Hidden orthodontic 3D printing dental model shelling method

Abstract

The invention discloses an invisible orthodontic 3D printing dental model shelling method which comprises the following steps: S1, acquiring an original dental model, traversing a three-dimensional model file in the original dental model, and generating a file set object containing all three-dimensional models; s2, extracting three-dimensional information data of the three-dimensional model in the step S1 one by one; s3, the three-dimensional model file is preprocessed according to the three-dimensional information data in the step S2, model hole repairing, self-intersecting patch cleaning and non-manifold structure correction are sequentially carried out, and a new triangular patch is formed; s4, extracting an internally biased mirror image model; s5, combining the original three-dimensional model and the reversed mirror image model into a new three-dimensional dental model to form a complete shelling structure; and S6, performing bottom resection treatment on the three-dimensional tooth jaw model after shell extraction to obtain an optimized three-dimensional model. According to the invention, the three-dimensional dental model shell extraction can be automatically realized in batches, the efficiency and the consistency of the three-dimensional dental model shell extraction are improved, and the labor cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of oral medicine, and in particular to a shell extraction method for an invisible orthodontic 3D printed dental and jaw model. Background Art

[0002] Invisible orthodontics, as a method of tooth correction, has been widely used. The production of braces is a key link in the current orthodontic business. The braces are made by pressing the membrane based on the 3D printed dental model. In order to reduce the cost of 3D printing materials, the three-dimensional dental model used for 3D printing needs to be pre-shelled. Currently, most of the methods are for production line workers to use CAD software to manually interact with the model to mark and hollow out operations, which is inefficient and inconsistent, and requires certain labor costs. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of low efficiency and poor consistency in the above-mentioned prior art, and to provide a method for extracting shells from invisible orthodontic 3D printed dental and maxillary models, which can automatically and batch-wise realize the extraction of shells from three-dimensional dental and maxillary models, thereby improving the efficiency and consistency of the extraction of shells from three-dimensional dental and maxillary models, reducing manual operations, and reducing labor costs.

[0004] To achieve the above object, the present invention provides a method for extracting a shell of an invisible orthodontic 3D printed dental model, comprising the following steps:

[0005] S1. Obtain the original dental model, traverse the three-dimensional model files therein, and generate a file collection object containing all three-dimensional models;

[0006] S2, extracting the three-dimensional information data of the three-dimensional model in step S1 one by one;

[0007] S3, preprocessing the 3D model file according to the 3D information data of step S2, successively repairing model holes, cleaning self-intersecting facets, and correcting non-manifold structures to form new triangular facets;

[0008] S4, based on the normal information of the new triangular facet in step S3 and the shell wall thickness parameter defined by the user, each triangular facet is moved in the opposite direction of the facet normal to form all vertex facets of the internal biased mirror image, and the mirror model after the internal bias is extracted;

[0009] S5, inverting the normal direction of the facet of the offset mirror model to ensure that the normal direction of the facet is consistent; merging the original three-dimensional model and the inverted mirror model into a new three-dimensional dental model to form a complete shell structure;

[0010] S6. Perform bottom excision processing on the three-dimensional dental model after shell extraction, and excise the bottom of the model according to the wall thickness parameter to obtain an optimized three-dimensional model.

[0011] Furthermore, the three-dimensional information data in step S2 includes the vertices of each three-dimensional model and the facets composed of the vertices, and a KD tree is constructed based on them.

[0012] Furthermore, the step S2 also includes establishing half-edge structure data, wherein the half-edge structure data includes a collection of half-edge structures formed by connecting the vertices of two facets.

[0013] Furthermore, the model hole repairing step in step S3 is: extracting the boundary edge used by only one facet from the half-edge structure data, constructing a closed ring along the boundary edge to form a hole edge ring, triangulating the hole edge ring, generating new vertices to form a new facet to form a repair area, and finally searching the vertex closest to the new vertex based on the KD tree, estimating the normal, smoothing the repair area along the normal, and obtaining a new vertex.

[0014] Furthermore, the calculation formula of the new vertex is:

[0015]

[0016] Among them, v i is the original position of the vertex; N(i) is the set of neighbor vertices of vertex i; Σ j∈N(i) V j is the sum of the positions of the neighboring vertices of vertex i; N is the number of neighboring vertices; v' i is the new position of vertex i after one smoothing iteration;

[0017] λ is the smoothing weight, and its value range is [0, 1].

[0018] When λ=0, the vertices remain in place and there is no smoothing.

[0019] When λ=1, the vertex moves completely to the center of the neighborhood.

[0020] Furthermore, the self-intersecting facets in step S3 are cleaned up as follows: the bounding box of each triangular facet is obtained according to the three-dimensional information data information, the triangular facets that overlap with the bounding boxes of other triangular facets are quickly screened through the KD tree, a triangle intersection test is performed on the found triangular facets, and finally the triangular facets that are finally tested to be self-intersecting are deleted.

[0021] Furthermore, the step of correcting the non-manifold structure in step S3 is: detecting and identifying non-popular vertices and non-popular edges; correcting the non-popular vertices and non-popular edges, and reallocating the facets connected to these edges.

[0022] Furthermore, the method for correcting the non-popular vertices and non-popular edges is: for the non-popular vertices, a new vertex is created to replace the original vertex; for the non-popular edges, the original non-popular edges are split to form two or more new edges.

[0023] Furthermore, the normal information in step S4 includes a patch normal vector, and the movement amount in the opposite direction of the patch normal in step S4 is: the product of the patch normal vector and the evacuated wall thickness parameter.

[0024] Furthermore, in step S4, the Marching Cubes algorithm is used to extract the mirror model after internal bias.

[0025] The present invention directly collects the three-dimensional information of multiple groups of original dental and jaw models, and generates a file collection object containing all models, which is convenient for subsequent batch processing and management. At the same time, the extracted information is used to construct a KD tree structure so as to efficiently perform spatial query and geometric calculation. With the cooperation of the KD tree structure, the model hole repair, self-intersecting facet cleaning and non-popular structure correction can be completed quickly and accurately; then based on the normal information of the triangular facets of the model, each triangular facet is moved in the opposite direction of the facet normal based on the shell wall thickness parameter defined by the user, and the mirror model after the internal bias is extracted; the original three-dimensional model and the inverted mirror model are merged into a new three-dimensional dental and jaw model to form a complete shell structure, and finally the three-dimensional dental and jaw model after shelling is subjected to bottom excision processing, the bottom of the model is excised according to the wall thickness parameter, and the optimized three-dimensional model is exported to generate a model file that can be used for 3D printing. The present invention can automatically realize the shelling of three-dimensional dental and jaw models in batches, improve the efficiency and consistency of the shelling of three-dimensional dental and jaw models, reduce manual operations, and reduce labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 is a schematic diagram of the original dental model to be processed in step S1;

[0028] Figure 2 is a schematic diagram of the mirror model after the bias in step S4;

[0029] Figure 3 This is a schematic diagram of the model after the normal direction of the face is reversed in step S5;

[0030] Figure 4 A schematic diagram of merging the original three-dimensional model and the inverted mirror image model into a new three-dimensional dental model;

[0031] Figure 5 for Figure 4 Network diagram of the new three-dimensional dental model;

[0032] Figure 6 This is a schematic diagram of the final model after the bottom cutting process is performed in step S6. DETAILED DESCRIPTION

[0033] The technical scheme in this embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in this embodiment of the present invention. Obviously, the described embodiment is one embodiment of the present invention, not all embodiments of the present invention. Based on this embodiment of the present invention, all other embodiments of the present invention obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Please refer to Figures 1 to 6 The present invention provides a method for extracting a shell of an invisible orthodontic 3D printed jaw model, comprising the following steps:

[0035] S1. Open the 3D model folder to be processed and obtain Figure 1 All the original dental models shown, traverse the 3D model files therein, and generate a file collection object containing all the 3D models to facilitate subsequent batch processing and management;

[0036] S2, extracting the three-dimensional information data of the three-dimensional models in step S1 one by one, the three-dimensional information data including the three-dimensional mesh information corresponding to all three-dimensional models, especially each three-dimensional vertex and face data, and constructing a KD tree structure based on this,

[0037] For example, the XYZ axis coordinates of each 3D vertex can be extracted and recorded as V1 (X1, Y1, Z1), V2 (X2, Y2, Z2), etc., and all the 3D vertices contained in each 3D model are extracted and recorded, and a vertex set is generated.

[0038] Similarly, the coordinates of the triangles formed by the three-dimensional vertices are recorded. The triangular patches are formed by connecting the three-dimensional vertices, which can be recorded as f1(V1, V2, V3), f2(V1, V2, V3)... and so on. All the patches contained in each three-dimensional model are extracted and a patch set is generated.

[0039] Establishing half-edge structure data, wherein the half-edge structure data includes a collection of half-edge structures formed by connecting the vertices of two face patches, that is, connecting the vertices of two face patches in sequence, such as f1(V1) and f2(V1), to form a half-edge structure, and generating a collection, so as to facilitate the subsequent identification of boundary edges and determination of hole positions;

[0040] S3, preprocessing the 3D model file according to the 3D information data of step S2, successively repairing model holes, cleaning self-intersecting facets, and correcting non-manifold structures to form new triangular facets;

[0041] The above steps for model hole repair are:

[0042] A) Extract the boundary edge used by only one face from the half-edge structure data;

[0043] B) Construct a closed loop along the boundary edges so that all boundary edges are connected to form a hole edge loop;

[0044] C) Triangulate the edge ring of the hole to generate new vertices to form a new patch to form a repair area;

[0045] D) Finally, based on the KD tree, find the vertex closest to the new vertex, estimate the normal and get the normal vector, smooth the patch area along the normal, and get the new vertex.

[0046] Preferably, the calculation formula of the new vertex is:

[0047]

[0048] Among them, v i is the original position of the vertex; N(i) is the set of neighbor vertices of vertex i; Σ j∈N(i) V j is the sum of the positions of the neighboring vertices of vertex i; N is the number of neighboring vertices; v' i is the new position of vertex i after one smoothing iteration;

[0049] λ is the smoothing weight, and its value range is [0, 1].

[0050] When λ=0, the vertices remain in place and there is no smoothing.

[0051] When λ=1, the vertex moves completely to the center of the neighborhood;

[0052] Preferably, the above-mentioned cleaning of self-intersecting facets is: obtaining the bounding box of each triangular facet according to the three-dimensional information data information, quickly screening the triangular facets overlapping with the bounding boxes of other triangular facets through the KD tree, performing a triangle intersection test on the found triangular facets, and finally deleting the triangular facets that are finally tested to be self-intersecting;

[0053] Preferably, the above-mentioned step of correcting the non-manifold structure is: detecting and identifying non-popular vertices and non-popular edges; correcting the non-popular vertices and non-popular edges, wherein the correction method for the non-popular vertices and non-popular edges is: for the non-popular vertices, a new vertex is created to replace the original vertex; for the non-popular edges, the original non-popular edges are split to form two or more new edges, and the facets connected to these edges are reallocated;

[0054] S4, based on the normal information of the new triangular facet in step S3, and based on the shell wall thickness parameter defined by the user, each triangular facet is moved in the opposite direction of the facet normal. Specifically, the normal information includes the facet normal vector. The movement amount in the opposite direction of the facet normal in step S4 is: the product of the facet normal vector and the shell wall thickness parameter, for example

[0055] Define the patch normal vector as n

[0056] Define the evacuated wall thickness parameter as d

[0057] Then the patch f 1( The corresponding built-in bias patch of V1, V2, V3) is f1'(V1', V2', V3'). From the above formula, we can get V1'=V1-n*d, V2'=V2-n*d, V3'=V3-n*d, thus we can get the vertex patch coordinates f1'(V1', V2', V3') after built-in bias.

[0058] The above operations are performed on all the faces of the model in sequence to form all the vertex faces of the internal paranoid mirror, and finally the Marching Cubes algorithm is used to extract the Figure 2 The mirror image model after internal biasing is shown;

[0059] S5, reverse the face normal of the offset mirror model to ensure that the face normal directions are consistent; merge the original three-dimensional model and the reversed mirror model into one. Figure 4 and Figure 5 The new three-dimensional dental model is shown to form a complete shell structure;

[0060] S6, the bottom of the three-dimensional jaw model after shell extraction is cut off, and the bottom of the model is cut off according to the wall thickness parameter to obtain the following Figure 6 The optimized three-dimensional model shown can be exported in subsequent operations to generate a model file that can be used for 3D printing.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for extracting a shell from an invisible orthodontic 3D printed dental model, characterized in that: The steps include: S1. Obtain the original dental model, traverse the three-dimensional model files therein, and generate a file collection object containing all three-dimensional models; S2, extracting the three-dimensional information data of the three-dimensional model in step S1 one by one; S3, preprocessing the 3D model file according to the 3D information data of step S2, successively repairing model holes, cleaning self-intersecting facets, and correcting non-manifold structures to form new triangular facets; S4, based on the normal information of the new triangular facet in step S3 and the shell wall thickness parameter defined by the user, each triangular facet is moved in the opposite direction of the facet normal to form all vertex facets of the internal biased mirror image, and the mirror model after the internal bias is extracted; S5, inverting the normal direction of the facet of the offset mirror model to ensure that the normal direction of the facet is consistent; merging the original three-dimensional model and the inverted mirror model into a new three-dimensional dental model to form a complete shell structure; S6. Perform bottom cutting processing on the three-dimensional jaw model after shell extraction, cut off the bottom of the model according to the wall thickness parameter, and obtain an optimized three-dimensional model.

2. The method for extracting a shell of an invisible orthodontic 3D printed dental model according to claim 1, characterized in that: The three-dimensional information data in step S2 includes the vertices of each three-dimensional model and the facets composed of the vertices, and a KD tree is constructed based on them.

3. The method for extracting a shell of an invisible orthodontic 3D printed dental model according to claim 2, characterized in that: The step S2 also includes establishing half-edge structure data, wherein the half-edge structure data includes a collection of half-edge structures formed by connecting the vertices of two facets.

4. The method for extracting a shell from an invisible orthodontic 3D printed dental model according to claim 3, characterized in that: The model hole repairing step in step S3 is as follows: extracting the boundary edge used by only one facet from the half-edge structure data, constructing a closed ring along the boundary edge to form a hole edge ring, triangulating the hole edge ring, generating new vertices to form a new facet to form a repair area, and finally searching for the vertex closest to the new vertex based on the KD tree, estimating the normal, smoothing the repair area along the normal, and obtaining a new vertex.

5. The method for extracting a shell from an invisible orthodontic 3D printed dental model according to claim 4, characterized in that: The calculation formula of the new vertex is: Among them, v i is the original position of the vertex; N ( i ) is the set of neighbor vertices of vertex i; ∑ j∈N(i0 V j is the sum of the positions of the neighboring vertices of vertex i; N is the number of neighboring vertices; v' i is the new position of vertex i after one smoothing iteration; λ is the smoothing weight, and its value range is [0, 1]. When λ=0, the vertices remain in place and there is no smoothing. When λ=1, the vertex moves completely to the center of the neighborhood.

6. The method for extracting a shell from an invisible orthodontic 3D printed dental model according to claim 4, characterized in that: The self-intersecting facets cleaned in step S3 are: obtaining the bounding box of each triangular facet according to the three-dimensional information data information, quickly screening the triangular facets that overlap with the bounding boxes of other triangular facets through the KD tree, performing a triangle intersection test on the found triangular facets, and finally deleting the triangular facets that are finally tested to be self-intersecting.

7. The method for extracting a shell from an invisible orthodontic 3D printed dental model according to claim 6, characterized in that: The steps of correcting the non-manifold structure in step S3 are: detecting and identifying non-popular vertices and non-popular edges; correcting the non-popular vertices and non-popular edges, and reallocating the facets connected to these edges.

8. The method for extracting a shell from an invisible orthodontic 3D printed dental model according to claim 7, characterized in that: The method for correcting the non-popular vertices and non-popular edges is as follows: for the non-popular vertices, a new vertex is created to replace the original vertex; for the non-popular edges, the original non-popular edges are split to form two or more new edges.

9. The method for extracting a shell of an invisible orthodontic 3D printed dental model according to claim 1, characterized in that: The normal information in step S4 includes a patch normal vector, and the movement amount in the opposite direction of the patch normal in step S4 is: the product of the patch normal vector and the evacuated wall thickness parameter.

10. The method for extracting a shell from an invisible orthodontic 3D printed dental model according to claim 1, characterized in that: In step S4, the Marching Cubes algorithm is used to extract the mirror image model after internal bias.

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