Shell-shaped dental appliance for correcting rear teeth and design method of shell-shaped dental appliance

Abstract

The invention relates to a shell-shaped dental appliance for correcting rear teeth and a design method of the shell-shaped dental appliance. The appliance comprises a first segment shell unit, a traction structure and a second segment shell unit, the first segment shell unit and the traction structure form a first tooth receiving cavity, and the second segment shell unit forms a second tooth receiving cavity; the first segment shell unit can accommodate canine teeth or premolar teeth of a patient, and the traction structure is fixedly connected with the first segment shell unit; the traction structure is used for hanging elastomers; the second segment shell unit can accommodate another premolar or molar of the patient, and the second tooth receiving cavity applies a second tooth moving force to the accommodated tooth; the second segment shell unit applies a second tooth moving force to the accommodated teeth; and the first segment shell unit is connected with the elastic body through a traction structure. Compared with the prior art, the orthodontic force is accurately controlled; personalized design is realized; and the stability and controllability of the treatment effect are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of oral orthodontics, and in particular to a shell-shaped dental appliance for posterior teeth correction and a design method thereof. Background Art

[0002] In traditional orthodontic treatment, posterior tooth correction usually relies on fixed or invisible appliances to mechanically move teeth, especially distal movement of posterior teeth (i.e., movement of posterior teeth backwards), which is a relatively complex correction task. Since posterior teeth are located further back and have special morphology and functions compared to anterior teeth, posterior tooth correction requires precise mechanical control. However, existing correction methods often have some problems in posterior tooth correction, which are manifested in the following aspects:

[0003] First, most current posterior orthodontic treatments rely on standardized designs and universal templates, which fail to fully account for individual patient differences. Factors such as individual patient morphology, tooth position, periodontal health, and implant placement can influence the distribution of orthodontic forces and the path of tooth movement. Consequently, appliances designed based on universal protocols may not meet the individual needs of all patients, compromising treatment outcomes.

[0004] Secondly, posterior tooth correction is not just a matter of simple tooth movement; it also involves the direction, magnitude, and distribution of force points. Existing appliance designs are mostly based on clinical experience, using empirical methods to determine the direction and magnitude of force. However, this empirical design does not fully consider the complex mechanical effects, especially when the force distribution is uneven or the tooth movement path is inaccurate, which can easily lead to unsatisfactory treatment results and may even cause adverse side effects.

[0005] Furthermore, although the introduction of finite element analysis (FEA) and biomechanical theory has provided mechanical support for oral orthodontic treatment, existing mechanical simulation models generally focus on the interaction between teeth and orthodontic appliances, lacking comprehensive consideration of the patient's overall oral structure (such as the resistance center of the posterior teeth). As a result, existing mechanical simulations cannot fully and accurately predict the precise movement trajectory of teeth during treatment and the actual effect of orthodontic forces.

[0006] With the rapid development of digital technology, computer-aided design (CAD) and computer-aided manufacturing (CAM) have been widely used in the personalized customization of oral appliances. These technologies use three-dimensional scanning and imaging techniques to model the patient's oral cavity, providing a foundation for appliance design. However, current digital technologies still focus more on tooth alignment and morphological changes, and are still insufficient for accurate simulation and mechanical support of corrective forces. Especially in complex posterior tooth correction, how to control the magnitude, direction, and distribution of corrective forces through precise mathematical models remains an urgent problem. In addition, existing appliance designs still have room for improvement in terms of comfort and stability. For example, the force application point and magnitude in existing designs often require repeated adjustments during treatment, resulting in increased patient discomfort and potentially affecting treatment effectiveness. Appliance designs lacking the support of precise mechanical analysis are prone to instability, preventing the required corrective forces from being continuously and effectively applied to the teeth during treatment.

[0007] Therefore, with the increasing demand for personalized treatment, how to combine mathematical models and digital technology to design more accurate and efficient posterior tooth correction solutions has become a key technical challenge in the field of orthodontics. To overcome the limitations of existing technologies, some studies in recent years have begun to attempt to introduce mathematical modeling, mechanical simulation, and optimization algorithms to accurately calculate the magnitude, direction, and distribution of correction forces, thereby optimizing appliance design and improving the predictability of treatment effects.

[0008] Patent KR20110078521 discloses a method for manufacturing an orthodontic treatment kit and an orthodontic correction kit for producing lingual pull wires used to align a transposition model of the patient's anterior portion with the teeth after correction by an instrument, thereby aligning the anterior portion of the patient's anterior portion with the teeth after correction. The kit also provides a setup model in which the anterior transposition model of the patient's teeth, corresponding to the dentist's, is aligned with the teeth after correction, thereby aligning the anterior portion of the patient's anterior portion with the teeth after correction. This setup model allows for the simultaneous manufacture of an orthodontic pre-calibration device for the anterior portion and a lingual pull wire for moving the anterior portion during the initial stages of orthodontic treatment, as well as an orthodontic correction kit using the kit. However, the kit cannot accurately simulate the corrective forces. Without the use of mathematical modeling tools, it is impossible to fully and accurately predict the precise movement trajectory of the teeth during treatment and the actual effect of the corrective forces. Summary of the Invention

[0009] The purpose of the present invention is to overcome the defects of the above-mentioned prior art such as inaccurate control of correction force and unstable treatment effect, and to provide a shell-shaped dental appliance for posterior teeth correction and its design method. Through digital modeling and mathematical optimization, the correction force can be accurately controlled; personalized design can be achieved; and the stability and controllability of the treatment effect can be improved.

[0010] By establishing a mathematical model based on the patient's oral data (such as skeletal morphology, tooth position, periodontal condition, and implant position), combined with the design of tooth movement paths, the present invention can accurately predict the magnitude and direction of the required correction force, thereby generating a customized posterior tooth brace, ultimately achieving more efficient and accurate posterior tooth correction treatment. Through this personalized design method, the present invention can not only optimize posterior tooth correction plans and reduce side effects during treatment, but also improve the stability of treatment effects and enhance the patient's treatment experience.

[0011] The present invention provides a shell-shaped dental appliance for posterior tooth correction, comprising: a first segment shell unit, a traction structure, and a second segment shell unit; the first segment shell unit and the traction structure constitute a first tooth receiving cavity, and the second segment shell unit constitutes a second tooth receiving cavity;

[0012] The first segment shell unit can accommodate the patient's canine or premolar, and the traction structure is fixedly connected to the first segment shell unit; the traction structure is used to suspend an elastomer so that the first tooth receiving cavity applies a first tooth-moving force to the accommodated tooth; the second segment shell unit can accommodate another premolar or molar of the patient, and the second tooth receiving cavity applies a second tooth-moving force to the accommodated tooth; the tensile force of the elastomer can be adjusted according to the patient's treatment needs.

[0013] The direction of the first tooth movement force is less than 45° relative to the angle formed by the line connecting the traction structure and the posterior tooth impedance center; the traction structure is located on the lingual or buccal side of the first segment shell unit corresponding to the canine or the first premolar, and is used to provide directional corrective force; the first segment shell unit and the second segment shell unit are connected by a connecting component, and the displacement of the first segment shell unit can be partially transmitted to the second segment shell unit; a transmission channel for corrective force is formed, which ensures the mechanical controllability of the entire correction system and pushes the target tooth to move in a predetermined direction.

[0014] The second segment housing unit applies a second tooth-moving force to the teeth it contains. The specific direction and magnitude of the force are determined by factors such as the orthodontic design for the first and second premolars, first and second molars, the material parameters of the posterior teeth's periodontal tissue, the rigidity of the elastomer, and the displacement of the first segment housing unit. This second tooth-moving force differs in direction and magnitude from the first tooth-moving force, ensuring controlled application of orthodontic force to multiple teeth during treatment.

[0015] The first segment shell unit is connected to the elastomer via a traction structure. One end of the elastomer is fixed to the traction structure, and the other end is fixed to the micro-implant, thereby providing a first tooth-moving force applied to the tooth through the elastomer. The micro-implant is usually fixed to the alveolar bone, thereby providing additional support without damaging the tooth itself. With the assistance of the micro-implant, the braces can apply a stable and continuous force during treatment, ensuring the precise displacement of the teeth during the correction process.

[0016] The design position of the traction structure can be selected on the lingual or buccal side of the canine or first premolar. Its main function is to effectively and directionally transmit the applied traction and tensile force to the target tooth, assisting in applying force to make it move along the predetermined path.

[0017] The first tooth-moving force and the second tooth-moving force are different in direction and magnitude;

[0018] The shell-like dental appliance can be installed and removed manually.

[0019] The surface of the shell-shaped dental appliance is provided with a plurality of additional structures for providing additional stability or correction force direction guidance function.

[0020] Furthermore, the connecting assembly is flexible to accommodate individual changes in the patient's oral cavity. This prevents the application of excessive corrective force, which can cause discomfort or damage, or cause the appliance to become dislodged. During treatment, the connecting assembly provides the necessary elastic support, ensuring that the appliance can adapt to changes in oral morphology.

[0021] Furthermore, the angle formed by the direction of the first tooth moving force and the line connecting the traction structure and the posterior tooth impedance center is less than 45 degrees, thereby ensuring that the correction force can be applied accurately, thereby avoiding the problem of uneven or inaccurate correction force direction.

[0022] Furthermore, an angle between the direction of the first tooth-moving force and the direction of the second tooth-moving force is less than 60°.

[0023] Furthermore, the elastic body connected to the traction structure is a rubber band, a spring or a combination of the two.

[0024] The structural design of the shell-shaped dental appliance ensures the precise application of the correction force. The elastic body provides continuous correction force F elastic, whose main function is to transmit the first tooth-moving force F1 to the target tooth in the first segment shell unit. The magnitude and direction of this force are determined through personalized design based on the patient's specific treatment needs, combined with factors such as each patient's tooth morphology, occlusion relationship, and treatment goals. The angle α formed by the direction of the first tooth-moving force F1 and the line connecting the traction structure to the posterior tooth impedance center is less than 45°, ensuring that the orthodontic force is accurately and stably applied to the target tooth throughout the treatment process, effectively controlling the non-design torque of the tooth's mesiodistal inclination and buccal-lingual inclination.

[0025] The direction of the first tooth-moving force F1 forms an angle of 0° with the line connecting the traction structure and the posterior tooth resistance center. This means the tooth-moving force is directed entirely along the traction structure toward the posterior tooth resistance center. Under these mechanical conditions, and in accordance with the physical principle of the resistance center, the posterior teeth will only move distally and intrude along the designed tooth arrangement path, without distal tilting. This ensures that the combined tooth movement is limited to the predetermined direction.

[0026] The direction and magnitude of the second tooth-moving force F2 differ from those of the first tooth-moving force F1. Its direction and magnitude are determined by a comprehensive design based on multiple factors, including the mechanical response of the patient's posterior periodontal tissues and the tooth movement path. This design ensures that the forces applied to the posterior teeth during treatment are within the optimal load range for biological bone remodeling of the posterior alveolar bone, avoiding adverse reactions caused by overcorrection.

[0027] The angle between the direction of the first tooth-moving force F1 and the direction and magnitude of the second tooth-moving force F2 is 10°. This design takes into account the coordinated movement of multiple teeth, ensuring the reasonable distribution of the force direction of each tooth during the correction process, while avoiding mutual interference of forces between different teeth. Specifically, through the synergy of the appliance structure and the traction design, the movement of each tooth is not limited to a single direction, but through a combination of multi-directional force directions and magnitudes, different intensities of force are applied to different teeth during the correction process, so that each tooth can be moved under appropriate mechanical conditions, and the mechanical consistency of the main movement direction is maintained as a whole, thereby achieving the overall correction goal of the dentition.

[0028] Patients can easily install the braces on their teeth. To do so, they first suspend one end of the elastic body from the traction structure, then wear the braces. Finally, they suspend the other end of the elastic body from the micro-implant, and the braces begin to function. During treatment, patients can remove and replace the braces and elastic body according to their doctor's instructions, ensuring flexibility and comfort throughout the treatment process.

[0029] The present invention also provides a method for designing a shell-shaped dental appliance for posterior tooth correction, wherein parameters are optimized based on the patient's oral data, correction requirements, and the direction and magnitude of the correction force, including the following steps:

[0030] S1: Acquire the patient's oral data, including bone morphology, tooth position, periodontal condition, and implant position, to determine the position of the posterior tooth impedance center;

[0031] The posterior tooth impedance center refers to a virtual point associated with the posterior teeth and their surrounding tissues (including the alveolar bone and periodontal ligament). The physical properties of this point are determined by the response of the teeth and their surrounding tissues to external forces. The impedance center is a key reference point when a tooth is subjected to force and is often used to describe its movement under external forces. When multiple posterior teeth are involved, the impedance center can be considered the collective response point of the entire dentition, its position determined by the impedance centers of each tooth and their interactions. In mechanics, the response of an object to force depends not only on the magnitude and direction of the force but also on its stiffness. For teeth and their supporting structures, stiffness reflects the tissue's ability to resist external forces. The impedance center (or "central stiffness") is typically a virtual point associated with the displacement response of a tooth under load. Near this point, the stiffness of the tooth reaches equilibrium, and the effects of the force are relatively concentrated. Simply put, the impedance center can be considered the "point of resistance" of the tooth and its surrounding tissues to external forces. In orthodontic mechanical analysis, the impedance center is closely related to the "center of resistance" or "center of torque." When an external force is applied to a tooth, the tooth responds by both translation and rotation. The impedance center is typically the intersection of the rotational axes generated by the force. In a multi-tooth model, the location of the impedance center of a posterior tooth can often be determined by a weighted average that accounts for the stiffness and displacement responses of each tooth.

[0032] S2: Design the tooth movement path according to the patient's orthodontic needs;

[0033] S3: Construct a mathematical model, which is a nonlinear programming model based on the SLSQP algorithm; the optimization parameters of the model include the traction force, traction position and traction method, wherein the boundary conditions include the traction force, traction position and the stiffness of the orthodontic material, and the objective function is the angle formed by the direction of the first tooth movement force relative to the line connecting the traction structure (102) to the posterior tooth impedance center; the purpose of the optimization design is to solve a set of design parameters to reduce the angle between the direction of the correction force and the line connecting the posterior tooth impedance center, thereby ensuring the accuracy of the correction force application, so that the correction force and the design of the tooth movement path can work together to achieve the best treatment effect and avoid unnecessary interference from the distal tilting torque and the buccal tilting torque. The traction force ranges from 0.5N to 5.0N.

[0034] S4: solving the mathematical model to obtain optimal design parameters;

[0035] S5: Generating a customized shell-shaped dental appliance product structure according to the optimal design parameters.

[0036] Furthermore, in S1, the patient's oral data is processed using a 3D oral model obtained through CT scanning, CBCT scanning, or other medical imaging technologies. The position of the posterior tooth impedance center is an important reference point in the model. It serves as a reference point during the correction process and determines the force distribution and force transmission path in mechanical calculations. For multiple posterior teeth, the overall posterior tooth impedance center position is the result of the impedance center positions of each tooth and their interaction.

[0037] Furthermore, in S2, the tooth movement path includes the predetermined movement direction and target position of each tooth. The movement path is used to calculate the magnitude and direction of the correction force. By properly designing the tooth movement trajectory, it is possible to ensure that the position and direction of the correction force are applied to maximize the movement of the target tooth.

[0038] Furthermore, S3 uses the Sequential Least Squares Quadratic Programming (SLSQP) algorithm to build and solve the model. The SLSQP algorithm is suitable for nonlinear constrained optimization problems. It iteratively calculates the objective function and constraints to ultimately find the optimal solution. This algorithm is particularly well-suited for problems involving multiple variables and constraints in appliance design, such as the magnitude of the traction force, the selection of the position, and the design of the appliance shape. The SLSQP algorithm is implemented using the minimize function in the SciPy library.

[0039] Furthermore, in S4, the optimal design parameters are obtained by solving the SLSQP method; in the process of solving the mathematical model, the first calculation is first performed based on the input initial parameters. These initial parameters include the size of the traction force, the setting of the traction position, and the material stiffness of the orthodontic appliance. The initial parameters are pre-set according to the patient's oral data and treatment needs; then, through the iterative process of the SLSQP algorithm, these design parameters are gradually adjusted to minimize the value of the objective function; finally, after several iterations, the algorithm will converge to the optimal solution and give an optimal design parameter such as the traction force, traction position, and orthodontic appliance stiffness that meets the patient's correction needs.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] (1) Improving the stability and controllability of treatment effects: The present invention adopts a mathematical modeling method based on the patient's oral data to construct an optimized mathematical model to calculate the design parameters of the orthodontic appliance, including the magnitude of the traction force, the traction position, the traction method, and the stiffness of the orthodontic appliance. This mathematical model uses an optimization algorithm to accurately control the direction, magnitude, and application position of the orthodontic force, ensuring the stability of mechanical transmission and the predictability of the treatment effect during the treatment process. Through this optimized design, the orthodontic appliance can maximize the stability and controllability of the treatment effect according to the patient's specific needs and treatment goals.

[0042] (2) Personalized design and precise control of correction force: The present invention provides a more precise correction scheme in posterior tooth correction treatment by combining personalized design, mathematical modeling and optimization algorithm. The present invention can accurately control the magnitude, direction and application point of the correction force, thereby achieving a more efficient, stable and comfortable treatment effect. This invention can not only provide each patient with a customized correction scheme, but also significantly improve the efficiency of treatment and the comfort of patients, solving the problems of mechanical inaccuracy and unstable treatment effect in traditional correction methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of the overall structure of a shell-shaped dental appliance for posterior tooth correction;

[0044] Figure 2 A schematic diagram of a shell-shaped dental appliance for posterior tooth correction being worn on a patient's dentition;

[0045] Figure 3 A schematic diagram of the mechanical system of a shell-shaped dental appliance for posterior tooth correction when worn on a patient's dentition;

[0046] Figure 4 Flowchart of a method for designing a shell-shaped dental appliance for posterior orthodontics.

[0047] Reference numerals: 101 - first segment housing unit; 102 - traction structure; 103 - connection assembly; 104 - second segment housing unit; 105 - elastomer; 106 - micro-implant. DETAILED DESCRIPTION

[0048] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0049] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0050] Example 1

[0051] This embodiment provides a shell-shaped dental appliance for posterior tooth correction, such as Figure 1 、 2 As shown, it includes: a first segment housing unit 101, a traction structure 102, and a second segment housing unit 104; the first segment housing unit 101 and the traction structure 102 constitute a first tooth receiving cavity, and the second segment housing unit 104 constitutes a second tooth receiving cavity;

[0052] The first segment shell unit 101 can accommodate the patient's canine or premolar, and the traction structure 102 is fixedly connected to the first segment shell unit 101; the traction structure 102 is used to suspend the elastomer 105, so that the first tooth receiving cavity applies a first tooth moving force to the accommodated tooth; the second segment shell unit 104 can accommodate another premolar or molar of the patient, and the second tooth receiving cavity applies a second tooth moving force to the accommodated tooth; the tensile force of the elastomer 105 can be adjusted according to the patient's treatment needs.

[0053] The direction of the first tooth movement force is less than 45° relative to the angle formed by the line connecting the traction structure 102 and the posterior tooth impedance center; the traction structure 102 is located on the lingual or buccal side of the first segment shell unit 101 corresponding to the canine or the first premolar, and is used to provide directional corrective force; the first segment shell unit 101 and the second segment shell unit 104 are connected by a connecting component 103, and the displacement of the first segment shell unit 101 can be partially transmitted to the second segment shell unit 104; a transmission channel for corrective force is formed, which ensures the mechanical controllability of the entire correction system and pushes the target tooth to move in a predetermined direction.

[0054] The second segmented housing unit 104 applies a second tooth-moving force to the teeth it contains. The specific direction and magnitude of the force are determined by factors such as the orthodontic design for the first and second premolars, first and second molars, the material parameters of the periodontal tissue of the posterior teeth, the rigidity of the elastomer 105, and the displacement of the first segmented housing unit 101. This second tooth-moving force differs in direction and magnitude from the first tooth-moving force, ensuring that multiple teeth receive controlled orthodontic forces during treatment.

[0055] The first segment housing unit 101 is connected to an elastomer 105 via a traction structure 102. One end of the elastomer 105 is fixed to the traction structure 102, and the other end is fixed to a micro-implant 106. This provides a first tooth-moving force applied to the tooth via the elastomer 105. The micro-implant 106 is typically fixed to the alveolar bone, providing additional support without damaging the tooth itself. With the assistance of the micro-implant 106, the appliance can apply a stable and continuous force during treatment, ensuring precise displacement of the tooth during correction.

[0056] The design position of the traction structure 102 can be selected on the lingual or buccal side of the canine or first premolar. Its main function is to effectively and directionally transmit the applied traction and tensile force to the target tooth, assisting in applying force to move it along a predetermined path.

[0057] The first tooth-moving force and the second tooth-moving force are different in direction and magnitude;

[0058] The shell-like dental appliance can be installed and removed manually.

[0059] The surface of the shell-shaped dental appliance is provided with a plurality of additional structures for providing additional stability or correction force direction guidance function.

[0060] In a specific embodiment, the connecting assembly 103 is flexible to accommodate individual changes in the patient's oral cavity. This prevents the application of excessive corrective force, which could cause discomfort or injury, or cause the appliance to become dislodged. During treatment, the connecting assembly 103 provides the necessary elastic support, ensuring that the appliance can adapt to changes in oral morphology.

[0061] In a specific embodiment, the angle formed by the direction of the first tooth moving force and the line connecting the traction structure 102 and the posterior tooth impedance center is less than 45 degrees, ensuring that the correction force can be applied accurately, thereby avoiding the problem of uneven or inaccurate correction force direction.

[0062] In a specific embodiment, the angle between the direction of the first tooth-moving force and the direction of the second tooth-moving force is less than 60°.

[0063] In a specific embodiment, the elastic body 105 connected to the traction structure 102 is a rubber band, a spring, or a combination of the two.

[0064] like Figure 3 As shown, the structural design of the shell-shaped dental appliance can ensure the precise application of the correction force. The elastic body provides a continuous correction force F elastic, whose main function is to transmit the first tooth-moving force F1 to the target tooth in the first segment shell unit. The magnitude and direction of this force are determined through personalized design based on the patient's specific treatment needs, combined with factors such as each patient's tooth morphology, occlusion relationship, and treatment goals. The angle α formed by the direction of the first tooth-moving force F1 and the line connecting the traction structure to the posterior tooth impedance center is less than 45°, ensuring that the orthodontic force is accurately and stably applied to the target tooth throughout the treatment process, effectively controlling the non-design torque of the tooth's mesiodistal inclination and buccal-lingual inclination.

[0065] The direction of the first tooth-moving force F1 forms an angle of 0° with the line connecting the traction structure and the posterior tooth resistance center. This means the tooth-moving force is directed entirely along the traction structure toward the posterior tooth resistance center. Under these mechanical conditions, and in accordance with the physical principle of the resistance center, the posterior teeth will only move distally and intrude along the designed tooth arrangement path, without distal tilting. This ensures that the combined tooth movement is limited to the predetermined direction.

[0066] The direction and magnitude of the second tooth-moving force F2 differ from those of the first tooth-moving force F1. Its direction and magnitude are determined by a comprehensive design based on multiple factors, including the mechanical response of the patient's posterior periodontal tissues and the tooth movement path. This design ensures that the forces applied to the posterior teeth during treatment are within the optimal load range for biological bone remodeling of the posterior alveolar bone, avoiding adverse reactions caused by overcorrection.

[0067] The angle between the direction of the first tooth-moving force F1 and the direction and magnitude of the second tooth-moving force F2 is 10°. This design takes into account the coordinated movement of multiple teeth, ensuring the reasonable distribution of the force direction of each tooth during the correction process, while avoiding mutual interference of forces between different teeth. Specifically, through the synergy of the appliance structure and the traction design, the movement of each tooth is not limited to a single direction, but through a combination of multi-directional force directions and magnitudes, different intensities of force are applied to different teeth during the correction process, so that each tooth can be moved under appropriate mechanical conditions, and the mechanical consistency of the main movement direction is maintained as a whole, thereby achieving the overall correction goal of the dentition.

[0068] Patients can install the braces on their teeth through simple procedures. To install, first hang one end of the elastic body 105 on the traction structure 102, then put on the braces, and finally hang the other end of the elastic body 105 on the micro-implant 106. The braces begin to work. During treatment, patients can remove and replace the braces and elastic body 105 according to the doctor's instructions, ensuring flexibility and comfort during treatment.

[0069] The present invention also provides a design method for a shell-shaped dental appliance for posterior teeth correction, wherein parameters are optimized according to the patient's oral data, correction requirements, and the direction and magnitude of the correction force, such as Figure 4 As shown, the following steps are included:

[0070] S1: Acquire the patient's oral data, including bone morphology, tooth position, periodontal condition, and implant position, to determine the position of the posterior tooth impedance center;

[0071] The posterior tooth impedance center refers to a virtual point associated with the posterior teeth and their surrounding tissues (including the alveolar bone and periodontal ligament). The physical properties of this point are determined by the response of the teeth and their surrounding tissues to external forces. The impedance center is a key reference point when a tooth is subjected to force and is often used to describe its movement under external forces. When multiple posterior teeth are involved, the impedance center can be considered the collective response point of the entire dentition, its position determined by the impedance centers of each tooth and their interactions. In mechanics, the response of an object to force depends not only on the magnitude and direction of the force but also on its stiffness. For teeth and their supporting structures, stiffness reflects the tissue's ability to resist external forces. The impedance center (or "central stiffness") is typically a virtual point associated with the displacement response of a tooth under load. Near this point, the stiffness of the tooth reaches equilibrium, and the effects of the force are relatively concentrated. Simply put, the impedance center can be considered the "point of resistance" of the tooth and its surrounding tissues to external forces. In orthodontic mechanical analysis, the impedance center is closely related to the "center of resistance" or "center of torque." When an external force is applied to a tooth, the tooth responds by both translation and rotation. The impedance center is typically the intersection of the rotational axes generated by the force. In a multi-tooth model, the location of the impedance center of a posterior tooth can often be determined by a weighted average that accounts for the stiffness and displacement responses of each tooth.

[0072] S2: Design the tooth movement path according to the patient's orthodontic needs;

[0073] S3: Construct a mathematical model, which is a nonlinear programming model based on the SLSQP algorithm; the optimization parameters of the model include the traction force, traction position and traction method, wherein the boundary conditions include the traction force, traction position and stiffness of the orthodontic material, and the objective function is the angle formed by the direction of the first tooth movement force relative to the line connecting the traction structure (102) to the posterior tooth impedance center; the purpose of the optimization design is to solve a set of design parameters to reduce the angle between the direction of the orthodontic force and the line connecting the posterior tooth impedance center, thereby ensuring the accuracy of the application of the orthodontic force, so that the design of the orthodontic force and the tooth movement path can work together to achieve the best treatment effect and avoid unnecessary interference from the distal tilting moment and the buccal tilting moment.

[0074] S4: solving the mathematical model to obtain optimal design parameters;

[0075] S5: Generate a customized shell-shaped dental appliance product structure based on the optimal design parameters. The calculated traction force is 1N, the traction structure is positioned on the lingual side of the first premolar, the stiffness of the appliance diaphragm is set to 1439MPa, and the diaphragm material can be selected as polyurethane (TPU) with a thickness of 0.75mm. This process combines the patient's personalized oral data and treatment needs to ensure that the appliance can maximize the treatment effect and guarantee the patient's comfort and controllability of the treatment.

[0076] In a specific embodiment, in S1, the method for processing the patient's oral data includes a 3D oral model obtained by CT scanning, CBCT scanning, or other medical imaging technology. The position of the posterior tooth impedance center is an important reference point in the model. It serves as a reference point during the correction process and determines the force distribution and force transmission path in mechanical calculations. For multiple posterior teeth, the overall posterior tooth impedance center position is the result of the impedance center positions of each tooth and their interaction.

[0077] In a specific embodiment, the three-dimensional oral data obtained by CBCT scanning is used to extract the bone structure, teeth and surrounding tissues (such as periodontal ligament, alveolar bone, etc.) in the patient's mouth using Mimics software to form a three-dimensional digital model. Based on the position and morphology of the teeth in the model and the mechanical properties of the surrounding supporting structures, we calculate the impedance center of each tooth by modeling the mechanical response of each tooth. For multiple posterior teeth, the calculation of the impedance center will take into account the mechanical interaction between each tooth and its adjacent teeth, as well as their stiffness characteristics when subjected to force. The calculation method of the impedance center of the posterior teeth is based on the weighted average of the stiffness value and position of each tooth.

[0078] Specifically, assuming the impedance center of each tooth is Z i , and its stiffness is K i , then the overall posterior tooth impedance center Z total Z can be expressed by the formula total =∑(K i· Z i ) / ∑K i , where K i is the stiffness of the i-th tooth, Z iis the impedance center of that tooth. This formula indicates that the position of the overall posterior tooth impedance center is determined by the weighted average of the stiffness and position of each tooth. This method allows us to determine the overall posterior tooth impedance center position, which serves as input data for the subsequent SLSQP algorithm, ensuring that the mechanical transfer path in the appliance design is effectively applied to the actual patient's oral situation.

[0079] For example, assuming that the patient's posterior tooth impedance center data is (-24.43, 17.31), this data will be used as an input parameter in the SLSQP algorithm to help optimize variables such as traction force, traction position, and orthodontic appliance stiffness to ensure the reasonable distribution of orthodontic force in the posterior tooth area and the precise movement of teeth.

[0080] In a specific embodiment, in S2, the tooth movement path includes the predetermined movement direction and target position of each tooth. The movement path is used to calculate the magnitude and direction of the correction force. By properly designing the tooth movement trajectory, it is possible to ensure that the position and direction of the correction force applied can maximize the movement of the target tooth.

[0081] The distal movement of the posterior teeth was designed, and the target vectors of the patient's first premolar, second premolar, first molar, and second molar were (-1.24, -0.21), (-1.22, -0.24), (-1.25, -0.29), and (-1.21, -0.22), respectively. Through finite element modeling and mechanical analysis, the magnitude and direction of the traction force required for each tooth can be calculated, and these data can be input into the subsequent mathematical model for further optimization.

[0082] In a specific implementation, S3 uses the Sequential Least Squares Quadratic Programming (SLSQP) algorithm to build and solve the model. The SLSQP algorithm is suitable for nonlinear constrained optimization problems, iterating through the objective function and constraints to ultimately find the optimal solution. This algorithm is particularly well-suited for problems involving multiple variables and constraints in appliance design, such as the magnitude of the traction force, the selection of the position, and the design of the appliance's shape. The SLSQP algorithm is implemented using the minimize function in the SciPy library.

[0083] In a specific implementation, in S4, the optimal design parameters are obtained by solving the SLSQP method; in the process of solving the mathematical model, the first calculation is first performed based on the input initial parameters, and these initial parameters include the size of the traction force, the setting of the traction position, and the material stiffness of the orthodontic appliance, etc. The initial parameters are pre-set according to the patient's oral data and treatment needs; then, through the iterative process of the SLSQP algorithm, these design parameters are gradually adjusted to minimize the value of the objective function; finally, after several iterations, the algorithm will converge to the optimal solution and give an optimal design parameter such as the traction force size, traction position, and orthodontic appliance stiffness that meets the patient's correction needs.

[0084] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0085] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A shell-shaped dental appliance for posterior tooth correction, characterized in that: include: A first segment housing unit (101), a traction structure (102), and a second segment housing unit (104); the first segment housing unit (101) and the traction structure (102) constitute a first tooth receiving cavity, and the second segment housing unit (104) constitutes a second tooth receiving cavity; The first segment housing unit (101) is capable of accommodating a patient's canine or premolar, and the traction structure (102) is fixedly connected to the first segment housing unit (101); the traction structure (102) is used to suspend an elastic body (105), so that the first tooth receiving cavity applies a first tooth moving force to the accommodated tooth; The second segment housing unit (104) is capable of accommodating another premolar or molar of the patient, and the second tooth receiving cavity applies a second tooth moving force to the accommodated tooth; The traction structure (102) is located on the lingual or buccal side of the first segment shell unit (101) corresponding to the canine or the first premolar, and is used to provide a directional correction force; the first segment shell unit (101) and the second segment shell unit (104) are connected via a connecting component (103); The first segment shell unit (101) is connected to the elastomer (105) through the traction structure (102), one end of the elastomer 105 is fixed on the traction structure (102), and the other end is fixed on the micro-implant (106), so that the first tooth movement force applied to the tooth is provided by the elastomer 105.

2. A shell-shaped dental appliance for posterior teeth correction according to claim 1, characterized in that: The connecting component (103) is a flexible connecting component to adapt to the personalized morphological changes of the patient's oral cavity.

3. A shell-shaped dental appliance for posterior teeth correction according to claim 1, characterized in that: The angle formed by the direction of the first tooth moving force and the line connecting the traction structure (102) to the posterior tooth impedance center is less than 45 degrees.

4. A shell-shaped dental appliance for posterior teeth correction according to claim 1, characterized in that: An angle between a direction of the first tooth-moving force and a direction of the second tooth-moving force is less than 60°.

5. The shell-shaped dental appliance for posterior teeth correction according to claim 1, characterized in that: The elastic body (105) connected to the traction structure (102) is a rubber band, a spring, or a combination of the two.

6. A method for designing a shell-shaped dental appliance for posterior teeth correction according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Acquire the patient's oral data, including bone morphology, tooth position, periodontal condition, and implant position, to determine the position of the posterior tooth impedance center; S2: Design the tooth movement path according to the patient's orthodontic needs; S3: Constructing a mathematical model, which is a nonlinear programming model based on the SLSQP algorithm; the optimization parameters of the model include the magnitude of the traction force, the traction position, and the traction method, wherein the boundary conditions include the magnitude of the traction force, the traction position, and the stiffness of the orthodontic appliance material; the objective function is the angle formed by the direction of the first tooth movement force relative to the line connecting the traction structure (102) to the posterior tooth impedance center; S4: solving the mathematical model to obtain optimal design parameters; S5: Generating a customized shell-shaped dental appliance product structure according to the optimal design parameters.

7. The method for designing a shell-shaped dental appliance for posterior teeth correction according to claim 6, characterized in that: In S1, the method for processing the patient's oral data includes CT scanning, CBCT scanning or a three-dimensional oral model obtained by other medical imaging technologies.

8. The method for designing a shell-shaped dental appliance for posterior teeth correction according to claim 6, characterized in that: In S2, the tooth movement path includes a predetermined movement direction and a target position of each tooth, and the movement path is used to calculate the magnitude and direction of the correction force.

9. The method for designing a shell-shaped dental appliance for posterior teeth correction according to claim 6, characterized in that: In S3, the SLSQP algorithm is used to build and solve the model; the SLSQP algorithm is implemented through the minimize function in the SciPy library.

10. The method for designing a shell-shaped dental appliance for posterior teeth correction according to claim 6, characterized in that: In S4, the optimal design parameters are obtained by the SLSQP method. During the mathematical model solution process, the first calculation is performed based on the input initial parameters. These initial parameters include the magnitude of the traction force, the setting of the traction position, and the material stiffness of the orthodontic appliance. The initial parameters are pre-set according to the patient's oral data and treatment needs. Then, through the iterative process of the SLSQP algorithm, these design parameters are gradually adjusted to minimize the value of the objective function; finally, after several iterations, the algorithm will converge to the optimal solution and give an optimal design parameter of traction force, traction position, and appliance stiffness that meets the patient's correction needs.

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