A method and device for cutting dental braces

Abstract

The present invention relates to the fields of flexible processing and artificial intelligence technology, and discloses a dental appliance cutting method and device, which are implemented based on a dental appliance model file and a dental appliance trajectory file provided by a customer, and include the following steps: Step 1: Obtain the coordinate system of the dental appliance model file, convert the coordinate system of the dental appliance model file in any coordinate system to the coordinate system of the robot end positioning plate model, and merge and fuse the two; Step 2: Perform corresponding conversion on the dental appliance trajectory file according to the coordinates of the dental appliance model file; Step 3: Inverse-solve the dental appliance trajectory coordinates to obtain the robot running trajectory coordinates, match the processing robot, and generate a corresponding processing trajectory file. Compared with the prior art, the present invention does not need to analyze the models of single teeth, greatly reduces the development cycle, and does not require operators or engineers to determine the robot TCP position before cutting, realizing fully automated cutting and improving adaptability.

Description

Technical Field

[0001] The present invention relates to the technical fields of flexible processing and artificial intelligence, and particularly relates to a method and device for cutting dental braces. Background Art

[0002] In orthodontic correction of teeth, the technology of invisible orthodontic appliances (invisible dental braces) has advantages such as being aesthetically pleasing, easy to clean, and having predictable final correction results. The production of invisible dental braces requires processes such as 3D scanning for digital modeling, gradual correction CAD modeling, manufacturing dental models and dental brace blanks, and cutting and processing of gradually corrected dental braces.

[0003] In the prior art, the cutting and processing of dental braces mainly rely on manual cutting by workers or automated cutting with the cooperation of dental brace cutting software and robots. Manual cutting by humans has a cutting effect that depends on the experience of workers, is labor-consuming during the cutting process, and has low production efficiency.

[0004] Currently, there are not many dental brace cutting software. For example, the invention patent with the publication number CN112022382A discloses an automatic cutting method and device for dental braces, which proposes to calculate the cutting trajectory according to the dental brace model file and single tooth model file provided by the customer based on an algorithm. However, this method has the following disadvantages:

[0005] 1. The files that the customer needs to provide are numerous and cumbersome. Currently, many customers have reported that they are unable to provide the single tooth model file, resulting in the failure to execute this solution properly.

[0006] 2. This solution needs to calculate the tooth model and then generate the trajectory based on the tooth model. Since this solution needs to analyze the characteristics of more than 30 teeth by itself, its development cycle is very long, the algorithms involved are also intricate, and even after the algorithm is developed, its versatility is not strong. For example, if it involves cutting the dental film of foreign personnel, the tooth characteristics are different from those of domestic personnel, resulting in the inapplicability of the algorithm.

[0007] 3. In this solution, before the project starts, it is necessary for operators or engineers to determine information such as the TCP position of the robot and the angle of dental brace conversion through complex steps. Specifically: after conversion in this solution, the coordinate points of the tooth model need to be recalculated and searched for, and a new coordinate system needs to be calculated. In this solution, engineers or operators need to go through the listed operation steps, such as selecting the tooth surface and selecting the dental floss, etc., and then they can determine the coordinate system. The method of determining the coordinate system is very complex.

[0008] Regarding the cutting trajectory of dental braces, the traditional method is that software algorithm personnel plan the cutting trajectory of dental braces according to certain rules of medical aesthetics. However, it is ultimately not as perfect as the dental brace trajectory given by professional doctors. Therefore, later, within the medical aesthetics of the dental brace association, it was proposed that the dental brace trajectory be drawn by doctors through medical aesthetics software to generate a dental brace trajectory file.

[0009] Therefore, in view of the above disadvantages, it is urgent to study a method based on the dental appliance trajectory file provided by the doctor that can quickly cut the dental film without affecting the cutting accuracy and reduce the workload of customers and operators. Summary of the Invention

[0010] Object of the Invention: Aiming at the problems existing in the prior art, the present invention provides a dental appliance cutting method and device. By using the dental appliance model file and the dental appliance trajectory file provided by the customer, it is not necessary to analyze the model of a single tooth, which greatly reduces the development cycle. Moreover, it is not necessary for operators or engineers to determine the robot TCP position before cutting, realizing fully automated cutting and improving adaptability.

[0011] Technical Solution: The present invention provides a dental appliance cutting method, which is implemented based on a dental appliance model file and a dental appliance trajectory file, and includes the following steps:

[0012] Step 1: Obtain the coordinate system of the dental appliance model file, convert the coordinate system of the dental appliance model file under any coordinate system to the coordinate system of the robot end positioning plate model, and merge and integrate the two.

[0013] Step 2: Perform corresponding conversion on the dental appliance trajectory file according to the coordinates of the dental appliance model file.

[0014] Step 3: Inverse-solve the dental appliance trajectory coordinates to obtain the robot running trajectory coordinates, match the processing robot, and generate the corresponding processing trajectory file.

[0015] Further, the specific operation of obtaining the coordinate system of the dental appliance model file in Step 1 is as follows:

[0016] Step 1.1: Use the principal component analysis method to determine the XYZ axes for the dental appliance model file.

[0017] Step 1.2: Use the minimum bounding box algorithm to calculate the center point of the dental appliance model file, which is the origin of the coordinate system.

[0018] Step 1.3: Use the clustering algorithm to determine the bottom surface of the dental appliance model file, and further determine the directions of the XYZ axes.

[0019] Further, the specific method for determining the XYZ axes in Step 1.1 is as follows:

[0020] According to the principal component analysis method, discover the basic structure of the dental appliance, and obtain the tangent of the outermost contour of the large tooth, which is the X axis.

[0021] According to the principal component analysis method, determine the vertex of the dental appliance contour, which is point A, find the center point of the X axis, which is point B, and connect the two points, which is the Y axis.

[0022] The cutting plane direction at point A is the Z-axis. Translating the Z-axis to point B gives the X, Y, and Z axes.

[0023] Further, the specific operation for calculating the center point of the dental appliance model file in step 1.2 is as follows:

[0024] Project the points on the dental appliance model file onto the X-axis. Taking the leftmost point on the X-axis as the starting point, generate a plane perpendicular to the X-axis along the points, which is plane A.

[0025] Using the same steps, find the other five planes.

[0026] The six planes form a box, and the center of the box is the origin of the coordinate system, which is the center point of the dental appliance model file.

[0027] Further, the specific method for determining the directions of the X, Y, and Z axes in step 1.3 is as follows:

[0028] The dental appliance model file provided by the customer is in stl file format and consists of N triangular patches. Using a clustering algorithm to traverse the normal vectors of the triangular patch grid of the dental appliance model file and measure the vector angles of the normal vectors, the point set with the smallest angle is the bottom surface, thereby determining the bottom surface of the dental appliance model file.

[0029] After determining the bottom surface of the dental appliance model file, the upward direction perpendicular to the bottom surface is the positive direction of the Z-axis, thereby determining the Z-axis direction.

[0030] Sort the points on the bottom surface of the dental appliance model file in two-dimensional coordinates in sequence. The coordinate values will form two difference domains: one is trough -> peak -> trough; the other is continuously rising. The direction from the trough to the peak is the Y-axis.

[0031] After determining the Z-axis direction and the Y-axis direction, determine the X-axis direction through the right-hand rule.

[0032] Further, the specific operation for converting the coordinate system of the dental appliance model file in any coordinate system to the coordinate system of the robot end positioning plate model in step 1 is as follows:

[0033] Calculate the center point of the positioning plate model and make the center point of the dental appliance model file coincide with the center point of the positioning plate model.

[0034] Calculate the bottom surface of the positioning plate model and overlap the bottom surface of the dental appliance model file with the bottom surface of the positioning plate model.

[0035] Finally, convert the coordinates of the dental appliance model file to the coordinate system of the positioning plate model.

[0036] Further, the dental appliance model file and the dental appliance trajectory file are in the same coordinate system.

[0037] The present invention also discloses a dental appliance cutting device, including:

[0038] A processing robot for driving the dental appliance to move and process along a processing trajectory;

[0039] A positioning plate for fixing the dental appliance and fixing it at the end of the processing robot;

[0040] A cutting tool, which is fixed on the operating table and used for cutting when the processing robot moves and processes along the processing trajectory;

[0041] A cutting control module, whose output end is connected to the control input end of the processing robot, and the steps of the dental appliance cutting method as described above are set on it.

[0042] Preferably, the positioning plate is triangular, its center point is fixed to the central part of the end of the processing robot, and its triangular positions respectively fix the large tooth end of the dental appliance and the vertex of the dental appliance contour. Beneficial effects

[0043] 1. In the present invention, through the dental appliance model file and dental appliance trajectory file provided by the customer, first use the principal component analysis method, minimum bounding box algorithm, and clustering algorithm to convert the coordinate system of the dental appliance model file into the coordinate system of the provided positioning plate model. Since the coordinate system of the dental appliance model file provided by the customer is arbitrary, after converting the coordinate system, the dental appliance model file and the positioning plate model can be fused, which is convenient for the subsequent docking of the positioning plate model and the end of the processing robot, reduces the subsequent coordinate conversion of the dental appliance model file, does not require the customer to provide a single tooth model, reduces the workload of the customer, and also reduces the analysis of the single tooth model in the dental appliance cutting analysis process, greatly shortening the development cycle.

[0044] 2. According to the dental appliance trajectory file provided by the customer, the customer only needs to obtain the dental appliance trajectory file according to the needs of the patient and provide the dental appliance trajectory file. After that, the coordinates of the dental appliance trajectory file are converted in the same way as the coordinates of the dental appliance model. After conversion, the trajectory of the robot processing can be easily achieved by inverse-solving the dental appliance trajectory. The whole operation process is simple and fast, and the operator does not need to determine the TCP position of the robot in advance. After the present invention imports the dental appliance model file, dental appliance trajectory file, and the provided positioning plate model by itself, it can automatically obtain the TCP position of the robot.

[0045] 3. In this application, the dental appliance model file and dental appliance trajectory file provided by the customer are in the same coordinate system. In this way, the coordinate conversion of the dental appliance trajectory file only needs to follow the coordinate system conversion of the dental appliance model file, which is convenient and simple.

[0046] 4. This application uses the principal component analysis algorithm, the minimum bounding box algorithm, and the clustering algorithm to determine the coordinate system of the dental appliance model file, directly determining and adjusting the coordinate system through the algorithm, eliminating the need for manual operation and adjustment by the operator, thus greatly shortening the development cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is the overall structural flowchart of the present invention;

[0048] Figure 2 is the structural schematic diagram of the dental appliance model document of the present invention without coordinate system conversion;

[0049] Figure 3 is the structural schematic diagram of the dental appliance model document of the present invention after coordinate system conversion;

[0050] Figure 4 is the structural schematic diagram of the fusion of the dental appliance model document and the positioning plate model of the present invention;

[0051] Figure 5 is the schematic diagram of obtaining the X-axis of the present invention;

[0052] Figure 6 is the schematic diagram of obtaining the Y-axis of the present invention;

[0053] Figure 7 is the schematic diagram of obtaining the Z-axis of the present invention;

[0054] Figure 8 is the schematic diagram of obtaining the center point using the minimum bounding box algorithm of the present invention;

[0055] Figure 9 is the partial structure enlarged view of the dental appliance model document of the present invention;

[0056] Figure 10 is the coordinate example schematic diagram when determining the Y-axis and X-axis directions of the present invention;

[0057] Figure 11 is the schematic diagram of the final obtained robot running trajectory of the present invention;

[0058] Figure 12 is the simulation data and cutting model based on the provided dental appliance model document of the present invention, (a) is the simulation data, and (b) is the model after on-site cutting. EMBODIMENTS

[0059] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the protection scope of the present invention.

[0060] The present invention discloses a dental appliance cutting method, which needs to be implemented based on the dental appliance model file and the dental appliance trajectory file provided by the customer, and includes the following steps:

[0061] Step 1: Obtain the coordinate system of the dental appliance model file, convert the coordinate system of the dental appliance model file under any coordinate system to the coordinate system of the positioning plate model fixed at the end of the processing robot, and merge and fuse the two.

[0062] Since the coordinate system of the dental appliance model file provided by the customer is not fixed, and the coordinate system of the positioning plate model provided by oneself is fixed, it is necessary to redefine the coordinate system of the dental appliance model and fuse the new coordinate system of the dental appliance model with the coordinate system of the bottom plate model. In the actual conversion and fusion process, first obtain the coordinate system of the dental appliance model file. During the process of obtaining the coordinate system of the dental appliance model, refer to Figures 5 - 8 :

[0063] Step 1.1: Use the principal component analysis method to determine the XYZ axes for the dental appliance model file. The principal component analysis method is a method for feature extraction. It is a commonly used unsupervised learning method. This method uses orthogonal transformation to convert the observed data represented by linearly correlated variables into data represented by a few linearly independent variables. The linearly independent variables are called principal components. Principal component analysis is mainly used to discover the basic structure in the data, that is, the relationship between variables in the data. It is a useful tool for data analysis and is also used for preprocessing other machine learning methods. Specifically as follows:

[0064] According to the principal component analysis algorithm, discover the basic structure of the dental appliance, and obtain the tangent line of the outermost contour of the large tooth, that is, the X axis, as Figure 5 shown.

[0065] According to the principal component analysis algorithm, determine the vertex of the dental appliance contour, that is, point A, find the center point of the X axis, that is, point B, and connect the two points, that is, the Y axis. Refer to Figure 6 .

[0066] The tangent direction of point A is the Z axis. Translate the Z axis to point B, that is, obtain the XYZ axes. Specifically refer to Figure 7 .

[0067] Step 1.2: Use the minimum bounding box algorithm to calculate the center point of the dental appliance model file, which is the origin of the coordinate system.

[0068] The dental appliance model is an stl model, that is, a point cloud model. Project the points on the dental appliance onto the X axis. The leftmost point on the X axis is used as the starting point, and a plane perpendicular to the X axis is generated along the points, that is, plane A. According to the same steps, find the other five planes. The six planes form a box, and the center of the box is the origin of the coordinate system. Refer to Figure 8 .

[0069] Step 1.3: Use the clustering algorithm to determine the bottom surface of the dental appliance model file, and further determine the XYZ axis directions.

[0070] The dental appliance model file provided by the customer is in stl file format and consists of N triangular patches. See Figure 9 , use the clustering algorithm to traverse the normal vectors of the triangular patch grid of the dental appliance model file (after magnifying the stl file, the points are on the triangular surface, and the direction perpendicular to the triangular surface is the normal vector), and measure the vector angles of the normal vectors. The point set with the smallest angle is the bottom surface, thereby determining the bottom surface of the dental appliance model file.

[0071] After determining the bottom surface, the upward direction perpendicular to the bottom surface is the positive direction of the Z axis, thereby determining the Z axis direction.

[0072] Sort the points on the bottom surface in two-dimensional coordinates in sequence. The coordinate differences will form two difference domains. One is: trough -> peak -> trough; the other is: continuous rise; the direction from the trough to the peak is the Y axis. After determining the Z axis direction and the Y axis direction, determine the X axis direction through the right-hand rule.

[0073] Specifically, when sorting, see Figure 10 , since the X and Y axis directions are unknown, arbitrarily select two perpendicular directions. Respectively obtain the coordinate data of the points on the dental appliance in these two directions. For example, A1(a1, b1), A2(a2, b2), A3(a3, b3), A4(a4, b4). Then compare the values in the two quadrants, sort the coordinate data from largest to smallest, and the direction from the trough to the peak is the Y axis. Suppose a1 < a2 < a3 < a4, that is, the quadrant where a is located is the Y axis. If b1 < b2 < b3 < b4, that is, the quadrant where b is located is the Y axis. After sorting, according to conventional data analysis, there must be one of the above results, so this rule algorithm is applied. The black line is similar to the dental appliance.

[0074] Finally, the specific operation of converting the coordinate system of the dental appliance model file in any coordinate system to the coordinate system of the positioning plate model used to be fixed at the end of the processing robot is as follows:

[0075] Calculate the center point of the positioning plate model, and make the center point of the dental appliance model file coincide with the center point of the positioning plate model.

[0076] Calculate the bottom surface of the positioning plate model, and overlap the bottom surface of the dental appliance model file with the bottom surface of the positioning plate model.

[0077] Finally, convert the coordinates of the dental appliance model file to the coordinate system of the positioning plate model.

[0078] Step 2: Perform corresponding conversion on the dental appliance trajectory file according to the dental appliance model coordinates.

[0079] In the present invention, the dental brace trajectory file provided by the customer and the dental brace model file are in the same coordinate system. Therefore, for the dental brace trajectory file, after undergoing the same transformation as the dental brace model file, it can be transformed to be consistent with the coordinate system of the positioning plate model.

[0080] Step 3: Inverse-solve the dental brace trajectory coordinates to obtain the robot running trajectory coordinates, match the processing robot, and generate the corresponding processing trajectory file. The running trajectory of the processing robot finally obtained in the embodiment of the present invention is shown in Figure 11 .

[0081] The above dental brace cutting method is implemented based on the following dental brace cutting device, which includes the following structures: a processing robot for driving the dental brace to move and process along the processing trajectory; a positioning plate for fixing the dental brace and fixing it at the end of the processing robot; a cutting tool fixed on the operating table for cutting when the processing robot moves and processes along the processing trajectory; a cutting control module, whose output end is connected to the control input end of the processing robot, and on which the steps of the above-mentioned dental brace cutting method are set.

[0082] See Figure 4 , the positioning plate is triangular in shape, its center point is fixed to the central part of the end of the processing robot, and its triangular positions respectively fix the large tooth end of the dental brace and the vertex of the dental brace contour.

[0083] Using the above method, the present invention provides the simulation data based on the dental brace model file and the dental brace trajectory file provided by the customer, as shown in Figure 12 , through Figure 11 and Figure 12 comparison, it can be seen that the cutting method of the present invention can accurately cut out the required tooth model, Figure 12 and the dental brace model cut on-site in (b) is complete, further proving that the present invention can accurately achieve the automated cutting of dental braces while shortening the development cycle.

[0084] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and should not be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A dental appliance cutting method, implemented based on a dental appliance model file and a dental appliance trajectory file, characterized in that It includes the following steps: Step 1: Obtain the coordinate system of the dental appliance model file, convert the coordinate system of the dental appliance model file under any coordinate system to the coordinate system of the robot end positioning plate model, and merge and fuse the two; The specific operation for obtaining the coordinate system of the dental appliance model file is as follows: Step 1.1: Use the principal component analysis method to determine the XYZ axes for the dental appliance model file; The specific method for determining the XYZ axes is as follows: Discover the basic structure of the dental appliance according to the principal component analysis method, and obtain the tangent of the outermost contour of the molar, which is the X axis; Determine the vertex of the dental appliance contour according to the principal component analysis method, that is, point A, find the center point of the X axis, that is, point B, and connect the two points, which is the Y axis; The tangent direction of point A is the Z axis. Translate the Z axis to point B, and then the XYZ axes are obtained; Step 1.2: Use the minimum bounding box algorithm to calculate the center point of the dental appliance model file, which is the origin of the coordinate system; Step 1.3: Use the clustering algorithm to determine the bottom surface of the dental appliance model file, and further determine the directions of the XYZ axes; The specific method for determining the directions of the XYZ axes is as follows: The dental appliance model file provided by the customer is in stl file format and consists of N triangular patches. Use the clustering algorithm to traverse the normal vectors of the triangular patch grid of the dental appliance model file and measure the vector angles of the normal vectors. The point set with the smallest angle is the bottom surface, and thus the bottom surface of the dental appliance model file is determined; After determining the bottom surface of the dental appliance model file, the upward direction perpendicular to the bottom surface is the positive direction of the Z axis, and thus the Z axis direction is determined; Sort the points on the bottom surface of the dental appliance model file in two-dimensional coordinates in sequence. The coordinate values will form two difference domains. One is: trough -> peak -> trough; The other is: continuously rising; the direction from the trough to the peak is the Y axis; After determining the Z axis direction and the Y axis direction, determine the X axis direction through the right-hand rule; Step 2: Convert the dental appliance trajectory file accordingly according to the coordinates of the dental appliance model file; Step 3: Inverse solve the dental appliance trajectory coordinates to obtain the robot running trajectory coordinates, match the processing robot, and generate the corresponding processing trajectory file.

2. The orthodontic appliance cutting method according to claim 1, wherein The specific operation for calculating the center point of the dental appliance model file in Step 1.2 is as follows: Project the points on the dental appliance model file onto the X axis. The leftmost point on the X axis is the starting point, and generate a plane perpendicular to the X axis along the points, that is, plane A; According to the same steps, find the other five planes; The six planes form a box, and the center of the box is the origin of the coordinate system, which is the center point of the dental appliance model file.

3. The dental appliance cutting method according to claim 1, wherein The specific operation for converting the coordinate system of the dental appliance model file under any coordinate system to the coordinate system of the robot end positioning plate model in Step 1 is as follows: Calculate the center point of the positioning plate model, and make the center point of the dental appliance model file coincide with the center point of the positioning plate model; Calculate the bottom surface of the positioning plate model, and overlap the bottom surface of the dental appliance model file with the bottom surface of the positioning plate model; Finally, convert the coordinates of the dental appliance model file to the coordinate system of the positioning plate model.

4. The orthodontic appliance cutting method according to claim 1, wherein The dental appliance model file and the dental appliance trajectory file are in the same coordinate system.

5. A dental brace cutting device, characterized in that, It includes: A processing robot, which is used to drive the dental appliance to move and process along the processing trajectory; A positioning plate, which is used to fix the dental appliance and fix it at the end of the processing robot; A cutting tool, which is fixed on an operating table and is used for cutting when a processing robot moves for processing along a processing trajectory; A cutting control module, whose output end is connected to the control input end of the processing robot, and the steps of the dental brace cutting method as described in any one of claims 1 to 4 are set thereon.

6. The dental appliance cutting device according to claim 5, characterized in that, The positioning plate is triangular in shape, its center point is fixed to the central part of the end of the processing robot, and the large tooth end of the dental brace and the vertex of the dental brace contour are respectively fixed at its three angular positions.

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