Digital design method, device and storage medium for oral restorations

Abstract

The present invention relates to a method, device, and storage medium for digital design of oral restorations, comprising: step S1: using CBCT images to obtain point clouds of the enamel, dentin, and pulp of the tooth to be restored and its reference tooth; step S2: determining the center point of the reference tooth based on the cusp positions of the enamel, dentin, and pulp of the reference tooth, and determining the center point of the tooth to be restored based on a first volume ratio between the reference tooth and the tooth to be restored; step S3: constructing a cone of infinite length with the center point of the tooth as the vertex for each of the tooth to be restored and the reference tooth, to obtain the volume coefficients of the dentin and enamel of the reference tooth and the tooth to be restored; and step S4: gradually enlarging the apex angle of the cone and reconstructing the enamel and dentin of the tooth to be restored layer by layer. Compared with existing technologies, the present invention accurately simulates the complex geometric morphology and biomechanical properties of enamel and dentin based on CBCT images, and sets weights at each level to achieve a biomimetic restoration that is more consistent with natural teeth.

Description

Technical Field

[0001] The present invention relates to the field of dental restoration design, and in particular to a digital design method, device and storage medium for dental restorations. Background Art

[0002] Tooth defects are a common clinical condition, severely impacting patients' oral function and quality of life. Dental restorations, by repairing tooth defects, can provide normal anatomical morphology, occlusion, and proximal connections, as well as excellent retention and resistance. Various ceramics and ceramic composites have become a common clinical restorative material due to their excellent mechanical properties and aesthetic qualities.

[0003] With the advancement of science and technology, computer-aided design and manufacturing (CAD / CAM) technology has been widely used in the field of dental restorations, among which the production method of restorations based on subtractive manufacturing technology has gradually become the mainstream. However, the currently commonly used machinable prefabricated ceramic blocks are usually made of a single type of ceramic. This design cannot fully meet the significant differences in mechanical properties between enamel and dentin. Although layered ceramic technology has been proposed, existing layered designs are mostly simple methods such as horizontal layering, which cannot accurately simulate the complex geometric morphology and functional properties of enamel and dentin.

[0004] In this regard, some existing technologies have proposed a method of using 3D printing technology to make restorations. For example, Chinese patent CN110478072A discloses a 3D printing method for making precise bionic ceramic dental restorations, which includes the following steps: 1) Scan the tooth to be repaired and adjacent teeth with an intraoral 3D scanner to obtain 3D surface morphology data and color texture data; 2) Use CAD software to design the 3D layered structure of the denture's strength, color, and translucency; 3) Design the denture's occlusal surface and mesiodistal proximal contact areas into two layers, with a surface layer thickness of 0.3-0.6 mm and an inner layer thickness of 0.4-0.7 mm; 4) The surface layer directly bears chewing pressure and wear, and the material is a bionic strength dental ceramic material; 5) The inner layer and other areas of the denture are all made of high-strength ceramics; 6) Print and form using a 3D printer.

[0005] However, the above-mentioned production methods only increase the corresponding production freedom, and do not provide a specific way to accurately simulate the complex geometric shapes and functional properties of enamel and dentin.

[0006] In addition, although some existing technologies provide layered designs, for example, Chinese patent CN112932707A discloses a method for manufacturing a dental full crown restoration that optimizes the elastic modulus distribution of the material, the specific process is as follows: after the patient's tooth preparation is completed, the digital impression data is obtained by intraoral scanning, and a three-dimensional model with a tooth preparation and a 4-8-layer layered full crown restoration is constructed according to the relevant anatomical dimensions, opposing teeth and occlusal relationship; then the layered full crown restoration and tooth preparation model are further imported into the finite element analysis software, the corresponding parameters are set, and the elastic modulus distribution of the 4-8-layer full crown model is optimized; finally, based on the elastic modulus distribution data of the optimized 4-8-layer full crown model, a dental full crown restoration with a personalized optimized elastic modulus distribution is produced using 3D printing.

[0007] However, this method requires the measurement or calculation of the elastic modulus, but the measurement of the elastic modulus will cause irreversible damage to the teeth. If the elastic modulus is obtained only by simulation calculation, due to the intervention of the elastic modulus, it will itself introduce more errors, and ultimately lead to the inability to provide accurate simulation of the complex geometric morphology and functional characteristics of enamel and dentin. Summary of the Invention

[0008] The purpose of the present invention is to provide a digital design method, device and storage medium for oral restorations. Based on CBCT imaging data, it can accurately simulate the complex geometric shapes and biomechanical properties of enamel and dentin, and combine personalized parameters to achieve bionic restorations that are more in line with the functions of natural teeth.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] A digital design method for oral restorations, comprising:

[0011] Step S1: using CBCT images to obtain point clouds of the enamel, dentin, and pulp of the tooth to be restored and its reference tooth, respectively, and fitting the surface function of the obtained interface;

[0012] Step S2: determining the tooth center of the reference tooth based on the cusp positions of the enamel, dentin, and pulp of the reference tooth, and determining the tooth center of the tooth to be restored based on the offset of the tooth center of the reference tooth relative to the center of mass and a first volume ratio between the reference tooth and the tooth to be restored;

[0013] Step S3: For each of the tooth to be restored and the reference tooth, based on an infinitely long cone with the center point of the tooth as the vertex, the apex angle of the cylinder is adjusted to the maximum so that the portion of the tooth to be restored within the cone is intact. The volume coefficients of the dentin and enamel of the reference tooth and the tooth to be restored are calculated based on the volumes of the enamel, dentin, and pulp within the cone;

[0014] Step S4: Gradually enlarge the apex angle of the cone, and based on the obtained volume coefficient and the pre-configured adjustment coefficient, reconstruct the enamel and dentin of the tooth to be repaired layer by layer until the defect of the tooth to be repaired is completely within the range of the cone to achieve reconstruction of the restoration.

[0015] The reference tooth is a tooth with the same name.

[0016] The step S1 comprises:

[0017] Step S1-1: Acquire CBCT image data and segment the teeth layer by layer to obtain the areas of the tooth to be restored and its reference tooth;

[0018] Step S1-2: For each layer of the tooth to be restored and its reference tooth area, extract the enamel, dentin and pulp boundaries respectively;

[0019] Step S1-3: Based on the layer-by-layer segmentation and boundary extraction results, the point clouds of the enamel, dentin and pulp of the tooth to be restored and its reference tooth are obtained respectively, and the surface function of the obtained interface is fitted.

[0020] The step S2 comprises:

[0021] Step S2-1: determining the positions of the cusps of the enamel, dentin, and pulp in the reference tooth, and registering the positions of the cusps of the enamel, dentin, and pulp, respectively, to obtain each cusp position of the enamel and its corresponding cusp positions of the dentin and pulp as a cusp group;

[0022] Step S2-2: Determine the fitting curve of each cusp group using a fitting method;

[0023] Step S2-3: inside the reference tooth, find the point with the smallest sum of distances to the fitting curves of all cusp groups of the reference tooth as the tooth center point of the reference tooth;

[0024] Step S2-4: Calculating the offset and offset direction of the center point of the reference tooth relative to the center of mass;

[0025] Step S2-5: Based on the relative positions of the tooth to be restored and the reference tooth, combined with the offset direction of the tooth center of the reference tooth relative to the center of mass, the offset direction of the tooth center of the tooth to be restored relative to the center of mass is obtained. Based on the volumes of the tooth to be restored and the reference tooth, combined with the offset of the tooth center of the reference tooth relative to the center of mass, the offset of the tooth center of the tooth to be restored relative to the center of mass is determined:

[0026]

[0027] in: is the offset of the center point of the tooth to be restored relative to the center of mass, is the offset of the center point of the reference tooth relative to the center of mass, is the volume of the tooth to be restored, V is the volume of the reference tooth;

[0028] Step S2-6: Determine the center point of the tooth to be restored based on the center of mass of the tooth to be restored and in combination with the offset amount and offset direction of the center point of the tooth to be restored relative to the center of mass.

[0029] The process of finding the tooth center point in step S2-3 adopts the gradient descent method.

[0030] The step S3 comprises:

[0031] Step S3-1: Create a cone of infinite length with the center point of the tooth to be restored as the vertex, the opening facing the crown, and the axis coinciding with the axis of the tooth;

[0032] Step S3-2: Under the condition that the defective part of the tooth to be repaired is completely outside the cone area, adjust the apex angle of the cone to the maximum and define it as the initial angle α ;

[0033] Step S3-3: Calculate the vertex angle as the initial angle α When , the volume ratio of the enamel to the pulp of the tooth to be restored located in the cone is taken as the first ratio of the tooth to be restored;

[0034] Step S3-4: Take the center point of the reference tooth as the vertex and the vertex angle as the initial angle α , establishing another infinitely long cone with its opening facing the crown and its axis coinciding with the axis of the tooth body; calculating the volume ratio of the enamel to the pulp of the reference tooth located within the cone as the first ratio of the reference tooth;

[0035] Step S3-5: taking the ratio of the first ratio of the tooth to be restored and the first ratio of the reference tooth as the volume coefficient of the enamel of the reference tooth and the tooth to be restored;

[0036] Step S3-6: Calculate the vertex angle as the initial angle α When the volume ratio of the dentin to the pulp of the tooth to be restored is located in the cone, the volume ratio of the dentin to the pulp of the tooth to be restored is taken as the second ratio of the tooth to be restored, and the vertex angle is the initial angle. α When , the volume ratio of dentin to pulp of the reference tooth located in the cone is taken as the second ratio of the reference tooth;

[0037] Step S3-7: The ratio of the second ratio of the tooth to be restored to the second ratio of the reference tooth is used as the volume coefficient of the dentin of the reference tooth and the tooth to be restored.

[0038] The tooth axis passes through the center point of the tooth and is obtained by fitting the center points of all vertices of the enamel, the center points of all vertices of the dentin, and the center points of all vertices of the pulp.

[0039] The step S4 comprises:

[0040] Step S4-1: increasing the top angle of the cone according to a pre-configured angle step;

[0041] Step S4-2: Calculate the ratio of the volume of the pulp portion of the tooth to be restored and the reference tooth within their respective cones, and update the enamel reconstruction volume coefficient by combining the volume coefficients of the enamel of the reference tooth and the tooth to be restored, as well as the pre-configured first weight, second weight, and adjustment coefficient;

[0042] Step S4-3: Determine the enamel increment of the tooth to be restored based on the obtained enamel reconstruction volume coefficient and the enamel increment of the reference tooth, and complete the reconstruction of the enamel portion within the cone based on the enamel increment;

[0043] Step S4-4: updating the dentin reconstruction volume coefficient based on the ratio of the pulp volume of the tooth to be restored and the reference tooth within their respective cones, combining the volume coefficients of the dentin of the reference tooth and the tooth to be restored, and the pre-configured third weight, fourth weight, and adjustment coefficient;

[0044] Step S4-5: Determine the dentin increment of the tooth to be restored based on the obtained dentin reconstruction volume coefficient and the dentin increment of the reference tooth, and complete the reconstruction of the dentin portion within the cone based on the dentin increment;

[0045] Step S4-6: Determine whether the top angle of the cone reaches the iteration angle β If yes, then the reconstruction is completed, otherwise, step S4-1 is executed, wherein the iteration angle β The minimum apex angle of the cone is required to ensure that the defect of the tooth to be restored is completely within the range of the cone.

[0046] The third weight is the same as the first weight, and the fourth weight is the same as the second weight.

[0047] A digital design device for oral restorations comprises a memory, a processor, and a program stored in the memory. When the processor executes the program, the method described above is implemented.

[0048] A storage medium stores a program, which implements the above method when executed.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] 1. The 3D structure of the reference tooth is obtained through CBCT image data, and the enamel, dentin, and pulp are segmented. Based on this segmentation result, the corresponding vertices in the enamel, dentin, and pulp are selected according to the number of cusps. The corresponding curves are connected by fitting vertices to determine the center point of the tooth. Based on this center point, the center point of the tooth to be restored is determined with assistance, which is accurate and universal.

[0051] By gradually increasing the apex angle of an infinitely long cone with the center point of the tooth as the vertex, the reconstruction of the enamel and dentin is gradually and iteratively completed based on the morphological relationship and proportion of the tooth to be restored and the corresponding tooth. Combining the tissue characteristics of the reference tooth in the patient's mouth and the tooth to be restored itself is more scientific, and also makes the reconstructed restoration more mechanically and morphologically consistent with the remaining tooth tissue of the tooth to be restored.

[0052] 2. Determining the offset of the tooth center relative to the center of mass of the tooth to be restored based on the volume ratio can obtain a more accurate position of the tooth center. During the initial reconstruction process, the problem of excessive deviation between the enamel and dentin and the original tooth caused by vertex and morphological errors can be solved.

[0053] 3. By adjusting the coefficients and weights, the output results are not fixed and can be flexibly modified to ensure a more realistic restoration shape. This effectively combines the data prediction results with the physician's experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a schematic diagram of the three-dimensional reconstruction result of the tooth to be restored in this application;

[0055] Figure 2 Schematic diagram of the top angle of the cylinder of the reference tooth;

[0056] Figure 3 Schematic diagram of the apex angle of the cone of the tooth to be restored;

[0057] Figure 4 This is a schematic diagram of the reconstruction results for this application;

[0058] Figure 5 Schematic diagram of the main steps of the method of the present invention. DETAILED DESCRIPTION

[0059] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0060] A digital design method for oral restorations, such as Figure 5 Shown, including:

[0061] Step S1: Using CBCT images, obtain point clouds of the enamel, dentin, and pulp of the tooth to be restored and its reference tooth, and fit the surface function of the obtained interface, including:

[0062] Step S1-1: Acquire CBCT image data and segment the teeth layer by layer to obtain the areas of the tooth to be restored and its reference tooth;

[0063] CBCT image data is a type of computed tomography scan, with each layer serving as a slice. Each tooth can be segmented using an image segmentation algorithm to obtain the region of the tooth to be restored and its reference tooth. The reference tooth can generally be selected from the contralateral maxillary or mandibular tooth with the same name. This provides better symmetry and, on the other hand, reduces errors based on the same round of tomography. For example, if the tooth to be restored is the left mandibular first molar, the reference tooth with the same name should be the right mandibular first molar.

[0064] Of course, although in general, considering the morphological differences between the maxillary and mandibular teeth with the same name, it is not appropriate to select the teeth with the same name, in some other embodiments and in some special cases, the teeth with the same name or adjacent teeth with a smaller difference can be selected.

[0065] Step S1-2: For each layer of the tooth to be restored and its reference tooth area, extract the enamel, dentin and pulp boundaries respectively;

[0066] In this embodiment, a dynamic threshold is used for boundary extraction. This is because the grayscale values ​​of enamel, dentin and dental pulp are different. Of course, in some other embodiments, a convolution operation can also be used to obtain the boundary.

[0067] Step S1-3: Based on the results of layer-by-layer segmentation and boundary extraction, the point clouds of the enamel, dentin, and pulp of the tooth to be repaired and its reference tooth are obtained respectively, and the surface function of the obtained interface is fitted to finally complete the 3D reconstruction of the entire tooth, such as Figure 1 shown.

[0068] For intact reference teeth, the surface functions of the interfaces can be directly fitted, including the surface functions of the interfaces between enamel and dentin, and the surface functions of the interfaces between dentin and pulp. However, for teeth to be repaired, fitting can be performed based on the remaining parts of the teeth to be repaired.

[0069] Step S2: Determining the center of the reference tooth based on the cusp positions of the enamel, dentin, and pulp of the reference tooth, and determining the center of the tooth to be restored based on the offset of the center of the reference tooth relative to the center of mass and the first volume ratio of the reference tooth to the tooth to be restored. In this embodiment, the steps include:

[0070] Step S2-1: determining the positions of the cusps of the enamel, dentin, and pulp in the reference tooth, and registering the positions of the cusps of the enamel, dentin, and pulp, respectively, to obtain each cusp position of the enamel and its corresponding cusp positions of the dentin and pulp as a cusp group;

[0071] A cusp is the end of a tooth that projects toward the crown. Molars typically have four cusps, while premolars have two. For canines, bisecting the teeth labially and lingually, group the labial and lingual parts of each cusp. For incisors and lateral incisors, bisecting the teeth mesiodistal-mesiodistal, group the mesial and distal parts of each cusp.

[0072] In this embodiment, a molar is used as an example, based on the position of the tooth tip, such as Figure 2 As shown in the figure, the top four points in the enamel point cloud are defined as (A1, A2, A3, A4); the top four points in the dentin point cloud are defined as (B1, B2, B3, B4), and the top four points in the pulp point cloud are defined as (C1, C2, C3, C4). (A1, B1, C1), (A2, B2, C2), (A3, B3, C3), and (A4, B4, C4) each represent a cusp vertex group, for a total of four cusp groups.

[0073] Step S2-2: Determine the fitting curve of each cusp group using a fitting method. In this embodiment, polynomial fitting is used. Of course, in other embodiments, other fitting methods can also be used.

[0074] Step S2-3: Inside the reference tooth, find the point with the smallest sum of distances to the fitting curves of all cusp groups of the reference tooth as the tooth center point of the reference tooth, wherein the process of finding the tooth center point adopts the gradient descent method.

[0075] By defining an arbitrary point P = (x, y, z), when the sum of the distances from P to the four fitting curves is the smallest, this point is recorded as the tooth center to obtain a more accurate tooth center.

[0076] Use the gradient descent method to minimize D(P), that is, find the optimal point P ∗ =(x ∗ ,y ∗ ,z ∗ ), so that D(P) reaches the minimum value. In this embodiment, the learning gradient can be set to 0.05, the descent gradient of D(P) can be calculated, and the coordinates of P can be iteratively updated to gradually approach the optimal solution. Update formula:

[0077] P k+1 = P k −0.05×∇D(P k )

[0078] Where: P k+1 is the position of point P in the k+1th step, P k is the position of point P at the kth step, ∇D(P k ) is the gradient of the k-th step.

[0079] Step S2-4: Calculating the offset and offset direction of the center point of the reference tooth relative to the center of mass;

[0080] In this embodiment, the dental pulp point cloud of the reference tooth is C pulp The center of mass of the reference tooth centroid pulp , calculate the dental pulp point cloud C pulp The average coordinates of all points in are obtained.

[0081] Step S2-5: Based on the relative positions of the tooth to be restored and the reference tooth, combined with the offset direction of the tooth center of the reference tooth relative to the center of mass, the offset direction of the tooth center of the tooth to be restored relative to the center of mass is obtained. Based on the volumes of the tooth to be restored and the reference tooth, combined with the offset of the tooth center of the reference tooth relative to the center of mass, the offset of the tooth center of the tooth to be restored relative to the center of mass is determined:

[0082]

[0083] in: is the offset of the center point of the tooth to be restored relative to the center of mass, is the offset of the center point of the reference tooth relative to the center of mass, is the volume of the tooth to be restored, V is the volume of the reference tooth;

[0084] Similarly, in this embodiment, the center of the pulp point cloud of the tooth to be restored is used as the centroid of the tooth to be restored.

[0085] Step S2-6: Determine the center of the tooth to be restored based on the center of mass of the tooth to be restored and in combination with the offset and offset direction of the center of the tooth to be restored relative to the center of mass:

[0086]

[0087] in: The center point of the tooth to be restored. is the centroid of the tooth to be restored.

[0088] Step S3: For each of the tooth to be restored and the reference tooth, based on an infinitely long cone with the center point of the tooth as the vertex, the apex angle of the cylinder is adjusted to the maximum so that the portion of the tooth to be restored within the cone is intact. The volume coefficients of the dentin and enamel of the reference tooth and the tooth to be restored are calculated based on the volumes of the enamel, dentin, and pulp within the cone. In this embodiment, the following steps are included:

[0089] Step S3-1: Create a cone of infinite length with the center point of the tooth to be restored as the vertex, the opening facing the crown, and the axis coinciding with the axis of the tooth;

[0090] Among them, in this embodiment, the tooth axis passes through the center point of the tooth body and is fitted by the center points of all vertices of the enamel, the center points of all vertices of the dentin and the center points of all vertices of the pulp. Of course, in other embodiments, other methods can also be used, such as using a line connecting the center point of the tooth body and the center points of the four vertices of the pulp.

[0091] Step S3-2: Under the condition that the defective part of the tooth to be repaired is completely outside the cone area, adjust the apex angle of the cone to the maximum and define it as the initial angle α ;

[0092] In particular, when it is necessary to explain, in addition to the initial angle α In addition, there is the iteration angle β In the whole process, the vertex angle of the cone changes from the initial angle α Gradually increase to the iteration angle β ,like Figure 3 As shown, when the apex angle of the cone is the iteration angle β When the cone is opened, the defective part of the tooth to be restored is completely included in the cone.

[0093] Step S3-3: Calculate the vertex angle as the initial angle α When , the volume ratio of the enamel to the pulp of the tooth to be restored located in the cone is taken as the first ratio of the tooth to be restored;

[0094] Step S3-4: Take the center point of the reference tooth as the vertex and the vertex angle as the initial angle α , establishing an infinitely long cone with its opening facing the crown and its axis coinciding with the axis of the tooth body; calculating the volume ratio of the enamel to the pulp of the reference tooth located within the cone as the first ratio of the reference tooth;

[0095] Step S3-5: The ratio of the first ratio of the tooth to be restored to the first ratio of the reference tooth is used as the volume coefficient κ of the enamel of the reference tooth and the tooth to be restored enamel ;

[0096] Step S3-6: Calculate the vertex angle as the initial angle αWhen the volume ratio of the dentin to the pulp of the tooth to be restored is located in the cone, the volume ratio of the dentin to the pulp of the tooth to be restored is taken as the second ratio of the tooth to be restored, and the vertex angle is the initial angle. α When , the volume ratio of dentin to pulp of the reference tooth located in the cone is taken as the second ratio of the reference tooth;

[0097] Step S3-7: The ratio of the second ratio of the tooth to be restored to the second ratio of the reference tooth is used as the volume coefficient κ of the dentin of the reference tooth and the tooth to be restored dentin .

[0098] Step S4: gradually enlarging the apex angle of the cone, and based on the obtained volume coefficient and the pre-configured adjustment coefficient, reconstructing the enamel and dentin of the tooth to be repaired layer by layer until the defect of the tooth to be repaired is completely within the range of the cone to achieve reconstruction of the restoration. In this embodiment, the following steps are included:

[0099] Step S4 - 1 : increasing the apex angle of the cone according to a preconfigured angle step dθ.

[0100] Step S4-2: Calculate the ratio of the volume of the pulp of the tooth to be restored and the reference tooth within their respective cones, and update the enamel reconstruction volume coefficient by combining the volume coefficients of the enamel of the reference tooth and the tooth to be restored, as well as the pre-configured first weight, second weight, and adjustment coefficient:

[0101]

[0102] in: is the enamel reconstruction volume coefficient, is the first weight, is the second weight, is the adjustment coefficient, is the volume of the pulp of the tooth to be restored within the cone, For the volume of the pulp of the reference tooth within the cone, the sum of the first weight and the second weight should be 1. The current vertex angle of the cone.

[0103] Step S4-3: Based on the obtained enamel reconstruction volume coefficient, the enamel increment of the tooth to be repaired is determined in combination with the enamel increment of the reference tooth. Specifically, the enamel reconstruction volume coefficient and the enamel increment of the reference tooth are multiplied to obtain the enamel increment of the tooth to be repaired, and the reconstruction of the enamel part within the cone is completed based on the enamel increment.

[0104] Step S4-4: Based on the ratio of the pulp volumes of the tooth to be restored and the reference tooth within their respective cones, combined with the dentin volume coefficients of the reference tooth and the tooth to be restored, as well as the pre-configured third weight, fourth weight, and adjustment coefficient, the dentin reconstruction volume coefficient is updated:

[0105]

[0106] in: is the dentin reconstruction volume coefficient, is the third weight, is the fourth weight, and similarly, the sum of the third weight and the fourth weight should be 1. In particular, in this embodiment, the third weight is the same as the first weight, and the fourth weight is the same as the second weight, both of which are 0.5. Of course, in other embodiments, the dentist, technician or staff can adjust the weight to other values ​​based on the reconstruction result to be generated, according to the morphology and structure of the reference tooth and / or the remaining teeth in the mouth, so as to achieve a more bionic purpose.

[0107] Step S4-5: Based on the obtained dentin reconstruction volume coefficient and combined with the dentin increment of the reference tooth, the dentin increment of the tooth to be repaired is determined, and the reconstruction of the dentin part within the cone is completed based on the dentin increment. Similarly, in this embodiment, the dentin reconstruction volume coefficient and the dentin increment of the reference tooth are the dentin increment of the tooth to be repaired. By obtaining the enamel increment and dentin increment of the tooth to be repaired, the reconstruction of the defective part within the cone at this time can be completed.

[0108] Step S4-6: Determine whether the top angle of the cone reaches the iteration angle β If yes, then Figure 4 As shown, the reconstruction can be completed, otherwise, step S4-1 is executed.

[0109] This embodiment also provides a digital fabrication method for a restoration. This method utilizes computer-aided additive manufacturing technology. Based on the designed morphology of the enamel and dentin regions, appropriate materials are selected for zoning the restoration: a lower-hardness ceramic material is used for the dentin region, while a higher-hardness ceramic material is used for the enamel region. Ultimately, the biomimetic restoration is precisely fabricated.

[0110] If the above functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program code, such as USB flash drives, mobile hard drives, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical disks.

Claims

1. A digital design method for oral restorations, characterized in that: include: Step S1: using CBCT images to obtain point clouds of the enamel, dentin, and pulp of the tooth to be restored and its reference tooth, respectively, and fitting the surface function of the obtained interface; Step S2: determining the tooth center of the reference tooth based on the cusp positions of the enamel, dentin, and pulp of the reference tooth, and determining the tooth center of the tooth to be restored based on the offset of the tooth center of the reference tooth relative to the center of mass and a first volume ratio between the reference tooth and the tooth to be restored; Step S3: For each of the tooth to be restored and the reference tooth, based on an infinitely long cone with the center point of the tooth as the vertex, the apex angle of the cone is adjusted to the maximum so that the portion of the tooth to be restored within the cone is intact. The volume coefficients of the dentin and enamel of the reference tooth and the tooth to be restored are calculated based on the volumes of the enamel, dentin, and pulp within the cone; Step S4: gradually enlarging the apex angle of the cone, and based on the obtained volume coefficient and the pre-configured adjustment coefficient, reconstructing the enamel and dentin of the tooth to be restored layer by layer until the defect of the tooth to be restored is completely within the range of the cone to achieve reconstruction of the restoration; The step S3 comprises: Step S3-1: Create a cone of infinite length with the center point of the tooth to be restored as the vertex, the opening facing the crown, and the axis coinciding with the axis of the tooth; Step S3-2: Under the condition that the defective part of the tooth to be repaired is completely outside the cone area, adjust the apex angle of the cone to the maximum and define it as the initial angle α ; Step S3-3: Calculate the vertex angle as the initial angle α When , the volume ratio of the enamel to the pulp of the tooth to be restored located in the cone is taken as the first ratio of the tooth to be restored; Step S3-4: Take the center point of the reference tooth as the vertex and the vertex angle as the initial angle α , establishing another infinitely long cone with its opening facing the crown and its axis coinciding with the axis of the tooth body; calculating the volume ratio of the enamel to the pulp of the reference tooth located within the cone as the first ratio of the reference tooth; Step S3-5: taking the ratio of the first ratio of the tooth to be restored and the first ratio of the reference tooth as the volume coefficient of the enamel of the reference tooth and the tooth to be restored; Step S3-6: Calculate the vertex angle as the initial angle α When the volume ratio of the dentin to the pulp of the tooth to be restored is located in the cone, the volume ratio of the dentin to the pulp of the tooth to be restored is taken as the second ratio of the tooth to be restored, and the vertex angle is the initial angle. α When , the volume ratio of dentin to pulp of the reference tooth located in the cone is taken as the second ratio of the reference tooth; Step S3-7: taking the ratio of the second ratio of the tooth to be restored and the second ratio of the reference tooth as the volume coefficient of the dentin of the reference tooth and the tooth to be restored; The step S4 comprises: Step S4-1: increasing the top angle of the cone according to a pre-configured angle step; Step S4-2: Calculate the ratio of the volume of the pulp portion of the tooth to be restored and the reference tooth within their respective cones, and update the enamel reconstruction volume coefficient by combining the volume coefficients of the enamel of the reference tooth and the tooth to be restored, as well as the pre-configured first weight, second weight, and adjustment coefficient; Step S4-3: Determine the enamel increment of the tooth to be restored based on the obtained enamel reconstruction volume coefficient and the enamel increment of the reference tooth, and complete the reconstruction of the enamel portion within the cone based on the enamel increment; Step S4-4: updating the dentin reconstruction volume coefficient based on the ratio of the pulp volume of the tooth to be restored and the reference tooth within their respective cones, combining the volume coefficients of the dentin of the reference tooth and the tooth to be restored, and the pre-configured third weight, fourth weight, and adjustment coefficient; Step S4-5: Determine the dentin increment of the tooth to be restored based on the obtained dentin reconstruction volume coefficient and the dentin increment of the reference tooth, and complete the reconstruction of the dentin portion within the cone based on the dentin increment; Step S4-6: Determine whether the top angle of the cone reaches the iteration angle β If yes, then the reconstruction is completed, otherwise, step S4-1 is executed, wherein the iteration angle β The minimum apex angle of the cone is required to ensure that the defect of the tooth to be restored is completely within the range of the cone.

2. A digital design method for oral restorations according to claim 1, characterized in that: The reference tooth is a tooth with the same name.

3. The method for digital design of oral restorations according to claim 1, characterized in that: The step S1 comprises: Step S1-1: Acquire CBCT image data and segment the teeth layer by layer to obtain the areas of the tooth to be restored and its reference tooth; Step S1-2: For each layer of the tooth to be restored and its reference tooth area, extract the enamel, dentin and pulp boundaries respectively; Step S1-3: Based on the layer-by-layer segmentation and boundary extraction results, the point clouds of the enamel, dentin and pulp of the tooth to be restored and its reference tooth are obtained respectively, and the surface function of the obtained interface is fitted.

4. The method for digital design of oral restorations according to claim 1, characterized in that: The step S2 comprises: Step S2-1: determining the positions of the cusps of the enamel, dentin, and pulp in the reference tooth, and registering the positions of the cusps of the enamel, dentin, and pulp, respectively, to obtain each cusp position of the enamel and its corresponding cusp positions of the dentin and pulp as a cusp group; Step S2-2: Determine the fitting curve of each cusp group using a fitting method; Step S2-3: inside the reference tooth, find the point with the smallest sum of distances to the fitting curves of all cusp groups of the reference tooth as the tooth center point of the reference tooth; Step S2-4: Calculating the offset and offset direction of the center point of the reference tooth relative to the center of mass; Step S2-5: Based on the relative positions of the tooth to be restored and the reference tooth, combined with the offset direction of the tooth center of the reference tooth relative to the center of mass, the offset direction of the tooth center of the tooth to be restored relative to the center of mass is obtained. Based on the volumes of the tooth to be restored and the reference tooth, combined with the offset of the tooth center of the reference tooth relative to the center of mass, the offset of the tooth center of the tooth to be restored relative to the center of mass is determined: in: is the offset of the center point of the tooth to be restored relative to the center of mass, is the offset of the center point of the reference tooth relative to the center of mass, is the volume of the tooth to be restored, V is the volume of the reference tooth; Step S2-6: Determine the center point of the tooth to be restored based on the center of mass of the tooth to be restored and in combination with the offset amount and offset direction of the center point of the tooth to be restored relative to the center of mass.

5. A digital design method for oral restorations according to claim 4, characterized in that: The process of finding the tooth center point in step S2-3 adopts the gradient descent method.

6. The method for digital design of oral restorations according to claim 1, characterized in that: The tooth axis passes through the center point of the tooth and is obtained by fitting the center points of all vertices of the enamel, the center points of all vertices of the dentin, and the center points of all vertices of the pulp.

7. A digital design device for oral restorations, comprising a memory, a processor, and a program stored in the memory, characterized in that: When the processor executes the program, the method according to any one of claims 1 to 6 is implemented.

8. A storage medium having a program stored thereon, characterized in that: When the program is executed, the method according to any one of claims 1 to 6 is implemented.

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