CN111027111B - Digital periodontal ligament model generation method and device - Google Patents
Digital periodontal ligament model generation method and device Download PDFInfo
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- CN111027111B CN111027111B CN201911245268.0A CN201911245268A CN111027111B CN 111027111 B CN111027111 B CN 111027111B CN 201911245268 A CN201911245268 A CN 201911245268A CN 111027111 B CN111027111 B CN 111027111B
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Abstract
The invention discloses a method and a device for generating a digital periodontal ligament model, wherein the method comprises the following steps: acquiring a plurality of first layer reference points of the digitized periodontal ligament model by using the digitized tooth model; respectively extending each first layer of datum points outwards to obtain a plurality of second layers of datum points; the method and the device can automatically generate the geometric model of the periodontal ligament, improve the efficiency of generating the periodontal ligament model, tightly connect the insides of the generated digital periodontal ligament models, have no gap and are closer to the actual intraoral condition of a patient, and the obtained three-dimensional model can also provide a basis for the follow-up simulation research by combining the digital tooth model and the digital alveolar bone model of the patient more accurately, such as the prediction of the stress trend of finite elements when the patient is simulated by combining the digital tooth model and the digital alveolar bone model of the patient to conduct tooth rearrangement.
Description
Technical Field
The invention relates to the technical field of medical appliances, in particular to a method and a device for generating a digital periodontal ligament model, electronic equipment, a computer storage medium and a method for designing a dental appliance.
Background
The invisible tooth appliance is more and more accepted by patients because of attractive appearance, comfort and convenience for the patients to pick up and wear by themselves, the invisible tooth appliance is designed according to the intraoral condition of the patients to carry out a virtual appliance scheme, then the invisible tooth appliance capable of repositioning the teeth from a first layout to a second layout is prepared according to the virtual appliance scheme, the prepared invisible tooth appliance is a series of polymer shell-shaped appliances capable of gradually adjusting the tooth layout, and when the patients wear the invisible tooth appliance, the teeth of the patients can be rearranged and gradually changed to the target appliance position. At present, when a virtual correction scheme is designed, teeth are rearranged according to intraoral data of a patient, but an alveolar bone and a periodontal ligament model are not used for arrangement analysis in the design process, as the periodontal ligament is connective tissue positioned between a tooth root and the alveolar bone, the periodontal ligament model is difficult to accurately obtain by the existing intraoral information acquisition means, orthodontic tooth movement is a very complex process, the orthotopic elastic deformation of periodontal tissues is generated, and the long-term displacement caused by reconstruction of the alveolar bone is also generated, so that the generation of osteoblasts and osteoclasts in the alveolar bone can be stimulated by stress/strain generated in the periodontal ligament under the action of orthodontic load. However, due to the structural characteristics of periodontal tissues of a human body and the specificity of biomechanical properties, the biomechanical influence condition of periodontal ligament under the action of orthodontic load cannot be directly measured by an experimental method. Therefore, in the current design of the virtual correction scheme, only the tooth model is considered for simulation arrangement, and the tooth model and the alveolar bone model are combined for simulation arrangement, but the simulation of the two methods has deviation from the actual intraoral structure of the patient. Therefore, it is important to introduce a digitized periodontal ligament model into the virtual appliance process, and to consider the stress condition of the periodontal ligament when performing stress analysis in the tooth rearrangement process.
Currently, it is difficult for a technician to accurately obtain a geometric model of periodontal ligament in a human body, and it is often necessary to estimate the shape of the periodontal ligament through teeth, alveolar bone, etc., and this process is usually performed by manual simulation operation on commercial software such as HyperMesh, but using this commercial software is not only costly, but also cumbersome and time-consuming to operate, and the commercial software can simulate a multi-domain model, and has poor accuracy of simulation effect on specialized dental fields.
The prior art discloses a tooth system modeling method, which comprises a model building step, a model correcting step, a grid dividing step and a physical attribute determining step, and can build a finite element model of a tooth system including a digital periodontal ligament model, wherein the method for generating the digital periodontal ligament model is to subtract the tooth model from an integral model of an alveolar bone to obtain an alveolar bone model containing periodontal ligament, and then subtract an alveolar bone body model to obtain the digital periodontal ligament model. The scheme has complicated steps and large operation amount.
Therefore, research on a method and a device capable of rapidly and accurately generating a digital periodontal ligament model has important significance.
Disclosure of Invention
The invention aims to provide a method and a device for generating a digital periodontal ligament model, electronic equipment, a computer storage medium and a design method of a dental appliance, which can automatically generate a geometrical model of a periodontal ligament, greatly improve the efficiency, have small calculation amount and have high generation speed of the digital periodontal ligament model.
The invention adopts the following technical scheme:
a method for generating a digitized periodontal ligament model, comprising: acquiring a plurality of first layer reference points of the digitized periodontal ligament model by using the digitized tooth model; wherein the digitized tooth model comprises a root portion wrapped by a digitized periodontal ligament model; respectively extending each first layer of datum points outwards to obtain a plurality of second layers of datum points; wherein the direction of the root portion pointing to the alveolar bone around the root portion is outward; a digitized periodontal ligament model outside the digitized tooth model is generated using the plurality of first layer reference points and the plurality of second layer reference points. Thus, the first layer datum point can be determined according to the digital geometric model of the teeth, the first layer datum point is extended to obtain the second layer datum point, and the two layers of datum points are utilized to generate the digital geometric model of the periodontal ligament.
Optionally, the extending each of the first layer datum points outward to obtain a plurality of second layer datum points includes: respectively acquiring an outward normal vector of each first layer datum point; and respectively extending each first layer datum point along the outward normal vector of each first layer datum point to obtain a plurality of second layer datum points. Therefore, the first layer of datum points extend outwards along the normal direction by taking the digital tooth model as a starting point, and the condition that extension routes of different datum points intersect can be avoided as much as possible relative to the condition that the first layer of datum points extend along any direction, so that subsequent calculation is facilitated.
Optionally, the separately obtaining the outward normal vector of each first layer datum point includes: taking a plurality of first layer datum points as vertexes of a digital triangular surface patch grid, and solving a normal vector v' of the vertexes outwards by utilizing normal vectors of a plurality of digital triangular surface patches formed by the adjacent points of the vertexes and the ring:
wherein n is the number of the grid vertexes of the digital triangular patch taking the first layer datum point as the vertex, and n is a positive integer greater than 1; i is a positive integer not greater than n; a is that i Is the area of the ith triangle taking the first layer datum point as the vertex; v i Is the normal vector of the ith triangle outwards taking the datum point of the first layer as the vertex. In this way, the normal vector of the first layer reference point as the vertex is calculated by using the normal vectors of a plurality of digitized triangular patches composed of a plurality of neighboring points in the digitized triangular patch grid.
Optionally, the extending each of the first layer datum points outward to obtain a plurality of second layer datum points includes: respectively extending each K-1 layer datum point outwards to obtain a plurality of K layer datum points, wherein K is any integer which is more than 1 and not more than K, K is the number of layers of the datum points, and K is an integer which is more than 1; the generating a digitized periodontal ligament model outside the digitized tooth model using the plurality of first layer reference points and the plurality of second layer reference points, comprising: generating a digitized periodontal ligament model outside the digitized tooth model by using the first layer datum points to the K layer datum points. Thus, a plurality of layers of datum points are obtained through multiple extensions, and the generated digital periodontal ligament model is more refined.
Optionally, the outward extending of each k-1 layer datum point is performed to obtain a plurality of k-layer datum points, wherein the movement distance of the m-1 layer datum points is D km M is any positive integer not greater than M, M is the number of the first layer datum points, M is an integer greater than 1, D km Is a positive number less than 1 mm. Thus, the outward extending distance of each datum point in each layer of datum points can be any value smaller than 1mm, and the proper extending distance can be conveniently selected according to the accuracy requirement in practical application, so that a digital periodontal ligament model with the preset thickness which is more similar to the intraoral condition of a patient can be generated. By the method of D km The thickness of periodontal ligament and the fineness of the model can be adjusted by specific setting, the personalized and customized requirements of patients are met, the use experience of the patients in the orthodontic process is improved, and the correction result is accurately predicted.
Alternatively, D km Is a constant that varies or is uniform with root depth. As the periodontal ligament thickness in the human body changes along with the depth of the tooth root, the generated digital periodontal ligament model is more in line with the actual situation of the human body.
Optionally, the generating a digitized periodontal ligament model outside the digitized tooth model using the plurality of the first layer reference points and the plurality of the second layer reference points includes: respectively taking the vertexes of the polygon surrounded by the plurality of the first layer datum points and the vertexes of the polygon surrounded by the plurality of the second layer datum points as vertexes for forming a polyhedron; respectively connecting the vertexes of the polygon surrounded by the plurality of first layer datum points with the vertexes of the polygon surrounded by the plurality of second layer datum points correspondingly along the extending direction of each first layer datum point to obtain a plurality of connecting lines; and forming a digital periodontal membrane model outside the digital tooth model by utilizing the vertexes of the polygon surrounded by the plurality of the first layer datum points, the vertexes of the polygon surrounded by the plurality of the second layer datum points and the plurality of connecting lines. In this way, the datum points of each layer are utilized to form a plurality of polygons, and the datum points of the two layers are correspondingly connected one by one to generate a digital periodontal ligament model.
Optionally, the forming the digitized periodontal ligament model outside the digitized tooth model by using the vertexes of the polygon surrounded by the plurality of the first layer datum points, the vertexes of the polygon surrounded by the plurality of the second layer datum points and the plurality of connecting lines includes: forming a three-dimensional model taking a polyhedron as a unit by utilizing vertexes of a polygon surrounded by the plurality of first-layer datum points, vertexes of a polygon surrounded by the plurality of second-layer datum points and the plurality of connecting lines; dividing each of the polyhedrons into a plurality of tetrahedrons; generating the digitized periodontal ligament model in units of the tetrahedrons. Thus, the inside of the digital periodontal ligament model is tightly connected, no gap exists, and the actual situation is met; the format of the generated digital periodontal ligament model is tetrahedron, and the digital periodontal ligament model can be directly used as a unit in finite element calculation, and the output result can be butted with commercial CAE (Computer Aided Engineering, computer aided engineering in engineering design) software such as Abaqus, and also can be butted with finite element analysis software which is developed independently.
Optionally, the polygon is a triangle, a quadrilateral or a pentagon. When the polygon is triangle, each layer of datum point respectively encloses into the digital triangular patch grid, in the process of generating the polyhedron, if the moving distance of the datum point of the same layer is the same, the polyhedron obtained after the corresponding connection of the two layers of datum points can be triangular prism, the triangular prism is the prism with the least side edges, and compared with the triangular prism with more side edges, the step of dividing the triangular prism into tetrahedrons is simplest, so that the efficiency of generating the digital periodontal film model can be improved. The quadrangle or pentagon is a preferable scheme next to the triangle, and the technical effect is similar to that of the triangle, and is not repeated here.
Optionally, the acquiring a plurality of first layer reference points of the digitized periodontal ligament model using the digitized tooth model includes: acquiring a boundary line of a tooth root part, and taking a part of the outer surface of the tooth root part extending from the boundary line to the tooth root part as a coverage area of the digital periodontal ligament model; a plurality of points on a coverage area of the digitized periodontal ligament model are acquired as a plurality of the first layer fiducial points. In this way, the root portion is determined from the digitized tooth model, and the starting surface from which the digitized periodontal ligament model is generated can be obtained using the boundary line of the root portion, and a plurality of points are obtained from the starting surface as the first layer reference points.
Optionally, the method for generating a digitized periodontal ligament model is used for generating a digitized periodontal ligament model outside at least one of the digitized tooth models. In the prior art, the models of each tooth are manually input respectively, each tooth is processed separately, and the result of each tooth is given.
Optionally, the thickness of the digitized periodontal film model is 0.2-0.38mm. Thus, the thickness of the generated digital periodontal ligament model is more in line with the actual condition of the human body.
A digitized periodontal ligament model generation device, comprising: an initial module for acquiring a plurality of first layer fiducial points of a digitized periodontal ligament model using the digitized tooth model, wherein the digitized tooth model includes a root portion wrapped by the digitized periodontal ligament model; the extension module is used for extending each first layer of datum points outwards to obtain a plurality of second layers of datum points; wherein the direction of the root portion pointing to the alveolar bone around the root portion is outward; a generation module for generating a digitized periodontal ligament model outside the digitized tooth model using a plurality of the first layer reference points and a plurality of the second layer reference points.
Optionally, the extension module includes: the normal unit is used for respectively acquiring the outward normal vector of each first layer datum point; and the extending unit is used for extending each first layer of datum point along the outward normal vector of each first layer of datum point to obtain a plurality of second layer of datum points.
Optionally, the normal unit is configured to: taking a plurality of first layer datum points as vertexes of a digital triangular surface patch grid, and solving a normal vector v' of the vertexes outwards by utilizing normal vectors of a plurality of digital triangular surface patches formed by the adjacent points of the vertexes and the ring:
wherein n is the number of the grid vertexes of the digital triangular patch taking the first layer datum point as the vertex, and n is a positive integer greater than 1The method comprises the steps of carrying out a first treatment on the surface of the i is a positive integer not greater than n; a is that i Is the area of the ith triangle taking the first layer datum point as the vertex; v i Is the normal vector of the ith triangle outwards taking the datum point of the first layer as the vertex.
Optionally, the extension module is configured to: respectively extending each K-1 layer datum point outwards to obtain a plurality of K layer datum points, wherein K is any integer which is more than 1 and not more than K, K is the number of layers of the datum points, and K is an integer which is more than 1; the generating module is used for: generating a digitized periodontal ligament model outside the digitized tooth model by using the first layer datum points to the K layer datum points.
Optionally, the m-th layer reference point has a moving distance D km M is any positive integer not greater than M, M is the number of the first layer datum points, M is an integer greater than 1, D km Is a positive number less than 1 mm.
Alternatively, D km Is a constant that varies or is uniform with root depth.
Optionally, the generating module includes: a vertex unit, configured to use vertices of a polygon enclosed by the plurality of first layer reference points and vertices of a polygon enclosed by the plurality of second layer reference points as vertices of a polygon; the connecting unit is used for correspondingly connecting the vertexes of the polygon surrounded by the plurality of first-layer datum points and the vertexes of the polygon surrounded by the plurality of second-layer datum points along the extending direction of each first-layer datum point to obtain a plurality of connecting lines; and the generating unit is used for forming a digital periodontal film model outside the digital tooth model by utilizing the vertexes of the polygon surrounded by the plurality of the first-layer datum points, the vertexes of the polygon surrounded by the plurality of the second-layer datum points and the plurality of connecting lines.
Optionally, the generating unit is configured to: forming a three-dimensional model taking a polyhedron as a unit by utilizing vertexes of a polygon surrounded by the plurality of first-layer datum points, vertexes of a polygon surrounded by the plurality of second-layer datum points and the plurality of connecting lines; dividing each of the polyhedrons into a plurality of tetrahedrons; generating the digitized periodontal ligament model in units of the tetrahedrons.
Optionally, the polygon is a triangle, a quadrilateral or a pentagon.
Optionally, the initial module is configured to: acquiring a boundary line of a tooth root part, and taking a part of the outer surface of the tooth root part extending from the boundary line to the tooth root part as a coverage area of the digital periodontal ligament model; a plurality of points on a coverage area of the digitized periodontal ligament model are acquired as a plurality of the first layer fiducial points.
Optionally, the digitized periodontal ligament model generating device is configured to generate a digitized periodontal ligament model outside at least one of the digitized tooth models.
Optionally, the thickness of the digitized periodontal film model is 0.2-0.38mm.
An electronic device comprising a processor and a memory, the processor executing computer instructions stored in the memory, causing the electronic device to perform any of the above-described digitized periodontal ligament model generation methods.
A computer storage medium comprising computer instructions which, when run on an electronic device, cause the electronic device to perform any of the above-described digitized periodontal ligament model generation methods.
The method for designing the dental appliance comprises the step of simulating and wearing a digital dental appliance model by utilizing the digital periodontal ligament model, the plurality of digital dental models and the digital alveolar bone model generated by any one of the digital periodontal ligament model generation methods, so that the digital periodontal ligament model, the plurality of digital dental models and the digital alveolar bone model are changed from a first layout to a second layout, wherein the first layout is changed to the second layout to be matched with a preset correction target displacement. In the simulation virtual correction process in the prior art, the influence of periodontal ligament is not considered, or the digital periodontal ligament model is obtained by means of the mode of subtracting the tooth model and the alveolar bone model through the integral model, so that the steps are complex, and the operation amount is large. The doctor can be better guided in the tooth alignment process after the periodontal ligament simulation is generated, and the stress trend in the tooth movement process can be accurately controlled when the virtual correction scheme is designed.
The invention discloses a method and a device for generating a digital periodontal ligament model, which can automatically generate a geometric model of a periodontal ligament, improve the efficiency of generating the periodontal ligament model, and the generated digital periodontal ligament model is a minimal tetrahedral three-dimensional model, the inside of the digital periodontal ligament model is tightly connected, and the digital periodontal ligament model is seamless and is more close to the actual intraoral condition of a patient, and the obtained three-dimensional model can also provide a basis for the follow-up simulation research by combining the digital tooth model and the digital alveolar bone model of the patient, such as the prediction of the stress trend of finite elements when the digital tooth model and the digital alveolar bone model of the patient simulate the patient to carry out tooth rearrangement. The invention discloses a design method of a dental appliance, which utilizes a digital periodontal ligament model, a plurality of digital tooth models and a digital alveolar bone model to simulate and wear the digital dental appliance model so as to change the digital periodontal ligament model, the plurality of digital tooth models and the digital alveolar bone model from a first layout to a second layout, wherein the first layout is changed to the second layout to be matched with a preset correction target displacement, and a foundation is provided for the design and manufacture of subsequent appliances or the prediction of stress trend of finite element simulation analysis.
Drawings
The invention will be further described with reference to the drawings and examples.
FIG. 1 is a schematic view of the overall structure of a dental model according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart of a method for generating a digitized periodontal ligament model according to an embodiment of the invention;
FIG. 3 is a schematic flow chart of step S1 in FIG. 2;
FIG. 4 is a schematic flow chart of step S2 in FIG. 2;
FIG. 5 is a schematic flow chart of step S3 in FIG. 2;
FIG. 6 is a schematic diagram of a specific flow chart of a method for generating a digitized periodontal ligament model according to an embodiment of the invention;
fig. 7 is a schematic structural diagram of a digitized periodontal ligament model generating device according to an embodiment of the present invention.
In the figure: 1. a dental crown; 2. periodontal ligament; 3. alveolar bone; 4. root of tooth; 10. an initial module; 20. an extension module; 21. a normal unit; 22. an extension unit; 30. a generating module; 31. a vertex unit; 32. a connection unit; 33. and a generating unit.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and detailed description, wherein it is to be understood that, on the premise of no conflict, the following embodiments or technical features may be arbitrarily combined to form new embodiments.
Referring to fig. 1, according to the structure of a human tooth, a dental model including a crown 1 and a root 4 is shown, a periodontal ligament 2 is wrapped around the root 4, and an alveolar bone 3 is wrapped around the periodontal ligament 2. In this embodiment, the direction of the crown 1 pointing to the root 4 is downward, and the direction of the root 4 pointing to the alveolar bone 3 around the root 4 is outward.
Referring to fig. 2, the invention provides a method for generating a digitized periodontal ligament model, which comprises steps S1 to S3.
The digitized periodontal ligament model in this embodiment refers to a virtual digitized periodontal ligament model generated by a processor or an electronic device.
The tooth stress analysis in orthodontic treatment often uses a finite element analysis method, and the focus is on the generation and combination of a geometric model and a constitutive model of periodontal ligament. In this embodiment, the generated digital periodontal ligament model can be used for tooth stress analysis in orthodontic treatment.
Step S1: a plurality of first layer fiducial points of a digitized periodontal ligament model are obtained using the digitized tooth model, wherein the digitized tooth model includes a root portion surrounded by the digitized periodontal ligament model, the first layer fiducial points being located on an outer surface of the root portion of the digitized tooth model. Alternatively, the digitized tooth model may include a root portion and a crown portion surrounded by the digitized periodontal film model. The root portion may be provided with a boundary line that demarcates the digitized crown portion. The first layer datum point may be located in a portion below the boundary line of the root portion.
Step S2: respectively extending each first layer of datum points outwards to obtain a plurality of second layers of datum points; wherein the direction of the root portion pointing towards the alveolar bone around the root portion is outwards. Based on the actual situation in the mouth of a human body, the tooth has a certain structure and shape, the periodontal ligament wraps the tooth root part of the tooth, and the alveolar bone wraps the periodontal ligament. In this embodiment, the second layer of reference points are obtained by extending the first layer of reference points one by one, so that the number of the second layer of reference points is the same as that of the first layer of reference points, and thus a limited operation amount can be maintained.
Step S3: a digitized periodontal ligament model outside the digitized tooth model is generated using the plurality of first layer reference points and the plurality of second layer reference points. The second layer of fiducial points may be located on an outer surface of the generated digitized periodontal ligament model.
The first layer datum point can be determined according to the first layer datum point by only the digital geometric model of the teeth, the second layer datum point is obtained by extending the first layer datum point, and the digital geometric model of the periodontal ligament is generated by utilizing the two layers of datum points.
Referring to fig. 3, in some embodiments, step S1 may include steps S11 to S12.
Step S11: the boundary line of the tooth root portion is obtained, and a portion of the outer surface of the tooth root portion extending from the boundary line toward the tooth root portion is used as a coverage area of the digital periodontal ligament model, which is also a starting surface for generating the digital periodontal ligament model.
Step S12: a plurality of points on a coverage area of the digitized periodontal ligament model is acquired as a plurality of first layer fiducial points. In this step, the manner of acquiring the plurality of points may be generated according to the position data of the registered reference points, or may be generated according to a predetermined selection rule, or may divide the coverage area into digitized triangular patch grids, and use the vertices of the digitized triangular patch grids as the plurality of first layer reference points.
In this way, the root portion is determined from the digitized tooth model, and the starting surface from which the digitized periodontal ligament model is generated can be obtained using the boundary line of the root portion, and a plurality of points are obtained from the starting surface as the first layer reference points.
In other embodiments, the step of obtaining the coverage area of the digitized periodontal ligament model can include: an intersection line of the digitized tooth model and the digitized alveolar bone model is obtained, with a portion of the exterior surface of the digitized tooth model extending from the intersection line toward the root portion as a coverage area of the digitized periodontal ligament model.
Referring to fig. 4, in some embodiments, step S2 may include steps S21 to S22.
Step S21: and respectively acquiring the outward normal vector of each first layer datum point.
Step S22: and respectively extending each first layer datum point along the outward normal vector of each first layer datum point to obtain a plurality of second layer datum points.
Therefore, the first layer of datum points extend outwards along the normal direction by taking the digital tooth model as a starting point, and the condition that extension routes of different datum points intersect can be avoided as much as possible relative to the condition that the first layer of datum points extend along any direction, so that subsequent calculation is facilitated.
In this embodiment, the process of determining the normal vector in step S21 may include: taking a plurality of first layer datum points as vertexes of the digital triangular patch grid, and solving a normal vector v' of the vertexes outwards by utilizing normal vectors of a plurality of digital triangular patches formed by vertex-ring neighborhood points:
wherein n is the number of the grid vertexes of the digital triangular patch taking the first layer datum point as the vertex, and n is a positive integer greater than 1; i is a positive integer not greater than n; a is that i Is the area of the ith triangle with the first layer datum point as the vertex; v i Is the normal vector of the ith triangle outward with the first layer datum point as the vertex.
In the present embodiment, when the following is obtainedAfter the normal vector v ', the normal vector v' can be normalized, so that subsequent calculation is convenient. The normalized normal vector v is calculated as:
in this way, the normal vector of the first layer reference point as the vertex is calculated by using the normal vectors of a plurality of digitized triangular patches composed of a plurality of neighboring points in the digitized triangular patch grid. The obtained normal vector is more accurate and reasonable than the case of taking the normal vector at a point nearby as the normal vector of the reference point of the first layer.
In some embodiments, step S2 may include: respectively extending each K-1 layer datum point outwards to obtain a plurality of K layer datum points, wherein K is any integer which is more than 1 and not more than K, K is the number of layers of the datum points, and K is an integer which is more than 1; step S3 may include: a digitized periodontal ligament model outside the digitized tooth model is generated using the plurality of first layer reference points to the plurality of K-th layer reference points. Thus, a plurality of layers of datum points are obtained through multiple extensions, and the generated digital periodontal ligament model is more refined. The fineness degree of the digitalized periodontal ligament model is determined by K, and the larger the K is, the finer the model is, and the value of the model can be adjusted according to the needs in practical application.
In this embodiment, the movement distance of the mth k-1 layer datum point can be D km M is any positive integer not greater than M, M is the number of reference points of the first layer, M is an integer greater than 1, D km Is a positive number less than 1 mm. In this way, the outward extending distance of each datum point in each layer of datum points can be any value smaller than 1mm, so that a patient can conveniently select a proper extending distance according to the precision requirement in practical application, and a digital periodontal ligament model with a preset thickness which is more similar to the intraoral condition of the patient is generated. By the method of D km The thickness of periodontal ligament and the fineness of the model can be adjusted by specific setting, the personalized and customized requirements of patients are met, the use experience of the patients in the orthodontic process is improved, and the correction result is accurately predicted.
For example, when m=1000, k=5, the value of M is an integer between 1 and 1000, and the value of k is 23, 4, 5, wherein the movement distance of the 3 rd layer 1 datum point is denoted as D 23 The distance of movement of the 5 th layer 2 datum point is denoted as D 35 And correspondingly marking the moving distances of the datum points on the k-1 layer to the datum points of the k layer according to the marking rule.
In the present embodiment, D km May be a constant that varies or is uniform with root depth. As the periodontal ligament thickness in the human body changes along with the change of the tooth root depth, the generated digital periodontal ligament model is more in line with the actual situation of the human body. When D is km The distance of movement of each reference point in the same layer is related to the change of the tooth root depth when the constant is changed along with the change of the tooth root depth. When D is km When the depth of the tooth root is uniform and constant, the moving distance of each datum point in the datum point of the same layer is the same.
In the present embodiment, D km Or may be a constant that varies or is uniform with the number of extended layers k. For example, D km The movement distance of the mth datum point can be a constant which changes along with the number k of the extended layers; d (D) km Or a constant which is uniform along with the number k of the extended layers, and the moving distance of the mth datum point between any two adjacent layers is kept unchanged.
When D is km When the constant d is uniform, the calculation formula of the periodontal film thickness at the reference point of the mth layer can be: u (u) k，m ＝u k-1，m +dv m . Wherein u is k，m As the mth and kth layer datum point, u k-1，m Is the m-th layer reference point, v m Is the normal vector of the m-th layer reference point outwards.
Referring to fig. 5, in some embodiments, step S3 may include steps S31-S33.
Step S31: and respectively taking the vertexes of the polygon surrounded by the plurality of first-layer datum points and the vertexes of the polygon surrounded by the plurality of second-layer datum points as vertexes for forming a polyhedron.
In this embodiment, the polygon may be a triangle, a quadrangle, or a pentagon. When the polygon is triangle, each layer of datum point respectively encloses into the digital triangular patch grid, in the process of generating the polyhedron, if the moving distance of the datum point of the same layer is the same, the polyhedron obtained after the corresponding connection of the two layers of datum points can be triangular prism, the triangular prism is the prism with the least side edges, and compared with the triangular prism with more side edges, the step of dividing the triangular prism into tetrahedrons is simplest, so that the efficiency of generating the digital periodontal film model can be improved. The quadrangle or pentagon is a preferable scheme next to the triangle, and the technical effect is similar to that of the triangle, and is not repeated here.
Step S32: and respectively connecting the vertexes of the polygon surrounded by the plurality of first layer datum points with the vertexes of the polygon surrounded by the plurality of second layer datum points along the extending direction of each first layer datum point to obtain a plurality of connecting lines.
In this embodiment, the connecting line may be a straight line, a broken line or a curved line.
Step S33: and forming a digital periodontal membrane model outside the digital tooth model by utilizing the vertexes of the polygon surrounded by the plurality of first-layer datum points, the vertexes of the polygon surrounded by the plurality of second-layer datum points and the plurality of connecting lines.
In this way, the datum points of each layer are utilized to form a plurality of polygons, and the datum points of the two layers are correspondingly connected one by one to generate a digital periodontal ligament model.
In this embodiment, step S33 may include the following steps:
forming a three-dimensional model taking a polyhedron as a unit by utilizing vertexes of a polygon surrounded by a plurality of first-layer datum points, vertexes of a polygon surrounded by a plurality of second-layer datum points and a plurality of connecting lines;
dividing each polyhedron into a plurality of tetrahedrons; wherein tetrahedra are the smallest polyhedral units;
a digitized periodontal ligament model is generated in tetrahedral units.
Thus, the inside of the digital periodontal ligament model is tightly connected, no gap exists, and the actual situation is met; the format of the generated digital periodontal ligament model is tetrahedron, and the digital periodontal ligament model can be directly used as a unit in finite element calculation, and the output result can be butted with commercial CAE software such as Abaqus or autonomously developed finite element analysis software.
In some embodiments, the digitized periodontal ligament model generation method may be used to generate a digitized periodontal ligament model outside of the at least one digitized tooth model. In the prior art, the models of each tooth are manually input respectively, each tooth is processed independently, and the result of each tooth is given, and the embodiment can input the digitized tooth models of a plurality of teeth of a patient at one time and process the digitized tooth models in batches to generate the periodontal ligament geometric model of the whole jaw teeth of the patient, so that the efficiency of generating the digitized periodontal ligament model is greatly improved, and the operation process is simplified.
In some embodiments, the resulting thickness of the digitized periodontal ligament model can be 0.2-0.38mm. Thus, the thickness of the generated digital periodontal ligament model is more in line with the actual condition of the human body.
Referring to fig. 6, a specific application scenario of the embodiment of the present invention may include steps R1 to R8.
Step R1: a geometric model of the left incisors of the digitized mandible containing the root portion is input in the format of a digitized triangular patch grid.
Step R2: the portion below the boundary line of the root portion in the digitized triangular patch grid is set as a first layer reference point.
Step R3: and calculating an outward normal vector of each first layer of datum points, carrying out weighted average according to the area of a triangle formed by the vertex-ring neighborhood points, and normalizing to obtain a unit normal vector.
Step R4: each starting point moves outwards by 0.1mm along the normal vector to obtain a second layer of datum points, and the second layer of datum points are connected according to the connection relation between the first layer of datum points, so that the second layer of datum points also form a digital triangular patch grid.
Step R5: repeating the step R4 for 3 times to obtain a first layer of datum points to a fourth layer of datum points, wherein the total thickness of the periodontal ligament is 0.3mm.
Step R6: for two adjacent layers of datum points, corresponding vertexes are connected to form a three-dimensional model taking a triangular prism as a unit, and 3 layers are formed.
Step R7: each triangular prism was divided into 3 tetrahedrons, wherein the diagonals of the 3 sides of the triangular prism were connected, and each side was divided into 2 triangles.
Step R8: the output format is a digitized periodontal ligament model of tetrahedral unit.
Referring to fig. 7, the embodiment of the invention further provides a digitized periodontal ligament model generating device, which comprises an initial module 10, an extension module 20 and a generating module 30, wherein the initial module 10 and the generating module 30 are respectively connected with the extension module 20.
The initial module 10 is for obtaining a plurality of first layer fiducial points of a digitized periodontal ligament model using the digitized tooth model, wherein the digitized tooth model includes a root portion wrapped by the digitized periodontal ligament model.
The extending module 20 is configured to extend each of the first layer reference points outwards to obtain a plurality of second layer reference points; wherein the direction of the root portion pointing towards the alveolar bone around the root portion is outwards.
The generating module 30 is configured to generate a digitized periodontal ligament model outside the digitized tooth model using the plurality of first layer reference points and the plurality of second layer reference points.
The present embodiment is an embodiment of a device corresponding to the method for generating a digitized periodontal ligament model, and the working principle, technical effects and method of the embodiment of the device are similar to those of the embodiment of the method, and are not repeated here.
In some embodiments, the extension module 20 includes a normal unit 21 and an extension unit 22 connected to each other.
The normal unit 21 is used for respectively acquiring an outward normal vector of each first layer reference point.
The extending unit 22 is configured to extend each first layer datum along an outward normal vector of each first layer datum to obtain a plurality of second layer datum.
In this embodiment, the normal unit 21 may be used to: taking a plurality of first layer datum points as vertexes of the digital triangular patch grid, and solving a normal vector v' of the vertexes outwards by utilizing normal vectors of a plurality of digital triangular patches formed by vertex-ring neighborhood points: 
Wherein n is the number of the grid vertexes of the digital triangular patch taking the first layer datum point as the vertex, and n is a positive integer greater than 1; i is a positive integer not greater than n; a is that i Is the area of the ith triangle with the first layer datum point as the vertex; v i Is the normal vector of the ith triangle outward with the first layer datum point as the vertex.
In some embodiments, the expansion module 20 may be configured to: respectively extending each K-1 layer datum point outwards to obtain a plurality of K layer datum points, wherein K is any integer which is more than 1 and not more than K, K is the number of layers of the datum points, and K is an integer which is more than 1; the generation module 30 may be configured to: a digitized periodontal ligament model outside the digitized tooth model is generated using the plurality of first layer reference points to the plurality of K-th layer reference points.
In this embodiment, the movement distance of the mth k-1 layer datum point can be D km M is any positive integer not greater than M, M is the number of reference points of the first layer, M is an integer greater than 1, D km Is a positive number less than 1 mm.
Wherein D is km May be a constant that varies or is uniform with root depth.
In some embodiments, the generating module 30 may include a vertex unit 31, a connection unit 32, and a generating unit 33, where the vertex unit 31 and the generating unit 33 are connected to the connection unit 32, respectively.
The vertex unit 31 is configured to use vertices of a polygon surrounded by a plurality of first-layer reference points and vertices of a polygon surrounded by a plurality of second-layer reference points as vertices forming a polyhedron, respectively.
The connection unit 32 is configured to respectively connect vertices of a polygon defined by the plurality of first-layer reference points with vertices of a polygon defined by the plurality of second-layer reference points along an extending direction of each first-layer reference point, so as to obtain a plurality of connecting lines.
The generating unit 33 is configured to form a digitized periodontal ligament model outside the digitized tooth model by using vertices of a polygon surrounded by the plurality of first-layer reference points, vertices of a polygon surrounded by the plurality of second-layer reference points, and a plurality of connecting lines.
In this embodiment, the generating unit 33 may be configured to: forming a three-dimensional model taking a polyhedron as a unit by utilizing vertexes of a polygon surrounded by a plurality of first-layer datum points, vertexes of a polygon surrounded by a plurality of second-layer datum points and a plurality of connecting lines; dividing each polyhedron into a plurality of tetrahedrons; a digitized periodontal ligament model is generated in tetrahedral units.
In this embodiment, the polygon may be a triangle, a quadrangle, or a pentagon.
In some embodiments, the initialization module 10 may be used to: acquiring a boundary line of the tooth root part, and taking a part of the outer surface of the tooth root part extending from the boundary line to the tooth root part as a coverage area of the digital periodontal ligament model; a plurality of points on a coverage area of the digitized periodontal ligament model is acquired as a plurality of first layer fiducial points.
In some embodiments, the digitized periodontal ligament model generation means is for generating a digitized periodontal ligament model outside the at least one digitized tooth model.
In some embodiments, the resulting thickness of the digitized periodontal ligament model is 0.2-0.38mm, approaching the actual thickness of the periodontal ligament, more closely fitting the simulation of the oral environment.
The embodiment of the invention also provides electronic equipment, which comprises a processor and a memory, wherein the processor executes computer instructions stored in the memory, so that the electronic equipment executes any one of the digital periodontal ligament model generation methods.
The embodiment of the invention also provides a computer storage medium, which comprises computer instructions, wherein the computer instructions, when running on the electronic equipment, cause the electronic equipment to execute any one of the digital periodontal ligament model generation methods.
The embodiment of the invention also provides a design method of the dental appliance, which utilizes the digital periodontal ligament model, the plurality of digital dental models and the digital alveolar bone model generated by any one of the digital periodontal ligament model generation methods to simulate wearing the digital dental appliance model so as to change the digital periodontal ligament model, the plurality of digital dental models and the digital alveolar bone model from a first layout to a second layout, wherein the first layout is changed to the second layout to be matched with the preset correction target displacement, and provides a basis for designing and manufacturing the subsequent appliance or carrying out finite element simulation analysis stress trend prediction and the like.
For example, the first layout is the initial layout of the entire dental model or of several of the teeth, where the position of a certain tooth is A 1 The second layout is the whole dental model or the layout after a plurality of teeth are moved, and the positions corresponding to the teeth are A 2 The predetermined orthodontic target displacement of the tooth is A 2 -A 1 。
The present invention has been described in terms of its practical and advantageous aspects, such as objectives, performance, improvements and novelty, which are all the functional improvements and advantages that will be emphasized by the patent laws, the above-described and accompanying drawings are merely preferred embodiments of the present invention and not intended to limit the invention thereto, and therefore all similar or identical structures, devices, features, etc. that are used in accordance with the invention are included in the scope of the invention.
Claims (17)
1. A method for generating a digitized periodontal ligament model, comprising:
acquiring a plurality of first layer reference points of the digitized periodontal ligament model by using the digitized tooth model; wherein the digitized tooth model comprises a root portion wrapped by a digitized periodontal ligament model;
respectively extending each first layer of datum points outwards to obtain a plurality of second layers of datum points; wherein the direction of the root portion pointing to the alveolar bone around the root portion is outward;
Generating a digitized periodontal ligament model outside the digitized tooth model using a plurality of the first layer reference points and a plurality of the second layer reference points;
wherein the extending each first layer datum point outward to obtain a plurality of second layer datum points includes: respectively acquiring an outward normal vector of each first layer datum point; respectively extending each first layer datum point along the outward normal vector of each first layer datum point to obtain a plurality of second layer datum points; the generating a digitized periodontal ligament model outside the digitized tooth model using the plurality of first layer reference points and the plurality of second layer reference points, comprising: respectively taking the vertexes of the polygon surrounded by the plurality of the first layer datum points and the vertexes of the polygon surrounded by the plurality of the second layer datum points as vertexes for forming a polyhedron; respectively connecting the vertexes of the polygon surrounded by the plurality of first layer datum points with the vertexes of the polygon surrounded by the plurality of second layer datum points correspondingly along the extending direction of each first layer datum point to obtain a plurality of connecting lines; forming a digital periodontal ligament model outside the digital tooth model by utilizing vertexes of a polygon surrounded by the plurality of first-layer datum points, vertexes of a polygon surrounded by the plurality of second-layer datum points and the plurality of connecting lines; or alternatively, the process may be performed,
Said extending each of said first layer datum outwardly to obtain a plurality of second layer datum comprises: respectively extending each K-1 layer datum point outwards to obtain a plurality of K layer datum points, wherein K is any integer which is more than 1 and not more than K, K is the number of layers of the datum points, and K is an integer which is more than 1; the generating a digitized periodontal ligament model outside the digitized tooth model using the plurality of first layer reference points and the plurality of second layer reference points, comprising: generating a digitized periodontal ligament model outside the digitized tooth model by utilizing a plurality of the first layer datum points to a plurality of the K-th layer datum points; the movement distance of the kth-1 layer datum point of the plurality of kth layer datum points obtained by outwards extending each kth-1 layer datum point is D km M is any positive integer not greater than M, M is the number of the first layer datum points, M is an integer greater than 1, D km Is a positive number less than 1 mm; d (D) km Is a constant that varies or is uniform with root depth.
2. The method of generating a digitized periodontal model of claim 1, wherein the separately obtaining the outward normal vector for each of the first layer fiducial points comprises:
taking a plurality of first layer datum points as vertexes of a digital triangular surface patch grid, and solving a normal vector v' of the vertexes outwards by utilizing normal vectors of a plurality of digital triangular surface patches formed by the adjacent points of the vertexes and the ring:
Wherein n is the number of the grid vertexes of the digital triangular patch taking the first layer datum point as the vertex, and n is a positive integer greater than 1; i is a positive integer not greater than n; a is that i Is the area of the ith triangle taking the first layer datum point as the vertex; v i Is the normal vector of the ith triangle outwards taking the datum point of the first layer as the vertex.
3. The method according to claim 1, wherein the forming the digitized periodontal ligament model outside the digitized tooth model using vertices of a polygon surrounded by the plurality of the first layer reference points, vertices of a polygon surrounded by the plurality of the second layer reference points, and the plurality of connecting lines, comprises:
forming a three-dimensional model taking a polyhedron as a unit by utilizing vertexes of a polygon surrounded by the plurality of first-layer datum points, vertexes of a polygon surrounded by the plurality of second-layer datum points and the plurality of connecting lines;
dividing each of the polyhedrons into a plurality of tetrahedrons;
generating the digitized periodontal ligament model in units of the tetrahedrons.
4. The method for generating a digitized periodontal ligament model according to claim 3, wherein the polygon is a triangle, a quadrangle or a pentagon.
5. The method of generating a digitized periodontal ligament model of claim 1, wherein the acquiring a plurality of first layer reference points of the digitized periodontal ligament model using the digitized tooth model comprises:
acquiring a boundary line of a tooth root part, and taking a part of the outer surface of the tooth root part extending from the boundary line to the tooth root part as a coverage area of the digital periodontal ligament model;
a plurality of points on a coverage area of the digitized periodontal ligament model are acquired as a plurality of the first layer fiducial points.
6. The digitized periodontal ligament model generation method of claim 1, wherein the digitized periodontal ligament model generation method is used to generate a digitized periodontal ligament model external to at least one of the digitized tooth models.
7. The method for generating a digitized periodontal ligament model according to claim 1, wherein the generated thickness of the digitized periodontal ligament model is 0.2 to 0.38mm.
8. A digitized periodontal ligament model generation device, comprising:
an initial module for acquiring a plurality of first layer reference points of the digitized periodontal ligament model using the digitized tooth model; wherein the digitized tooth model comprises a root portion wrapped by a digitized periodontal ligament model;
The extension module is used for extending each first layer of datum points outwards to obtain a plurality of second layers of datum points; wherein the direction of the root portion pointing to the alveolar bone around the root portion is outward;
a generation module for generating a digitized periodontal ligament model outside the digitized tooth model using a plurality of the first layer reference points and a plurality of the second layer reference points;
wherein, the extension module includes: the normal unit is used for respectively acquiring the outward normal vector of each first layer datum point; the extending unit is used for extending each first layer of datum point along the outward normal vector of each first layer of datum point to obtain a plurality of second layers of datum points; the generating module comprises: a vertex unit, configured to use vertices of a polygon enclosed by the plurality of first layer reference points and vertices of a polygon enclosed by the plurality of second layer reference points as vertices of a polygon; the connecting unit is used for correspondingly connecting the vertexes of the polygon surrounded by the plurality of first-layer datum points and the vertexes of the polygon surrounded by the plurality of second-layer datum points along the extending direction of each first-layer datum point to obtain a plurality of connecting lines; a generating unit, configured to form a digitized periodontal ligament model outside the digitized tooth model by using vertices of a polygon surrounded by the plurality of first layer reference points, vertices of a polygon surrounded by the plurality of second layer reference points, and the plurality of connecting lines; or alternatively, the process may be performed,
The extension module is used for: respectively extending each K-1 layer datum point outwards to obtain a plurality of K layer datum points, wherein K is any integer which is more than 1 and not more than K, K is the number of layers of the datum points, and K is an integer which is more than 1; the generating module is used for: generating a digitized periodontal ligament model outside the digitized tooth model by utilizing a plurality of the first layer datum points to a plurality of the K-th layer datum points; the m-th k-1 layer datum point has a moving distance D km M is any positive integer not greater than M, M is the number of the first layer datum points, M is an integer greater than 1, D km Is a positive number less than 1 mm; d (D) km Is a constant that varies or is uniform with root depth.
9. The digitized periodontal ligament model generation device of claim 8, wherein the normal unit is configured to:
taking a plurality of first layer datum points as vertexes of a digital triangular surface patch grid, and solving a normal vector v' of the vertexes outwards by utilizing normal vectors of a plurality of digital triangular surface patches formed by the adjacent points of the vertexes and the ring:
wherein n is a digitized triangular surface taking the first layer datum point as a vertexThe number of the vertexes of the piece grid, n is a positive integer greater than 1; i is a positive integer not greater than n; a is that i Is the area of the ith triangle taking the first layer datum point as the vertex; v i Is the normal vector of the ith triangle outwards taking the datum point of the first layer as the vertex.
10. The digitized periodontal ligament model generation device of claim 8, wherein the generation unit is configured to:
forming a three-dimensional model taking a polyhedron as a unit by utilizing vertexes of a polygon surrounded by the plurality of first-layer datum points, vertexes of a polygon surrounded by the plurality of second-layer datum points and the plurality of connecting lines;
dividing each of the polyhedrons into a plurality of tetrahedrons;
generating the digitized periodontal ligament model in units of the tetrahedrons.
11. The digitized periodontal ligament model generation device of claim 10, wherein the polygon is a triangle, a quadrangle, or a pentagon.
12. The digitized periodontal ligament model generation device of claim 8, wherein the initialization module is configured to:
acquiring a boundary line of a tooth root part, and taking a part of the outer surface of the tooth root part extending from the boundary line to the tooth root part as a coverage area of the digital periodontal ligament model;
a plurality of points on a coverage area of the digitized periodontal ligament model are acquired as a plurality of the first layer fiducial points.
13. The digitized periodontal ligament model generation device of claim 8, wherein the digitized periodontal ligament model generation device is configured to generate a digitized periodontal ligament model external to at least one of the digitized tooth models.
14. The digitized periodontal ligament model generation device of claim 8, wherein the generation thickness of the digitized periodontal ligament model is 0.2-0.38mm.
15. An electronic device comprising a processor and a memory, the processor executing computer instructions stored in the memory, causing the electronic device to perform the digitized periodontal ligament model generation method of any of claims 1 to 7.
16. A computer storage medium comprising computer instructions which, when run on an electronic device, cause the electronic device to perform the digitized periodontal ligament model generation method of any of claims 1 to 7.
17. A method of designing a dental appliance, characterized in that the digital dental appliance model is simulated to be worn using the digital periodontal ligament model, the plurality of digital dental models, and the digital alveolar bone model generated by the digital periodontal ligament model generation method according to claims 1 to 7, such that the digital periodontal ligament model, the plurality of digital dental models, and the digital alveolar bone model are changed from a first layout to a second layout, wherein the first layout is changed to the second layout to be matched with a predetermined correction target displacement.
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