CN112836371A - Method for measuring the actual shrinkage of dental restorations - Google Patents
Method for measuring the actual shrinkage of dental restorations Download PDFInfo
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Abstract
本发明提供了一种牙科修复体的实际收缩率的测算方法，该方法包括：根据预定的牙科修复体创建原始设计模型；对所述原始设计模型进行基于笛卡尔直角坐标系的三维放大，以获得放大设计模型；按照所述放大设计模型制造修复体实物；对所述修复体实物进行三维重建，以生成所述修复体实物对应的逆向建模模型；将所述逆向建模模型和所述原始设计模型进行拟合对齐，并选取所述逆向建模模型和所述原始设计模型中的兴趣区域的坐标数据集合；进一步地，计算在笛卡尔直角坐标系中的预定维度方向上所述原始设计模型相对于所述逆向建模模型的缩放比系数，并计算所述预定维度方向上所述逆向建模模型相对于所述原始设计模型的实际收缩率。
The invention provides a method for measuring the actual shrinkage rate of a dental restoration, the method comprising: creating an original design model according to a predetermined dental restoration; Obtain an enlarged design model; manufacture a prosthesis object according to the enlarged design model; perform three-dimensional reconstruction on the prosthesis object to generate an inverse modeling model corresponding to the prosthesis object; combine the inverse modeling model with the The original design model is fitted and aligned, and the coordinate data set of the region of interest in the inverse modeling model and the original design model is selected; A scaling factor of the design model relative to the inverse modeling model, and calculating the actual shrinkage ratio of the inverse modeling model relative to the original design model in the predetermined dimension direction.
Description
Technical Field
The invention relates to the field of manufacturing of dental restorations and digital computer-aided design of oral cavities, in particular to a method for measuring and calculating the actual shrinkage rate of a dental restoration.
Background
The ceramic has the aesthetic property similar to that of natural teeth, good biocompatibility, stable chemical property, poor heat conduction and electrical conductivity, no irritation to dental pulp, abrasion resistance, smooth surface and difficult plaque attachment, so the ceramic is a dental prosthesis material which is commonly selected in anterior oral cavity repair treatment.
When the dental prosthesis is manufactured by combining a digital technology, because of the characteristics of zirconia in ceramics, the ceramic shrinkage of a regulation and control sintering link in the forming process of the dental all-ceramic prosthesis has obvious influence on the dimensional precision of the prosthesis, in order to realize shrinkage compensation, a method for adjusting the scaling of a prosthesis model file is generally adopted in the past, namely, the original model file is amplified according to the linear shrinkage rates of a standard test piece in three dimensional directions in a Cartesian rectangular coordinate system before the digital manufacturing, so as to compensate the dimensional shrinkage caused by sintering densification. However, practice shows that the volume shrinkage generated in sintering cannot be completely compensated by amplification based on the shrinkage rate of the standard test piece, and clinical characteristics such as the adhesion and the like closely related to the size precision of the prosthesis are influenced. Therefore, the measurement and evaluation of the actual shrinkage rate of the all-ceramic restoration body have important significance for effectively compensating shrinkage and improving dimensional accuracy.
The oral cavity all-ceramic prosthesis has the characteristics of atypical geometric characteristics and irregular surface morphology, and in most application scenes, the direct contact measurement of the shrinkage rate cannot be carried out by using a tool or an instrument for accurate measurement such as a vernier caliper and the like, so that the shrinkage rate measurement can be carried out by adopting a non-contact measurement method based on reverse engineering in the prior art, for example, reverse engineering three-dimensional measurement software is used for manually selecting a measurement site according to the key anatomical characteristics of the prosthesis to calculate the linear shrinkage rate, but the method for manually selecting the measurement site can only obtain a single coordinate value of point cloud data every time, the efficiency is low due to large workload of the instrument, and the actual shrinkage rate of the whole oral cavity all-ceramic prosthesis cannot be objectively reflected under the condition of insufficient sampling of. The existing method for measuring and calculating the shrinkage rate of the oral all-ceramic restoration has the defects of low efficiency, large error and the like.
Disclosure of Invention
In order to overcome the above-mentioned defects in the prior art, the present invention provides a method for measuring and calculating the actual shrinkage rate of a dental restoration, the method comprising:
creating an original design model from a predetermined dental restoration;
performing three-dimensional amplification on the original design model based on a Cartesian rectangular coordinate system to obtain an amplified design model;
manufacturing a prosthesis real object according to the enlarged design model;
carrying out three-dimensional reconstruction on the prosthesis real object to generate a reverse modeling model corresponding to the prosthesis real object;
fitting and aligning the reverse modeling model and the original design model, and selecting a coordinate data set of an interest area in the reverse modeling model and the original design model;
calculating a scaling factor of the original design model relative to the reverse modeling model in a predetermined dimensional direction in a Cartesian rectangular coordinate system according to the coordinate data set;
and calculating the actual shrinkage rate of the reverse modeling model relative to the original design model in the preset dimension direction according to the scaling ratio coefficient.
According to one aspect of the present invention, the step of performing cartesian rectangular coordinate system-based three-dimensional amplification on the original design model in the method comprises: setting a mesial-distal direction of the dental restoration to an X direction based on the Cartesian rectangular coordinate system,
setting the gingival direction as Y direction and the buccolingual direction as Z direction; and carrying out proportional amplification based on the center of mass of the dental prosthesis on the original design model according to a preset amplification factor parameter in each direction in the Cartesian rectangular coordinate system.
According to another aspect of the present invention, the magnification parameter in the method is determined by shrinkage of the master specimen.
According to another aspect of the invention, the prosthesis object in the method comprises a zirconia all-ceramic crown manufactured using a sinter-forming process.
According to another aspect of the present invention, the step of fitting and aligning the inverse modeling model and the original design model in the method comprises: and fitting and aligning the reverse modeling model and the original design model with a preset reference object respectively, and registering the reverse modeling model and the original design model to the same Cartesian rectangular coordinate system.
According to another aspect of the present invention, the predetermined reference object in the method is the enlarged design model which inversely performs the three-dimensional enlargement.
According to another aspect of the invention, the region of interest in the method includes the inverse modeling model and the inner crown surface in the original design model.
According to another aspect of the present invention, the step of calculating the scaling factor of the original design model relative to the inverse modeling model in the predetermined dimension direction in the cartesian rectangular coordinate system according to the coordinate data set in the method comprises: setting a plurality of local calculation areas; screening out a plurality of coordinate data of the original design model and the reverse modeling model falling into the local calculation region from the coordinate data set; calculating a local scaling factor of the original design model relative to the reverse modeling model according to the coordinate data for each local calculation region; storing an average of a plurality of the local scaling factors as the scaling factor.
According to another aspect of the invention, the step of calculating local scaling coefficients of the original design model relative to the inverse modeling model from the plurality of coordinate data in the method comprises: calculating a first length average value of the part of the original design model belonging to the local calculation region in the direction of the predetermined dimension, and calculating a second length average value of the part of the reverse modeling model belonging to the local calculation region in the direction of the predetermined dimension; calculating the local scaling factor according to the first average value and the second average value, wherein the calculation formula is as follows: the local scaling factor is the first length average/the second length average.
According to another aspect of the invention, the method further comprises including the centroids of the dental restoration corresponding to the original design model and the inverse modeling model in the plurality of local calculation regions.
According to another aspect of the present invention, the step of calculating the actual shrinkage of the reverse modeling model relative to the original design model in the predetermined dimension direction according to the scaling factor in the method comprises: calculating the actual magnification by taking the zoom ratio coefficient as a compensation coefficient in combination with the existing known magnification parameter; and calculating the actual shrinkage rate according to the actual magnification ratio.
According to another aspect of the invention, said actual magnification in the method is denoted as M1Said known magnification parameter is denoted as M2The scaling coefficient is recorded as F, and the actual shrinkage rate is recorded as S;
the calculation formula of the actual magnification is M1＝M2×F；
The actual shrinkage is calculated by the formula S ═ M (M)1-1)/M1。
The invention provides a method for measuring and calculating the actual shrinkage rate of a dental restoration, which utilizes coordinate data of a plurality of points in an interest area to approximately calculate the actual shrinkage rate of the dental restoration, and compared with the existing manual measurement method for selecting the mark points of anatomical features of the restoration, the method expands the calculation basis from data points into a data set, greatly improves the calculation precision and the calculation efficiency of the actual shrinkage rate, and solves the defects of error defect and lower calculation efficiency caused by the subjectivity of measurement in the existing manual measurement method.
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Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings:
fig. 1 is a schematic flow chart of one embodiment of a method for measuring and calculating the actual shrinkage of a dental restoration according to the present invention;
FIG. 2 is a schematic flow chart diagram of an alternative embodiment of step S600 shown in FIG. 1;
fig. 3 is a schematic diagram for explaining a specific application scenario of step S600 shown in fig. 1.
The same or similar reference numbers in the drawings identify the same or similar elements.
Detailed Description
For a better understanding and explanation of the present invention, reference will now be made in detail to the present invention as illustrated in the accompanying drawings. The invention is not limited to these embodiments. Rather, modifications and equivalents of the invention are intended to be included within the scope of the claims.
It should be noted that numerous specific details are set forth in the following detailed description. It will be understood by those skilled in the art that the present invention may be practiced without these specific details. In the following detailed description of various embodiments, structures and components well known in the art are not described in detail in order to not unnecessarily obscure the present invention.
The invention provides a method for measuring and calculating the actual shrinkage of a dental restoration, as shown in fig. 1, fig. 1 is a flow diagram of a specific embodiment of the method for measuring and calculating the actual shrinkage of a dental restoration according to the invention, the method comprising:
step S100, creating an original design model according to a predetermined dental prosthesis;
s200, carrying out three-dimensional amplification on the original design model based on a Cartesian rectangular coordinate system to obtain an amplified design model;
step S300, manufacturing a prosthesis real object according to the amplified design model;
step S400, performing three-dimensional reconstruction on the prosthesis real object to generate a reverse modeling model corresponding to the prosthesis real object;
step S500, fitting and aligning the reverse modeling model and the original design model, and selecting a coordinate data set of an interest area in the reverse modeling model and the original design model;
step S600, calculating a scaling ratio coefficient of the original design model relative to the reverse modeling model in a predetermined dimension direction in a Cartesian rectangular coordinate system according to the coordinate data set;
step S700, calculating the actual shrinkage rate of the reverse modeling model relative to the original design model in the preset dimension direction according to the scaling ratio coefficient.
Specifically, in the present specification, the term "predetermined dental prosthesis" in step S100 refers to design data corresponding to a prosthesis in the form of an inlay, a denture, a crown, or the like, which is intended to be provided in the dental restoration to match the restoration target effect of the above-described treatment object, against the already existing treatment object such as a tooth defect, a tooth row missing, or the like. In the execution phase of step S100, the dental restoration may not have formed a solid structure yet, and therefore the dental restoration may exist in the form of computer data, said original design model being computer data created using computer aided design software for describing the shape of the dental restoration, and accordingly, the skilled person will understand that said original design model is an editable data object readable by computer aided design software and presented on a suitable computer graphic display device.
Because the selected ceramic material has the characteristic of size shrinkage in sintering and forming in the all-ceramic prosthesis forming process, if the original design model which is not subjected to size adjustment can be directly used for manufacturing the prosthesis according to the design parameters, the sizes of all parts of the manufactured prosthesis finished product are smaller, and the finished product cannot be accurately matched with a repair object in the oral cavity. Therefore, in order to realize shrinkage compensation, a method for adjusting the scaling of a restoration model file is generally adopted at present, that is, the original design model is amplified according to the linear shrinkage rates of the standard test piece in three dimensional directions in a cartesian rectangular coordinate system before digitalized manufacturing so as to compensate the size shrinkage caused by sintering densification. Using the data editability of the original design model, in step S200, a cartesian rectangular coordinate system-based three-dimensional amplification is performed on the original design model to obtain an amplified design model.
Optionally, the sourceThe method for three-dimensional amplification of the initial design model based on the Cartesian rectangular coordinate system comprises the following steps of: setting a mesial-distal direction of the dental restoration to an X direction based on the Cartesian rectangular coordinate system,
setting the gingival direction as Y direction and the buccolingual direction as Z direction; further, respectively carrying out scale up based on the center of mass of the dental restoration on the original design model according to a preset magnification parameter in each direction in the cartesian rectangular coordinate system, specifically, the scale up refers to taking the center of mass of the dental restoration as an extension starting point, carrying out scale up on the original design model at the level of data editing, and extending the overall shape around the center of mass of the dental restoration corresponding to the original design model to the external space according to the preset magnification parameter, thereby obtaining the enlarged design model. Preferably, the magnification parameter is determined by shrinkage of a standard test piece, for example, the shrinkage may be determined by measuring the shrinkage after sintering the standard test piece using a predetermined ceramic material, and if the predetermined ceramic material is zirconia, specifically, according to experiments, the magnification parameters in the X direction and the Y direction range from 1.285 to 1.286, and the magnification parameter in the Z direction ranges from 1.331 to 1.332.
As can be understood by those skilled in the art, although the enlarged design model can be directly used for manufacturing a prosthesis, since the exact actual shrinkage rate of a prosthesis real object manufactured according to the enlarged design model relative to the original design model cannot be determined, the prosthesis manufactured according to the enlarged design model may still have size deviation and cannot completely reach the expected ideal size of the prosthesis. Therefore, the subsequent step of this embodiment is to consider using the real object of the restoration made according to the enlarged design model to approximately calculate its exact actual shrinkage rate relative to the original design model, so as to calibrate the magnification parameter selected when enlarging the original design model into the enlarged design model.
Further, step S300 is executed, that is, a real prosthesis object is manufactured according to the enlarged design model, and a process of manufacturing the real prosthesis object is, for example: firstly, the enlarged design model is subjected to model processing such as slicing and the like, then the enlarged design model is led into ceramic three-dimensional photoetching forming equipment, and then the processes such as blank printing, degreasing sintering and the like are carried out, and finally the restoration real object is obtained. Typically, the prosthesis object comprises a zirconia full-ceramic crown manufactured using a sinter molding process.
In step S400, the real object of the prosthesis may be three-dimensionally reconstructed by means of a processing device such as a scanner to obtain the reverse modeling model corresponding to the real object of the prosthesis, and it will be understood by those skilled in the art that one characteristic of the reverse modeling model is that the external shape and size of the real object of the prosthesis can be accurately recorded.
After the reverse modeling model is generated, in order to approximately calculate the accurate actual shrinkage rate of the reverse modeling model relative to the original design model, step S500 is executed, first, in order to facilitate placing the reverse modeling model and the original design model in the same coordinate space position for overall comparison and reduce errors as much as possible, the reverse modeling model and the original design model are considered to be fitted and aligned. Optionally, when a typical type of reverse engineering three-dimensional measurement software (e.g., geogic) is used to perform the step of fitting and aligning the reverse modeling model and the original design model, according to an operation logic defined by the type of reverse engineering three-dimensional measurement software, the reverse modeling model and the original design model may be set as test objects, another predetermined reference model may be set as a predetermined reference object, and the reverse modeling model and the original design model are respectively fitted and aligned with the predetermined reference object by means of manual registration and best fit, so that the reverse modeling model and the original design model are registered in the same cartesian rectangular coordinate system. The process of fitting an alignment is typically performed based on the predetermined reference object, the inverse modeling model, and the point cloud data of the original design model outline. Preferably, the predetermined reference object is the enlarged design model for performing the three-dimensional enlargement inversely, that is, the enlarged design model is scaled down in each dimension direction of the cartesian rectangular coordinate system based on the centroid of the enlarged design model according to the reciprocal of the magnification parameter corresponding to the enlarged design model in each dimension direction, so that the enlarged design model is reduced to the same size as the original design model. And when the reverse modeling model and the original design model reach a fitting and aligning state, deleting the preset reference object.
Further, in order to avoid the excessive calculation amount and improve the calculation efficiency within the error tolerance range, the local scaling ratio of the reverse modeling model and the original design model is considered to be approximately calculated to calculate the overall scaling ratio of the reverse modeling model and the original design model, so the coordinate data sets of the regions of interest in the reverse modeling model and the original design model are selected in step S500, generally, the regions of interest are the regions where the shrinkage phenomenon of the prosthesis real object described by the reverse modeling model is most obvious in the sintering process, and typically, the regions of interest include the inner crown surface in the reverse modeling model and the original design model. The coordinate data set is selected, for example, by intercepting all available point cloud data contained in the region of interest, and removing noise data that is not worth calculating from the point cloud data, thereby forming the coordinate data set containing coordinate data in an instrument such as an STL format.
In step S600, scaling factor of the original design model relative to the inverse modeling model in predetermined dimensional directions in a cartesian rectangular coordinate system, specifically, the predetermined dimensional directions include an X direction, a Y direction and a Z direction of the cartesian rectangular coordinate system, and the scaling factor of the original design model relative to the inverse modeling model in each of the dimensional directions is independently calculated according to the coordinate data set. An alternative embodiment of step S600 is shown in fig. 2, and fig. 2 is a schematic flow chart of the alternative embodiment of step S600 shown in fig. 1, wherein step S600 includes the following steps:
step S610, setting a plurality of local calculation regions;
step S620, screening out a plurality of coordinate data of the original design model and the reverse modeling model falling into the local calculation region from the coordinate data set;
step S630, calculating a local scaling factor of the original design model relative to the reverse modeling model according to the plurality of coordinate data for each local calculation region;
in step S640, an average value of the plurality of local scaling coefficients is stored as the scaling coefficient.
Specifically, the specific manner of setting the local calculation regions in step S610 may be implemented by setting a calculation boundary parameter in the region of interest, and since the model included in the region of interest may have an irregular shape, the positions and the number of the local calculation regions in the cartesian rectangular coordinate system may be determined according to the specific situation of the region of interest, which is not limited by the present invention.
In step S620, the processed data object is a subset of the coordinate data set, that is, the data object is a plurality of coordinate data in which the original design model and the reverse modeling model fall into the local calculation region, which are screened from the coordinate data set. Further, in step S630, for each of the local calculation regions, a local scaling factor of the original design model relative to the reverse modeling model is calculated according to the coordinate data, where the local scaling factor may reflect a scaling of the original design model relative to the reverse modeling model in the corresponding local calculation region, but when a model included in the region of interest has a more irregular shape, the overall scaling of the original design model relative to the reverse modeling model in the region of interest is not sufficiently reflected, and therefore, further considering performing step S640, an average value of a plurality of the local scaling factors is stored as the scaling factor.
It should be particularly noted that obtaining the plurality of coordinate data machines in step S620 refers to a final executed result state, and does not limit or imply that step S630 subsequent to step S620 must be implemented after step S620 is completely executed, and on the contrary, in the case that a plurality of the local calculation regions exist, step S620 and step S630 may be executed in parallel.
In general, when setting the plurality of local calculation regions, it is necessary to consider whether the positions and the numbers of the plurality of local calculation regions satisfy the error control requirement for calculating the scaling factor. More preferably, to reduce errors, the centroids of the dental restoration to which the original design model and the inverse modeling model correspond are contained within the plurality of local calculation regions.
In an exemplary embodiment of step S630, it comprises the following steps:
firstly, calculating a first length average value of a part of the original design model, which belongs to the local calculation region, in the direction of the preset dimension, and calculating a second length average value of the part of the reverse modeling model, which belongs to the local calculation region, in the direction of the preset dimension;
then, the local scaling factor is calculated according to the first average value and the second average value, and the calculation formula is as follows: the local scaling factor is the first length average/the second length average.
To better illustrate the steps included in the flowchart shown in fig. 2, please refer to fig. 3, fig. 3 is a schematic diagram illustrating a specific application scenario of step S600 shown in fig. 1, and more particularly, in conjunction with fig. 3 and the foregoing description of fig. 2, the principle of how to calculate the scaling factor in the X direction in the cartesian rectangular coordinate system shown in fig. 3 can be easily understood.
Referring to fig. 3, the local model placed in the cartesian orthogonal coordinate system is a region of interest selected after the original design model and the inverse modeling model are fitted and aligned, the parameter dmin _ X and the parameter dmax _ X set in the X direction are used to mark a calculation region in the X direction, and a cubic region is divided from the local model by combining the set parameter xdirYR, parameter xdirYL, parameter xdirZR, and parameter xdirZL on the YOZ half-plane, and by means of the above parameters, the cubic region is further divided, so that the scaling factor of the original design model relative to the inverse modeling model in the local model in the X direction can be approximately calculated. The further splitting may, for example, divide the cubic region into a plurality of local cubes, and record the side length of the local cube as a parameter sideliden, for example, the value of the parameter sideliden shown in fig. 3 is 1.
Based on the foregoing description of fig. 3, in a typical algorithm, the step of approximately calculating the scaling factor of the original design model relative to the inverse modeling model in the X direction can be implemented as follows: for the two data models, i.e., the original design model and the reverse modeling model, respectively, calculating the average value of the X coordinates of all points with X coordinate values smaller than dmin _ X and the average value of the X coordinates of all points with X coordinate values larger than dmax _ X, and then assigning the two sets of average values to the original design model as X1_ ref and X2_ ref, the two sets of average values to the reverse modeling model as X1_ test and X2_ test, and the scaling ratio coefficient as xRatio, the xRatio is known to be (X2_ ref-X1_ ref)/(X2_ test-X1_ test).
Similarly, for the Y direction or the Z direction in the cartesian rectangular coordinate system, the scaling factor of the original design model relative to the inverse modeling model may also be obtained according to the above algorithm, and is not described herein again.
With continued reference to fig. 1, after calculating the scaling factor of the original design model relative to the reverse modeling model in the predetermined dimension direction in step S600, step S700 is considered to be executed, that is, the actual shrinkage rate of the reverse modeling model relative to the original design model in the predetermined dimension direction is calculated according to the scaling factor. Typically, the known magnification parameter may be modified taking into account the scaling factor as a compensation factor. In a preferred embodiment, step S700 further comprises: and calculating the actual magnification by using the zoom ratio coefficient as a compensation coefficient in combination with the existing known magnification parameter, and further calculating the actual shrinkage rate according to the actual magnification.
Specifically, if the actual magnification is recorded as M1Said known magnification parameter is denoted as M2The scaling coefficient is recorded as F, and the actual shrinkage rate is recorded as S;
the calculation formula of the actual magnification is M1＝M2×F；
The actual shrinkage is calculated by the formula S ═ M (M)1-1)/M1。
It is noted that while the operations of the method of the present invention are depicted in the drawings in a particular order, this is not intended to require or imply that these operations must be performed in this particular order, or that all of the illustrated operations must be performed, to achieve desirable results. Rather, the steps depicted in the flowcharts may change the order of execution. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions.
The part of the method for measuring and calculating the actual shrinkage of a dental restoration provided by the present invention, which involves software logic, may be implemented using a programmable logic device, or may be implemented as a computer program product for causing a computer to execute the method for demonstration. The computer program product includes a computer-readable storage medium having computer program logic or code portions embodied therein for performing the various steps described above with respect to the portions of software logic. The computer-readable storage medium may be a built-in medium installed in the computer or a removable medium detachable from the computer main body (e.g., a hot-pluggable storage device). The built-in medium includes, but is not limited to, rewritable nonvolatile memories such as RAM, ROM, and hard disk. The removable media include, but are not limited to: optical storage media (e.g., CD-ROMs and DVDs), magneto-optical storage media (e.g., MOs), magnetic storage media (e.g., magnetic tapes or removable hard disks), media with a built-in rewritable non-volatile memory (e.g., memory cards), and media with a built-in ROM (e.g., ROM cartridges).
Those skilled in the art will appreciate that any computer system having suitable programming means will be capable of executing the steps of the method of the invention as embodied in a computer program product. Although most of the specific embodiments described in this specification focus on software routines, alternative embodiments for implementing the methods provided by the present invention in hardware are also within the scope of the invention as claimed.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are, therefore, to be considered as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it will be obvious that the term "comprising" does not exclude other elements, units or steps, and the singular does not exclude the plural. A plurality of components, units or means recited in the claims may also be implemented by one component, unit or means in software or hardware.
The invention provides a method for measuring and calculating the actual shrinkage rate of a dental restoration, which utilizes coordinate data of a plurality of points in an interest area to approximately calculate the actual shrinkage rate of the dental restoration, and compared with the existing manual measurement method for selecting the mark points of anatomical features of the restoration, the method expands the calculation basis from data points into a data set, greatly improves the calculation precision and the calculation efficiency of the actual shrinkage rate, and solves the defects of error defect and lower calculation efficiency caused by the subjectivity of measurement in the existing manual measurement method.
The above-disclosed embodiments are merely exemplary of the present invention, which should not be construed as limiting the scope of the invention, but rather as equivalent variations of the invention are covered by the appended claims.
Claims (12)
1. A method for measuring and calculating an actual shrinkage of a dental restoration, the method comprising:
creating an original design model from a predetermined dental restoration;
performing three-dimensional amplification on the original design model based on a Cartesian rectangular coordinate system to obtain an amplified design model;
manufacturing a prosthesis real object according to the enlarged design model;
carrying out three-dimensional reconstruction on the prosthesis real object to generate a reverse modeling model corresponding to the prosthesis real object;
fitting and aligning the reverse modeling model and the original design model, and selecting a coordinate data set of an interest area in the reverse modeling model and the original design model;
calculating a scaling factor of the original design model relative to the reverse modeling model in a predetermined dimensional direction in a Cartesian rectangular coordinate system according to the coordinate data set;
and calculating the actual shrinkage rate of the reverse modeling model relative to the original design model in the preset dimension direction according to the scaling ratio coefficient.
2. The method of claim 1, wherein the step of performing a cartesian rectangular coordinate based three-dimensional magnification of the original design model comprises:
setting a mesial-distal direction of the dental restoration to an X direction based on the Cartesian rectangular coordinate system,
setting the gingival direction as Y direction and the buccolingual direction as Z direction;
and carrying out proportional amplification based on the center of mass of the dental prosthesis on the original design model according to a preset amplification factor parameter in each direction in the Cartesian rectangular coordinate system.
3. The method of claim 2, wherein:
the magnification parameter is determined by the shrinkage of the standard test piece.
4. The method of claim 1, wherein:
the prosthesis real object comprises a zirconia full-ceramic dental crown manufactured by using a sintering forming process.
5. The method of claim 1, wherein the step of fitting and aligning the inverse modeling model and the original design model comprises:
and fitting and aligning the reverse modeling model and the original design model with a preset reference object respectively, and registering the reverse modeling model and the original design model to the same Cartesian rectangular coordinate system.
6. The method of claim 5, wherein:
the predetermined reference object is the enlarged design model that inversely performs the three-dimensional enlargement.
7. The method of claim 1, wherein:
the region of interest includes the inverse modeling model and the inner crown surface in the original design model.
8. The method of claim 1, wherein the step of calculating scaling factors of the original design model relative to the inverse modeling model in predetermined dimensional directions in a cartesian rectangular coordinate system from the set of coordinate data comprises:
setting a plurality of local calculation areas;
screening out a plurality of coordinate data of the original design model and the reverse modeling model falling into the local calculation region from the coordinate data set;
calculating a local scaling factor of the original design model relative to the reverse modeling model according to the coordinate data for each local calculation region;
storing an average of a plurality of the local scaling factors as the scaling factor.
9. The method of claim 8, wherein the step of calculating local scale coefficients of the original design model relative to the inverse modeling model from the plurality of coordinate data comprises:
calculating a first length average value of the part of the original design model belonging to the local calculation region in the direction of the predetermined dimension, and calculating a second length average value of the part of the reverse modeling model belonging to the local calculation region in the direction of the predetermined dimension;
calculating the local scaling factor according to the first average value and the second average value, wherein the calculation formula is as follows:
the local scaling factor is the first length average/the second length average.
10. The method of claim 8, wherein:
the centroids of the dental restorations to which the original design model and the inverse modeling model correspond are contained within the plurality of local calculation regions.
11. The method of claim 1, wherein the step of calculating an actual shrinkage of the reverse modeling model relative to the original design model in the predetermined dimension direction according to the scaling factor comprises:
calculating the actual magnification by taking the scaling factor as a compensation factor by combining the existing known magnification parameter;
and calculating the actual shrinkage rate according to the actual magnification ratio.
12. The method of claim 11, wherein:
the actual magnification is recorded as M1Said known magnification parameter is denoted as M2The scaling coefficient is recorded as F, and the actual shrinkage rate is recorded as S;
the calculation formula of the actual magnification is M1＝M2×F；
The actual shrinkage is calculated by the formula S ═ M (M)1-1)/M1。
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