and predictability of correction are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of orthodontic medical devices and technology, specifically relating to the design and fabrication method of a personalized gradient thickness invisible aligner model. Background Technology

[0002] Invisible aligners, due to their aesthetic appeal, comfort, and hygiene, have become one of the mainstream methods of orthodontic treatment. Traditional invisible aligners are primarily manufactured using a thermoforming process, where a polymer film is heated and pressed onto a plaster or resin model before being trimmed at the edges. However, this thermoforming process has inherent and insurmountable drawbacks: during heating and stretching, the material undergoes uncontrollable and uneven plastic deformation and thinning. This thinning is particularly pronounced in areas with significant curvature changes, such as the buccal and lingual surfaces of the crown and the marginal ridges of interproximal spaces, leading to a discrepancy between the actual thickness distribution of the final product and the design expectations. This "uncontrollable thickness" problem prevents the precise application of the orthodontic force system pre-set by the dentist, severely impacting the accuracy, predictability, and reliability of the treatment results, representing a long-standing technical bottleneck in the field.

[0003] Although direct 3D printing technology provides a new way to manufacture invisible aligners, most existing technologies only replace materials and replicate processes of traditional uniform thickness aligners, or simply adjust the thickness based on experience. They fail to fundamentally utilize computer simulation technology to make forward-looking predictions and optimize the mechanical properties of aligners, nor do they systematically leverage the absolute advantages of direct 3D printing technology in achieving complex, precise, and non-uniform geometric structures to solve the inherent drawbacks of thermoforming processes.

[0004] In existing technologies, even when 3D printing is used to manufacture orthodontic appliances, their design still largely relies on the doctor's experience or simple rules, lacking systematic simulation and verification of the appliance's mechanical properties. Because biomechanical analysis is not conducted in conjunction with the patient's actual tooth root and bone tissue structure, it is difficult to predict whether the orthodontic force will lead to unintended tooth tilting or root resorption, limiting the accuracy and safety of the treatment. Patent CN110101469A provides a design method for variable-thickness invisible aligners. It obtains a digital model of the jaw and uses the vertex normal vector formula and Laplace operator to generate a variable-thickness invisible aligner. However, it focuses on the geometric modeling and algorithm development of the variable-thickness aligner, lacking consideration for biological effects. Patent CN111643202A discloses a method for optimizing orthodontic appliance structure based on finite element analysis. It generates a digital model of the jawbone through oral scanning, constructing an initial model of an invisible orthodontic appliance with uniform thickness. Finite element analysis is then performed on this model to establish a linear relationship (e.g., y=1.2x) between the "thickness compensation" at different locations of the appliance and the required "corrective force." However, it does not mention specific evaluation indicators for the finite element analysis results. Furthermore, due to the special geometry of the orthodontic appliance, the diversity of tooth movement types, and the influence of material nonlinearity, the proposed "linear relationship" assumption lacks scientific basis and rigor. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a fully personalized invisible aligner customization method, aligner product, and system based on patient medical imaging and computer biomechanical simulation, and precisely manufactured using direct 3D printing technology. This overcomes the dual defects of existing invisible aligner designs that rely on experience and cannot effectively control overall tooth movement, as well as the uncontrollable thickness and inability to accurately achieve preset mechanical properties caused by traditional thermoforming processes. It provides a personalized gradient thickness invisible aligner and its design method and system that starts from the patient's CBCT, optimizes the design through multi-scheme finite element simulation comparison, and precisely manufactures it using direct 3D printing technology.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for designing a personalized gradient thickness invisible aligner model, comprising the following steps: Based on cone-beam CT data of the maxillofacial region, a personalized three-dimensional digital model including the crown, root, periodontal ligament and jawbone structure was reconstructed. Based on a personalized three-dimensional digital model, at least two candidate invisible orthodontic appliances with different gradient thickness structural parameters are designed. The gradient thickness structure refers to the thickness of the orthodontic appliance in the gingival margin region being greater than the thickness of the occlusal surface region. A finite element model was created for each candidate clear aligner, and biomechanical simulations were performed to simulate the process of aligner insertion and tooth movement. By comparing and analyzing the simulation results of each candidate clear aligner, and based on the predetermined biomechanical optimization objectives, the optimal clear aligner is selected from the candidate clear aligners through quantitative comparative analysis. Output the 3D model data corresponding to the optimal invisible aligner.

[0007] Furthermore, a finite element model was created for each candidate clear aligner, and biomechanical simulations were performed to simulate the aligner insertion and tooth movement process, including the following steps: Based on the patient's actual dental and jaw anatomy, a high-precision three-dimensional finite element model including the crown, root, periodontal ligament, and jawbone was constructed, and the biomechanical properties of each tissue material, including elastic modulus and Poisson's ratio, were set. By performing nonlinear static or transient dynamic simulations on candidate orthodontic appliances with different gradient thicknesses, the stress distribution, strain state, and displacement response of the appliances on the teeth and surrounding tissues after placement are simulated.

[0008] Furthermore, the predetermined biomechanical optimization goals include: promoting the overall movement of the target tooth, making the periodontal ligament stress distribution more uniform, or maximizing the efficiency of the orthodontic force system; among them, promoting the overall movement of the target tooth is specifically quantified by whether the displacement ratio between the crown center point and the root center point in the finite element simulation results approaches 1.

[0009] Further, the quantitative comparative analysis includes the following biomechanical indicators: the crown-to-root displacement ratio, which approaches 1 when the tooth is close to overall movement; the uniformity of periodontal ligament stress distribution, assessed through the standard deviation or coefficient of variation of stress distribution; the stress concentration coefficient of the root surface and key areas of alveolar bone; the efficiency index of the orthodontic force system based on the ratio of the target tooth displacement to the total stress applied by the appliance; and the deviation between the actual movement path of the target tooth and the preset ideal path. Weights are assigned to each biomechanical indicator, and a multi-objective decision-making method is used to comprehensively evaluate each candidate scheme, selecting the gradient thickness appliance scheme that best performs in promoting overall tooth movement, reducing the risk of tissue damage, and improving orthodontic efficiency.

[0010] Furthermore, different gradient thickness structural parameters include: different gingival to occlusal thickness ratios, different gradient transition forms, or local thickness distributions for different teeth.

[0011] Furthermore, the thin-shell structure of the invisible aligner has a gradient thickness structure with the thickness decreasing from the gingival direction to the occlusal direction.

[0012] Secondly, the present invention provides a method for preparing a personalized gradient thickness invisible aligner based on 3D printing. The method obtains the three-dimensional model data of the optimal invisible aligner scheme obtained by the above-mentioned personalized gradient thickness invisible aligner model design method, and uses direct 3D printing technology to produce a personalized gradient thickness invisible aligner corresponding to the three-dimensional model data of the optimal invisible aligner scheme.

[0013] Thirdly, the present invention provides a personalized gradient thickness invisible aligner based on 3D printing, which is obtained by the method for preparing a personalized gradient thickness invisible aligner based on 3D printing as described in claim 6. The measured thickness of the invisible aligner at any position deviates from the thickness at the corresponding position of the design model by no more than ±0.05 mm.

[0014] Fourthly, the present invention can also provide an orthodontic treatment system, comprising a series of personalized gradient thickness invisible aligners obtained by the above-described 3D printing-based personalized gradient thickness invisible aligner fabrication method.

[0015] Fifthly, the present invention provides a personalized gradient thickness invisible aligner model design system, including a personalized three-dimensional digital model construction module, a candidate invisible aligner design module, a finite element simulation module, and a comparison and output module; The personalized 3D digital model construction module reconstructs personalized 3D digital models containing tooth crowns, roots, periodontal ligaments, and jawbone structures based on maxillofacial cone-beam CT data. The candidate clear aligner design module is based on a personalized three-dimensional digital model and designs at least two candidate clear aligners with different gradient thickness structural parameters. The gradient thickness structure refers to the thickness of the aligner in the gingival margin region being greater than the thickness of the occlusal surface region. The finite element simulation module is used to create a finite element model for each candidate clear aligner and perform biomechanical simulation to simulate the process of aligner insertion and tooth movement. The geometric dimensions of each clear aligner are obtained through biomechanical simulation to simulate the process of aligner insertion and tooth movement, and are selected according to the predetermined biomechanical optimization target. The comparison and output module compares and analyzes the simulation results of each candidate clear aligner, selects the optimal clear aligner from the candidates based on the predetermined biomechanical optimization objectives, and outputs the three-dimensional model data corresponding to the optimal clear aligner.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: This application utilizes direct 3D printing technology, fundamentally solving the industry problem of "uncontrollable thickness" in traditional hot-pressing processes. This ensures that invisible orthodontic appliances, especially those with complex gradient thickness structures, can be precisely manufactured, providing a reliable physical basis for achieving pre-set precise mechanical control. Starting from the source of CBCT, the design is based on the patient's unique root-periodontal-bone system, achieving a leap from crown fitting to biomechanical system fitting.

[0017] By adopting a multi-scheme design-simulation comparison-optimization approach, the design decision-making process is transformed from subjective experience-based judgment to objective selection based on quantitative data, ensuring that the mechanical performance of the final scheme is the best among all candidate schemes. By deeply integrating medical imaging, 3D reconstruction, CAD and high-precision additive manufacturing, a complete, efficient and technologically advanced personalized customization solution has been formed. By constructing personalized finite element models encompassing the tooth root-periodontal-bone system, accurate prediction and optimization of the biomechanical behavior of orthodontic appliances can be achieved. This method not only simulates tooth movement paths but also assesses periodontal tissue stress, ensuring the safety and effectiveness of treatment from a biomechanical perspective, significantly outperforming traditional experience-based design methods.

[0018] Furthermore, when creating a finite element model for each candidate orthodontic appliance, a high-precision three-dimensional finite element model was constructed based on the patient's actual dental and jaw anatomy. The biomechanical properties of each tissue material were also defined. This high-precision finite element model, combined with real material properties (such as elastic modulus and Poisson's ratio), makes the simulation results closer to physiological reality, improving the accuracy of stress distribution and displacement prediction. This enhances the reliability of the simulation, provides a credible basis for optimized design, and reduces clinical risks caused by model simplification.

[0019] Furthermore, the predetermined biomechanical optimization goals include promoting overall tooth movement, achieving uniform periodontal ligament stress distribution, or maximizing the efficiency of the orthodontic force system. These clear optimization goals provide directional guidance for appliance design. Quantifying overall movement by ensuring the crown-to-root displacement ratio approaches 1 ensures controllable tooth movement and avoids undesirable phenomena such as tilting. Uniform stress distribution reduces the risk of localized overload on periodontal tissues, while efficiency metrics maximize the utilization of orthodontic forces, thereby shortening treatment time and improving therapeutic efficacy.

[0020] Furthermore, the quantitative comparative analysis included multiple biomechanical indicators and employed a multi-objective decision-making method. Multi-indicator analysis (such as displacement ratio, stress uniformity, stress concentration factor, efficiency index, and path deviation) comprehensively evaluated the overall performance of the orthodontic appliance. Weighting settings allowed for prioritization based on patient-specific needs (such as periodontal condition), making the selection more personalized. The multi-objective decision-making method avoided subjective bias, ensuring a balance between promoting movement, reducing damage, and improving efficiency.

[0021] Furthermore, different gradient thickness structural parameters, including thickness ratios, gradient transition forms, or local thickness distributions, allow for parametric design to flexibly adjust appliance thickness to accommodate different types of tooth movement (such as rotation and translation) or anatomical variations in patient tooth morphology. Local thickness variations tailored to anterior and posterior teeth can optimize the force transmission path, enhancing the design's adaptability and improving the appliance's ability to handle complex cases.

[0022] Furthermore, the thin-shell structure of the invisible aligner has a gradient thickness structure with decreasing thickness on the occlusal surface from the gingival direction. This gradient structure conforms to the biomechanical principles of tooth movement. The thicker gingival margin provides stable anchorage and makes the center of force application closer to the center of tooth resistance. The thinner occlusal surface reduces occlusal interference and reduces uncontrolled tilting movement caused by "leverage". This promotes overall tooth movement, reduces unnecessary torque, and improves orthodontic accuracy and patient comfort. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the overall process of personalized customization and direct 3D printing manufacturing of this invention.

[0024] Figure 2 This is a personalized dental and jaw model reconstructed based on CBCT data, and a finite element simulation (including tooth roots and bone tissue).

[0025] Figure 3 A schematic diagram of three candidate orthodontic appliances with different gradient thicknesses designed for the same orthodontic stage. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0028] This invention provides a method for designing a personalized gradient thickness invisible aligner model, comprising the following steps: Based on maxillofacial cone-beam CT data, a personalized three-dimensional digital model including the crown, root, periodontal ligament and jawbone structure was reconstructed. Based on a personalized three-dimensional digital model, at least two candidate invisible orthodontic appliances with different gradient thickness structural parameters are designed. The gradient thickness structure refers to the thickness of the orthodontic appliance in the gingival margin region being greater than the thickness of the occlusal surface region. A finite element model was created for each candidate clear aligner, and biomechanical simulations were performed to simulate the process of aligner insertion and tooth movement. By comparing and analyzing the simulation results of each candidate clear aligner, and selecting the optimal clear aligner from the candidates based on the predetermined biomechanical optimization objectives, the three-dimensional model data corresponding to the optimal clear aligner is output.

[0029] refer to Figure 1 This invention provides a method for customizing personalized gradient thickness invisible orthodontic appliances via direct 3D printing, constructing a closed-loop process from personalized modeling and multi-scheme simulation optimization to high-precision manufacturing. The method includes the following steps: S1. Personalized Model Establishment: Utilizing the patient's oral and maxillofacial cone-beam CT data, a personalized 3D digital model is precisely reconstructed, including individualized tooth roots, periodontal ligaments, and surrounding bone tissue, laying the anatomical foundation for accurate biomechanical simulation. In the specific implementation process, based on the DICOM format image data from the patient's oral and maxillofacial cone-beam CT, image noise reduction and threshold segmentation are used to separate the hard tissue regions, including teeth and jawbones. Tooth roots are separated according to their anatomical features and grayscale differences. Based on the reconstructed tooth model, a uniform thickness (e.g., 0.2-0.3 mm) is added to the root surface to generate a connecting layer representing the periodontal ligament. The thickness is set based on the clinical crown shape to generate a model of the invisible aligner. Simultaneously, based on the grayscale characteristics of bone tissue in CBCT, models of the maxilla and mandible, including alveolar ridges, cortical bone, and cancellous bone, are reconstructed. Finally, the teeth, periodontal ligament, jawbone, and invisible aligner components are assembled in 3D space to form a personalized 3D digital model of the dentofacial system incorporating the patient's anatomical features.

[0030] S2, Multi-scheme design: Based on the aforementioned three-dimensional digital model including the crown, root, periodontal ligament, and jawbone structure, at least three candidate schemes for invisible aligners with different gradient thickness structural parameters are designed according to clinical treatment goals. The overall average thickness of these candidate schemes is set to 0.75 mm, with maximum gingival thicknesses of 0.8 mm, 1.0 mm, and 1.2 mm, respectively. Different thickness transition forms can be adopted: including linear transitions, where the thickness decreases uniformly and linearly from the gingival margin to the occlusal surface; and non-linear transition forms, including curved transitions and stepped transitions, such as setting a thicker reinforcing structure in the clinical crown center region. By combining different gingival thicknesses and transition forms, candidate schemes with different mechanical properties are generated, providing a comparative basis for subsequent finite element analysis. Figure 3 .

[0031] refer to Figure 2 S3, Personalized Finite Element Analysis: A finite element model is established for each gradient thickness orthodontic candidate design, and independent biomechanical simulation calculations are performed to quantitatively evaluate its orthodontic effect. This personalized finite element analysis step is the core component of this invention for achieving precise mechanical control, and specifically includes: Based on the patient's actual dental and jaw anatomy, a high-precision three-dimensional finite element model including the crown, root, periodontal ligament, and jawbone is constructed, and each tissue material is given real biomechanical properties, such as elastic modulus and Poisson's ratio. By conducting nonlinear static or transient dynamic simulations on candidate orthodontic appliance designs with different gradient thicknesses, the stress distribution, strain state, and displacement response of the teeth and surrounding tissues after appliance placement are simulated. This analysis can quantitatively assess whether the orthodontic force promotes overall tooth movement, avoids the risk of root resorption, and keeps periodontal ligament stress within a physiologically safe range. By comparing the simulation results of each design, it is possible to scientifically determine which gradient thickness structure is most conducive to achieving the preset orthodontic goals.

[0032] S4, Scheme Optimization: Based on the simulation results of each candidate scheme obtained from the personalized finite element analysis step, the optimal orthodontic appliance scheme is selected through quantitative comparative analysis. The quantitative comparative analysis includes the following quantifiable biomechanical indicators: the ratio of crown to root displacement, which indicates that the tooth is close to overall movement when the ratio approaches 1; the uniformity of periodontal ligament stress distribution, assessed by the standard deviation or coefficient of variation of stress distribution; the stress concentration coefficient of the root surface and key areas of alveolar bone; the efficiency index of the orthodontic force system based on the ratio of the target tooth displacement to the total stress applied by the appliance; and the deviation between the actual movement path of the target tooth and the preset ideal path. By setting the weights of each biomechanical indicator, a multi-objective decision-making method is used to comprehensively evaluate each candidate scheme, and finally select the gradient thickness appliance scheme with the best overall performance in promoting overall tooth movement, reducing the risk of tissue damage, and improving orthodontic efficiency.

[0033] S5, 3D Printing Production: The digital model of the orthodontic appliance corresponding to the optimal gradient thickness candidate design is manufactured as a single unit using direct 3D printing technology. This step is crucial to ensuring the accurate realization of the design, enabling the complex gradient thickness structure, which has been simulated and verified in digital space, to be faithfully transformed into a physical entity, completely avoiding the uncontrollable thickness issues caused by thermoforming processes.

[0034] Based on cone-beam computed tomography (CBCT) data of the maxillofacial region, a personalized 3D digital model including the crown, root, periodontal ligament, and jawbone structures was reconstructed, achieving precise digital reconstruction of the patient's dentition system and providing a high-fidelity individual anatomical basis for appliance design. By including key structures such as the crown, root, periodontal ligament, and jawbone, the model comprehensively reflects the tooth's support environment and biomechanical properties. This ensures a high degree of matching between the subsequent appliance design and the patient's anatomical structure, improving the personalization and accuracy of treatment, reducing errors caused by model simplification, and providing reliable input for biomechanical simulation. Based on the personalized 3D digital model, at least two candidate invisible appliances with different gradient thickness structural parameters were designed. The gradient thickness structure (thicker at the gingival margin and thinner at the occlusal surface) optimizes the appliance's mechanical performance: a thicker gingival margin enhances the appliance's retention force, preventing dislodgement, and makes the appliance's force center closer to the tooth's resistance center; a thinner occlusal surface improves wearing comfort and chewing function. Designing multiple candidate appliances allows for the exploration of the impact of different thickness parameters (such as thickness ratio and gradient transition form) on mechanical behavior, thereby finding the optimal thickness distribution through comparison, achieving customized allocation of orthodontic forces, and improving treatment efficiency. A finite element model is established for each candidate appliance, and biomechanical simulation is performed to simulate the appliance insertion and tooth movement process. Finite element analysis enables simulation of the orthodontic process, predicting the stress distribution, strain, and displacement response of the forces applied by the appliance on the teeth, periodontal ligament, and jawbone. This allows for the evaluation of the biomechanical effects of the appliance before physical manufacturing, avoiding blind trial and error. Through nonlinear static or transient dynamic simulation, the complex mechanical behavior after appliance insertion can be captured, ensuring that the orthodontic force is within a safe range, reducing the risk of tissue damage, and improving the controllability of treatment. Comparative analysis of the simulation results of each candidate appliance is conducted, and the optimal appliance is selected through quantitative comparative analysis based on predetermined biomechanical optimization goals. Quantitative analysis transforms biomechanical goals (such as promoting overall tooth movement and stress distribution uniformity) into measurable parameters (such as the crown-to-root displacement ratio and stress standard deviation), making the evaluation more objective. Multi-objective decision-making methods (such as weighted scoring) comprehensively weigh various indicators to ensure that the selected orthodontic appliance achieves optimal efficiency, safety, and comfort. This improves the scientific rigor of the treatment plan, avoids the limitations of a single indicator, and personalizes treatment outcomes. Directly outputting the optimal design's 3D data and connecting it to digital manufacturing (such as 3D printing) shortens the appliance production cycle and ensures consistency from design to manufacturing. This helps improve treatment efficiency, reduces human error, and enables precise and rapid appliance delivery.

[0035] This invention also provides a personalized gradient thickness invisible aligner manufactured using the above method. This aligner is made from biocompatible photocurable resin using direct 3D printing (such as DLP or SLA technology). The gradient thickness structure at every point on the aligner achieves a high degree of consistency between the design value and the actual product. Its manufacturing precision is far superior to that of thermoforming processes, thus enabling the precise application of optimized mechanical properties verified by finite element analysis to the physical aligner.

[0036] The present invention can also provide an orthodontic treatment system, including a series of personalized gradient thickness invisible aligners obtained by the aforementioned 3D printing-based personalized gradient thickness invisible aligner preparation method.

[0037] Based on the concept of the design method described above, the present invention can also provide a personalized gradient thickness invisible aligner model design system, including a personalized three-dimensional digital model construction module, a candidate invisible aligner design module, a finite element simulation module, and a comparison and output module. The personalized 3D digital model construction module reconstructs personalized 3D digital models containing tooth crowns, roots, periodontal ligaments, and jawbone structures based on maxillofacial cone-beam CT data. The candidate clear aligner design module is based on a personalized three-dimensional digital model and designs at least two candidate clear aligners with different gradient thickness structural parameters. The gradient thickness structure refers to the thickness of the aligner in the gingival margin region being greater than the thickness of the occlusal surface region. The finite element simulation module is used to create a finite element model for each candidate clear aligner and perform biomechanical simulations to simulate the process of aligner insertion and tooth movement. The comparison and output module compares and analyzes the simulation results of each candidate clear aligner, selects the optimal clear aligner from the candidates based on the predetermined biomechanical optimization objectives, and outputs the three-dimensional model data corresponding to the optimal clear aligner.

[0038] In summary, this invention provides a personalized gradient thickness invisible aligner model design and fabrication method. Based on the patient's CBCT data, a personalized dental and jaw model including tooth roots and bone tissue is reconstructed. Based on this, multiple gradient thickness aligner schemes are designed. Through finite element analysis simulation, the optimal scheme that best achieves orthodontic effects such as overall tooth movement is selected. The selected aligner scheme is manufactured using direct 3D printing technology in a single piece. Direct 3D printing ensures that the complex gradient thickness structure of the aligner, thicker at the gingival surface and thinner at the occlusal surface, can be manufactured with high precision and high fidelity. This allows the optimized mechanical properties verified by simulation to be accurately reproduced in the physical object, completely overcoming the inherent drawbacks of the thermoforming process and significantly improving the accuracy and predictability of orthodontic treatment.

[0039] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for designing a personalized gradient thickness invisible aligner model, characterized in that, The method comprises the following steps: reconstructing a personalized three-dimensional digital model comprising tooth crown, tooth root, periodontal membrane and jawbone structure based on dental cone beam CT data; designing at least two candidate invisible aligners with different gradient thickness structure parameters based on the personalized three-dimensional digital model, wherein the gradient thickness structure refers to a thickness of a gum edge region of the aligner being greater than a thickness of a bite surface region; establishing a finite element model for each candidate invisible aligner and performing biomechanical simulation to simulate the process of wearing the aligner and tooth movement; comparatively analyzing simulation results of each candidate invisible aligner, and selecting an optimal invisible aligner from the candidate invisible aligners according to a predetermined biomechanical optimization target through quantitative comparative analysis; outputting three-dimensional model data corresponding to the optimal invisible aligner.

2. The method of designing a personalized, gradient thickness, invisible aligner model according to claim 1, wherein, The method comprises the following steps of establishing a finite element model for each candidate invisible aligner and performing biomechanical simulation to simulate the process of wearing the aligner and tooth movement: constructing a high-precision three-dimensional finite element model comprising tooth crown, tooth root, periodontal membrane and jawbone based on the real dental and jaw anatomical structure of the patient, and setting biomechanical properties of each tissue material, including elastic modulus and Poisson's ratio; performing nonlinear statics or transient dynamics simulation on different gradient thickness candidate aligners to simulate the stress distribution, strain state and displacement response of the tooth and surrounding tissue after wearing the aligner.

3. The method of designing a personalized, gradient thickness, invisible aligner model according to claim 1, wherein, The predetermined biomechanical optimization target includes promoting the overall movement of the target tooth, making the periodontal membrane stress distribution more uniform, or making the orthodontic force system most efficient; wherein the promotion of the overall movement of the target tooth is quantitatively judged by whether the displacement ratio of the center point of the tooth crown to the center point of the tooth root in the finite element simulation result tends to 1.

4. The method of designing personalized, gradient thickness, invisible aligner models of claim 1, wherein, The quantitative comparative analysis includes the following biomechanical indexes: the displacement ratio of the tooth crown to the tooth root, which tends to 1 when the tooth approaches overall movement; periodontal membrane stress distribution uniformity, evaluated by the standard deviation or coefficient of variation of stress distribution; stress concentration coefficient of the tooth root surface and alveolar bone key area; orthodontic force system efficiency index based on the ratio of target tooth displacement to total stress applied by the aligner, and deviation degree of the actual movement path of the target tooth from the preset ideal path; setting the weight of each biomechanical index, and comprehensively evaluating each candidate scheme by using a multi-objective decision method to select the gradient thickness aligner scheme that has the best overall performance in promoting the overall movement of the tooth, reducing the risk of tissue damage and improving the efficiency of the treatment.

5. The method of designing personalized orthodontic aligner models of varying thicknesses according to claim 1, wherein, Different gradient thickness structure parameters include different gum side to bite surface thickness ratios, different gradient transition forms, or local thickness distribution for different teeth.

6. The method of designing personalized, gradient thickness, invisible aligner models of claim 1, wherein, The thin shell structure of the invisible aligner has a gradient thickness structure with thickness decreasing from the gum direction to the bite surface direction.

7. A method for manufacturing a personalized gradient thickness invisible aligner based on 3D printing, characterized in that, The three-dimensional model data corresponding to the optimal invisible aligner scheme obtained by the personalized gradient thickness invisible aligner model design method of any one of claims 1-6 is used to manufacture the personalized gradient thickness invisible aligner corresponding to the three-dimensional model data of the optimal invisible aligner scheme by using a direct 3D printing process.

8. A 3D printing based personalized gradient thickness clear aligner, characterized in that, The invisible aligner entity obtained by the preparation method of the personalized gradient thickness invisible aligner based on 3D printing according to claim 7 has a thickness deviation of no more than ±0.05 mm at any position.

9. An orthodontic treatment system, characterized by The invisible aligner entity obtained by the preparation method of the personalized gradient thickness invisible aligner based on 3D printing according to claim 7 has a thickness deviation of no more than ±0.05 mm at any position.

10. A personalized gradient thickness, invisible aligner model design system, characterized in that, The system comprises a personalized three-dimensional digital model construction module, a candidate invisible aligner design module, a finite element simulation module, and a comparison and selection output module. The personalized three-dimensional digital model construction module reconstructs a personalized three-dimensional digital model containing tooth crown, tooth root, periodontal membrane, and jaw bone structure based on cone beam CT data of the jaw face. The candidate invisible aligner design module designs at least two candidate invisible aligners with different gradient thickness structure parameters based on the personalized three-dimensional digital model, wherein the gradient thickness structure refers to a structure in which the thickness of the aligner at the gum edge is greater than the thickness at the occlusal surface. The finite element simulation module is used to establish a finite element model for each candidate invisible aligner and perform biomechanical simulation to simulate the process of aligner wearing and tooth movement. The comparison and selection output module compares and analyzes the simulation results of each candidate invisible aligner, selects the optimal invisible aligner from the candidate invisible aligners according to a predetermined biomechanical optimization target, and outputs the three-dimensional model data corresponding to the optimal invisible aligner.

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