Method and system for generating dental implant guide

Abstract

The present invention belongs to the technical field of dental implant guide generation, and specifically is a method and system for generating a dental implant guide. The generation method comprises the following steps: obtaining an image image obtained by performing CBCT scanning on a patient, segmenting the preprocessed image, interpolating the segmented image using single linear interpolation, generating voxels of the interpolated image sequence, marking them as virtual points if the vertices of the voxels come from the interpolation, and marking them as real points if the vertices of the voxels come from the image; generating a three-dimensional model based on the real points and virtual points of the voxels using a three-dimensional reconstruction method, and smoothing the three-dimensional model; obtaining the patient's intraoral scanning data, aligning the intraoral scanning data with the three-dimensional model, and adding a guide sleeve hole to the three-dimensional model; and printing the three-dimensional model using a 3D printing device to obtain a dental implant guide. The present invention improves the speed and accuracy of guide generation.

Description

Technical Field

[0001] The present invention belongs to the technical field of dental implant guide plate generation, and specifically relates to a dental implant guide plate generation method and system. Background Art

[0002] Teeth not only have the important functions of chewing food, helping pronunciation and maintaining facial beauty, but are also closely related to overall health. Due to various reasons such as caries, periodontal disease and trauma, some people face the problem of tooth loss. Tooth loss not only affects oral function, but may also cause problems such as indigestion, nutrient absorption disorders and alveolar bone atrophy, seriously affecting the quality of life. Traditional denture restoration methods such as removable dentures and fixed bridges have defects such as discomfort and affect taste during use, and it is difficult to restore the function of natural teeth. As an advanced tooth restoration method, dental implants have gradually become the preferred option for tooth restoration with their advantages of high stability, good bionic effects and good long-term use effects.

[0003] The key to dental implant technology lies in the precise implantation of the implant, that is, the proper placement of the artificial tooth root in the alveolar bone. This process requires extremely high technical skills and preoperative design from the doctor. Traditional dental implant surgery relies on the doctor's experience and judgment during surgery. Although it can complete the restoration, there are problems such as implant angle deviation and inaccurate depth control, which affect the effect of dental implants and may even damage the patient's nerves or blood vessels. Dental implant guides combine digital technology with the patient's three-dimensional CT image data to help doctors accurately guide the implant position, angle and depth during surgery, greatly improving the accuracy and safety of the surgery. With the help of guide technology, it can not only shorten the intraoperative operation time and reduce the risk of complications, but also provide patients with a more personalized and comfortable treatment experience, becoming an important innovation in modern oral implant technology. The size and shape of the guide are related to the precise implantation of the implant during the subsequent surgery, which requires the guide to have good accuracy. However, if the three-dimensional model of the guide is required to be accurate, a large amount of calculation is required. How to balance the calculation speed and accuracy has become an urgent problem to be solved in guide generation. Summary of the invention

[0004] In order to improve the speed and accuracy of guide plate generation, the present invention provides a method for generating a dental implant guide plate, comprising the following steps:

[0005] Obtain an image obtained by performing a CBCT scan on a patient, segment the preprocessed image, interpolate the segmented image using single linear interpolation, generate voxels of an interpolated image sequence, and mark the vertices of the voxels as virtual points if they come from the interpolation, and mark the vertices of the voxels as real points if they come from the image;

[0006] Generate a three-dimensional model using a three-dimensional reconstruction method based on the real points and virtual points of the voxels, and perform smoothing on the three-dimensional model;

[0007] The patient's intraoral scan data is obtained, the intraoral scan data is registered with the three-dimensional model, and a guide sleeve hole is added to the three-dimensional model; the three-dimensional model is printed using a 3D printing device to obtain an implant guide.

[0008] Preferably, the three-dimensional model is generated by using a three-dimensional reconstruction method based on the real points and virtual points of the voxels, specifically:

[0009] Obtain an isosurface. For each edge of a voxel intersecting the isosurface, if at least one of the two vertices of the edge is a virtual point, calculate the intersection of the isosurface and the edge, find two real points that are on the same straight line as the edge and closest to the intersection, and use cubic spline interpolation and the two real points to calculate the value at the intersection.

[0010] If the absolute value of the difference between the value at the intersection and the value of the isosurface is greater than the threshold, the position of the intersection is adjusted on the edge where the intersection is located according to the preset step size, and the position of the intersection is updated until the absolute value of the difference between the value at the intersection and the value of the isosurface is not greater than the threshold;

[0011] The vertex coordinates of each patch are calculated by minimizing the quadratic error function.

[0012] Preferably, after obtaining the vertex coordinates of each facet by minimizing the quadratic error function, the method further comprises:

[0013] Get the normal vector of the vertex of the patch and its eight real point neighbors, use the eight real point neighbors to calculate the value of the patch vertex, if the absolute value of the difference between the value of the patch vertex and the value of the isosurface is greater than a threshold, adjust the position of the patch vertex on the straight line where the normal is located according to a preset step size, and update the position of the patch vertex until the absolute value of the difference between the value at the patch vertex and the value of the isosurface is not greater than the threshold.

[0014] Preferably, the registering of the intraoral scan data and the three-dimensional model is specifically performed as follows:

[0015] Convert the 3D model into a point cloud, calculate the principal curvature and gradient of each point in the point cloud, and obtain the feature points of the 3D model point cloud based on the principal curvature and gradient;

[0016] Calculate the principal curvature and gradient of each point in the point cloud composed of the intraoral scanning data, and obtain the characteristic points of the intraoral point cloud according to the principal curvature and gradient;

[0017] Roughly match the feature points of the 3D model point cloud with the feature points of the intraoral point cloud;

[0018] After the coarse matching, the ICP method is used for fine registration.

[0019] Preferably, the three-dimensional model is smoothed by:

[0020] If virtual points are involved in determining the vertices of the patch in the three-dimensional model, the positions of the vertices of the patch are updated using the Laplace smoothing method.

[0021] In addition, the present invention also provides a dental implant guide plate generation system, comprising the following modules:

[0022] A scanning data processing module, used for acquiring an image obtained by performing a CBCT scan on a patient, segmenting the pre-processed image, interpolating the segmented image by using a single linear interpolation, generating voxels of an interpolated image sequence, and marking a virtual point if the vertex of the voxel comes from the interpolation, and marking a real point if the vertex of the voxel comes from the image;

[0023] A three-dimensional model construction module, used to generate a three-dimensional model based on the real points and virtual points of the voxels by using a three-dimensional reconstruction method, and perform smoothing on the three-dimensional model;

[0024] The registration and printing module is used to obtain the patient's intraoral scan data, register the intraoral scan data with the three-dimensional model, add guide sleeve holes to the three-dimensional model; use a 3D printing device to print the three-dimensional model to obtain an implant guide.

[0025] Preferably, the three-dimensional model is generated by using a three-dimensional reconstruction method based on the real points and virtual points of the voxels, specifically:

[0026] Obtain an isosurface. For each edge of a voxel intersecting the isosurface, if at least one of the two vertices of the edge is a virtual point, calculate the intersection of the isosurface and the edge, find two real points that are on the same straight line as the edge and closest to the intersection, and use cubic spline interpolation and the two real points to calculate the value at the intersection.

[0027] If the absolute value of the difference between the value at the intersection and the value of the isosurface is greater than the threshold, the position of the intersection is adjusted on the edge where the intersection is located according to the preset step size, and the position of the intersection is updated until the absolute value of the difference between the value at the intersection and the value of the isosurface is not greater than the threshold;

[0028] The vertex coordinates of each patch are calculated by minimizing the quadratic error function.

[0029] Preferably, after obtaining the vertex coordinates of each facet by minimizing the quadratic error function, the method further comprises:

[0030] Get the normal vector of the vertex of the patch and its eight real point neighbors, use the eight real point neighbors to calculate the value of the patch vertex, if the absolute value of the difference between the value of the patch vertex and the value of the isosurface is greater than a threshold, adjust the position of the patch vertex on the straight line where the normal is located according to a preset step size, and update the position of the patch vertex until the absolute value of the difference between the value at the patch vertex and the value of the isosurface is not greater than the threshold.

[0031] Preferably, the registering of the intraoral scan data and the three-dimensional model is specifically performed as follows:

[0032] Convert the 3D model into a point cloud, calculate the principal curvature and gradient of each point in the point cloud, and obtain the feature points of the 3D model point cloud based on the principal curvature and gradient;

[0033] Calculate the principal curvature and gradient of each point in the point cloud composed of the intraoral scanning data, and obtain the characteristic points of the intraoral point cloud according to the principal curvature and gradient;

[0034] Roughly match the feature points of the 3D model point cloud with the feature points of the intraoral point cloud;

[0035] After the coarse matching, the ICP method is used for fine registration.

[0036] Preferably, the three-dimensional model is smoothed by:

[0037] If virtual points are involved in determining the vertices of the patch in the three-dimensional model, the positions of the vertices of the patch are updated using the Laplace smoothing method.

[0038] In addition, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.

[0039] The present invention uses a simple single linear interpolation method in image insertion to generate images between slice images, which can improve the calculation speed. When determining the intersection of isosurfaces, a more accurate interpolation method is used to ensure the accuracy of the intersection position. Moreover, when generating patch vertices, the position of the patch vertices is further adjusted by using the real points closest to the patch vertices, which further improves the accuracy of the guide plate three-dimensional model. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of Embodiment 1;

[0041] Figure 2 is a schematic diagram of voxels;

[0042] Figure 3 is a schematic diagram of the intersection;

[0043] Figure 4Schematic diagram of the patch vertices. DETAILED DESCRIPTION

[0044] In this article, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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 creative work are within the scope of protection of the present invention.

[0046] In a first embodiment of the present invention, the present invention provides a method for generating a dental implant guide plate, such as Figure 1 As shown, the following steps are included:

[0047] S1, obtaining an image obtained by performing CBCT scanning on a patient, segmenting the preprocessed image, interpolating the segmented image using single linear interpolation, generating voxels of an interpolated image sequence, and marking a virtual point if the vertex of the voxel comes from the interpolation, and marking a real point if the vertex of the voxel comes from the image;

[0048] Through CBCT (Cone beam CT) scanning, the patient's oral cavity tomographic image is obtained to generate a series of two-dimensional slice images, namely DICOM image sequences, which intercept the internal structure of the patient's oral cavity in different directions. After the image is preprocessed, the image is segmented, wherein the preprocessing method includes but is not limited to denoising, contrast enhancement, artifact correction and other operations, and after image segmentation, the teeth, gums, bones, etc. are retained, and the segmentation method includes but is not limited to threshold segmentation, region growing, etc.

[0049] There is a certain interval between the slice images scanned by CBCT. This interval is called the interlayer spacing. The interlayer spacing is much larger than the distance between two pixels in the slice, which requires image interpolation. The so-called image interpolation is to insert one or more images between two images. The values ​​of the pixels in the inserted images are obtained according to the image scanned by CBCT. In an optional embodiment, the pixel value of each pixel in the inserted image is obtained by unilinear interpolation to fill the gap between the original image data. Although unilinear interpolation is not accurate enough, it has a fast calculation speed and can quickly generate an inserted image between two slice images.

[0050] After interpolating the captured image, voxels are further generated. A voxel is a cube consisting of 8 vertices. The values ​​of the voxel vertices come from the interpolated image sequence. Figure 2 A voxel is shown. The values ​​of the 8 vertices of the voxel come from the interpolated image. If the values ​​of the vertices of the voxel come from interpolation, they are marked as virtual points. The virtual points do not exist in the image obtained by CBCT scanning, but are obtained through subsequent interpolation; if the values ​​of the vertices of the voxel come from the image obtained by CBCT scanning, they are marked as real points. The real points are the points that originally existed. Since the virtual points are obtained by single linear interpolation later, their values ​​have certain errors.

[0051] S2, generating a three-dimensional model by using a three-dimensional reconstruction method based on the real points and virtual points of the voxels, and performing smoothing on the three-dimensional model;

[0052] For the interpolated image sequence, a 3D model can be obtained through a 3D model generation algorithm, wherein the 3D model reconstruction or 3D model generation algorithm includes but is not limited to Marching Cubes (MC) algorithm and Dual Contouring (DC) algorithm. Since the virtual point is not a real value, after the 3D model is generated, the 3D model is smoothed.

[0053] In an optional embodiment, in order to eliminate the error caused by the virtual points, a three-dimensional model is generated by using a three-dimensional reconstruction method based on the real points and virtual points of the voxels, specifically:

[0054] Get the isosurface. For each edge of a voxel that intersects the isosurface, if at least one of the two vertices of the edge is a virtual point, calculate the intersection of the isosurface and the edge, and find the two real points that are on the same line as the edge and closest to the intersection, such as Figure 3 As shown, real point 1 and real point 2 are two real points, and the value at the intersection is calculated using the cubic spline interpolation method and the two real points;

[0055] The accuracy of cubic spline interpolation is higher than that of single linear interpolation, but the calculation speed is slower than that of single linear interpolation, and the resource requirements are higher. In the present invention, a simple single linear interpolation is used in image insertion, which can quickly complete the image interpolation. If cubic spline interpolation is used, the amount of calculation is large. When determining the exact position of the intersection, the number of cubic spline interpolations used is much less than that in image interpolation. For example, each slice image, that is, the image image is 1024×1024, there will be more than 1 million pixels. To insert an image between every two slice images, more than 1 million cubic spline interpolations are required. If at least one of the edges where there are 100,000 intersections is a dotted line, only 100,000 cubic spline interpolations are required, and the amount of calculation is much smaller than 1 million times.

[0056] In some embodiments, the edge where the isosurface intersects each voxel is obtained. If at least one of the two vertices of the edge is a virtual point, the two nearest neighbors of the virtual point are obtained. It is required that these two nearest neighbors are real points and are on the same straight line as the edge. The pixel value at the intersection is recalculated using the cubic spline interpolation method.

[0057] If the absolute value of the difference between the value at the intersection and the value of the isosurface is greater than the threshold, the position of the intersection is adjusted on the edge where the intersection is located according to the preset step size, and the position of the intersection is updated until the absolute value of the difference between the value at the intersection and the value of the isosurface is not greater than the threshold;

[0058] If the absolute value of the difference between the recalculated pixel value and the isosurface value is greater than the threshold, the intersection is moved on the edge where the intersection is located, and the pixel value at the intersection after the move is recalculated using the 2 nearest neighbors until the absolute value of the difference between the value at the intersection and the isosurface value is no greater than the threshold; or the condition for stopping the loop iteration is to set the number of loops. When the number of loops is reached, the point with the smallest absolute value of the difference between the value after the move and the isosurface value is found as the intersection.

[0059] The vertex coordinates of each facet are calculated by minimizing the quadratic error function. After the intersection point is obtained, the vertex coordinates are calculated according to the facet vertex solution method in the Dual Contouring method. Specifically, a point is found in the voxel to minimize the value of the minimization quadratic error function.

[0060] In an ideal state, the vertices of the patch are located on the isosurface, and their values ​​are the same as those of the isosurface. However, virtual points and minimizing the quadratic error function will cause errors. In an optional embodiment, after the coordinates of the vertices of each patch are calculated by minimizing the quadratic error function, the following steps are also included:

[0061] Get the normal vector of the vertex of the patch and its eight real point neighbors, and use the eight real point neighbors to calculate the value of the patch vertex. If the absolute value of the difference between the value of the patch vertex and the value of the isosurface is greater than the threshold, adjust the position of the patch vertex on the straight line where the normal is located according to the preset step size, and update the position of the patch vertex until the absolute value of the difference between the value at the patch vertex and the value of the isosurface is not greater than the threshold.

[0062] Vertex Figure 4 As shown, the 8 real point neighbors of a vertex are the real points closest to the vertex of the patch. Figure 4 The black dots are the 8 real point neighbors of the patch vertex. This patch vertex is located in the cube composed of the 8 real point neighbors. The value at the patch vertex is calculated using the 8 real points. If the absolute value of the difference with the value of the isosurface is greater than the threshold, the patch vertex is moved on the normal line, and the value of the patch vertex after the move is recalculated based on the 8 real points. The above process is repeated until the absolute value of the difference between the value at the patch vertex and the value of the isosurface is not greater than the threshold, or the condition for stopping the loop iteration is to set the number of loops. When the number of loops is reached, the point with the smallest absolute value of the difference with the isosurface value after the move is found as the patch vertex. Among them, the value at the patch vertex is calculated using 8 real points, preferably using the trilinear interpolation method.

[0063] In an optional embodiment, if virtual points are involved in determining the vertices of the face in the three-dimensional model, the positions of the vertices of the face are updated using the Laplace smoothing method. If no vertex of the face is involved in determining, and all are real points, no smoothing is performed.

[0064] S3, obtaining the patient's intraoral scan data, aligning the intraoral scan data with the three-dimensional model, adding a guide sleeve hole to the three-dimensional model; using a 3D printing device to print the three-dimensional model to obtain a dental implant guide.

[0065] The three-dimensional surface data of the oral cavity is collected by a digital oral scanner to obtain the intraoral scanning data, and the intraoral scanning data is registered with the three-dimensional model. In one embodiment, the three-dimensional model is converted into a point cloud, the principal curvature and gradient of each point in the point cloud are calculated, and the feature points of the three-dimensional model point cloud are obtained according to the principal curvature and gradient; the principal curvature and gradient of each point in the point cloud composed of the intraoral scanning data are calculated, and the feature points of the intraoral point cloud are obtained according to the principal curvature and gradient;

[0066] Roughly match the feature points of the 3D model point cloud with the feature points of the intraoral point cloud;

[0067] After the coarse matching, the ICP method is used for fine registration.

[0068] Among them, the feature points obtained according to the principal curvature and gradient are specifically to take the points with larger principal curvature and gradient as feature points, and specifically set the threshold corresponding to the principal curvature and the threshold corresponding to the gradient. If the principal curvature of a point is greater than the threshold corresponding to the principal curvature and the gradient is greater than the threshold corresponding to the gradient, then this point is taken as a feature point. After selecting the feature points of the 3D model and the feature points of the intraoral scan data, a rough alignment is performed. After the rough configuration, ICP (Iterative Closest Point) is used for fine alignment.

[0069] After registration, the intraoral scan data and the 3D model are fused into a new 3D model, and then the guide sleeve hole is added according to the position of the tooth to be implanted, and the guide sleeve hole (positioning hole) is adjusted. In this way, a 3D model of the guide plate is generated, and the 3D model is imported into the 3D printing device to complete the printing of the implant guide plate.

[0070] In a second embodiment of the present invention, the present invention further provides a dental implant guide plate generation system, comprising the following modules:

[0071] A scanning data processing module is used to obtain an image obtained by performing a CBCT scan on a patient, segment the pre-processed image, interpolate the segmented image using a single linear interpolation, generate voxels of an interpolated image sequence, and mark the voxel as a virtual point if the voxel vertex comes from the interpolation, and mark the voxel as a real point if the voxel vertex comes from the image sequence;

[0072] A three-dimensional model building module is used to generate a three-dimensional model based on the real points and virtual points of the voxels by using a three-dimensional reconstruction method, and to perform smoothing on the three-dimensional model;

[0073] The registration and printing module is used to obtain the patient's intraoral scan data, register the intraoral scan data with the three-dimensional model, add guide sleeve holes to the three-dimensional model; use a 3D printing device to print the three-dimensional model to obtain an implant guide.

[0074] Preferably, a three-dimensional model is generated by using a three-dimensional reconstruction method based on real points and virtual points of voxels, specifically:

[0075] Get the isosurface. For each edge of a voxel that intersects the isosurface, if at least one of the two vertices of the edge is a virtual point, calculate the intersection of the isosurface and the edge, find the two real points that are on the same line as the edge and closest to the intersection, and use the cubic spline interpolation method and the two real points to calculate the value at the intersection.

[0076] If the absolute value of the difference between the value at the intersection and the value of the isosurface is greater than the threshold, the position of the intersection is adjusted on the edge where the intersection is located according to the preset step size, and the position of the intersection is updated until the absolute value of the difference between the value at the intersection and the value of the isosurface is not greater than the threshold;

[0077] The vertex coordinates of each patch are calculated by minimizing the quadratic error function.

[0078] Preferably, after calculating the vertex coordinates of each facet by minimizing the quadratic error function, the method further includes:

[0079] Get the normal vector of the vertex of the patch and its eight real point neighbors, and use the eight real point neighbors to calculate the value of the patch vertex. If the absolute value of the difference between the value of the patch vertex and the value of the isosurface is greater than the threshold, adjust the position of the patch vertex on the straight line where the normal is located according to the preset step size, and update the position of the patch vertex until the absolute value of the difference between the value at the patch vertex and the value of the isosurface is not greater than the threshold.

[0080] Preferably, the intraoral scan data and the three-dimensional model are registered, specifically:

[0081] Convert the 3D model into a point cloud, calculate the principal curvature and gradient of each point in the point cloud, and obtain the feature points of the 3D model point cloud based on the principal curvature and gradient;

[0082] Calculate the principal curvature and gradient of each point in the point cloud composed of the intraoral scanning data, and obtain the characteristic points of the intraoral point cloud according to the principal curvature and gradient;

[0083] Roughly match the feature points of the 3D model point cloud with the feature points of the intraoral point cloud;

[0084] After the coarse matching, the ICP method is used for fine registration.

[0085] Preferably, the three-dimensional model is smoothed, specifically:

[0086] If virtual points are involved in determining the vertices of the patch in the three-dimensional model, the positions of the vertices of the patch are updated using the Laplace smoothing method.

[0087] In a third embodiment of the present invention, the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method of the first embodiment is implemented.

[0088] In a fourth embodiment of the present invention, the present invention further provides a computer device, the computer device includes at least a memory and a processor, a computer program is stored in the memory, and the computer program implements the method of the first embodiment when executed by the processor.

[0089] Through the description of the above implementation methods, technicians in this field can clearly understand that each implementation method can be implemented by adding a necessary general hardware platform, and of course can also be implemented by combining hardware and software. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a computer product, and the present invention can be in the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it, and other embodiments may also be used. Although the present invention has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for generating a dental implant guide, characterized in that: The following steps are involved: Obtain an image obtained by performing a CBCT scan on a patient, segment the preprocessed image, interpolate the segmented image using single linear interpolation, generate voxels of an interpolated image sequence, and mark the vertices of the voxels as virtual points if they come from the interpolation, and mark the vertices of the voxels as real points if they come from the image; Generate a three-dimensional model using a three-dimensional reconstruction method based on the real points and virtual points of the voxels, and perform smoothing on the three-dimensional model; Obtain the patient's intraoral scan data, align the intraoral scan data with the three-dimensional model, and add a guide sleeve hole to the three-dimensional model; use a 3D printing device to print the three-dimensional model to obtain a dental implant guide; The three-dimensional model is generated by using a three-dimensional reconstruction method based on the real points and virtual points of the voxels, specifically: Obtain an isosurface. For each edge of a voxel intersecting the isosurface, if at least one of the two vertices of the edge is a virtual point, calculate the intersection of the isosurface and the edge, find two real points that are on the same straight line as the edge and closest to the intersection, and use cubic spline interpolation and the two real points to calculate the value at the intersection. If the absolute value of the difference between the value at the intersection and the value of the isosurface is greater than the threshold, the position of the intersection is adjusted on the edge where the intersection is located according to the preset step size, and the position of the intersection is updated until the absolute value of the difference between the value at the intersection and the value of the isosurface is not greater than the threshold; The vertex coordinates of each patch are calculated by minimizing the quadratic error function.

2. The method according to claim 1, characterized in that After obtaining the vertex coordinates of each facet by minimizing the quadratic error function, the method further includes: Get the normal vector of the vertex of the patch and its eight real point neighbors, use the eight real point neighbors to calculate the value of the patch vertex, if the absolute value of the difference between the value of the patch vertex and the value of the isosurface is greater than a threshold, adjust the position of the patch vertex on the straight line where the normal is located according to a preset step size, and update the position of the patch vertex until the absolute value of the difference between the value at the patch vertex and the value of the isosurface is not greater than the threshold.

3. The method according to claim 1, characterized in that The intraoral scan data and the three-dimensional model are registered, specifically: Convert the 3D model into a point cloud, calculate the principal curvature and gradient of each point in the point cloud, and obtain the feature points of the 3D model point cloud based on the principal curvature and gradient; Calculate the principal curvature and gradient of each point in the point cloud composed of the intraoral scanning data, and obtain the characteristic points of the intraoral point cloud according to the principal curvature and gradient; Roughly match the feature points of the 3D model point cloud with the feature points of the intraoral point cloud; After the coarse matching, the ICP method is used for fine registration.

4. The method according to claim 1, characterized in that The smoothing process of the three-dimensional model is specifically as follows: If virtual points are involved in determining the vertices of the patch in the three-dimensional model, the positions of the vertices of the patch are updated using the Laplace smoothing method.

5. A dental implant guide generation system, characterized in that: Includes the following modules: A scanning data processing module, used for acquiring an image obtained by performing a CBCT scan on a patient, segmenting the pre-processed image, interpolating the segmented image by using a single linear interpolation, generating voxels of an interpolated image sequence, and marking a virtual point if the vertex of the voxel comes from the interpolation, and marking a real point if the vertex of the voxel comes from the image; A three-dimensional model construction module, used to generate a three-dimensional model based on the real points and virtual points of the voxels by using a three-dimensional reconstruction method, and perform smoothing on the three-dimensional model; The registration and printing module is used to obtain the intraoral scan data of the patient, register the intraoral scan data with the three-dimensional model, add a guide sleeve hole to the three-dimensional model; use a 3D printing device to print the three-dimensional model to obtain a dental implant guide; The three-dimensional model is generated by using a three-dimensional reconstruction method based on the real points and virtual points of the voxels, specifically: Obtain an isosurface. For each edge of a voxel intersecting the isosurface, if at least one of the two vertices of the edge is a virtual point, calculate the intersection of the isosurface and the edge, find two real points that are on the same straight line as the edge and closest to the intersection, and use cubic spline interpolation and the two real points to calculate the value at the intersection. If the absolute value of the difference between the value at the intersection and the value of the isosurface is greater than the threshold, the position of the intersection is adjusted on the edge where the intersection is located according to the preset step size, and the position of the intersection is updated until the absolute value of the difference between the value at the intersection and the value of the isosurface is not greater than the threshold; The vertex coordinates of each patch are calculated by minimizing the quadratic error function.

6. The system according to claim 5, characterized in that After obtaining the vertex coordinates of each facet by minimizing the quadratic error function, the method further includes: Get the normal vector of the vertex of the patch and its eight real point neighbors, use the eight real point neighbors to calculate the value of the patch vertex, if the absolute value of the difference between the value of the patch vertex and the value of the isosurface is greater than a threshold, adjust the position of the patch vertex on the straight line where the normal is located according to a preset step size, and update the position of the patch vertex until the absolute value of the difference between the value at the patch vertex and the value of the isosurface is not greater than the threshold.

7. The system according to claim 5, characterized in that The intraoral scan data and the three-dimensional model are registered, specifically: Convert the 3D model into a point cloud, calculate the principal curvature and gradient of each point in the point cloud, and obtain the feature points of the 3D model point cloud based on the principal curvature and gradient; Calculate the principal curvature and gradient of each point in the point cloud composed of the intraoral scanning data, and obtain the characteristic points of the intraoral point cloud according to the principal curvature and gradient; Roughly match the feature points of the 3D model point cloud with the feature points of the intraoral point cloud; After the coarse matching, the ICP method is used for fine registration.

8. A computer storage device having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the computer program implements the method according to any one of claims 1 to 4.

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