Method for fusing dental three-dimensional digital models

Abstract

An aspect of the present application provides a computer-implemented method for fusing a three-dimensional digital model of a tooth, comprising: obtaining a first three-dimensional digital model representing a first tooth crown, a second three-dimensional digital model representing the first tooth as a whole, and a first segmentation scheme, the first segmentation scheme dividing the second three-dimensional digital model into a first part and a second part corresponding to the tooth crown and the tooth root respectively; performing point cloud registration on the first three-dimensional digital model and the first part of the second three-dimensional digital model; based on the result of the point cloud registration, calculating a set of points on the second three-dimensional digital model closest to points on the edge of the first three-dimensional digital model, and deleting the part of the second three-dimensional digital model corresponding to the first three-dimensional digital model based on the set of closest points to obtain a third part of the second three-dimensional digital model; performing surface stitching on the first three-dimensional digital model and the third part of the second three-dimensional digital model to obtain a fused three-dimensional digital model; and performing triangular mesh deformation on the stitched area of the fused three-dimensional digital model.

Description

Technical Field

[0001] This application generally relates to a method for fusing three-dimensional digital models of teeth. Background Technology

[0002] With the continuous development of computer science, dental professionals are increasingly using computer technology to improve the efficiency of dental treatment. Three-dimensional digital models of teeth are frequently used in computer-assisted dental treatment.

[0003] Currently, by performing intraoral scanning on patients, or by scanning impressions or physical models of patients' teeth, it is possible to obtain a highly accurate three-dimensional digital model of the patient's tooth crown. However, this method cannot obtain information about the patient's tooth roots.

[0004] Computed tomography (CT) can be used to obtain a three-dimensional digital model of a patient's teeth (including the crown and root), but its accuracy is not high.

[0005] Some treatments (such as orthodontic treatment) require a complete 3D digital model of the tooth, but only the crown portion needs high precision; for the root portion, only its general shape and location are required. Therefore, a solution has emerged that combines a high-precision 3D digital model of the crown with a lower-precision 3D digital model of the root to obtain a complete 3D digital model of the tooth.

[0006] For ease of description, the digital dataset representing the crown with higher precision will be referred to as the target crown, and the digital dataset representing the whole tooth with lower precision will be referred to as the reference tooth.

[0007] Currently, there are two main fusion methods. The first is the direct splicing method, which involves first registering the reference tooth with the target crown, then manually removing the crown portion representing the reference tooth to obtain the root portion, based on the registration result, and finally splicing the target crown and the root portion of the reference tooth to obtain the fused result. However, this method has the following drawbacks: firstly, the transition between the crown and root differs significantly from the actual situation; secondly, manually removing the crown is time-consuming, and the consistency of the result cannot be guaranteed.

[0008] The second method is the mesh deformation method. This involves first registering the reference tooth with the target crown, and then using the target crown as control points to perform non-rigid mesh deformation on the triangular mesh data of the reference tooth to obtain the fused result. However, this method has the following drawbacks: since the crown portion is based on the deformation of the reference crown according to the target crown, its accuracy cannot be guaranteed.

[0009] In view of the above, it is necessary to provide a new method for generating three-dimensional digital models of teeth. Summary of the Invention

[0010] One aspect of this application provides a computer-executed method for fusing three-dimensional digital models of teeth, comprising: acquiring a first three-dimensional digital model representing the crown of a first tooth, a second three-dimensional digital model representing the entire first tooth, and a first segmentation scheme, wherein the first segmentation scheme divides the second three-dimensional digital model into a first part and a second part corresponding to the crown and root of the tooth, respectively; performing point cloud registration on the first three-dimensional digital model and the first part of the second three-dimensional digital model; based on the result of the point cloud registration, calculating the set of points on the second three-dimensional digital model that are closest to the points on the edge of the first three-dimensional digital model, and deleting the part of the second three-dimensional digital model corresponding to the first three-dimensional digital model based on the set of closest points to obtain a third part of the second three-dimensional digital model; performing surface stitching on the first three-dimensional digital model and the third part of the second three-dimensional digital model to obtain a fused three-dimensional digital model; and performing triangular mesh deformation on the stitching area of ​​the fused three-dimensional digital model.

[0011] In some implementations, the point cloud registration is performed using a sparse iterative nearest-point sampling method.

[0012] In some embodiments, the computer-based fusion method for three-dimensional digital models of teeth may further include: aligning the centroids of the first three-dimensional digital model and the first part of the second three-dimensional digital model by centroid offset, wherein the point cloud registration is performed based on the centroid offset.

[0013] In some embodiments, the computer-based fusion method for three-dimensional digital models of teeth further includes: deleting a ring neighborhood of the set of nearest points of the second three-dimensional digital model, and deleting the portion of the second three-dimensional digital model corresponding to the first three-dimensional digital model based on the number of connected components after deleting the ring neighborhood and the number of faces of these connected components.

[0014] In some embodiments, the computer-based fusion method for three-dimensional digital models of teeth may further include: calculating a set of nearest point pairs between the edges of the first three-dimensional digital model and the edges of a third part of the second digital model, and performing subsurface partitioning based on the set of nearest point pairs during the surface stitching.

[0015] In some embodiments, the computer-based fusion method for three-dimensional digital models of teeth may further include: triangulating a subsurface composed of four vertices, wherein the triangulation is performed using a subdivision scheme with a larger minimum interior angle.

[0016] In some embodiments, the computer-based fusion method for three-dimensional digital models of teeth may further include: subdividing a subsurface consisting of more than four vertices, first subdividing a subsurface consisting of four vertices, and then triangulating it using a subdivision scheme with a larger minimum interior angle. At this time, the remaining part of the subsurface has a first vertex remaining on one edge and multiple vertices remaining on the other edge. The remaining part is triangulated in such a way that every two adjacent vertices among the multiple vertices form a triangle with the first vertex.

[0017] In some implementations, the Laplace-Beltrami harmonic deformation algorithm is used to perform the triangular mesh deformation.

[0018] In some embodiments, the computer-based fusion method for three-dimensional digital models of teeth may further include: calculating a w-ring neighborhood covering the suture area based on the edge line of the third part of the second three-dimensional digital model and the number of facets, and performing the triangular mesh deformation on the w-ring neighborhood.

[0019] In some embodiments, the computer-based fusion method for three-dimensional digital models of teeth may further include: smoothing the second three-dimensional digital model before deleting the portion of the second three-dimensional digital model corresponding to the first three-dimensional digital model, wherein the smoothing process includes forward smoothing and reverse smoothing.

[0020] In some embodiments, the computer-based fusion method for three-dimensional digital models of teeth may further include: simplifying the second three-dimensional digital model before deleting the portion of the second three-dimensional digital model corresponding to the first three-dimensional digital model, wherein the simplification is an adaptive simplification based on the number of faces in the first three-dimensional digital model.

[0021] In some implementations, the first three-dimensional digital model is obtained by one of the following methods: intraoral scanning, scanning dental impressions or solid models, and the second three-dimensional digital model is obtained by computed tomography (CT) technology. Attached Figure Description

[0022] The above and other features of this application will be further described below with reference to the accompanying drawings and their detailed description. It should be understood that these drawings only illustrate several exemplary embodiments according to this application and should not be considered as limiting the scope of protection of this application. Unless otherwise specified, the drawings are not necessarily to scale, and similar reference numerals denote similar parts.

[0023] Figure 1 This is a schematic flowchart of a computer-implemented method for fusing three-dimensional digital models of teeth in one embodiment of this application;

[0024] Figure 2 A three-dimensional digital model of a first jaw obtained by intraoral scanning in one embodiment of this application is shown;

[0025] Figure 3 A three-dimensional digital model of a first dental jaw obtained by computed tomography is shown in one embodiment of this application;

[0026] Figure 4a The diagram illustrates one example of a triangle partitioning scheme.

[0027] Figure 4b schematically shown Figure 4a Another triangulation scheme for the example shown; and

[0028] Figure 5 The diagram illustrates a triangular partitioning scheme in one example. Detailed Implementation

[0029] The following detailed description references the accompanying drawings, which form part of this specification. The illustrative embodiments mentioned in the specification and drawings are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art will understand, based on the teachings of this application, that many other embodiments can be employed and various changes can be made to the described embodiments without departing from the spirit and scope of this application. It should be understood that the various aspects of this application illustrated herein can be arranged, substituted, combined, separated, and designed in many different configurations, all of which are within the scope of this application.

[0030] One aspect of this application provides a method for fusing three-dimensional digital models of teeth, used to fuse a first three-dimensional digital model representing the crown of a tooth and the root portion of a second three-dimensional digital model representing the entire tooth, to obtain a fused three-dimensional digital model representing the entire tooth. The first three-dimensional digital model is obtained using a first technical means; the second three-dimensional digital model is obtained using a second technical means different from the first technical means. In one example, the first three-dimensional digital model has a higher degree of conformity to the actual crown compared to the crown portion of the second three-dimensional digital model.

[0031] In one embodiment, the first technical means may be intraoral scanning, or scanning of the patient's dental impressions or physical models.

[0032] In one embodiment, the second technical means can be tomography, such as cone-beam computed tomography (CBCT).

[0033] Please refer to Figure 1 This is a schematic flowchart of a method 100 for generating a three-dimensional digital model of teeth in one embodiment of this application.

[0034] In 101, a first three-dimensional digital model of the crown of the first tooth and a second three-dimensional digital model of the entire first tooth are obtained.

[0035] There are several methods for obtaining digital 3D models of dental crowns. In one embodiment, an intraoral scan of the patient can be performed to obtain a 3D digital model of all crowns in the patient's maxilla and / or mandible. In another embodiment, a solid model of the patient's jaw, such as a plaster cast, can be scanned to obtain a 3D digital model of all crowns in that jaw. In yet another embodiment, an impression of the patient's jaw can be scanned to obtain a 3D digital model of all crowns in that jaw. The 3D digital model of the jaw obtained by scanning can be segmented to obtain the 3D digital model of each crown. The techniques for obtaining 3D digital models of the jaw by scanning and segmenting them are well known in the industry and will not be described in detail here.

[0036] Please refer to Figure 2 This paper presents a three-dimensional digital model of the first jaw obtained by intraoral scanning in one example of this application.

[0037] In one embodiment, a three-dimensional digital model of the entire tooth can be obtained using computed tomography (CT) technology. The raw data obtained using CT technology includes information about the jawbone and teeth. Existing technologies can be used to process the raw data obtained from CT scans to remove jawbone information, extract tooth information, and segment the crown and root of the teeth. This segmentation is referred to as the first segmentation scheme.

[0038] Please refer to Figure 3 This paper presents a three-dimensional digital model of a first jaw obtained by CBCT in one example of this application.

[0039] In step 103, the first three-dimensional digital model and the second three-dimensional digital model are registered.

[0040] First, the first three-dimensional digital model and the second three-dimensional digital model are registered. Then, based on the registration result, the part of the second three-dimensional digital model corresponding to the first digital model is deleted. Finally, the remaining parts of the first three-dimensional digital model and the second three-dimensional digital model are merged.

[0041] For ease of explanation, the crown portion obtained by segmenting the second three-dimensional digital model according to the first segmentation scheme will be referred to as the first portion.

[0042] In one embodiment, point cloud registration can be used to register the first three-dimensional digital model and the first part of the second three-dimensional digital model.

[0043] In one embodiment, registration based on a single tooth may result in a large error. Therefore, to ensure registration accuracy, registration can be performed based on multiple teeth, such as the entire dentition (maxillary or mandibular dentition).

[0044] In one embodiment, point cloud registration can be performed using the following method.

[0045] In one embodiment, the first three-dimensional digital model can be directly used as the crown portion of the three-dimensional digital model of the fused tooth as a whole. If the triangular mesh density (i.e., the number of triangular meshes per unit area) of the second three-dimensional digital model is significantly higher than that of the first three-dimensional digital model, in order to improve the computational efficiency of registration and increase the convergence speed, the crown portion of the second three-dimensional digital model can be downsampled.

[0046] In one embodiment, the second three-dimensional digital model can be downsampled using the following method.

[0047] First, a rectangular bounding box is established to enclose the first part of the second three-dimensional digital model. Then, the bounding box is divided into multiple sub-cubes with a side length of L1 of the average side length of the triangular mesh of the first three-dimensional digital model. The first searched point is retained in each sub-cube. After traversing all sub-cubes, the point cloud downsampling of the first part of the second three-dimensional digital model is completed.

[0048] After downsampling the point cloud of the first part of the second 3D digital model, before point cloud registration, the first 3D digital model and the first part of the second 3D digital model can be roughly aligned by centroid shifting to improve the accuracy and efficiency of subsequent point cloud registration. In one embodiment, the centroids (i.e., average coordinates) of the first 3D digital model and the first part of the second 3D digital model can be calculated separately, and then the centroid of one of them can be shifted to the centroid of the other to complete the approximate alignment of the two.

[0049] In one embodiment, the Sparse Iterative ClosestPoint (SICP) method can be used for point cloud registration. In another embodiment, point cloud registration can be performed using the point cloud of the first 3D digital model as a reference, and the position of the point cloud of the first part of the second 3D digital model can be updated.

[0050] In one embodiment, the conditions for the SICP registration method can be set as follows: if the number of registrations is less than k1, then calculate the distance d1 between each point in the point cloud of the first part of the second three-dimensional digital model and the nearest point in the point cloud of the first three-dimensional digital model. If d1 > k2*L1, then the point is considered abnormal and deleted, completing one update of the point cloud of the first part of the second three-dimensional digital model; repeat the above operation until the number of registrations is greater than or equal to k1, at which point the registration is completed.

[0051] In one embodiment, the parameters can be set as follows: k1 is set to 3; the initial value of k2 is set to 6, and the value of k2 is decreased by 2 with each iteration; the norm p of the SICP registration method is set to a range of 0.4 to 2; and the number of iterations n is set to a range of 30 to 100. It is understood that the above parameters can be adjusted according to specific circumstances and requirements.

[0052] It is understood that in embodiments involving registration based on multiple teeth, the three-dimensional digital models of the multiple teeth can be treated as a whole for the above operations. For example, they can be based on... Figure 2 The three-dimensional digital model shown is Figure 3 The aforementioned three-dimensional digital model is registered.

[0053] The edge of the tooth crown represented by the first 3D digital model is the gingival line, while the first part of the second 3D digital model is obtained based on planar segmentation from computed tomography. Therefore, there may be significant differences between the edges of the two models. Since the SICP registration method does not consider points with large differences, it can achieve high registration accuracy in this case.

[0054] In step 105, a smoothing operation is performed on the second three-dimensional digital model.

[0055] The second 3D digital model obtained using computed tomography (CT) scans may contain some imperfections; therefore, it can be smoothed before fusion to eliminate these imperfections. Furthermore, smoothing allows it to more closely approximate the actual shape of teeth.

[0056] In one embodiment, a combination of forward smoothing and inverse smoothing can be used to smooth the second 3D digital model. This combination can, to some extent, prevent the smoothed 3D digital model from shrinking or expanding.

[0057] In one embodiment, smoothing can be performed using the Laplace smoothing operator. The following equation (1) expresses the forward smoothing based on the Laplace smoothing operator.

[0058] V iP =V i +λ P Equation (1) of D(V)

[0059] Among them, V i Represents the current vertex, λ p λ represents the step size parameter for positive smoothing. In one embodiment, λ p The value range can be 0.5 to 0.7. It can be understood that this range can be adjusted according to specific circumstances.

[0060]

[0061] Where, N i For the current vertex V i The ring neighborhood is defined as n, where n is the number of vertices within the ring neighborhood. The system performs forward smoothing k3 times. In one embodiment, the value of k3 can range from 15 to 25.

[0062] Equation (3) below expresses inverse smoothing based on the Laplace smoothing operator.

[0063] V iR =V i -λ R Equation (3) of D(V)

[0064] Where, λ R λ represents the step size parameter for inverse smoothing, which iterates inverse smoothing k3 times. In one embodiment, λ R The value range can be 0.25 to 0.35. It can be understood that this range can be adjusted according to specific circumstances.

[0065] Extensive experiments have shown that a combination of forward and reverse smoothing can maintain the original mesh size while achieving the desired smoothing effect, keeping the average accuracy loss within 0.03mm. In the orthodontic industry, the effective step size for tooth arrangement is approximately 0.2mm. The accuracy loss of this smoothing method is far less than the step size, thus it effectively meets the requirements of this application.

[0066] Based on the teachings of this application, it is understood that, in addition to the Laplacian smoothing operator, the second three-dimensional digital model can also be smoothed based on any other algorithm suitable for surface smoothing, such as the patch normal mean filtering algorithm, or the weighted mean filtering algorithm, etc.

[0067] In 107, the smoothed second three-dimensional digital model is simplified.

[0068] In one embodiment, the patch density of the second 3D digital model is much higher than that of the first 3D digital model. To make the topology of the fused 3D digital model natural, the smoothed second 3D digital model can be simplified.

[0069] In one embodiment, the simplification of the second three-dimensional digital model can be an adaptive simplification based on the number of faces in the first three-dimensional digital model.

[0070] In one embodiment, the adaptive simplification method may include the following operation: it employs different simplification methods based on the classification of crown size.

[0071] First, calculate the bounding box volume ratio ratio1 between the second three-dimensional digital model and the first three-dimensional digital model, and classify the crown based on ratio1. If ratio1 > k4, the crown is classified as a "small crown"; otherwise, it is classified as a "normal crown".

[0072] If the crown is a "normal crown", then the number of faces in the second 3D digital model is equal to the product of the number of faces in the first 3D digital model and atio1. If the crown is a "small crown", then iterative simplification is performed, and the simplification rate can be set to 80%. After each simplification, the average side length L2 of the face is calculated. If L2-L1 < minL, then simplification stops; otherwise, simplification continues.

[0073] In one embodiment, k4 can be set to 5, and minL can be set to 0.2mm.

[0074] According to experimental comparisons, compared to setting a fixed number of target facets, adaptive simplification can achieve better consistency in the facet morphology of the fused crown and root, resulting in a more natural topology.

[0075] In step 109, based on the registration result, the portion of the smoothed and simplified second three-dimensional digital model corresponding to the first three-dimensional digital model (i.e., the crown portion) is deleted.

[0076] In one embodiment, deletion can be performed using the following method.

[0077] First, based on the registration result, calculate the set of points on the smoothed and simplified second three-dimensional digital model that are closest to the points on the edge of the first three-dimensional digital model, and delete the ring neighborhood patches (including the patches on both sides of the nearest point) of these nearest points.

[0078] Next, the number of connected components on the second 3D digital model after deleting the ring neighbor is calculated. If the number of connected components is greater than 1, then the connected components of the crown portion are traced, and the ratio of its number of faces to the total number of faces, ratio2, is calculated. If ratio2 > R1 and the number of faces of the connected components of the crown portion is greater than k5, then the crown portion is successfully segmented, the connected components of the crown portion are deleted, and the process ends. In one embodiment, R1 can be 0.1, and k5 can be in the range of 300 to 400. It can be understood that the range of k5 can be adjusted according to the accuracy of the smoothed and simplified second 3D digital model. If ratio2 or the number of faces of the connected components of the crown portion does not meet the set conditions, or the number of connected components is less than or equal to 1, then the ratio of the number of faces of the connected components of the root portion to the total number of faces of the second 3D digital model, ratio3, is calculated, and the number of times the ring neighbor face is deleted based on the nearest point, m, is counted. If ratio3 > R2 (the smaller the ratio3, the more faces are deleted; R2 is equivalent to a warning line for the number of remaining faces) and m < k6, then the nearest point set is updated based on the existing triangular mesh, and the above operation continues. In one embodiment, R2 can be 0.5, and k6 can be 10. If ratio3 < R2 or m > k6 (either of these two conditions indicates that too many faces have been deleted, and continuing deletion may seriously affect the morphological characteristics of the tooth root; therefore, once this condition is triggered, the deletion operation stops), then the connected components of the crown portion are deleted, and the process ends.

[0079] The crown portion of the simplified and smoothed second three-dimensional digital model is removed to obtain a third three-dimensional digital model representing the tooth root.

[0080] In step 111, the edges of the third three-dimensional digital model and the first three-dimensional digital model are stitched together using curved surfaces.

[0081] In one embodiment, to ensure smoothness in subsequent surface stitching, the edges of the third 3D digital model can be smoothed before surface stitching. In one embodiment, the Laplacian smoothing method can be used. The specific operation in one embodiment is as follows.

[0082] Obtain the point set p of the edge of the third 3D digital model re Calculate p re Mid-vertex v i With adjacent vertex v i+1 and V i-1 If the included angle α, Then Laplace smoothing is applied to vi. In one embodiment, Laplace smoothing can be expressed by the following equation (4).

[0083]

[0084] Where n = 3,

[0085] Obtain the smoothed vertex set p re ', calculate p again re The angles between each vertex and its adjacent vertices, if Then perform Laplace smoothing on that vertex, and repeat this process until all vertices no longer satisfy the condition. conditions.

[0086] Next, the vertices of the edges of the first and third 3D digital models are sorted. In one embodiment, the set of points p of the edges of the first 3D digital model can be found first. c With p re The pair of points {P} with the smallest distance between them c i, p re ′j}, then, with p c Starting from i, rotate p again in a counter-clockwise direction. c Sort by p re Starting from 'j', rotate p again in a counter-clockwise direction. re 'Sort.'

[0087] Then, subsurfaces can be partitioned based on the sorted point set. In one embodiment, subsurface partitioning can be performed using the following method.

[0088] First calculate p c With p re The number of midpoints, with the smaller number defined as p. short The larger quantity is defined as p. long .

[0089] Next, calculate p. short and p long The nearest pair of points, where p short and p long The first point forms a nearest pair, p short and p long The last point forms a nearest pair.

[0090] Then, calculate each nearest point pair p long The index position of the midpoint (index) and the previous nearest point (p) long The difference d between the index positions of the midpoints, where p is not calculated between the first and last nearest point pairs. long The difference in the index position of the midpoint.

[0091] If d > Sp long / 2, then the current nearest point pair p longThe index position of the midpoint is replaced with index', where Sp long For p long The number of midpoints. That is, the number of midpoints from the current nearest pair of points p. shor Point t and the previous nearest point pair form a triangle, which is formed by p in the next nearest point pair. short p in the current nearest point pair short p in the current nearest point pair long p in the pair of points and the previous nearest point long Points and the p between them long Points form new subsurfaces.

[0092] Each pair of two adjacent nearest points (4 points) and the p between them long The points in the matrix form a subsurface, where the first nearest pair of points and the last nearest pair of points form another subsurface. If adjacent subsurfaces intersect, the nearest pair of points {pi} corresponding to the intersecting lines is deleted first. short ,pj long Next, find pi. short The previous point pil short and the next point pi2 short And find the pj1 corresponding to these two points. long and pj2 long Then, calculate pi. short to pj1 long and pj2 long The point pj0 corresponding to the minimum distance between all points is the distance between them. long As a new pj long Repeat the above steps until there are no intersections between any of the subsurfaces.

[0093] Next, the subsurface is triangulated. In one embodiment, the subsurface can be triangulated based on the interior angles of the triangles.

[0094] First, calculate the subsurface belonging to p in each subsurface. long The number of vertices, np.

[0095] If np = 1, it means that the subsurface is triangular and does not need to be subdivided.

[0096] If np = 2, the subsurface will be divided into two triangles. There are two methods for this division, as follows: Figure 4a and 4b As shown. Calculate the minimum interior angle for both partitioning methods, and use the partitioning method with the larger minimum interior angle.

[0097] If np > 2, the subsurface is first divided into two parts, f1 and f2. f1 consists of 4 vertices and is divided using the same method as when np = 2. f2 consists of np vertices, including one p. short vertex p short d and np-1 p long The vertex of p. At this time, p shortd and the np-1 p long Each pair of adjacent vertices in the subsurface forms a triangle, thus completing the triangular partitioning of the subsurface, as shown below. Figure 5 As shown.

[0098] After completing the surface stitching, the stitched area can be refined. In one embodiment, a side length threshold k7 can be set. If any side of a triangular mesh is longer than k7, it is segmented. In one embodiment, k7 can be in the range of 1.2 to 1.5 mm. It is understood that the range of k7 can be adjusted according to specific circumstances and requirements.

[0099] At this point, a preliminary fused fourth three-dimensional digital model is obtained. However, the geometry at the tooth neck may not be natural enough. In addition, due to the difference in precision between the first and second three-dimensional digital models, the transition between the two (i.e., the tooth neck) may not be natural enough after fusion. Therefore, triangular mesh deformation processing can be performed on this part.

[0100] In step 113, triangular mesh deformation processing is performed on the tooth neck of the fourth three-dimensional digital model.

[0101] In one embodiment, the w-ring neighborhood (i.e., the cervical region) on the fourth three-dimensional digital model can be subjected to triangular mesh deformation based on the smoothed edge lines of the third three-dimensional digital model. In one embodiment, the w-ring neighborhood encompasses the sutured surface.

[0102] In one embodiment, the number of w can be determined based on the ratio of the number of faces in the w-ring neighborhood to the total number of faces in the fourth 3D digital model, and whether it completely covers the stitching area. In another embodiment, a ring neighborhood can be searched on the fourth 3D digital model using the edge line of the third 3D digital model as a reference. If the ratio of its face number to the total number of faces is greater than a predetermined value and it completely covers the stitching area, then the search stops; otherwise, the search continues for a ring neighborhood based on the already searched faces, and so on until the above conditions are met.

[0103] In one embodiment, the points of the fourth three-dimensional digital model above the w-ring neighborhood (the part near the crown) can be used as the first control point set, and the points of the part below the w-ring neighborhood (the part near the root) can be used as the second control point set. Based on the first and second control point sets, the Laplace-Beltrami harmonic deformation algorithm is used to deform the patches of the w-ring neighborhood, and finally the patches are relaxed to obtain a fused three-dimensional digital model representing the whole tooth.

[0104] In one embodiment, the tooth three-dimensional digital model fusion method of this application can be executed automatically by a computer without human intervention, which can greatly improve efficiency.

[0105] Although various aspects and embodiments of this application have been disclosed herein, other aspects and embodiments of this application will be apparent to those skilled in the art upon inspiration from this application. The various aspects and embodiments disclosed herein are for illustrative purposes only and not for limiting purposes. The scope and spirit of this application are determined solely by the appended claims.

[0106] Similarly, the diagrams may illustrate exemplary architectures or other configurations of the disclosed methods and systems, which aid in understanding the features and functions that may be included in the disclosed methods and systems. The claims are not limited to the exemplary architectures or configurations shown, and the desired features may be implemented with various alternative architectures and configurations. Furthermore, the order of the blocks given herein with respect to flowcharts, functional descriptions, and method claims should not be limited to various embodiments implemented in the same order to perform the said functions, unless explicitly indicated in the context.

[0107] Unless otherwise expressly stated, the terms and phrases used herein, and their variations thereof, should be interpreted as open-ended rather than restrictive. In some instances, the appearance of extended words and phrases such as “one or more,” “at least,” “but not limited to,” or other similar expressions should not be construed as an intention or necessity to indicate a narrower scope in examples where such extended expressions might not exist.

Claims

1. A method for fusing computer-executed three-dimensional digital models of teeth, comprising: A first three-dimensional digital model representing the crown of the first tooth, a second three-dimensional digital model representing the entire first tooth, and a first segmentation scheme are obtained. The first segmentation scheme divides the second three-dimensional digital model into a first part and a second part, which correspond to the crown and the root of the tooth, respectively. Perform point cloud registration between the first three-dimensional digital model and the first part of the second three-dimensional digital model; Based on the point cloud registration results, the set of points on the edge of the second three-dimensional digital model that are closest to the points on the first three-dimensional digital model is calculated. The ring neighborhood on both sides of the set of the closest points of the second three-dimensional digital model and the part corresponding to the first three-dimensional digital model are deleted to obtain the third part of the second three-dimensional digital model. The first three-dimensional digital model and the third part of the second three-dimensional digital model are stitched together to obtain a fused three-dimensional digital model. Using the edge line of the third part of the second 3D digital model as a reference, a w-ring neighborhood is searched on the fused 3D digital model, wherein the ratio of the number of faces in the w-ring neighborhood to the total number of faces in the fused 3D digital model is greater than a predetermined value, and the w-ring neighborhood completely covers the stitched area; and Using the points on both sides of the w-ring neighborhood as control points, the surface patches of the w-ring neighborhood are deformed.

2. The method as described in claim 1, characterized in that, The point cloud registration is performed using the sparse iterative nearest point sampling method.

3. The method as described in claim 2, characterized in that, It also includes: aligning the centroids of the first three-dimensional digital model and the first part of the second three-dimensional digital model by centroid offset, wherein the point cloud registration is performed based on the centroid offset.

4. The method as described in claim 1, characterized in that, It also includes: calculating the set of nearest point pairs between the edges of the first three-dimensional digital model and the edges of the third part of the second three-dimensional digital model, and performing subsurface partitioning based on the set of nearest point pairs during surface stitching.

5. The method as described in claim 4, characterized in that, It also includes: performing triangular subdivision of the subsurface consisting of four vertices, wherein the subdivision scheme with the larger minimum interior angle is used.

6. The method as described in claim 5, characterized in that, It also includes: dividing a subsurface consisting of more than four vertices, first dividing a subsurface consisting of four vertices, and then triangulating it using a division scheme with a larger minimum interior angle. At this time, the remaining part of the subsurface has a first vertex on one edge and multiple vertices on the other edge. The remaining part is triangulated in such a way that every two adjacent vertices among the multiple vertices form a triangle with the first vertex.

7. The method as described in claim 1, characterized in that, The deformation was performed using the Laplace-Beltrami harmonic deformation algorithm.

8. The method as described in claim 1, characterized in that, It also includes: smoothing the second three-dimensional digital model before deleting the portion of the second three-dimensional digital model corresponding to the first three-dimensional digital model, the smoothing process including forward smoothing and reverse smoothing.

9. The method as described in claim 1, characterized in that, It also includes: simplifying the second three-dimensional digital model before deleting the portion of the second three-dimensional digital model that corresponds to the first three-dimensional digital model, the simplification being an adaptive simplification based on the number of faces in the first three-dimensional digital model.

10. The method as described in claim 1, characterized in that, The first three-dimensional digital model is obtained through one of the following methods: intraoral scanning, scanning dental impressions or solid models, and the second three-dimensional digital model is obtained through computed tomography (CT) technology.

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