Structural optimization method for tooth-missing cavitation bubble of bracket-free invisible orthodontic appliance
By establishing a digital model and shell replacement model in a bracketless invisible aligner, using waveform superposition method and Bezier curved surface design, the structure at the gap of missing teeth is optimized, the problem of uncontrollable tilt movement is solved, and the problem of uncontrollable teeth is improved Controllability of correction effects and treatment course.
Patent Information
- Application Number
- CN202411234222.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-04
- Publication Date
- 2024-12-20
AI Technical Summary
There is uncontrollable and unpredictable tooth tilt movement in the gap between the missing teeth, resulting in poor orthodontic effect and extended treatment time. The existing optimizations are mainly focused on attachment and stepping design, and lack of vacuole areas. Mechanical properties considerations.
By establishing a digital initial model of the patient, building a shell replacement model, using waveform superposition method and Bezier surface design, the structure at the missing tooth gap is optimized, and finite element analysis is carried out to verify material parameters and mechanical properties to ensure that the teeth can move Control and predictive.
The controllability and predictability of tooth movement in the gap between the missing teeth is achieved, uncontrollable tilt movement is reduced, the correction effect and treatment course are optimized, and the method is carried out in the digital design stage of the orthodontic device, and the subsequent processing technology does not need to be changed.
Smart Images
Figure CN119167703A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of invisible orthodontic appliances, and in particular relates to a structural optimization method for tooth-missing cavitation of a bracketless invisible orthodontic appliance. Background Art
[0002] At present, in the cases of tooth extraction correction in bracketless invisible orthodontics, there is a common problem of tooth tilting and movement on both sides of the missing teeth gap. The uncontrollable and unpredictable tooth tilting and movement is also one of the main reasons for poor correction treatment effect, prolonged correction time, and restart of correction design. This phenomenon is called the "roller coaster effect (Roller Coaster Effect, or Bowing Effect)". Compared with the steel wire retraction of the anterior teeth used in traditional fixed correction, the invisible braces are limited by the material properties and have weaker rigidity. Therefore, when closing the missing teeth gap, the teeth before and after the gap tilt toward the gap and stretch at the same time, causing the anterior overbite to further deepen, affecting the correction effect and treatment course. The existing invisible braces for the missing teeth gap are in the form of a traditional connecting rod design or a denture cavitation shape (Ponticdesign) designed to improve aesthetics (reference Figure 1 ). However, the biomechanical properties of these two types of invisible braces in the edentulous space are not considered. Existing optimizations for extraction cases of invisible braces are focused on the improvement of accessories, optimization of the step design of the braces, and the combination of different tractions. At present, there is still a lack of research on optimizing the cavitation of the edentulous space of bracketless invisible braces to improve the controllability and predictability of orthodontic movement of teeth. Summary of the invention
[0003] Purpose of the invention: In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for structural optimization of edentulous cavities of bracketless invisible braces, which can optimize the structure of edentulous gaps or other tooth gaps of invisible braces.
[0004] Technical solution: In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:
[0005] A method for optimizing the structure of tooth-missing cavitation of a bracketless invisible orthodontic appliance comprises the following steps:
[0006] According to the clinical data of the patients to be treated, an initial digital model of the invisible braces is established. Based on the initial model, a shell replacement model for the gap between missing teeth of the invisible braces is built. The shell is parametrically designed based on the waveform superposition method, and the design is optimized for the problems that are prone to occur in tooth extraction cases of invisible braces.
[0007] Furthermore, the method for optimizing the structure of the toothless invisible brace appliance cavitation comprises the following steps:
[0008] 1) Obtaining and fitting the three-dimensional model of the patient's jaws to be treated;
[0009] 2) Determination of target position and step design of invisible correction teeth;
[0010] 3) Establish the initial digital model of invisible braces;
[0011] 4) Build a shell replacement model for the gap between missing teeth of the invisible braces;
[0012] 5) Material parameter determination and mechanical property verification of shell replacement model;
[0013] 6) Shell parametric design based on waveform superposition method;
[0014] 7) Optimize the design for problems that may occur during correction;
[0015] 8) Verify the optimization results.
[0016] As a specific implementation scheme, in step 1), a three-dimensional dental model of the patient including teeth, periodontal membrane, and jaw model is constructed based on the three-dimensional dental model of the patient in combination with CBCT data.
[0017] As a specific implementation scheme, in step 2), the target position of the teeth for invisible orthodontic treatment is determined based on the tooth arrangement design, and the step-by-step design of invisible orthodontic treatment is clarified, that is, the target position of the teeth at each step during the treatment process.
[0018] As a specific implementation scheme, in step 3), based on the three-dimensional model of the jaw constructed in step 1), the three-dimensional model of the crown part is selected, and a digital initial model of the virtual invisible orthodontic appliance is constructed by the three-dimensional model shelling method.
[0019] As a specific implementation scheme, in step 4), for the initial model established in step 3), the middle surface of the appliance and the gingival direction of the toothless gap is confirmed, a coordinate system is drawn for the middle surface, and based on this coordinate system, a replacement shell is established, and the contact relationship between the shell and the anterior teeth appliance and the posterior teeth appliance on both sides is set.
[0020] As a specific implementation plan, in step 5), the initial braces model and the shell replacement model designed with the same target tooth displacement are respectively included in the finite element analysis, and the corresponding material parameters and contact relationships are set. Finite element analysis calculations are performed separately, and the displacement amounts and displacement methods of different teeth in the calculation results are compared. The material parameters of the shell are modified accordingly so that the difference between its calculation results and the calculation results of the corresponding initial braces model meets the requirements.
[0021] As a specific implementation scheme, in step 6), a curve data profile is determined according to the waveform superposition method, and the coordinates of the key points are determined accordingly, and the smooth surface drawing is completed using the Bezier surface to achieve a smooth connection between the shell structure and the anterior and posterior appliances on both sides, and generate a shell height data set. The corresponding relationship between the local coordinates in the mesiodistal and buccolingual directions and the shell height data set is used to determine the change height of each node of the shell structure;
[0022] Among them, the edge height Z of the control point set is set to 0, and the internal point height Zn is optimized and obtained by using the data contour formed by the waveform superposition method;
[0023]
[0024] As a specific implementation scheme, in step 6), the plane distance relationship of the three-dimensional data points on the local coordinate system is constructed, and only the distance on the two-dimensional plane is evaluated. When the distance of the point in formula (2) is less than the specified threshold, the method of formula (3) is used to participate in the height data transmission. In the formula, p1 and p2 are two points, p1[0] and p2[0] are the X coordinates of the two points, and p1[1] and p2[1] are the Y coordinates of the two points. n is the Z coordinate of point Xn, and N is the number of points within the threshold.
[0025] distance(p1,p2)=sqrt((p1[0]-p2[0])**2+(p1[1]-p2[1])**2)(2)
[0026]
[0027] As a specific implementation plan, in step 7), first determine the optimization target, such as the amount of tooth movement or the trend of tooth movement, and then determine the deformation constraint conditions, such as the height of the missing tooth gap must not exceed the height of the adjacent crown apex on both sides, and then perform experimental design, such as using DOE) method, and finally obtain the optimal solution, such as using Gaussian process regression or genetic algorithm.
[0028] As a specific implementation plan, in step 8), a corresponding invisible braces solid model is built based on the optimized model, and finite element analysis calculations are performed respectively. The optimization target calculation results of the two groups are compared and verified to be the same, and are compared with the optimization target results of the initial braces model.
[0029] Beneficial effects: Existing optimizations for closing missing-edentulous spaces in invisible braces focus on optimizing accessories, over-correction design, and improvement of correction movement steps. Existing invisible braces do not have mechanical designs for missing-edentulous cavitation areas. Existing improvements to missing-edentulous cavitation areas in invisible braces are limited to improvements for aesthetic considerations.
[0030] During the process of closing edentulous spaces with existing invisible orthodontics, the teeth on both sides of the edentulous space are tilted toward the space and elongated at the same time, and the orthodontic appliance at the edentulous space is squeezed and deformed, affecting the correction effect and course of treatment. Optimizing the orthodontic appliance at the edentulous space helps to make the force on the adjacent teeth closer to the impedance center when closing the space, so as to reduce the uncontrollable tilting movement of the adjacent teeth on both sides. The method of the present invention can be personalized and carried out for the specific target movement of specific teeth of specific patients, and can be performed separately for each step of the tooth movement. Moreover, this method is only performed in the digital design stage of the orthodontic appliance, and its subsequent processing technology does not need to be changed, and can be completed based on the existing orthodontic appliance die-casting manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 This is a real picture of an existing invisible orthodontic appliance, where: A is a connecting rod-shaped cavitation in the tooth-missing gap, and B is a crown-shaped cavitation in the tooth-missing gap.
[0032] Figure 2 It is a line diagram of an existing invisible brace appliance, where: A is a connecting rod-shaped cavitation in the tooth-missing gap, and B is a crown-shaped cavitation in the tooth-missing gap.
[0033] Figure 3 The figure is a flow chart of the method of the present invention.
[0034] Figure 4 The figure shows the construction of a shell replacement model for the invisible braces at the edentulous gap, where a is the invisible braces physical model including the edentulous cavitation structure; b is the cross-sectional view and the middle surface of the edentulous cavitation physical model; c is the coordinate system of the constructed edentulous cavitation shell model; d is the invisible braces model including the edentulous cavitation structure shell; e is the contact relationship setting between the edentulous cavitation structure shell and the physical appliance; f is a partial enlarged view of the contact relationship setting between the edentulous cavitation structure shell and the physical appliance.
[0035] Figure 5 It is a schematic diagram of the mesiodistal section of the edentulous space area.
[0036] Figure 6 It is a schematic diagram of the buccolingual section of the edentulous space area.
[0037] Figure 7 Schematic diagram of the vertical height of the shell surface. DETAILED DESCRIPTION
[0038] The present invention is further described by the following examples. These examples are purely illustrative and are only used to specifically describe the present invention and should not be construed as limiting the present invention. The invention is further described below in conjunction with the accompanying drawings and examples:
[0039] Existing invisible braces are all made of transparent polymer materials made by hot pressing film technology. For example, the gap between missing teeth of invisible braces can be optimized. Figure 2 As shown, the tooth gap portion of the existing invisible braces is a connecting rod-shaped cavity or a crown-shaped cavity. The braces are divided into anterior teeth area (marked 1), tooth gap area (marked 2) and posterior teeth area (marked 3).
[0040] Example
[0041] The specific process of the method of the present invention is as follows: Figure 3 shown):
[0042] ① Obtaining and fitting the patient's three-dimensional dental model:
[0043] Based on the patient's three-dimensional dental arch model (which can be obtained through intraoral scanning or in vitro scanning of the plaster model) combined with CBCT data, a three-dimensional model of the patient's jaw, including teeth, periodontal membrane, and jaw model, is constructed.
[0044] ②Determination of target position and step design of invisible correction teeth:
[0045] The target position of teeth for invisible orthodontic treatment is determined based on the tooth arrangement design, and the step-by-step design of invisible orthodontic treatment is clarified, that is, the target position of teeth at each step in the treatment process.
[0046] ③ Establishment of the initial digital model of the invisible braces (hereinafter referred to as the initial brace model):
[0047] Based on the above-mentioned three-dimensional model of the jaw, the three-dimensional model of the crown is selected, and the initial digital model of the virtual invisible orthodontic appliance is constructed by means of three-dimensional model shell extraction. The toothless area can be designed as the initial standard tunnel type ( Figure 2 The digital initial model structure of the appliance includes the anterior tooth area ( Figure 2 Mark 1, Figure 4 Mark 1), tooth gap area ( Figure 2 Middle mark 2, Figure 4 Mark 2) and the posterior area ( Figure 2 Mark 3, Figure 4 Mark 3).
[0048] ④Construction of the shell replacement model for the gap between missing teeth of the invisible braces:
[0049] like Figure 4 As shown, first, for the initial model of the braces with the initial standard tunnel-type edentulous space appliance, the middle surface of the gingival-oriented appliance in the edentulous space is confirmed ( Figure 4 Mark 4), draw the coordinate system of its middle surface ( Figure 4 c), the gingival height is Zz, the buccal and lingual width is Wx, and the mesiodistal length is Yy. Based on this coordinate system, the replacement shell ( Figure 4 d), and set the shell and the anterior teeth appliance and the posterior teeth appliance on both sides ( Figure 4 Mark 1, Figure 4 The contact relationship marked 3).
[0050] ⑤ Material parameter determination and mechanical property verification of shell replacement model:
[0051] The initial brace model and the shell replacement model designed with the same target tooth displacement are included in the finite element analysis. The corresponding material parameters, i.e., contact relationships, are set, such as the elastic modulus of the teeth, alveolar bone, and periodontal membrane, and the position binding relationship between the teeth and the inner surface of the periodontal membrane. Finite element analysis calculations are performed separately, and the displacement amounts and displacement modes of different teeth in the calculation results are compared. The material parameters of the shell are modified accordingly, so that the difference between its calculation results and the calculation results of the corresponding initial brace model meets the requirements. At this point, the material parameter determination and mechanical property verification of the shell replacement model have been completed.
[0052] ⑥ Shell parameterization design based on waveform superposition method:
[0053] Figure 5 It is a schematic diagram of the mesiodistal section of the edentulous space area, and H1 and H2 on both sides are the occlusal heights of the mesiodistal interproximal space, which are considered unchanged. L3 is the waveform deformation area of the edentulous space area, and L1 and L2 on both sides are the Bezier curve deformation areas, respectively. The deformation of the Bezier curve realizes the smooth connection between the high point of the waveform deformation area (L3) and the high points of the mesiodistal interproximal space on both sides (H1, H2).
[0054] akin, Figure 6 It is a schematic diagram of the buccolingual section of the edentulous space area. The La and Lin points on both sides are the buccolingual edge points, and their heights are generally considered to be consistent with the gingival height of the interproximal spaces of the adjacent teeth on both sides, and can also be changed at will. Similarly, W3 is the waveform deformation area of the edentulous space area, and its two sides W1 and W2 are the Bezier curve deformation areas, respectively. The deformation of the Bezier curve realizes the smooth connection between the high point of the waveform deformation area (W3) and the buccolingual edge points (La, Lin) on both sides.
[0055] The vertical fluctuation height (Z) of the comprehensive shell structure in the mesiodistal and buccolingual directions is constructed by using the waveform amplitude superposition method, considering the changes of three factors: amplitude, wavelength and phase angle in the two directions, and controlling the shell morphology by changing the above variables. Among them, the characteristics of multiple waves can be superimposed in each direction.
[0056]
[0057] In the above formula, A, A n , B m is the amplitude, λ n , m is the wavelength, x n 、x mis the phase angle of the wave.
[0058] A curve data profile is determined by the waveform superposition method, and the key point coordinates are determined accordingly. The Bezier surface is used to complete the smooth surface drawing and generate the shell height data set. The corresponding relationship between the local coordinates in the mesiodistal and buccolingual directions and the shell height data set is used to determine the change height of each node of the shell structure.
[0059] The edge height Z of the control point set is set to 0, and the internal point height Z n Optimization is obtained by using the data profile formed by the waveform superposition method.
[0060]
[0061] Among them, the undulating height data set is composed of discrete points on a smooth curved surface, which itself has local coordinates based on the mesiodistal and buccolingual directions. Each node of the shell structure also has coordinates in the same local coordinate system. The varying height of each node of the shell structure is assigned according to the proximity of the coordinates.
[0062] Construct the plane distance relationship of the three-dimensional data points on the local coordinate system, and only evaluate the distance on the two-dimensional plane. When the distance (Formula 2) is less than the specified threshold, the method of Formula 3 is used to participate in the height data transmission. In the formula, p1 and p2 are two points, p1[0] and p2[0] are the X coordinates of the two points, and p1[1] and p2[1] are the Y coordinates of the two points. n is the Z coordinate of point Xn, and N is the number of points within the threshold.
[0063] distance(p1,p2)=sqrt((p1[0]-p2[0])**2+(p1[1]-p2[1])**2)(2)
[0064]
[0065] like Figure 7 The shell structure nodes are in the two-dimensional plane, and the nodes involved in data processing in the height data set can be determined by specifying the distance threshold (r) (e.g. Figure 7 In the example, X1, X2, X3 and X4 are used, and then the vertical height is averaged using formula (3), and the weighting factor can be further determined according to the distance. Through the data transfer relationship, the height data is used as the data amount of the shell structure node movement, and finally the target shell is generated.
[0066] ⑦Optimized design
[0067] 1) Determine the optimization target: The optimization target can be the amount of tooth movement or the trend of tooth movement, etc. For example, for the problem of lingual inclination of anterior teeth during extraction correction, the optimization index can be set as: the average of the lingual inclination rotation angle of the central incisor and lateral incisor and the distal inclination angle of the canine; or another optimization index can be: the lingual inclination angle (° / mm) when the crown of the central incisor moves lingually per unit.
[0068] 2) Determine the deformation constraints: Figure 6 The heights H1 and H2 of the connection between the anterior and posterior areas of the appliance on both sides of the central edentulous gap remain unchanged. The height of the edentulous gap shall not exceed the height of the crown apex of the adjacent teeth on both sides, such as 4mm, and shall not be lower than the gingival margin, that is, 0mm. Figure 7 The position of the buccal and lingual gingival edge points La and Lin remains unchanged.
[0069] 3) Design of Experiment (DOE): Common DOE methods such as super Latin square sampling can be used.
[0070] 4) Solver: Common methods such as Gaussian process regression and genetic algorithm can be used to obtain the optimal solution.
[0071] ⑧Verification of optimization results:
[0072] Based on the optimized subject model, a corresponding full-thickness invisible brace appliance model was built, and finite element analysis was performed respectively. The optimization target calculation results of the two groups were the same, and compared with the optimization target results of the initial brace model for verification.
[0073] ⑨Processing of invisible braces:
[0074] The invisible braces are manufactured based on the hot pressing film technology or direct 3D printing technology commonly used in existing invisible braces.
[0075] The above describes the implementation mode of the present invention in detail with reference to the accompanying drawings and specific embodiments. However, the present invention is not limited to the above implementation mode. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.
Claims
1. A method for optimizing the structure of tooth-missing cavitation in a bracketless invisible brace appliance, characterized in that: The following steps are involved: According to the clinical data of the patients to be treated, an initial digital model of the invisible braces is established. Based on the initial model, a shell replacement model for the gap between missing teeth of the invisible braces is built. The shell is parametrically designed based on the waveform superposition method, and the design is optimized for the problems that are prone to occur in tooth extraction cases of invisible braces.
2. The method for optimizing the structure of a bracketless invisible orthodontic appliance for edentulous cavitation according to claim 1, characterized in that: The following steps are involved: 1) Obtaining and fitting the three-dimensional model of the patient's jaws to be treated; 2) Determination of target position and step design of invisible correction teeth; 3) Establish the initial digital model of invisible braces; 4) Build a shell replacement model for the gap between missing teeth of the invisible braces; 5) Material parameter determination and mechanical property verification of shell replacement model; 6) Shell parametric design based on waveform superposition method; 7) Optimize the design for problems that may occur during correction; 8) Verify the optimization results.
3. The structural optimization method of the toothless invisible appliance cavitation according to claim 2, characterized in that: In step 1), a three-dimensional dental model of the patient including teeth, periodontal membrane, and jaw model is constructed based on the patient's three-dimensional dental model combined with CBCT data.
4. The method for optimizing the structure of edentulous cavitation of bracketless invisible braces according to claim 2, characterized in that: In step 2), the target position of the teeth for invisible orthodontic treatment is determined based on the tooth arrangement design, and the step-by-step design of invisible orthodontic treatment is clarified, that is, the target position of the teeth at each step during the treatment process.
5. The method for optimizing the structure of edentulous cavitation of bracketless invisible braces according to claim 2, characterized in that: In step 3), based on the three-dimensional model of the jaw constructed in step 1), the three-dimensional model of the crown part is selected, and a digital initial model of the virtual invisible orthodontic appliance is constructed by the three-dimensional model shelling method.
6. The method for optimizing the structure of edentulous cavitation of bracketless invisible braces according to claim 2, characterized in that: In step 4), for the initial model established in step 3), the middle surface of the appliance in the gingival direction of the missing tooth gap is confirmed, and a coordinate system is drawn for the middle surface. Based on this coordinate system, a replacement shell is established, and the contact relationship between the shell and the anterior and posterior appliances on both sides is set.
7. The method for optimizing the structure of edentulous cavitation of bracketless invisible braces according to claim 2, characterized in that: In step 5), the initial brace model and the shell replacement model designed with the same target tooth displacement are respectively included in the finite element analysis, and the corresponding material parameters and contact relationships are set. Finite element analysis calculations are performed separately, and the displacement amounts and displacement modes of different teeth in the calculation results are compared. The material parameters of the shell are modified accordingly, so that the difference between its calculation results and the calculation results of the corresponding initial brace model meets the requirements.
8. The method for optimizing the structure of edentulous cavitation of bracketless invisible braces according to claim 2, characterized in that: In step 6), a curve data profile is determined according to the waveform superposition method, and the coordinates of the key points are determined accordingly, and the smooth surface drawing is completed using the Bezier surface to achieve a smooth connection between the shell structure and the anterior and posterior appliances on both sides, and generate a shell height data set. The corresponding relationship between the local coordinates in the mesiodistal and buccolingual directions and the shell height data set is used to determine the change height of each node of the shell structure; Among them, the edge height Z of the control point set is set to 0, and the internal point height Zn is optimized and obtained by using the data contour formed by the waveform superposition method; 9. The method for optimizing the structure of edentulous cavitation of bracketless invisible braces according to claim 2, characterized in that: In step 6), the plane distance relationship of the three-dimensional data points on the local coordinate system is constructed, and only the distance on the two-dimensional plane is evaluated. When the distance of formula (2) is less than the specified threshold, the method of formula (3) is used to participate in the height data transmission. Where p1 and p2 are two points, p1[0] and p2[0] are the X coordinates of the two points, and p1[1] and p2[1] are the Y coordinates of the two points. n is the Z coordinate of point Xn, and N is the number of points within the threshold. distance(p1,p2)=sqrt((p1[0]-p2[0])**2+(p1[1]-p2[1])**2)(2) 10. The method for optimizing the structure of edentulous cavitation of bracketless invisible braces according to claim 2, characterized in that: In step 7), first determine the optimization target, such as the amount of tooth movement or the trend of tooth movement, and then determine the deformation constraint conditions, such as the height of the missing tooth gap must not exceed the height of the adjacent crown apex on both sides, and then perform experimental design, such as using the Design of Experiments (DOE) method, and finally obtain the optimal solution, such as using Gaussian process regression or genetic algorithm.
11. The method for optimizing the structure of edentulous cavitation of bracketless invisible orthodontic appliance according to claim 2, characterized in that: In step 8), a corresponding invisible braces solid model is built based on the optimized model, and finite element analysis calculations are performed respectively, the optimization target calculation results of the two groups are compared, and the optimization target results of the initial braces model are compared and verified.