A re-entrant shrink wrap envelope method, system, apparatus, and storage medium for clear aligner design

Abstract

This invention relates to the field of digital orthodontics, and discloses a method, system, device, and storage medium for concave shrinkage envelope design of invisible aligners. The method acquires a three-dimensional model of the patient's dentition and a target dentition model, generates an initial wrapping mesh on the outer side of the target dentition model, and gradually approximates the target dentition model through local mesh control and iterative shrinkage. Simultaneously, tight fit or gap retention constraints are set for different areas, and smoothing processing is combined to improve mesh stability, ultimately obtaining a continuous, watertight inner surface model of the aligner. This invention improves envelope efficiency, fit, and adaptability for removal and wearing.

Description

Technical Field

[0001] This invention relates to the field of digital orthodontics, and more particularly to a concave shrinkage envelope method, system, device, and storage medium for the design of invisible aligners. Background Technology

[0002] Invisible aligners are typically designed individually based on the target position of the patient's dentition, and the orthodontic force is transmitted through the fit between the inner surface of the aligner and the teeth. With the development of digital orthodontic design and additive manufacturing technology, directly constructing a three-dimensional model of the aligner suitable for manufacturing has become an important technical direction in the design of invisible aligners.

[0003] In existing technologies, the construction of the inner surface of invisible aligners typically relies on offset, envelope, or shrinkage fitting of the target dentition model. Some methods use regular bounding volumes as the initial mesh and gradually approximate the dentition surface through iterative shrinkage. This type of method is applicable to objects with relatively simple shapes, but dentition models usually have complex structures such as many cusps, incisal edges, proximal transitions, local depressions, and undercuts. If the initial bounding volume is far from the dentition surface, the iterative process is prone to problems such as long ineffective shrinkage paths, local bridging, insufficient identification of depression areas, and mesh instability.

[0004] Furthermore, the inner surface of the clear aligner is not suitable for complete adhesion in all areas. For protruding areas that bear the main functions of retention and force transmission, a higher degree of adhesion is usually required; while for proximal concave areas, local undercut areas, and deep transition areas of the cervical region, if it is completely adhered after shrinkage, it may lead to increased resistance to insertion and removal, local locking, or even mechanical locking, which is not conducive to clinical use.

[0005] Therefore, there is an urgent need for an envelope construction technique suitable for complex dentition morphology, which can take into account geometric fitting accuracy, mesh stability, and the clinical placement and removal requirements of clear aligners. Purpose of the invention

[0006] The purpose of this invention is to provide a concave shrinkage envelope method, system, device, and storage medium for the design of invisible aligners, so as to at least solve the problems existing in the prior art, such as insufficient adaptation of the initial mesh to the dental arch topology, low iterative shrinkage efficiency, excessive attachment of the concave area, and poor mesh stability. Technical solution

[0007] To achieve the above objectives, the present invention provides the following technical solution.

[0008] This invention provides a concave shrinkage envelope method for designing invisible aligners. The method first acquires a three-dimensional digital model of the patient's dentition and then determines the target dentition model based on the orthodontic treatment plan. The three-dimensional digital model can be obtained through intraoral scanning, model scanning, cone-beam computed tomography (CBCT) reconstruction, or other methods.

[0009] Subsequently, based on the target dentition model, an initial wrapping mesh adapted to the topology of the target dentition model is generated on its outer side. Compared with using a simple regular bounding volume, this initial wrapping mesh is closer to the shape of the dentition, thereby reducing invalid paths in the subsequent shrinkage process and improving the envelope efficiency.

[0010] After generating the initial wrapping mesh, local mesh adjustments are made based on the local geometric features of the target dentition model. For areas with significant geometric changes, such as cusps, incisal edges, proximal transitions, and undercuts, the mesh density can be appropriately increased to enhance the representation of local details; for relatively flat areas such as labial, buccal, lingual, or palatal surfaces, the mesh density can be moderately reduced to control the overall computational scale.

[0011] Next, iterative shrinkage is performed on the initial wrapping mesh, gradually bringing it closer to the target tooth arch model. During each iteration, each vertex in the wrapping mesh moves inward according to its correspondence with the surface of the target tooth arch model. The movement amplitude can be a fixed value or dynamically adjusted according to the iteration stage. Preferably, a larger shrinkage intensity is used in the early stages of iteration, and the shrinkage intensity is gradually reduced in the later stages of iteration to balance shrinkage efficiency and stability.

[0012] During the iterative shrinkage process, this invention divides the surface of the target dentition model into a close-fitting zone and a buffer retention zone. The close-fitting zone may include important areas that bear the functions of retention and force transmission, such as cusps, incisal edges, and major convex surfaces; the buffer retention zone may include areas that are not suitable for complete attachment, such as proximal concave areas, local undercut areas, and deep transition areas at the cervical region. For the buffer retention zone, this invention sets a minimum retention gap so that the wrapping mesh still maintains a certain distance from the target dentition model after shrinkage, thereby helping to reduce the resistance of appliance insertion and removal and reducing the risk of mechanical locking.

[0013] During the iterative shrinkage process, the wrapped mesh can also be smoothed and its stability controlled. The smoothing process can employ methods such as neighborhood averaging smoothing, volume-preserving smoothing, and curvature-constrained smoothing to suppress local mesh folding, vertex clustering, bridging, or uneven deformation. Stability control may also include measures such as abnormal vertex correction, local penetration detection, and topology consistency maintenance.

[0014] Once the preset convergence conditions are met, a continuous and watertight envelope mesh is output. The convergence conditions may include: the deviation between the envelope mesh and the target tooth row model is less than a preset threshold, the vertex change in two adjacent iterations is less than a preset threshold, the tight fit region and the buffer retention region meet their respective requirements, and the mesh does not have obvious penetration, bridging or folding.

[0015] In one implementation, after obtaining the envelope mesh, thickness offsetting and edge trimming can be further performed on it to generate a shell model for manufacturing invisible orthodontic appliances. The shell model can be used for subsequent CNC manufacturing, thermoforming, or 3D printing.

[0016] The present invention also provides a concave shrinkage envelope system for the design of invisible orthodontic appliances, including a data acquisition module, an initialization module, a grid control module, a shrinkage iteration module, a region constraint module, a smoothing and stabilization module, and an output module, each module being used to implement the corresponding function of the above method.

[0017] The present invention also provides an electronic device, including a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, it implements the above-described method.

[0018] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of the concave hull shrinkage envelope method in an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the initial wrapping mesh generation in an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the iterative shrinkage process in an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Implementation Method 1

[0023] In this embodiment, a three-dimensional digital model of the patient's dentition is first acquired. This three-dimensional digital model can be obtained using an intraoral scanning device, or from model scan data or cone-beam computed tomography (CBCT) reconstruction data. After acquiring the model, the target dentition model corresponding to the current treatment step is determined according to the orthodontic treatment plan.

[0024] Then, based on the target dentition model, an initial wrapping mesh is generated on its outer side. This initial wrapping mesh is preferably obtained by offsetting it outwards along the outer surface of the target dentition model, maintaining an initial distance from it. This initial distance can be adaptively set according to the overall size of the dentition, or it can be locally adjusted according to the morphological characteristics of different tooth positions.

[0025] Subsequently, local mesh adjustments are made to the initial wrapping mesh. For high-curvature areas such as cusps, incisal edges, proximal transition lines, and undercut boundaries, adaptive subdivision can be performed; for relatively flat areas such as the labial, buccal, lingual, or palatal surfaces, appropriate simplification can be applied. This method allows for control of the mesh size while maintaining the ability to express key anatomical features.

[0026] Subsequently, iterative shrinking is performed on the initial wrapping mesh, gradually bringing it closer to the target tooth arch model. In each iteration, the vertex positions are updated based on the closest correspondence between the vertices of the wrapping mesh and the surface of the target tooth arch model. This update process can employ a gradual shrinking strategy, causing each vertex to move gradually toward the target tooth arch model. Preferably, a larger movement amplitude is used in the initial stage to shorten the overall shrinking time; the movement amplitude is reduced as the model approaches the target surface to improve stability and detail control.

[0027] During the iterative shrinkage process, the surface of the target dentition model is divided into a tight-fitting zone and a buffer retention zone. The tight-fitting zone may include at least a portion of the cusps, incisal edges, major protruding areas of the labial / buccal surfaces, and major protruding areas of the lingual / palatal surfaces. The buffer retention zone may include at least a portion of the proximal concave areas, local undercut areas, and deep transition areas of the cervical region. For the buffer retention zone, during the shrinkage process, a gap of not less than a preset threshold is maintained between the wrapping mesh and the target dentition model, preferably between 0.15 mm and 0.25 mm.

[0028] To suppress local mesh folding, vertex clustering, or bridging, the wrapping mesh is smoothed and stability controlled during iterative shrinkage. Smoothing improves local mesh quality without compromising key anatomical features. Stability control helps avoid anomalous shrinkage, local penetration, and topological distortion.

[0029] Once the preset convergence condition is met, a continuous and watertight envelope mesh is output. This envelope mesh can be used directly as the inner surface of the clear aligner, or it can be further processed with thickness offset and edge trimming to generate a clear aligner shell model for manufacturing. Implementation Method 2

[0030] In this embodiment, a concave shrinkage envelope system for the design of invisible orthodontic appliances is provided, including a data acquisition module, an initialization module, a grid control module, a shrinkage iteration module, a region constraint module, a smoothing and stabilization module, and an output module.

[0031] The data acquisition module is used to acquire a three-dimensional digital model of the patient's dentition and a target dentition model; the initialization module is used to generate an initial enveloping mesh that is adapted to the topological morphology of the target dentition model; the mesh control module is used to locally subdivide and / or simplify the initial enveloping mesh; the shrinkage iteration module is used to perform iterative shrinkage of the enveloping mesh to the target dentition model; the region constraint module is used to apply different shrinkage controls to the close fit area and the buffer retention area; the smoothing and stabilization module is used to perform mesh smoothing and stability control; and the output module is used to output the envelope mesh or generate an invisible aligner model based on the envelope mesh. Implementation Method 3

[0032] In this embodiment, an electronic device is provided, including a processor and a memory. The memory stores a computer program, which, when executed by the processor, implements the steps of the concave hull shrinking envelope method described above. Implementation Method 4

[0033] In this embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, it implements the steps of the concave hull shrinking envelope method described above.

[0034] It should be noted that the above embodiments are only preferred embodiments of the present invention. Equivalent substitutions, modifications or improvements made by those skilled in the art without departing from the spirit and substance of the present invention should all fall within the protection scope of the present invention.

Claims

1. A concave shrinkage envelope method for designing invisible orthodontic appliances, characterized in that, The process includes the following steps: acquiring a three-dimensional digital model of the patient's dentition and determining the target dentition model based on the orthodontic treatment plan; generating an initial wrapping mesh on the outside of the target dentition model that is adapted to its topological morphology; The initial enveloping mesh is locally adjusted based on the local geometric features of the target dentition model; iterative shrinkage is performed on the initial enveloping mesh to gradually approach the target dentition model; during the iterative shrinkage process, the surface of the target dentition model is divided into a close-fitting area and a buffer retention area, and a minimum retention gap constraint is applied to the buffer retention area; during the iterative shrinkage process, the enveloping mesh is smoothed and / or stability controlled; after satisfying the preset convergence condition, a continuous and watertight envelope mesh is output as the inner surface of the clear aligner or used to generate the inner surface of the clear aligner.

2. The concave hull shrinkage envelope method according to claim 1, characterized in that, The three-dimensional digital model is obtained from at least one of intraoral scan data, model scan data, or cone-beam CT reconstruction data.

3. The concave hull shrinkage envelope method according to claim 1, characterized in that, The initial wrapping mesh is generated by offsetting the outer surface of the target dentition model outwards, and maintains a preset initial distance from the target dentition model.

4. The concave hull shrinkage envelope method according to claim 1, characterized in that, The local mesh control includes refining the mesh in high-curvature areas of cusps, incisal edges, proximal transition lines, or undercut boundaries, and / or simplifying the mesh in relatively flat areas of the labial, buccal, lingual, and palatal surfaces.

5. The concave hull shrinkage envelope method according to claim 1, characterized in that, The iterative shrinkage is achieved by gradually moving the vertices in the wrapping mesh toward the corresponding positions on the surface of the target tooth row model, and the shrinkage intensity is a fixed value, a piecewise variable value, or a dynamic value that decreases with the number of iterations.

6. The concave hull shrinkage envelope method according to claim 1, characterized in that, The close-fitting area includes at least a portion of the cusp, incisal edge, major protrusion area of ​​the labial or buccal surface, and major protrusion area of ​​the lingual or palatal surface; the buffer retention area includes at least a portion of the proximal recess area, local undercut area, and deep transition area of ​​the cervical region.

7. The concave hull shrinkage envelope method according to claim 1, characterized in that, In the buffer retention area, the distance between the control wrapping mesh and the target tooth row model is not less than a preset minimum retention gap, which is preferably 0.15 mm to 0.25 mm.

8. The concave hull shrinkage envelope method according to claim 1, characterized in that, The smoothing process employs at least one of neighborhood average smoothing, volume-preserving smoothing, or curvature-constrained smoothing to suppress local mesh folding, vertex clustering, bridging, or anomalous deformation.

9. A concave shrinkage envelope system for the design of invisible orthodontic appliances, characterized in that, include: The data acquisition module is used to acquire the three-dimensional digital model of the patient's dentition and the target dentition model; the initialization module is used to generate an initial wrapping mesh that is adapted to the topology of the target dentition model. The mesh control module is used to locally control the initial wrapping mesh; The shrinkage iteration module is used to perform iterative shrinkage of the wrapping mesh towards the target tooth row model; the region constraint module is used to apply different constraints to the tight fit region and the buffer retention region. The smoothing and stabilization module is used for mesh smoothing and stability control; The output module is used to output an envelope mesh or generate an invisible orthodontic model based on the envelope mesh.

10. An electronic device or computer-readable storage medium, characterized in that, It includes a processor and a memory, or stores a computer program that, when executed, implements the concave hull shrinking envelope method according to any one of claims 1 to 8.

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