Method and device for optimizing undercut shape of digital tooth model

Abstract

The present invention provides a method and device for optimizing the undercut morphology of a digital tooth model. The method comprises the following steps: obtaining a digital tooth model according to a correction plan; forming a pair of digital tooth models with two adjacent teeth in the digital tooth model, obtaining an initial undercut area in the middle of each pair of digital tooth models and forming an initial undercut model; obtaining a target undercut area in the digital tooth model pair; obtaining a group of first sampling points according to a first tooth model and a second tooth model; obtaining a second sampling point and a second corresponding point according to the first sampling point, and iteratively updating the second corresponding point to obtain a target corresponding point; adding interpolation circles between the two groups of target corresponding points, and connecting the interpolation points in the interpolation circles and the two groups of target corresponding points through a triangular mesh to form a closed mesh of tooth undercuts. By optimizing the undercuts of the digital tooth model, the present invention can avoid forming new undercuts and effectively reduce the undercut area.

Description

Technical Field

[0001] The present invention relates to the technical field of tooth correction, and in particular to a method and device for optimizing the undercut shape of a digital tooth model. Background Art

[0002] A brace is a device for treating malocclusion, also known as an orthodontic appliance. It can generate force, or the functional force of the masticatory muscles and perioral muscles can cause the deformed frontal bone and misplaced teeth to change through the periodontal supporting tissues through the appliance, so as to facilitate the normal growth and development of the maxillofacial region. It is generally divided into fixed appliances and invisible appliances. The use of invisible appliances to correct teeth is increasingly accepted by patients because they are beautiful, comfortable, and convenient for patients to wear and take off by themselves. Invisible dental appliances are designed based on the patient's oral conditions. A shell-shaped dental appliance is prepared based on the virtual treatment plan to reposition the teeth from a first layout to a second layout. The prepared shell-shaped dental appliance is a series of polymer shell-shaped devices that gradually adjust the tooth layout. When the patient wears the shell-shaped dental appliance, the patient's teeth can be rearranged and gradually changed to the target correction position.

[0003] When making a shell-shaped dental appliance model, it is necessary to fill the undercuts of adjacent teeth. When the crowns of canines and incisors are too long due to gum recession, new undercuts will still be formed after the existing undercut filling method is used to complete the undercut treatment between the canines and incisors with too long crowns. The undercut filling grid formed by the existing undercut filling method cannot be adjusted according to the changes in tooth morphology to eliminate the new undercuts.

[0004] Therefore, it is necessary to provide a new method and device for optimizing the undercut shape of a digital tooth model to solve the above-mentioned problems in the prior art. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and device for optimizing the filling of undercuts in a digital tooth model. By optimizing the method for filling undercuts in a digital tooth model, new undercuts can be avoided and the undercut area can be effectively reduced.

[0006] To achieve the above-mentioned purpose, the method for optimizing the undercut shape of a digital tooth model of the present invention comprises:

[0007] Obtain digital models of teeth according to the treatment plan;

[0008] Two adjacent teeth in the tooth digital model are combined into a pair of tooth digital model pairs, and an initial undercut area is obtained in the middle of each pair of the tooth digital model pairs;

[0009] forming an initial undercut model according to the initial undercut area of the tooth digital model pair;

[0010] Acquire a target undercut area in the center of the digital tooth model according to the digital tooth model;

[0011] The pair of digital tooth models includes a first adjacent tooth model and a second adjacent tooth model, and a set of first sampling points is obtained according to the first tooth model and the second tooth model;

[0012] Obtaining a set of first corresponding points of the first tooth model and the second tooth model respectively according to the distances between the first tooth model and the second tooth model and the first sampling point;

[0013] Acquire a set of second sampling points according to the first corresponding points on the first tooth model, the first corresponding points on the second tooth model, and the first sampling points;

[0014] Obtaining a set of second corresponding points of the first tooth model and the second tooth model respectively according to the distance between the first tooth model and the second tooth model and the second sampling point, and performing iterative update based on the second corresponding points and the second sampling points to obtain a target corresponding point;

[0015] Add interpolation circle points between the two groups of target corresponding points, and connect the interpolation points in the interpolation circle points and the two groups of target corresponding points through a triangular mesh to form a closed mesh of the tooth undercut, which covers the area where the initial undercut model is located and the target undercut area.

[0016] The beneficial effect of the undercut morphology optimization method of the tooth digital model of the present invention is that: after obtaining the tooth digital model according to the correction plan, the adjacent teeth are grouped into a pair of tooth digital model pairs, and the initial undercut area of each tooth digital model pair is obtained, and the target undercut area in each pair of tooth digital model pairs is obtained at the same time, and then a group of first sampling points are respectively obtained according to the first tooth model and the second tooth model in each pair of tooth digital models, and a group of first corresponding points are respectively obtained on the first tooth model and the second tooth model according to the first sampling points, and then a group of second sampling points are obtained according to the first sampling points and the two groups of first corresponding points, and then the first tooth model and the second tooth model are respectively obtained according to the distance between the second sampling points and the first tooth model. A set of second corresponding points of a tooth model and the second tooth model, thereby updating the first corresponding points to second corresponding points, and then updating and iterating according to the second sampling points and the second corresponding points to obtain target corresponding points that meet the requirements, so that after the interpolation points and the obtained target corresponding points are connected through a triangular mesh to form a closed mesh of the tooth undercut, the closed mesh of the tooth undercut can cover the area where the initial undercut model is located and the target undercut area, and obtain the target corresponding points that meet the requirements through multiple iterative updates, thereby completing the optimization process of the undercut model. While forming a closed mesh of the tooth undercut that meets the conditions, not only the undercut area is reduced, but also new undercuts will not be formed, thereby effectively optimizing the undercut model.

[0017] Optionally, acquiring a set of second sampling points according to the first corresponding points on the first tooth model, the first corresponding points on the second tooth model, and the first sampling points includes:

[0018] forming a first triangle with each of the first sampling points, a first corresponding point of the first sampling point on the first tooth model, and a first corresponding point of the first sampling point on the second tooth model;

[0019] Obtaining the altitude direction of the first sampling point on the first triangle;

[0020] Calculating the angle between the outer normal direction of the first corresponding point and the demoulding direction;

[0021] determining a preset angle according to the included angle;

[0022] A preset extension distance is calculated based on the preset angle and the first corresponding point, and the first sampling point is extended by the preset extension distance in the direction of the height line to obtain the second sampling point. This advantageously allows the preset angle to be determined based on the angle between the outer normal direction of the first corresponding point and the demolding direction, thereby facilitating the acquisition of a satisfactory second sampling point and improving the accuracy of the subsequently formed closed mesh of the tooth undercut.

[0023] Optionally, determining the preset angle according to the included angle includes:

[0024] When the included angle between the external normal direction of at least one of the two first corresponding points of the first tooth model and the second tooth model and the demolding direction is less than an angle threshold, determining the preset angle as the initial angle;

[0025] When the angles between the external normals of the two first corresponding points on the first and second tooth models and the demolding direction are both greater than an angle threshold, the preset angle is determined to be the optimized angle, and the optimized angle is greater than the initial angle. This advantageously allows the accuracy of the subsequent second corresponding point positions to be effectively improved by determining the preset angle based on the relationship between the angle and the angle threshold.

[0026] Optionally, the iterative updating according to the second corresponding point and the second sampling point to obtain the target corresponding point includes:

[0027] S201, taking the second corresponding point on the first tooth model and the second corresponding point on the second tooth model as initial corresponding points, and taking the second sampling point as an initial sampling point;

[0028] S202, obtaining a current preset angle based on the initial corresponding point, calculating a distance difference between the initial corresponding point on the first tooth model and the initial corresponding point on the second tooth model, and calculating a current preset extension distance based on the current preset angle and the distance difference;

[0029] S203, increasing the initial sampling point by the current preset extension distance along the corresponding height line direction to obtain an intermediate sampling point, and obtaining a set of intermediate corresponding points on the first dental model and the second dental model based on the shortest distances between the vertices of the digital tooth model on the first dental model and the vertices of the digital tooth model on the second dental model and the intermediate sampling point, and recording the number of iterations;

[0030] S204, determining whether the number of iterations is less than a set number, if the number of iterations is less than the set number, executing step S205, otherwise executing step S206;

[0031] S205, using the intermediate sampling point as the initial sampling point for the next round, using the intermediate corresponding point as the initial corresponding point for the next round, and repeating steps S202 to S204;

[0032] S206: The middle corresponding point obtained in the last step is used as the target corresponding point. This advantageously allows for iterative updates of the second corresponding points to obtain target corresponding points that meet the requirements, after obtaining the second sampling points and two sets of second corresponding points. This facilitates optimization and adjustment of the second corresponding points, allowing for subsequent acquisition of a more optimal tooth-sealed undercut mesh and optimization of the undercut filling model.

[0033] Optionally, the current optimization angle is 1.1 to 1.3 times the previous optimization angle.

[0034] Optionally, the set number of times is three to fifteen times.

[0035] Optionally, the calculation process of the preset extension distance satisfies the following formula:

[0036] L=Y / 2×tanθ

[0037] Wherein, L represents the preset extension distance, Y represents the distance between the first corresponding point P1 corresponding to the first sampling point on the first tooth model and the first corresponding point P2 corresponding to the second tooth model, and angle θ represents the size of the preset angle.

[0038] Optionally, obtaining a set of first sampling points according to the first tooth model and the second tooth model includes:

[0039] respectively obtaining the center points of the tooth digitized grids of the first tooth model and the second tooth model;

[0040] Taking the center position of the line connecting the center points of the first tooth model and the second tooth model as the center of the circle, obtaining an initial sampling circle according to a preset radius, wherein the plane where the initial sampling circle lies is perpendicular to the line connecting the center points of the adjacent teeth;

[0041] A set of first sampling points is obtained by uniformly sampling on the circumference of the initial sampling circle.

[0042] Optionally, the acquiring a set of first corresponding points of the first tooth model and the second tooth model respectively according to the distances between the first tooth model and the second tooth model and the first sampling point includes:

[0043] Calculating a first distance between each vertex in the digital tooth mesh of the first tooth model and each of the first sampling points, and a second distance between each vertex in the digital tooth mesh of the second tooth model and each of the first sampling points;

[0044] In the dental digitized mesh of the first dental model, a vertex whose first distance is less than a first threshold distance is selected as the first corresponding point on the first dental model, and in the dental digitized mesh of the second dental model, a vertex whose second distance is less than a second threshold distance is selected as the first corresponding point on the second dental model.

[0045] Optionally, the method further comprises: performing a smoothing process on the tooth undercut closed mesh, which has the beneficial effect of obtaining a more humane tooth undercut closed mesh.

[0046] The present invention also provides a device for optimizing the undercut shape of a digital tooth model, comprising:

[0047] A tooth model acquisition module is used to obtain a digital tooth model according to the correction plan;

[0048] an initial undercut region acquisition module, configured to group two adjacent teeth in the dental digital model into a pair of dental digital model pairs, and to acquire an initial undercut region in the middle of each pair of the dental digital model pairs;

[0049] an initial model acquisition module, configured to form an initial undercut model according to the initial undercut area of the tooth digital model;

[0050] a target undercut region acquisition module, configured to acquire a target undercut region in the tooth digital model according to the tooth digital model;

[0051] A first sampling acquisition module is configured to acquire a set of first sampling points according to the first and second adjacent tooth models of the tooth digital model pair;

[0052] a first corresponding acquisition module, configured to acquire a set of first corresponding points of the first tooth model and the second tooth model respectively according to the distances between the first tooth model and the second tooth model and the first sampling point;

[0053] A second sampling acquisition module is used to acquire a set of second sampling points according to the positions of the first corresponding points on the first tooth model and the first corresponding points on the second tooth model on the digital tooth model;

[0054] an optimization and adjustment module, configured to obtain a set of second corresponding points of the first tooth model and the second tooth model respectively according to the distance between the first tooth model and the second tooth model and the second sampling point, and to iteratively update the second corresponding points and the second sampling points to obtain a target corresponding point;

[0055] An interpolation molding module is used to add interpolation circle points between the two groups of target corresponding points, and connect the interpolation points in the interpolation circle points and the two groups of target corresponding points through a triangular mesh to form a closed mesh of the dental undercut, and the closed mesh of the dental undercut covers the area where the initial undercut model is located and the target undercut area.

[0056] The beneficial effects of the device for optimizing the undercut shape of a digital tooth model of the present invention and the aforementioned method for optimizing the undercut shape of a digital tooth model are substantially the same, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a flow chart of the method for optimizing the undercut shape of a digital tooth model according to an embodiment of the present invention;

[0058] Figure 2 This is a flowchart of iteratively updating and obtaining target corresponding points according to the second corresponding points and the second sampling points in the method for optimizing the undercut of a digital tooth model according to an embodiment of the present invention;

[0059] Figure 3 For the embodiment of the present invention Figure 2 Schematic diagram of the process execution process;

[0060] Figure 4 This is a structural block diagram of the device for optimizing the undercut shape of a digital tooth model according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The words "including" and similar words used in this article mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0062] In view of the problems existing in the prior art, the embodiment of the present invention provides a method for optimizing the undercut shape of a digital tooth model. Figure 1 As shown, including:

[0063] S101. Obtain a digital tooth model according to the correction plan.

[0064] The treatment plan may be a plan from a database or a treatment plan obtained in real time based on the patient's teeth. After the treatment plan is obtained, the corresponding digital tooth model may be obtained.

[0065] S102: Two adjacent teeth in the tooth digital model are combined into a pair of tooth digital model pairs, and an initial undercut region is obtained in the middle of each pair of the tooth digital model pairs.

[0066] Since undercuts are formed between adjacent teeth in a digital dental model, they are generally filled. Therefore, the adjacent teeth in the digital dental model are grouped into a pair of digital dental models, and an initial undercut-filled area is obtained in the middle area of each digital dental model pair, so as to facilitate the subsequent acquisition of an undercut-filled model inside the initial undercut-filled area.

[0067] In this embodiment, after the tooth models in the digital tooth model are numbered according to the FDI tooth position representation method, the teeth with adjacent numbers are used as adjacent teeth in the digital tooth model. The FDI (Fédération Dentaire Internationale) tooth position representation method is a method of numbering each human tooth in dentistry, and the upper and lower teeth are divided into four areas: upper, lower, left and right. The upper right area is also called area A, the upper left area is also called area B, the lower right area is also called area C, and the lower left area is also called area D.

[0068] S103: forming an initial undercut model according to the initial undercut area of the tooth digital model.

[0069] S104: Acquire a target undercut region in the center of the digital tooth model according to the digital tooth model.

[0070] By determining the target undercut area, the subsequent undercut filling grid can cover the target undercut area, thereby avoiding the formation of new undercuts after the undercut filling.

[0071] S105 , the pair of digital teeth models includes a first tooth model and a second adjacent tooth model, and a group of first sampling points is acquired according to the first tooth model and the second tooth model.

[0072] In some embodiments, the teeth in the digital tooth model are numbered according to the FDI tooth position representation method, and two tooth models with adjacent numbers in the digital tooth model pair are recorded as the first tooth model and the second tooth model, so as to obtain a set of first sampling points on the first tooth model and the second tooth model.

[0073] In some embodiments, acquiring a set of first sampling points according to the first tooth model and the second tooth model includes:

[0074] respectively obtaining the center points of the tooth digitized grids of the first tooth model and the second tooth model;

[0075] Taking the center position of the line connecting the center points of the first tooth model and the second tooth model as the center of the circle, obtaining an initial sampling circle according to a preset radius, wherein the plane where the initial sampling circle lies is perpendicular to the line connecting the center points of the adjacent teeth;

[0076] A set of first sampling points is obtained by uniformly sampling on the circumference of the initial sampling circle.

[0077] Specifically, after determining the first tooth model and the second tooth model, the center points of the tooth digitized grids of the first tooth model and the second tooth model are obtained, and recorded as the first center point and the second center point respectively. Then, the first center point and the second center point are connected together with a straight line, and the center position of the straight line connecting the first center point and the second center point is used as the center of the initial sampling circle, and the plane perpendicular to the line connecting the first center point and the second center point is used as the plane where the initial sampling circle is located. Then, according to the preset radius, the complete initial sampling circle can be obtained, and then a group of first sampling points are obtained by uniformly sampling on the circumference of the initial sampling circle.

[0078] In this embodiment, the number of the first sampling points is 30, and the first sampling points are sampled uniformly and equidistantly on the circumference of the initial sampling circle to ensure that the first sampling points obtained by sampling are not too concentrated and affect the accuracy of the final result.

[0079] In some embodiments, the preset radius is 3 mm.

[0080] S106: Obtain a group of first corresponding points of the first tooth model and the second tooth model respectively according to the distances between the first tooth model and the second tooth model and the first sampling point.

[0081] A group of first corresponding points are respectively acquired on the first tooth model and the second tooth model according to the distances between the first tooth model and the second tooth model and the first sampling point, so as to acquire first corresponding points that meet the requirements.

[0082] In some embodiments, obtaining a set of first corresponding points of the first tooth model and the second tooth model respectively according to the distances between the first tooth model and the second tooth model and the first sampling point includes:

[0083] Calculating a first distance between each vertex in the digital tooth mesh of the first tooth model and each of the first sampling points, and a second distance between each vertex in the digital tooth mesh of the second tooth model and each of the first sampling points;

[0084] In the dental digitized mesh of the first dental model, a vertex whose first distance is less than a first threshold distance is selected as the first corresponding point on the first dental model, and in the dental digitized mesh of the second dental model, a vertex whose second distance is less than a second threshold distance is selected as the first corresponding point on the second dental model.

[0085] In this embodiment, for each vertex in the dental digitized grid of the first dental model and each vertex in the dental digitized grid of the second dental model, the first distance between each vertex in the dental digitized grid of the first dental model and each of the first sampling points, and the second distance between each vertex in the dental digitized grid of the second dental model and each of the first sampling points are calculated respectively, and the vertices corresponding to the first distances of each vertex in the dental digitized grid of the first dental model that are less than the first threshold are taken as a group of first corresponding points, and the vertices corresponding to the second distances of each vertex in the dental digitized grid of the second dental model that are less than the second threshold are taken as a group of first corresponding points, thereby selecting a group of first corresponding points on the first dental model and the second dental model respectively.

[0086] In this embodiment, since the number of the first sampling points is 30, the number of the first corresponding points acquired on the first tooth model and the second tooth model is 30.

[0087] Specifically, first obtain the distance between each vertex in the digital tooth grid of the first dental model and each first sampling point, and select the vertices with the smallest distance between each vertex in the digital tooth grid of the first dental model and each first sampling point in turn as a group of first corresponding points, thereby obtaining 30 first corresponding points on the first dental model; use the same method to obtain the distance between each vertex in the digital tooth grid of the second dental model and each first sampling point, and select the vertices with the smallest distance between each vertex in the digital tooth grid of the second dental model and each first sampling point in turn as another group of first corresponding points, thereby obtaining another 30 first corresponding points on the second dental model.

[0088] S107: Acquire a group of second sampling points according to the first corresponding points on the first tooth model, the first corresponding points on the second tooth model, and the first sampling points.

[0089] After obtaining a set of first sampling points and two sets of first corresponding points, a set of second sampling points is re-acquired based on the first sampling points and the first corresponding points, so as to subsequently obtain new second corresponding points based on the second sampling points, thereby obtaining a more optimal tooth-sealed undercut grid.

[0090] In some embodiments, acquiring a set of second sampling points according to the first corresponding points on the first tooth model, the first corresponding points on the second tooth model, and the first sampling points includes:

[0091] forming a first triangle with each of the first sampling points, a first corresponding point of the first sampling point on the first tooth model, and a first corresponding point of the first sampling point on the second tooth model;

[0092] Obtaining the altitude direction of the first sampling point on the first triangle;

[0093] Calculating the angle between the outer normal direction of the first corresponding point and the demoulding direction;

[0094] determining a preset angle according to the included angle;

[0095] A preset extension distance is calculated according to the preset angle and the first corresponding point, and the first sampling point is extended by the preset extension distance in the height line direction to obtain the second sampling point.

[0096] In this embodiment, after obtaining a group of first sampling points, a group of first corresponding points on the first dental model, and a group of first corresponding points on the second dental model, these three groups of points are respectively formed into a group of first triangles. Specifically, in a group of first sampling points, the first first sampling point is formed with the first corresponding point corresponding to the first dental model and the corresponding point corresponding to the second dental model to form the first first triangle. Similarly, the second first sampling point is formed with the first corresponding point corresponding to the first dental model and the corresponding point corresponding to the second dental model to form the second first triangle, and so on, thereby obtaining a group of first triangles.

[0097] Then, the height line direction of each first sampling point on the corresponding first triangle is obtained respectively, and the angle between the external normal direction of the first corresponding point and the demolding direction is calculated, so as to determine the preset angle according to the size of the angle, and then calculate the extension distance according to the preset angle and the first corresponding point. After the first sampling point is extended by the preset extension distance in the height line direction, the end point of the first sampling point after being extended by the preset extension distance along the height line direction is used as the second sampling point. The above process is performed for each first sampling point, so as to obtain a set of second sampling points corresponding to the first sampling point.

[0098] Specifically, after forming a group of first triangles with each of the first sampling points and the first corresponding point of the first sampling point on the first tooth model and the first corresponding point on the second tooth model, the height line direction of each of the first sampling points on the corresponding first triangle is obtained, and then the angle between the external normal direction of each first corresponding point and the demolding direction is calculated, wherein the demolding direction can be the long axis direction of the digital tooth model, and then the preset angle is determined according to the size of the angle, that is, the preset extension distance can be calculated according to the preset angle and the first corresponding point, so as to facilitate extending the first sampling point along the height line direction by the preset extension distance according to the calculated preset extension distance to obtain a group of second sampling points.

[0099] The preset extension distance is determined according to a preset angle and a distance between two first corresponding points corresponding to the same first sampling point on the first tooth model and the second tooth model.

[0100] In some further embodiments, the calculation process of the preset extension distance satisfies the following formula:

[0101] L=Y / 2×tanθ

[0102] Wherein, L represents the preset extension distance, Y represents the distance between the first corresponding point P1 corresponding to the first sampling point on the first tooth model and the first corresponding point P2 corresponding to the second tooth model, and angle θ represents the size of the preset angle.

[0103] The preset extension distance is calculated using the above formula. The first sampling point is then extended along the height line by the preset extension distance, and the end point after the extension is used as the second sampling point. The above process is then performed on the remaining first sampling points and the corresponding first corresponding points to obtain the remaining second sampling points, thereby obtaining a set of second sampling points corresponding to the first sampling points.

[0104] In some embodiments, determining the preset angle according to the included angle includes:

[0105] When the included angle between the external normal direction of at least one of the two first corresponding points of the first tooth model and the second tooth model and the demolding direction is less than an angle threshold, determining the preset angle as the initial angle;

[0106] When the included angles between the external normal directions of the two first corresponding points of the first tooth model and the second tooth model and the demolding direction are both greater than an angle threshold, the preset angle is determined to be an optimized angle, and the optimized angle is greater than the initial angle.

[0107] Specifically, when the angle between the external normal direction of at least one of the two first corresponding points in the first tooth model and the second tooth model and the demolding direction is less than the angle threshold, it can be determined that one of the two first corresponding points is located in the undercut area of the tooth, so there is no need to adjust the preset angle, and the preset angle can be set to the initial angle; and when the angle between the external normal direction of the two first corresponding points in the first tooth model and the second tooth model and the demolding direction is greater than or equal to the angle threshold, it can be determined that the two second corresponding points are both located in the target undercut area of the tooth, and the size of the preset angle needs to be adjusted so that a new second corresponding point can be updated according to the second sampling point.

[0108] It should be noted that in this embodiment, the angle threshold is 90°. By determining the angle between the outer normal direction and the demolding direction of the two first corresponding points corresponding to each first sampling point and the angle threshold, it is determined whether the second corresponding point corresponding to the first sampling point is within the target undercut region, thereby facilitating optimization and adjustment of the preset angle. However, this solution is not limited to determining by angle; other methods can also be used to determine the positional relationship between the two first corresponding points and the target undercut region, and this solution does not impose any particular restrictions on this.

[0109] In this embodiment, the optimized angle is 1.15 times the initial angle, that is, based on the initial angle, the optimized angle is increased by 15%.

[0110] S108: Obtain a set of second corresponding points of the first tooth model and the second tooth model respectively according to the distance between the first tooth model and the second tooth model and the second sampling point, and perform iterative update based on the second corresponding points and the second sampling points to obtain target corresponding points.

[0111] In order to further obtain a more optimal closed mesh of the tooth undercut, the second corresponding points may be optimized in an iterative updating manner to obtain new corresponding points, so as to optimize the closed mesh of the tooth undercut.

[0112] After obtaining a set of second sampling points, a set of second corresponding points is obtained on the first tooth model and the second tooth model respectively according to the second sampling points in a manner of obtaining first corresponding points according to the first sampling points.

[0113] In some embodiments, the process of respectively acquiring a set of second corresponding points of the first tooth model and the second tooth model according to the distances between the first tooth model and the second tooth model and the second sampling point includes:

[0114] After obtaining a set of second sampling points, the third distance between each vertex in the first dental model's digitized dental mesh and each second sampling point is calculated, as is the fourth distance between each vertex in the second dental model's digitized dental mesh and each second sampling point. The vertex in the first dental model's digitized dental mesh with the smallest first distance is then selected as the second corresponding point on the first dental model, and the vertex in the second dental model's digitized dental mesh with the smallest fourth distance is selected as the second corresponding point on the second dental model. Thus, a set of second corresponding points is obtained on the first and second dental models based on the set of second sampling points.

[0115] In some embodiments, as Figure 2 The process of iteratively updating and acquiring the target corresponding point according to the second corresponding point and the second sampling point includes the following steps:

[0116] S201, taking the second corresponding point on the first tooth model and the second corresponding point on the second tooth model as initial corresponding points, and taking the second sampling point as an initial sampling point;

[0117] S202, obtaining a current preset angle based on the initial corresponding point, calculating a distance difference between the initial corresponding point on the first tooth model and the initial corresponding point on the second tooth model, and calculating a current preset extension distance based on the current preset angle and the distance difference;

[0118] S203, increasing the initial sampling point by the current preset extension distance along the corresponding height line direction to obtain an intermediate sampling point, and obtaining a set of intermediate corresponding points on the first dental model and the second dental model based on the shortest distances between the vertices of the digital tooth model on the first dental model and the vertices of the digital tooth model on the second dental model and the intermediate sampling point, and recording the number of iterations;

[0119] S204, determining whether the number of iterations is less than a set number, if the number of iterations is less than the set number, executing step S205, otherwise executing step S206;

[0120] S205, using the intermediate sampling point as the initial sampling point for the next round, using the intermediate corresponding point as the initial corresponding point for the next round, and repeating steps S202 to S204;

[0121] S206: The middle corresponding point obtained last time is used as the target corresponding point.

[0122] The second corresponding point is updated to a target corresponding point that meets the requirements through the above-mentioned iterative updating method, so as to complete the optimization processing of the closed mesh of the tooth undercut.

[0123] Specifically, refer to Figure 3 First, the second corresponding point on the first tooth model and the second corresponding point on the second tooth model are used as the initial corresponding points, and the second sampling point corresponding to the second corresponding point is used as the initial sampling point. The subsequent process is continued to be executed. The current preset angle is obtained according to the obtained set of initial sampling points and the initial corresponding points corresponding to the initial sampling points on the first tooth model and the second tooth model respectively, and the distance difference between the initial corresponding point on the first tooth model and the initial corresponding point on the second tooth model corresponding to the same initial sampling point is calculated, so as to calculate the current preset extension distance according to the current preset angle and distance difference.

[0124] Among them, the process of obtaining the current preset angle is basically the same as the aforementioned preset angle acquisition process. Specifically, when the angle between the external normal direction of at least one of the two initial corresponding points of the first tooth model and the second tooth model and the demolding direction is less than the angle threshold, the current preset angle is determined to be the initial angle.

[0125] When the included angles between the external normal directions of the two initial corresponding points of the first tooth model and the second tooth model and the demolding direction are both greater than an angle threshold, the preset angle is determined to be an optimized angle, and the optimized angle is greater than the initial angle.

[0126] Then, the distance difference between the initial corresponding point on the first tooth model and the initial corresponding point on the second tooth model corresponding to the same initial sampling point is calculated, so that the current preset extension distance can be obtained based on the current preset angle and distance difference. The calculation process of the current preset extension distance is the same as the calculation formula of the aforementioned preset extension distance, which will not be repeated here.

[0127] After obtaining the current preset extension distance, execute step S203, increase the current preset extension distance of the initial sampling point along the corresponding high line direction to obtain an intermediate sampling point, and obtain a set of intermediate corresponding points on the first dental model and the second dental model according to the shortest distance between the vertices of the digital tooth model on the first dental model, the vertices of the digital tooth model on the second dental model and the intermediate sampling point, and record the number of iterations.

[0128] The process of obtaining the height-line direction corresponding to the initial sampling point is basically similar to that of obtaining the height-line direction corresponding to the first sampling point. Specifically, the initial sampling point and the corresponding two groups of initial corresponding points are respectively used to form several initial triangles, and the height-line direction of the initial sampling point on the initial triangle is the height-line direction corresponding to the initial sampling point.

[0129] After determining the high-line direction corresponding to the initial sampling point, the intermediate sampling point is obtained by extending the current preset extension distance along the high-line direction of the initial sampling point at the initial sampling point. Then, a group of intermediate corresponding points on the first dental model and the second dental model are obtained respectively according to the shortest distance between the vertices of the digital tooth model on the first dental model, the vertices of the digital tooth model on the second dental model and the intermediate sampling point.

[0130] In this embodiment, after obtaining the intermediate sampling point, two groups of intermediate corresponding points are obtained in accordance with the aforementioned method of obtaining two groups of first corresponding points based on the first sampling point. Specifically, the distances between the vertices of the digital tooth model on the first dental model and the vertices of the digital tooth model on the second dental model and each intermediate sampling point are first calculated, and the vertices with the minimum distance from each intermediate sampling point are selected from the vertices of the digital tooth model on the first dental model and the vertices of the digital tooth model on the second dental model as the intermediate corresponding points. Since the process is basically the same as the aforementioned content, it will not be repeated here.

[0131] After obtaining a set of intermediate sampling points and two sets of intermediate corresponding points, the number of iterations is recorded. Each time a new set of intermediate sampling points and two sets of intermediate corresponding points are obtained, the number of iterations is increased by 1.

[0132] Then, step S204 is executed to determine whether the number of iterations is less than the set number. If the number of iterations is less than the set number, step S205 is executed to use the intermediate sampling point as the initial sampling point of the next round, and the intermediate corresponding point as the initial corresponding point of the next round, and steps S202 to S204 are repeated until the number of iterations is greater than or equal to the set number, indicating that the current iterative update process has met the requirements, and then step S206 is executed to use the corresponding point obtained for the last time as the target corresponding point to complete the iterative update process.

[0133] In some embodiments, the current optimization angle is 1.1 to 1.3 times the previous optimization angle.

[0134] In some embodiments, the set number of times is three to fifteen times.

[0135] S109. Add interpolation circle points between the two groups of target corresponding points, and connect the interpolation points in the interpolation circle points and the two groups of target corresponding points through a triangular mesh to form a closed mesh of the dental undercut, wherein the closed mesh of the dental undercut covers the area where the initial undercut model is located and the target undercut area.

[0136] After obtaining a group of target corresponding points on the first tooth model and the second tooth model respectively, several groups of interpolation circle points are added between the two groups of target corresponding points, wherein the interpolation circle points include a circle of interpolation points, and then the interpolation points in the interpolation circle points are respectively connected with the two groups of target corresponding points through a triangular grid to form a closed grid of the tooth undercut, so that the closed grid of the tooth undercut covers the area where the initial undercut model is located and the target undercut filling area, so that the tooth undercut filling model can be obtained according to the closed grid of the tooth undercut, and the optimization of the tooth undercut filling model is completed. Since the closed grid of the tooth undercut covers the area where the initial undercut model is located and the target undercut filling area, no new undercut will be generated after filling the undercut.

[0137] The number of interpolation points is determined according to the distance between the two sets of target corresponding points. The number of interpolation points is at least 2 and at most 6.

[0138] Before adding interpolation circle points between the two groups of target corresponding points, the method also includes filling holes in the two circles of target corresponding points. Specifically, the target corresponding points are projected onto a two-dimensional plane, and after calculating the topological information, the information is applied back to the three-dimensional points to obtain the two-dimensional information of the boundary points, and the average value I of the boundary side length is calculated. Then, the angle between the two adjacent sides of each target corresponding point is calculated, and the target corresponding point with the smallest angle is found. The distance H between its two adjacent boundary points is calculated, and then it is determined whether H<2×I is true. If so, a triangular mesh is added; if not, two triangular meshes are added.

[0139] In some embodiments, the method further includes: smoothing the closed mesh of the tooth undercut, setting the two circles of target corresponding points on the tooth surface as fixed points, and performing Laplace smoothing on the final closed mesh again. Since Laplace smoothing is a part of the existing technology, this solution does not involve any improvement to it itself and will not be described in detail here.

[0140] The present invention also provides a device for optimizing the undercut shape of a digital tooth model, referring to Figure 4 ,include:

[0141] The tooth model acquisition module 401 is used to obtain a digital tooth model according to the correction plan;

[0142] An initial undercut region acquisition module 402 is configured to form a pair of tooth digital models from two adjacent teeth in the tooth digital model, and to acquire an initial undercut region in the middle of each pair of the tooth digital model;

[0143] An initial model acquisition module 403 is configured to form an initial undercut model based on the initial undercut area of the tooth digital model pair;

[0144] A target undercut region acquisition module 404 is configured to acquire a target undercut region in the tooth digital model according to the tooth digital model;

[0145] A first sampling acquisition module 405 is configured to acquire a set of first sampling points according to the first and second adjacent tooth models of the tooth digital model pair;

[0146] A first correspondence obtaining module 406 is configured to obtain a set of first corresponding points of the first tooth model and the second tooth model respectively according to the distances between the first tooth model and the second tooth model and the first sampling point;

[0147] A second sampling acquisition module 407 is configured to acquire a set of second sampling points based on the positions of the first corresponding points on the first tooth model and the first corresponding points on the second tooth model on the digital tooth model;

[0148] an optimization and adjustment module 408, configured to obtain a set of second corresponding points of the first tooth model and the second tooth model respectively based on the distances between the first tooth model and the second tooth model and the second sampling point, and to iteratively update the second corresponding points and the second sampling point to obtain a target corresponding point;

[0149] The interpolation molding module 409 is used to add interpolation circle points between the two groups of target corresponding points, and connect the interpolation points in the interpolation circle points and the two groups of target corresponding points through a triangular mesh to form a closed mesh of the tooth undercut, and the closed mesh of the tooth undercut covers the area where the initial undercut model is located and the target undercut area.

[0150] Since the working principle of the above-mentioned device for optimizing the undercut shape of a digital tooth model corresponds one-to-one to the above-mentioned method for optimizing the undercut shape of a digital tooth model, it will not be described in detail here.

[0151] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A method for optimizing the undercut shape of a digital tooth model, characterized in that: include: Obtain digital models of teeth according to the treatment plan; Two adjacent teeth in the tooth digital model are combined into a pair of tooth digital model pairs, and an initial undercut area is obtained in the middle of each pair of the tooth digital model pairs; forming an initial undercut model according to the initial undercut area of the tooth digital model pair; Acquire a target undercut area in the center of the digital tooth model according to the digital tooth model; The pair of tooth digital models includes a first tooth model and a second adjacent tooth model, and the center points of the tooth digitized grids of the first tooth model and the second tooth model are obtained respectively; Taking the center position of the line connecting the center points of the first tooth model and the second tooth model as the center of the circle, obtaining an initial sampling circle according to a preset radius, wherein the plane where the initial sampling circle lies is perpendicular to the line connecting the center points of the adjacent teeth; uniformly sampling on the circumference of the initial sampling circle to obtain a set of first sampling points; Obtaining a set of first corresponding points of the first tooth model and the second tooth model respectively according to the distances between the first tooth model and the second tooth model and the first sampling point; forming a first triangle with each of the first sampling points, a first corresponding point of the first sampling point on the first tooth model, and a first corresponding point of the first sampling point on the second tooth model; Obtaining the altitude direction of the first sampling point on the first triangle; Calculating the angle between the outer normal direction of the first corresponding point and the demoulding direction; determining a preset angle according to the included angle; Calculating a preset extension distance according to the preset angle and the first corresponding point, and extending the first sampling point by the preset extension distance in the direction of the height line to obtain a set of second sampling points; Obtaining a set of second corresponding points of the first tooth model and the second tooth model respectively according to the distance between the first tooth model and the second tooth model and the second sampling point, and performing iterative update based on the second corresponding points and the second sampling points to obtain a target corresponding point; Add interpolation circle points between the two groups of target corresponding points, and connect the interpolation points in the interpolation circle points and the two groups of target corresponding points through a triangular mesh to form a closed mesh of the tooth undercut, which covers the area where the initial undercut model is located and the target undercut area.

2. The method for optimizing the undercut shape of a digital tooth model according to claim 1, characterized in that: Determining the preset angle according to the included angle includes: When the included angle between the external normal direction of at least one of the two first corresponding points of the first tooth model and the second tooth model and the demolding direction is less than an angle threshold, determining the preset angle as the initial angle; When the included angles between the external normal directions of the two first corresponding points of the first tooth model and the second tooth model and the demolding direction are both greater than an angle threshold, the preset angle is determined to be an optimized angle, and the optimized angle is greater than the initial angle.

3. The method for optimizing the undercut shape of a digital tooth model according to claim 2, characterized in that: The iterative updating according to the second corresponding point and the second sampling point to obtain the target corresponding point includes: S201, taking the second corresponding point on the first tooth model and the second corresponding point on the second tooth model as initial corresponding points, and taking the second sampling point as an initial sampling point; S202, obtaining a current preset angle based on the initial corresponding point, calculating a distance difference between the initial corresponding point on the first tooth model and the initial corresponding point on the second tooth model, and calculating a current preset extension distance based on the current preset angle and the distance difference; S203, increasing the initial sampling point by the current preset extension distance along the corresponding height line direction to obtain an intermediate sampling point, and obtaining a set of intermediate corresponding points on the first dental model and the second dental model based on the shortest distances between the vertices of the digital tooth model on the first dental model and the vertices of the digital tooth model on the second dental model and the intermediate sampling point, and recording the number of iterations; S204, determining whether the number of iterations is less than a set number, if the number of iterations is less than the set number, executing step S205, otherwise executing step S206; S205, using the intermediate sampling point as the initial sampling point for the next round, using the intermediate corresponding point as the initial corresponding point for the next round, and repeating steps S202 to S204; S206: The middle corresponding point obtained last time is used as the target corresponding point.

4. The method for optimizing the undercut shape of a digital tooth model according to claim 3, characterized in that: The current optimization angle is 1.1 to 1.3 times the previous optimization angle.

5. The method for optimizing the undercut shape of a digital tooth model according to claim 3, wherein: The set number of times is three to fifteen times.

6. The method for optimizing the undercut shape of a digital tooth model according to claim 4, wherein: The calculation process of the preset extension distance satisfies the following formula: Wherein, L represents the preset extension distance, Y represents the distance between the first corresponding point P1 corresponding to the first sampling point on the first tooth model and the first corresponding point P2 corresponding to the second tooth model, and the angle Indicates the size of the preset angle.

7. The method for optimizing the undercut shape of a digital tooth model according to claim 1, wherein: The acquiring a set of first corresponding points of the first tooth model and the second tooth model respectively according to the distances between the first tooth model and the second tooth model and the first sampling point includes: Calculating a first distance between each vertex in the digital tooth mesh of the first tooth model and each of the first sampling points, and a second distance between each vertex in the digital tooth mesh of the second tooth model and each of the first sampling points; In the dental digitized mesh of the first dental model, a vertex whose first distance is less than a first threshold distance is selected as the first corresponding point on the first dental model, and in the dental digitized mesh of the second dental model, a vertex whose second distance is less than a second threshold distance is selected as the first corresponding point on the second dental model.

8. The method for optimizing the undercut shape of a digital tooth model according to claim 1, wherein: The method further comprises: performing a smoothing process on the tooth undercut closed grid.

9. A device for optimizing the undercut shape of a digital tooth model, characterized in that: include: A tooth model acquisition module is used to obtain a digital tooth model according to the correction plan; an initial undercut region acquisition module, configured to group two adjacent teeth in the dental digital model into a pair of dental digital model pairs, and to acquire an initial undercut region in the middle of each pair of the dental digital model pairs; an initial model acquisition module, configured to form an initial undercut model according to the initial undercut area of the tooth digital model; a target undercut region acquisition module, configured to acquire a target undercut region in the tooth digital model pair according to the tooth digital model; a first sampling acquisition module, configured to obtain the center points of the tooth digitized grids of the first and second tooth models, respectively, for the pair of tooth digital models, including adjacent first and second tooth models; obtain an initial sampling circle according to a preset radius, using the center position of a line connecting the center points of the first and second tooth models as the center of a circle, wherein the plane on which the initial sampling circle lies is perpendicular to the line connecting the center points of the adjacent teeth; and uniformly sample the circumference of the initial sampling circle to obtain a set of first sampling points; a first corresponding acquisition module, configured to acquire a set of first corresponding points of the first tooth model and the second tooth model respectively according to the distances between the first tooth model and the second tooth model and the first sampling point; a second sampling acquisition module, configured to form a first triangle by respectively forming each of the first sampling points with a first corresponding point of the first sampling point on the first tooth model and a first corresponding point on the second tooth model; obtaining a height line direction of the first sampling point on the first triangle; calculating an angle between an external normal direction of the first corresponding point and a demolding direction; determining a preset angle based on the angle; calculating a preset extension distance based on the preset angle and the first corresponding point, and extending the first sampling point by the preset extension distance in the height line direction to obtain a set of second sampling points; an optimization and adjustment module, configured to obtain a set of second corresponding points of the first tooth model and the second tooth model respectively according to the distance between the first tooth model and the second tooth model and the second sampling point, and to iteratively update the second corresponding points and the second sampling points to obtain a target corresponding point; An interpolation molding module is used to add interpolation circle points between the two groups of target corresponding points, and connect the interpolation points in the interpolation circle points and the two groups of target corresponding points through a triangular mesh to form a closed mesh of the dental undercut, and the closed mesh of the dental undercut covers the area where the initial undercut model is located and the target undercut area.

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