Automatic, personalized and digital split type pile-core crown design and manufacturing methodTechnical Field
The invention relates to a design and manufacturing method of a split type pile core crown.
Background
Tooth defect refers to the destruction, defect or developmental deformity of the appearance and structure of tooth hard tissue with different degrees, which causes abnormal tooth form, occlusion and adjacent relation. The stump residual crown caused by the large-area tooth defect can be repaired by the post-pit crown after perfect dental pulp and periodontal treatment. Compared with the method of planting and repairing after the extraction, the stake nuclear crown can reserve the tooth root and periodontal ligament of the natural tooth, reserve the physiological pressure sensor, is favorable for improving the chewing efficiency of patients and avoiding the bite wound.
The stake nuclear crown comprises three parts: (1) crown: the restoration body completely covering the surface of the dental crown can select different materials according to different dental positions, pile core backgrounds and expected restoration effects, and the materials comprise full porcelain crowns, metal crowns and the like; (2) core: the preparation structure which is connected with the pile and is formed by metal or nonmetal and residual tooth tissue is a full crown retention type structure, and the materials comprise composite resin, ceramic, metal and the like; (3) pile: the part inserted into the root canal is fixed with the inner side wall of the root canal by using adhesive by using friction force and adhesive force, so as to provide the fixation for the nucleus and the crown, and can be divided into fiber piles, metal piles and ceramic piles according to materials.
The personalized pile-core integrated design refers to a mode that piles and cores are manufactured by casting or CAD/CAM technology with the same material according to the shape of root canal, and finally, the whole crown is repaired. This reduces the bonding interface between the stake and the core and reduces the stress concentration area. Compared with commercial finished piles, the personalized pile body is more attached to the inner side wall of the root canal, the personalized pile body can be well adapted to the personalized prepared root canal space, the damage of the root canal prepared tissue is reduced, the damage to the root canal prepared tissue is facilitated, torsional stress is resisted, and in a plurality of teeth with a great loss of tooth structures, the personalized pile cores can resist the rotation force and mutually lock and tie to assist in the retention of dental crowns. In addition, the personalized pile core can form certain compression on the root canal wall in the placing process, so that friction retention is facilitated to be increased, the probability of generation of adhesive bubbles is reduced, and the risk of adhesion failure is further reduced. Therefore, the integrity of the stake/core+crown and the design concept of taking the stake/core+crown as the beginning need to be considered in the design process of the stake-core crown, firstly, the dental crown shape is designed, the nucleation shape is regenerated, and finally, the stake/core integrated one-piece design is carried out through the personalized root canal shape, wherein the stake/core design of a plurality of teeth can strengthen the retention force for the split mutually restricted latch design.
The digitizing technology plays a revolutionary role in the application of the stake nuclear crown, and improves the accuracy and efficiency of the design and manufacture of the stake nuclear crown. The Chinese patent application with publication number CN101385665A published in 2009, 03 and 18 discloses a tooth-grinding split casting pile core and a manufacturing method thereof, and provides a mechanically-embedded casting metal pile core design. However, the nuclear elastic modulus of the metal cast pile is far greater than that of the dental tissue, and the material is gradually replaced by fiber pile cores and other products with the elastic modulus closer to that of the dental tissue. Meanwhile, the method is manual, and has the defects of long working time, high technical sensitivity, difficult avoidance of casting defects and incapability of mass production in clinical and technical rooms.
The chinese patent application with publication number CN113813057a discloses a full digital design method (hereinafter referred to as "prior art D1") for synchronously designing dental stumps and crowns by computer, which is published in 12 months 21 of 2021, the chinese patent application with publication number CN114366349a, which is published in 04 months 19 of 2022, discloses a manufacturing method and guide plate (hereinafter referred to as "prior art D2") for shaping and repairing stumps and crowns, the chinese patent application with publication number CN116650151a, which is published in 08 months 29 of 2023, discloses a detachable digital guide plate and manufacturing method (hereinafter referred to as "prior art D3") for assisting in repairing fibrous stumps and resin cores, the chinese patent application with publication number CN116616926a, which is published in 22 months 2023, discloses a pile channel preparation guide device and manufacturing method (hereinafter referred to as "prior art D4") for preparing personalized fibrous stumps, which is published in 10 months 31 of 2023, and the chinese patent application with publication number CN116965951a, which is published in 2023, and the following is referred to as "prior art D5". The technical proposal provides a new method for introducing a digital new technology according to the clinical 'starting from the end' design concept, designing the stake core according to the tooth crown shape and accurately preparing the tooth tissue. Except the prior scheme D5, the prior patent only aims at the digital description of the 'core' shape modeling of the stake core crown and the digital guidance of the stake channel, and the most important stake core design in the stake core crown still adopts the traditional stake core design and manufacturing method or only adopts the digital expression form, and the whole design process needs the participation of technicians. The prior art D5 proposes a method for customizing fiber pile cores in a personalized way, but the design concept still stays at the 'starting from the end'.
The prior art D1 discloses a digital design core and crown technical scheme, which achieves the sealing between the rest tooth tissue, the core and the crown. However, the existing solution D1 does not involve the design of the stake way, which is a finished product prepared in advance in the mouth, and the existing solution D1 does not consider the interlocking and retention of the stake way and the core.
In the existing scheme D2, a resin core model is designed by utilizing a digital technology, a guide plate is manufactured, and resin is injected to form a pile core crown. However, the prior art solution D2 is a finished fiber stake mated with a personalized resin core, which focuses on the guide-guided shaping of the core. The existing scheme D2 has the risk of poor pile-core binding force and interface separation.
The prior art D3 discloses a method for digitally designing the nuclear morphology and assisting in accurate positioning and bonding of fiber piles during simultaneous restoration of a plurality of teeth. However, in the existing scheme D3, on one hand, the finished fiber piles are matched with the personalized resin cores, the guide plates of the cores are focused on guiding and shaping, and the risks of poor pile-core binding force and interface separation exist. In another aspect, the prior art solution D3 focuses on the design of the guide plate, and the lane in place for a particular stake core is described only as "digital design determination" and does not relate to a particular digital design method.
The prior proposal D4 digitally designs a guide plate device to guide doctors to accurately restore the designed pile track position in the mouth of patients. The existing solution D4 focuses on how to implement a given design with the guide plate, and does not involve the digital design of the stake core itself.
The prior scheme D5 provides a method for personalized customizing of fiber pile cores, but only aims at a single root canal, and the requirement of mutually locking a plurality of teeth is not met.
Disclosure of Invention
The invention aims to solve the technical problems that: the existing technical scheme does not provide a digital design principle of the stake core, and can not realize the computer automatic design of the stake core.
In order to solve the technical problems, the technical scheme of the invention provides an automatic, personalized and digital split type pile-core crown design and manufacturing method, which is characterized by comprising the following steps:
step 1, after a digitized pile channel preparation model of a patient is established, a pile channel 3D file is obtained; after establishing a digital nuclear model of a patient, obtaining a nuclear design 3D file;
Step 2, building the shape of the root canal of the pile canal in the pile canal 3D file so as to eliminate undercut in the preparation of the pile canal in the body;
Step 3, connecting the pile channel 3D file obtained in the step 2 with the core design 3D file, extracting a UV parameter curve of the designed curved surface along the long axis direction of the root, copying the original UV parameter Qu Xianxiang near the orifice of the root in the direction of the tooth surface, so that the obtained new UV parameter curve is completely positioned on the side of the inner wall of the medullary cavity, forming a straight line surface by using the original UV parameter curve and the new UV parameter curve, intersecting the straight line surface with the inner wall of the medullary cavity into a closed intersecting curve, and re-fitting the appearance of the pile by using the intersecting curve generated by combining all the UV parameter curves;
Step 4, automatically dividing the core, which comprises the following steps:
Step 401, segmenting a pile core 3D file by utilizing a root canal orifice interface to obtain a section, wherein the section comprises a core section S0 and two pile sections S1、S2;
Step 402, taking a straight line passing through the center point O1 of the pile section S1 and the center point O2 of the pile section S2, and taking an intersection point A1 of the straight line and the pile section S1 and an intersection point A2 of the straight line and the pile section S2, wherein the intersection point A1 and the intersection point A2 deviate from each other;
Step 403, using the intersection point a1 and the intersection point a2 as two end points to make a line segment, and using the line segment as a diameter to draw a circle S3;
Step 404, moving the circle S3 so that the edge of the circle S3 passes through the center point O0 of the core section S0 and is tangential to the stake section S2, thereby obtaining a circle S4;
step 405, moving the circle S3 so that the circle S3 is tangential to both the pile section S1 and the circle S4, thereby obtaining a circle S5;
Step 406, obtaining a segmentation curve for dividing the core section S0 into two parts by using the edges of the circle S4 and the circle S5;
step 407, cutting the core along the long axis of the root by using a segmentation curve to form two split type pile cores, and generating a 3D file;
Step 5, digital manufacturing and clinical trial wearing: and (3) digitally manufacturing a split type pile core according to the 3D file generated in the step (4), and clinically fitting and modifying.
Preferably, in said step 1, the digitized crown model of the patient is reduced to obtain a digitized core model of said patient.
Preferably, in the step 2, the inner side wall curves are drawn every 0.1 mm-0.5 mm until the root canal orifice, and then the smooth and continuous NURBS curved surfaces of all layers are formed by automatic lofting in computer graphics, so that the appearance of the pile canal root canal is built.
Preferably, in the step 3, in order to form the smooth continuous transition of the curved surface at the connection position of the pile channel 3D file obtained in the step 2 and the core design 3D file, a radius-fixing fillet treatment is performed at the connection position of the pile channel 3D file obtained in the step 2 and the core design 3D file.
The invention discloses an automatic, personalized and digital split type stake nuclear crown design and manufacturing method of stake nuclear crown, which fully embodies the advantages of digital automatic design on the basis of improving stake nuclear retention force: the whole design is completely based on a graphic algorithm, and a computer can automatically realize that a mechanic is not required to operate, so that the pile core has high sealing degree and strong interlocking retention force, and the bonding failure possibility of a pile core bonding interface is reduced. By adopting the technical scheme disclosed by the invention, the pile core retention capacity can be improved, the patient visit times can be reduced, the visit time can be shortened, the visit efficiency can be improved, the material usage amount can be reduced, the predictability and consistency of treatment results can be enhanced, remote design and cooperation can be realized, and the work load of technicians can be greatly reduced. The segmentation curve clipping kernel obtained by the method provided by the invention can be: the surface of the pile core is smoothed to the greatest extent, redundant edge lines are reduced, and printing or casting errors are reduced; and the shortest overflow channel of the adhesive in the root canal is provided, so that the pile core and the root canal are effectively formed and sealed, the pile core is promoted to be in place, and the later micro leakage is reduced.
Drawings
FIG. 1 is a schematic cross-sectional design;
FIG. 2A is a three-dimensional overall view of a split type pile core in one direction;
FIG. 2B is a three-dimensional overall view of a split type pile core in another direction;
FIG. 3A is a split pile core three-dimensional segmentation diagram;
fig. 3B is another split stake core three-dimensional segmentation diagram.
Detailed Description
The application will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the teachings of the present application, and such equivalents are intended to fall within the scope of the application as defined in the appended claims.
When the teeth to be restored are a plurality of teeth of the rear teeth and the root tubes are not parallel, and the common positioning channels are not available for each root tube and the operation is difficult, the embodiment of the invention discloses an automatic, personalized and digital design and manufacturing method of a pile core crown, which achieves the aims of guiding type positioning and improving the pile core retention effect, and particularly comprises the following steps of:
Step one, data acquisition: and acquiring dental dentition and occlusion relation data of a patient, a stake track preparation model, CBCT imaging data and the like.
Secondly, establishing a crown model: the data collected in the first step is input into a crown design system (3shape automate,3shape, copenhagen, denmark) supported by artificial intelligence technology, the crown is automatically designed by using the intelligent dental design platform, a crown prosthesis design file is saved and exported as an STL file 1, and a scanned post channel preparation model is saved and exported as an STL file 2.
Thirdly, establishing a core model, namely reducing the model on the basis of the STL file 1 to obtain a core design file, and exporting the core design file into the STL file 3. In the embodiment of the invention, the reduction is performed by cutting/face reduction of 1-2mm, lip/cheek reduction of 0.5-1.5 mm, lip/cheek reduction gradually becomes smaller from cutting/face to neck margin, and tongue/palate cheek reduction of 0.5-1 mm.
Fourth, personalized split pile core design, further comprising the following steps:
And 1, in the STL file 2, drawing an inner side wall curve to a root orifice every 0.1-0.5 mm, automatically lofting by computer graphics to form smooth and continuous NURBS (Non uniform rational B-spline) curved surfaces of each layer, establishing the appearance of the root canal of the pile canal so as to achieve the purpose of eliminating undercut in the preparation of the pile canal in the body, and storing the modified pile canal file as the STL file 2'.
And 2, connecting the STL file 2' with the STL file 3, extracting the UV parameter curve of the designed curved surface along the long axis direction of the root, and copying the original UV parameter Qu Xianxiang near the root orifice in the direction of the affected tooth surface so that the obtained new UV parameter curve is completely positioned on the inner wall of the medullary cavity. The straight line surface is formed by the original UV parameter curve and the new UV parameter curve, and is intersected with the inner wall of the marrow cavity in a closed intersection curve. The NURBS surface of the stake is re-fitted with the intersection curve generated by combining all of the UV parameter curves so that the tissue surface of the stake meets the intramedullary canal wall. Finally, a fixed-radius round corner treatment of 0.2mm is carried out at the joint of the STL file 2' and the STL file 3, so that the curved surface is smoothly and continuously transited, and the STL file 4 is derived.
Step 3, automatically dividing the core, and further comprising the following steps:
Step 301, dividing the STL file 4 by using a root canal orifice interface to obtain a section as shown in fig. 1, wherein in the section, S0 is a nuclear section, and S1 and S2 are pile sections of two piles.
Step 302, calculating to obtain a center point O0 of the core section S0, a center point O1 of the stake section S1, and a center point O2 of the stake section S2. In the embodiment of the invention, the center point O0, the center point O1 and the center point O2 are obtained by a method for calculating the average value of the coordinates of all the vertexes of the polygon, and related codes are written by using the Python language to realize the algorithm.
In step 303, the straight line passing through the center point O1 and the center point O2 is taken as shown in fig. 1, and the intersection point a1 of the straight line and the pile section S1 and the intersection point a2 of the straight line and the pile section S2 are taken.
In step 303, a line segment is drawn with the intersection point a1 and the intersection point a2 as two end points, and a circle is drawn with the line segment as a diameter S3.
Step 304, the circle S3 is moved such that the edge of the circle S3 passes through the center point O0 and is tangential to the stake section S2, thereby obtaining a circle S4.
Step 305, moving circle S3 so that circle S3 is tangential to both stake section S1 and circle S4, thereby obtaining circle S5.
Step 306, using the circle S4 and the edge of the circle S5 (as shown in the solid line portion in fig. 1), a split curve is obtained that splits the core section S0 into two parts, the split curve being S-shaped and tangential to the stake section S1 and the stake section S2.
Step 307, along the root long axis, cutting the core by using the partition curve to form two split type pile cores, as shown in fig. 2A, 2B, 3A and 3B, and generating the STL file.
Fifth, digital manufacturing and clinical trial wearing: and 3D printing or cutting the split type pile core according to the STL file generated in the third step, and clinically fitting and modifying.