Method for generating three-dimensional digital model of tooth

Abstract

Provided in one aspect of the present application is a computer-executed method for generating a three-dimensional digital model of a tooth, the method comprising: acquiring a three-dimensional digital model of a dental crown of a tooth of a patient; acquiring a three-dimensional digital model of the tooth of the patient; registering the three-dimensional digital model of the dental crown with the three-dimensional digital model of the tooth; after the registration, finding, on the three-dimensional digital model of the tooth, all vertices having distances from vertices on the boundary of the three-dimensional digital model of the dental crown that are less than a first predetermined distance, and segmenting, on the basis of these vertices, a three-dimensional digital model of a closed-loop band from the three-dimensional digital model of the tooth; by using a minimum-cut algorithm for a graph, performing calculation to obtain a sequence of edges for segmenting the three-dimensional digital model of the closed-loop band; segmenting a three-dimensional digital model of a tooth root from the three-dimensional digital model of the tooth by using the sequence of edges that is obtained by means of calculation; and fusing the three-dimensional digital model of the tooth crown and the three-dimensional digital model of the tooth root, so as to obtain a new three-dimensional digital model of the tooth.

Description

Method for generating a three-dimensional digital model of a tooth TECHNICAL FIELD

[0001] The present application relates generally to a method for generating a three-dimensional digital model of a tooth, and in particular to a method for fusing a three-dimensional digital model of a dental crown with a three-dimensional digital model of a dental root to obtain a three-dimensional digital model of a complete tooth. BACKGROUND

[0002] Nowadays, more and more dental field scenarios require a three-dimensional digital model of a complete tooth (including a dental crown and a dental root).

[0003] Although methods for fusing a three-dimensional digital model of a dental crown obtained by intraoral scanning and a three-dimensional digital model of a dental root obtained by Cone-Beam Computed Tomography (CBCT) to obtain a three-dimensional digital model of a complete tooth have appeared, the performance of these methods is not good enough in many aspects, which can adversely affect diagnosis and treatment based on the three-dimensional digital model of a tooth generated by using these methods.

[0004] Therefore, it is necessary to provide a new method for generating a three-dimensional digital model of a tooth. SUMMARY

[0005] One aspect of the present application provides a computer-implemented method for generating a three-dimensional digital model of a tooth, comprising: obtaining a three-dimensional digital model of a dental crown of a tooth of a patient, the three-dimensional digital model of the dental crown being obtained by scanning using a first means; obtaining a three-dimensional digital model of the tooth of the patient, the three-dimensional digital model of the tooth being obtained by scanning using a second means, the first means being different from the second means; registering the three-dimensional digital model of the dental crown and the three-dimensional digital model of the tooth; after the registration, finding all vertices on the three-dimensional digital model of the tooth that are less than a first predetermined distance from vertices on a boundary of the three-dimensional digital model of the dental crown, and based on these vertices, segmenting a three-dimensional digital model of a closed-loop band from the three-dimensional digital model of the tooth; calculating a sequence of edges of the three-dimensional digital model of the closed-loop band using a minimum cut algorithm of a graph; segmenting a three-dimensional digital model of a dental root from the three-dimensional digital model of the tooth using the calculated sequence of edges; and fusing the three-dimensional digital model of the dental crown and the three-dimensional digital model of the dental root to obtain a new three-dimensional digital model of the tooth.

[0006] In some embodiments, the fusion of the three-dimensional digital model of the dental crown and the three-dimensional digital model of the dental root is achieved by constructing new triangular facets between the boundaries of the two.

[0007] In some embodiments, the fusing of the crown 3D digital model and the root 3D digital model comprises: finding a vertex on a boundary of one of the crown 3D digital model and the root 3D digital model that is closest to a vertex on a boundary of the other, to obtain a plurality of vertex pairs; and constructing a triangular patch connecting the boundaries of the crown 3D digital model and the root 3D digital model based on each of the vertex pairs.

[0008] In some embodiments, the registering comprises: iteratively optimizing the relative positions between the crown 3D digital model and the tooth 3D digital model based on chamfer distance.

[0009] In some embodiments, the registering comprises: calculating chamfer distance of the crown 3D digital model and the tooth 3D digital model; calculating a direction based on the calculated chamfer distance; moving one of the crown 3D digital model and the tooth 3D digital model along the direction by a second predetermined distance; and repeating the above operations for a plurality of times to complete the registering.

[0010] In some embodiments, the second predetermined distance is calculated according to an average edge length of the crown 3D digital model and / or the tooth 3D digital model.

[0011] In some embodiments, the method of generating a tooth 3D digital model further comprises: obtaining a first 3D digital model representing crowns of a first dentition of a patient, the crown 3D digital model being segmented from the first 3D digital model; obtaining a second 3D digital model representing the first dentition of the patient, the tooth 3D digital model being segmented from the second 3D digital model; preliminarily registering the first and second 3D digital models using a RANSAC algorithm; and further registering the preliminarily registered first and second 3D digital models using an ICP algorithm, wherein the crown 3D digital model and the tooth 3D digital model are registered based on the further registering.

[0012] In some embodiments, the crown 3D digital model is obtained by scanning a surface of one of: a tooth of the patient, an impression of the tooth of the patient, and a physical model of the tooth of the patient, and the tooth 3D digital model is obtained by scanning the tooth of the patient using CBCT.

[0013] Yet another aspect of the present application provides a computer system for generating a tooth 3D digital model, comprising a storage device and a processor, the storage device storing a computer program which, when executed, causes the processor to perform the method of generating a tooth 3D digital model. BRIEF DESCRIPTION OF DRAWINGS

[0014] The above and other features of the present application will be further understood and appreciated, along with one or more other aspects thereof, from the following detailed description of certain exemplary embodiments, taken in conjunction with the accompanying drawings. It will be apparent, however, that the application can be practiced in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. In the drawings, like reference numerals indicate like components, and the various drawings are not necessarily drawn to scale.

[0015] FIG. 1 is a schematic flow chart of a method of generating a three-dimensional digital model of a tooth according to an embodiment of the present application;

[0016] FIG. 2 is a three-dimensional digital model of the crowns of a dentition according to an example of the present application;

[0017] FIG. 3 is a three-dimensional digital model of a dentition obtained by scanning the dentition shown in FIG. 2 using CBCT according to an example of the present application;

[0018] FIG. 4 illustrates a three-dimensional digital model of one of the crowns of the dentition shown in FIG. 2 according to an example of the present application;

[0019] FIG. 5 illustrates a three-dimensional digital model of a tooth corresponding to the crown shown in FIG. 4 in the three-dimensional digital model of the dentition shown in FIG. 3 according to an example of the present application;

[0020] FIG. 6 illustrates a three-dimensional digital model of a band of closed loops between the crown and the root of the tooth obtained by segmenting the three-dimensional digital model of the tooth shown in FIG. 5 according to an example of the present application;

[0021] FIG. 7 schematically illustrates two triangular facets constructed based on a pair of vertices according to an example of the present application; and

[0022] FIG. 8 illustrates a new three-dimensional digital model of a tooth obtained by fusing the three-dimensional digital model of the crown shown in FIG. 4 with the root of the tooth in the three-dimensional digital model of the tooth shown in FIG. 5 according to an example of the present application. DETAILED DESCRIPTION

[0023] The detailed description set forth below in connection with the appended drawings is intended as a description of certain exemplary embodiments of the application and is not intended to represent the only exemplary embodiments in which the application can be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments of the application. However, it will be apparent to those skilled in the art that the exemplary embodiments of the application can be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the exemplary embodiments of the application.

[0024] One aspect of the present application provides a method for generating a three-dimensional digital model of a tooth. First, the relative positions between a three-dimensional digital model of a crown and a three-dimensional digital model of a tooth are iteratively optimized based on chamfer distance to register the two. Then, based on the registration result and the boundary of the three-dimensional digital model of the crown, a closed band is found on the three-dimensional digital model of the tooth for segmenting the crown part and the root part of the three-dimensional digital model of the tooth. Finally, the three-dimensional digital model of the root obtained by segmenting the three-dimensional digital model of the tooth with the band is fused with the three-dimensional digital model of the crown to obtain a fused three-dimensional digital model of the tooth. The method for generating a three-dimensional digital model of a tooth in one embodiment of the present application is described in detail below with reference to the accompanying drawings.

[0025] Please refer to FIG. 1 for a schematic flowchart of the method 100 for generating a three-dimensional digital model of a tooth in one embodiment of the present application.

[0026] In 101, a first three-dimensional digital model representing the crowns of a first dentition of a patient is obtained.

[0027] In one embodiment, the first three-dimensional digital model can be obtained by intraoral scanning, or scanning a cast or a physical model of the first dentition, etc. The first dentition is the upper or lower dentition of the patient.

[0028] Generally, the scanning described above obtains a three-dimensional digital model of the first dentition and part of the gingiva. The gingiva part can be removed by segmentation, and the remaining crown part can be segmented to make each single crown independent.

[0029] Please refer to FIG. 2 for a three-dimensional digital model representing the crowns of a dentition in one example of the present application.

[0030] In 103, a second three-dimensional digital model representing the first dentition of the patient is obtained.

[0031] Each tooth in the second three-dimensional digital model is a complete tooth of the patient, i.e., including the crown and the root.

[0032] In one embodiment, the second three-dimensional digital model is obtained by CBCT scanning the first dentition of the patient. Similarly, the CBCT scanning obtains a three-dimensional digital model of the first dentition as a whole, which can be segmented to make each single tooth independent.

[0033] Please refer to FIG. 3 for a three-dimensional digital model representing the dentition shown in FIG. 2 obtained by CBCT scanning the dentition in one example of the present application.

[0034] In 105, the first and second three-dimensional digital models are registered as a whole.

[0035] By aligning the first and second three-dimensional digital models as a whole, the correspondence between each crown in the first three-dimensional digital model and the corresponding tooth in the second three-dimensional digital model can be obtained, and the crown in the first three-dimensional digital model can be substantially aligned with the corresponding tooth in the second three-dimensional digital model.

[0036] In one embodiment, the first and second three-dimensional digital models can be roughly aligned by using a Random Sample Consensus (RANSAC) algorithm, and then the roughly aligned first and second three-dimensional digital models can be registered with higher accuracy by using an Iterative Closest Point (ICP) algorithm.

[0037] In 107, after the overall registration, the relative positions of the three-dimensional digital model of one crown in the first three-dimensional digital model and the three-dimensional digital model of the corresponding tooth in the second three-dimensional digital model are iteratively optimized based on chamfer distance, so that the two are accurately registered.

[0038] Please refer to FIG. 4, which shows the three-dimensional digital model of one of the crowns in the three-dimensional digital model of the dentition shown in FIG. 2.

[0039] Please refer to FIG. 5, which shows the three-dimensional digital model of the tooth corresponding to the crown shown in FIG. 4 in the three-dimensional digital model of the dentition shown in FIG. 3.

[0040] Let the three-dimensional digital model of one crown in the first three-dimensional digital model be m c , and let the three-dimensional digital model of the tooth paired with the crown in the second three-dimensional digital model be m t . The chamfer distance between the vertices of the two can be calculated according to the following equation (1).

[0041] where D chamfer (m c ,m t ) represents the chamfer distance between m c and m t , c represents any vertex on m c , and t represents the vertex on m t closest to c.

[0042] In one embodiment, m c may be kept stationary, and m tin the direction. Then, m t is moved a predetermined distance along the direction, obtaining m c and m t a new relative position. Then, based on m c and m t at the new relative position, the above operation is repeated for several times to obtain precisely registered m c and m t .

[0043] In one embodiment, the predetermined distance can be set according to specific circumstances, for example, it can take the average side length of the crown three-dimensional digital model or the tooth three-dimensional digital model.

[0044] In one embodiment, a fixed number of iterations can be set, for example, 5 times, and after the iteration is completed, it is considered that m c and m t are precisely registered. In another embodiment, a chamfer distance threshold value can also be set, and when the iteration is calculated to be less than the threshold value, it is considered that m c and m t are precisely registered.

[0045] It can be understood that in the above precise registration, m t can also be kept stationary, and the relative position of the two is changed by moving m c .

[0046] In 109, a tooth root three-dimensional digital model is cut from the tooth three-dimensional digital model.

[0047] First, the vertices on the boundary of the crown three-dimensional digital model are identified, and an ordered vertex list is constructed, denoted as V list , wherein each pair of adjacent vertices is connected by an edge on the boundary.

[0048] In order to improve the calculation accuracy, the vertices in V list can be interpolated so that the distance between each pair of adjacent vertices is less than a predetermined distance threshold, obtaining a new vertex list V' list .

[0049] In one embodiment, the distance threshold can be set according to specific requirements, for example, 0.01mm.

[0050] Then, all vertices on the tooth three-dimensional digital model that are less than a predetermined distance threshold D filter from any point in V' list are found, obtaining a vertex set A part is segmented from the tooth 3D digital model, denoted as m The 3D digital model is required to be a closed loop with two open boundaries. If the segmented part does not meet the above requirement, the distance threshold D filter is adjusted and the above calculation is performed again until a 3D digital model of a closed loop strip with two open boundaries is segmented.

[0051] In an embodiment, the distance threshold D filter is set according to experience or experiment, for example, between 0.1 and 1 mm. The purpose is to find a narrowest closed loop strip connecting the crown and the root on the tooth 3D digital model.

[0052] Please refer to FIG. 6, which shows a 3D digital model of a closed loop strip between the crown and the root segmented from the tooth 3D digital model shown in FIG. 5 in an example.

[0053] Then, V is taken as a graph, and the sequence E cut of edges cutting the graph is calculated using the minimum cut algorithm of the graph. cut Finally, E t is mapped back to m list , which is segmented into two parts, and the root part is retained, denoted as m , i.e., the 3D digital model of the root.

[0054] In an embodiment, in the minimum cut algorithm of the graph, the weight of the edge of the graph can be set as the average of the distance between the two end vertices and the nearest point in V list . Then, two vertices, denoted as P and Q, are added to the graph, and edges are connected between P and Q and all other vertices in the graph, and the weight of these edges is set as a maximum value.

[0055] The distance between the boundary of the root 3D digital model segmented in this way and the boundary of the crown 3D digital model is minimal, which is beneficial for subsequent root-crown fusion.

[0056] In 111, the crown 3D digital model and the root 3D digital model are fused to obtain a new tooth 3D digital model.

[0057] m c and m are taken as a whole, denoted as m comb , which is a 3D digital model with two open boundaries and two separated parts.

[0058] In m comba vertex pair set is obtained, where each vertex pair has one vertex on the first boundary and one vertex on the second boundary. Then, two triangular patches are constructed based on each vertex pair, and the two boundaries are connected as a whole. c and connected as a whole.

[0059] Please refer to FIG. 7, which schematically shows two triangular patches 201 and 203 constructed based on a vertex pair A and B in an example, where vertex A is a vertex on the boundary of m c and vertex B is the closest vertex to A on the boundary of m .

[0060] Then, the boundary of m c and m may be equally divided into N parts, and the triangular patches are constructed based on the new vertex pairs obtained by the equal division in a similar way as described above.

[0061] It can be understood that the method of constructing triangular patches between the boundaries of m c and m is not limited to the above method, for example, M points can be equally sampled on the boundary of m c or m , and the closest points to the M points on the other boundary are found, and then the triangular patches are constructed based on the point pairs. Wherein, M is significantly smaller than the number of vertices on the boundary being sampled.

[0062] After the above operation of constructing triangular patches, there can be many small holes between m c and m . At this time, the small holes can be filled to obtain a new closed three-dimensional digital model of the tooth. The three-dimensional digital model constructed by connecting m c and m is denoted as m filled .

[0063] In an embodiment, the EarClip algorithm can be used to fill the small holes. It can be understood that in addition to the EarClip algorithm, any other applicable algorithm can also be used to fill the small holes.

[0064] Finally, the area of m filled and the adjacent area on the new three-dimensional digital model of the tooth can be smoothed according to requirements to obtain a three-dimensional digital model of the tooth with more natural geometric shape. In an embodiment, the Laplace smoothing method can be used for the smoothing. It can be understood that in addition to the Laplace smoothing method, any other applicable smoothing method can also be used for the smoothing.

[0065] Compared with the root crown fusion by morphing, the root crown fusion by constructing triangular facets between the boundaries of the crown three-dimensional digital model and the root three-dimensional digital model of the tooth preserves the original geometry of the crown three-dimensional digital model and the root three-dimensional digital model of the tooth to the greatest extent. c and Compared with the root crown fusion by morphing, the root crown fusion by constructing triangular facets between the boundaries of the crown three-dimensional digital model and the root three-dimensional digital model of the tooth preserves the original geometry of the crown three-dimensional digital model and the root three-dimensional digital model of the tooth to the greatest extent.

[0066] Please refer to FIG. 8, which shows the new tooth three-dimensional digital model obtained by fusing the crown three-dimensional digital model shown in FIG. 4 and the tooth root of the tooth three-dimensional digital model shown in FIG. 5.

[0067] In one embodiment, the above operation can be repeated until the three-dimensional digital model of all the crowns in the first three-dimensional digital model is fused with the three-dimensional digital model of the root of the corresponding tooth in the second three-dimensional digital model, obtaining a new three-dimensional digital model representing the first dentition.

[0068] In one embodiment, if a tooth in the second three-dimensional digital model has no corresponding crown in the first three-dimensional digital model, the three-dimensional digital model of the tooth can be directly placed in the new three-dimensional digital model representing the first dentition.

[0069] Another aspect of the present application provides a computer system for generating a tooth three-dimensional digital model, which comprises a storage device and a processor, the storage device storing a computer program which, when executed, will cause the processor to perform the method 100 for generating a tooth three-dimensional digital model.

[0070] Although various aspects and embodiments of the present application are disclosed herein, other aspects and embodiments of the present application will be apparent to those skilled in the art from the disclosure herein. The various aspects and embodiments disclosed herein are for purposes of illustration only and are not intended to limit the scope of the present application. The scope of the present application is solely determined by the claims that follow.

[0071] Similarly, the various diagrams can illustrate example architectures or other configurations for implementing the disclosed methods and systems, which are presented for the purpose of illustrating functional concepts related to the features and functions described herein. The claimed subject matter is not limited to the illustrated example architectures or configurations, but rather can employ unillustrated architectures and configurations. Additionally, the order in which steps are presented in the flowcharts, functional descriptions, and method claims does not inherently portray the order in which the steps must be performed, unless explicitly stated in the context.

[0072] Unless specifically stated otherwise, the terms and phrases used herein are to be construed as open-ended, rather than limiting. In some instances, the terms and phrases, such as "one or more" and "at least," "but not limited to," and other similar language, do not exclude the possibility that an additional item, optional or required, can be added to some examples.

Claims

1. A computer-implemented method of generating a three-dimensional digital model of a tooth, comprising: obtaining a three-dimensional digital model of a crown of a tooth of a patient, the three-dimensional digital model of the crown being obtained by scanning using a first modality; obtaining a three-dimensional digital model of the tooth of the patient, the three-dimensional digital model of the tooth being obtained by scanning using a second modality, the first modality being different from the second modality; registering the three-dimensional digital model of the crown and the three-dimensional digital model of the tooth; after the registering, finding all vertices on the three-dimensional digital model of the tooth that are within a first predetermined distance from vertices on a boundary of the three-dimensional digital model of the crown, and segmenting a three-dimensional digital model of a closed-loop band from the three-dimensional digital model of the tooth based on the vertices; computing a sequence of edges that cuts the three-dimensional digital model of the closed-loop band using a min-cut algorithm of a graph; segmenting a three-dimensional digital model of a root from the three-dimensional digital model of the tooth using the computed sequence of edges; and fusing the three-dimensional digital model of the crown and the three-dimensional digital model of the root to obtain a new three-dimensional digital model of the tooth.

2. The method of generating a three-dimensional digital model of teeth according to claim 1, wherein, The fusing of the three-dimensional digital model of the crown and the three-dimensional digital model of the root is achieved by constructing new triangular facets between boundaries of the two.

3. The method of generating a three-dimensional digital model of a tooth according to claim 2, wherein, The fusing of the three-dimensional digital model of the crown and the three-dimensional digital model of the root comprises: finding vertices on a boundary of one of the three-dimensional digital model of the crown and the three-dimensional digital model of the root that are closest to vertices on a boundary of the other to obtain a plurality of vertex pairs; and constructing two triangular facets that connect the boundaries of the three-dimensional digital model of the crown and the three-dimensional digital model of the root based on each of the vertex pairs.

4. The method of generating a three-dimensional digital model of teeth according to claim 1, wherein, The registering comprises iteratively optimizing a relative position between the three-dimensional digital model of the crown and the three-dimensional digital model of the tooth based on chamfer distance.

5. The method of generating a three-dimensional digital model of teeth according to claim 4, wherein, The registering comprises: computing chamfer distance between the three-dimensional digital model of the crown and the three-dimensional digital model of the tooth; computing a direction based on the computed chamfer distance; moving one of the three-dimensional digital model of the crown and the three-dimensional digital model of the tooth in the direction by a second predetermined distance; iterating the above operations a plurality of times to complete the registering.

6. The method of generating a three-dimensional digital model of teeth according to claim 5, wherein, The second predetermined distance is computed based on an average edge length of the three-dimensional digital model of the crown and / or the three-dimensional digital model of the tooth.

7. The method of generating a three-dimensional digital model of teeth according to claim 1, wherein, It further comprises: obtaining a first three-dimensional digital model representing crowns of a first dentition of a patient, the three-dimensional digital model of the crowns being segmented from the first three-dimensional digital model; obtaining a second three-dimensional digital model representing the first dentition of the patient, the three-dimensional digital model of the teeth being segmented from the second three-dimensional digital model; preliminarily registering the first and second three-dimensional digital models using a RANSAC algorithm; and further registering the preliminarily registered first and second three-dimensional digital models using an ICP algorithm, wherein the three-dimensional digital model of the crowns and the three-dimensional digital model of the teeth are registered based on the further registering.

8. The method of generating a three-dimensional digital model of teeth according to claim 1, wherein, The three-dimensional digital model of the crown is obtained by scanning the surface of one of: the patient's teeth, an impression of the patient's teeth, and a physical model of the patient's teeth, the three-dimensional digital model of the teeth being obtained using a CBCT scan of the patient's teeth.

9. A computer system for generating a three-dimensional digital model of teeth, comprising a storage device and a processor, the storage device storing a computer program which, when executed, causes the processor to perform the method of generating a three-dimensional digital model of teeth according to claim 1.

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