CN107357949B - Technological data optimization method of shell-shaped dental instrument manufacturing process based on hot-pressing film forming technology - Google Patents

Technological data optimization method of shell-shaped dental instrument manufacturing process based on hot-pressing film forming technology Download PDF

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CN107357949B
CN107357949B CN201710286752.2A CN201710286752A CN107357949B CN 107357949 B CN107357949 B CN 107357949B CN 201710286752 A CN201710286752 A CN 201710286752A CN 107357949 B CN107357949 B CN 107357949B
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shell
digital model
process data
dental instrument
model
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CN107357949A (en
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周可拓
黄雷
田杰
李华敏
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Wuxi Ea Medical Instruments Technologies Ltd
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Wuxi Ea Medical Instruments Technologies Ltd
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C7/00—Orthodontics, i.e. obtaining or maintaining the desired position of teeth, e.g. by straightening, evening, regulating, separating, or by correcting malocclusions
    • A61C7/002—Orthodontic computer assisted systems
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C19/00—Dental auxiliary appliances
    • A61C19/06—Implements for therapeutic treatment
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C7/00—Orthodontics, i.e. obtaining or maintaining the desired position of teeth, e.g. by straightening, evening, regulating, separating, or by correcting malocclusions
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/08—Thermal analysis or thermal optimisation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/18—Manufacturability analysis or optimisation for manufacturability

Abstract

One aspect of the present application provides a method for optimizing process data of a shell-shaped dental instrument manufacturing process based on a hot-pressing film forming technique, including: acquiring a first set of process data of a shell-shaped dental instrument manufacturing process based on a hot-pressing film forming technology; calculating a first shell-like dental instrument geometry based on the first set of process data; and modifying the first set of process data based on the first shell-like dental instrument geometry to at least partially offset deviations of the first shell-like dental instrument geometry from the design caused by elasto-plastic deformation in the shell-like dental instrument fabrication process, resulting in a second set of process data.

Description

Technological data optimization method of shell-shaped dental instrument manufacturing process based on hot-pressing film forming technology
Technical Field
The present application relates generally to a method for computer-aided optimization of process data for a shell-like dental instrument manufacturing process based on hot-pressing film forming technology.
Background
Shell-like orthodontic appliances based on polymeric materials are becoming more and more popular due to their advantages of aesthetic appearance, convenience, and ease of cleaning.
Currently, shell-shaped dental appliances (including but not limited to orthodontic appliances and retainers) are typically manufactured based on a hot-press film forming process. Due to the existence of complex thermal coupling effect, the dynamic distribution of the temperature field in the hot-pressing film forming process directly influences the total internal stress (namely residual stress) level of the shell-shaped dental appliance after cooling and shaping, and when the shell-shaped dental appliance is cut off from the surrounding material, partial residual stress in the material is released, the original stress balance state is broken, and the elastoplastic deformation is caused. Therefore, the expansion spring back deformation of the shell-like dental instrument is inevitable. For a shell-like orthodontic appliance, this can cause the appliance to exert forces that are not in accordance with the design forces and thus not as effective as desired. For a shell-like dental retainer, this can cause the retainer to exert unnecessary force on the dentition, thereby altering the otherwise ideal tooth layout.
In view of the above, there is a need to provide a method for optimizing process data of a shell-shaped dental instrument manufacturing process based on a hot-pressing film forming process to solve the above problems.
Disclosure of Invention
One aspect of the present application provides a method for optimizing process data of a shell-shaped dental instrument manufacturing process based on a hot-pressing film forming technique, including: acquiring a first set of process data of a shell-shaped dental instrument manufacturing process based on a hot-pressing film forming technology; calculating a first shell-like dental instrument geometry based on the first set of process data; and modifying the first set of process data based on the first shell-like dental instrument geometry to at least partially offset deviations of the first shell-like dental instrument geometry from the design caused by elasto-plastic deformation in the shell-like dental instrument fabrication process, resulting in a second set of process data.
In some embodiments, the method for optimizing process data of the shell-shaped dental instrument manufacturing process based on the hot-pressing film forming technology further comprises: fabricating a shell-shaped dental appliance based on the second set of process data.
In some embodiments, the modification to the first set of process data is a modification to at least one of the following process data: the method comprises the following steps of forming a convex mold, wherein the convex mold is fixed on a base in the film pressing process.
In some embodiments, the modification to the first set of process data is primarily to at least partially offset a deviation of an arch width of the first shell-like dental instrument geometry from a design arch width.
In some embodiments, a shell-like dental instrument fabrication process is simulated using a multi-mesh model calculation method based on the first set of process data to obtain a first shell-like dental instrument multi-mesh digital model that includes the first shell-like dental instrument geometry.
In some embodiments, the method for optimizing process data of the shell-shaped dental instrument manufacturing process based on the hot-pressing film forming technology further comprises: acquiring a multi-grid digital model of a jaw, wherein the multi-grid digital model of the jaw comprises a multi-grid digital model of a plurality of teeth of the jaw, a periodontal ligament multi-grid digital model and an alveolar bone multi-grid digital model; and wearing the first shell-shaped dental instrument multi-grid digital model on the multi-grid digital model of the dental jaw, and calculating the model by using a multi-grid model calculation method to obtain a calculation result comprising at least one of the following components: a new layout of the multi-mesh digital model of the plurality of teeth achieved under the action of the multi-mesh digital model of the first shell-like dental appliance; wherein the modification to the first set of process data is based on the calculated results.
In some embodiments, the periodontal ligament multi-grid digital model encapsulates a root portion of the multi-grid digital model of the plurality of teeth, and the alveolar bone multi-grid digital model encapsulates the periodontal ligament multi-grid digital model.
In some embodiments, the periodontal ligament multi-grid digital model and the multi-grid digital model of the plurality of teeth have limited relative degrees of freedom of nodes at their interfaces.
In some embodiments, the periodontal ligament multi-grid digital model and the multi-grid digital model of the plurality of teeth share a node on the interface.
In some embodiments, the periodontal ligament multi-grid digital model and the alveolar bone multi-grid digital model are constrained in relative degrees of freedom of nodes at the interface between the two.
In some embodiments, the periodontal ligament multi-grid digital model and the alveolar bone multi-grid digital model share a node on the interface.
In some embodiments, after the first shell-like dental instrument multi-mesh digital model is worn on the multi-mesh digital model of the dental jaw and the fluctuation of the interaction force between the two is smaller than a predetermined value and is kept for a predetermined time period, the layout of the multi-mesh digital model of the plurality of teeth at that time is taken as the new layout.
In some embodiments, the modification to the first set of process data is based on a comparison of a new layout and a design layout of the multi-grid digital model of the plurality of teeth.
In some embodiments, the multi-mesh digital model is a finite element model and the multi-mesh model calculation method is a finite element analysis method.
Drawings
The above and other features of the present application will be further explained with reference to the accompanying drawings and detailed description thereof. It is appreciated that these drawings depict only several exemplary embodiments in accordance with the disclosure and are therefore not to be considered limiting of its scope. The drawings are not necessarily to scale and wherein like reference numerals refer to like parts, unless otherwise specified.
FIG. 1 is a schematic flow chart of a process data optimization method for a shell-like dental instrument fabrication process based on hot-pressing film formation in one embodiment of the present application;
FIG. 2 is a schematic flow chart of a finite element analysis method of a shell-like dental instrument fabrication process based on a hot-pressing film forming technique in one embodiment of the present application; and
fig. 3 is a schematic flow chart of a method of verifying an orthodontic appliance based on computer finite element analysis in one embodiment of the present application.
Detailed Description
The following detailed description refers to the accompanying drawings, which form a part of this specification. The exemplary embodiments mentioned in the description and drawings are for illustrative purposes only and are not intended to limit the scope of the present application. Those skilled in the art, having benefit of this disclosure, will appreciate that many other embodiments can be devised which do not depart from the spirit and scope of the present application. It should be understood that the aspects of the present application, as described and illustrated herein, may be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are within the scope of the present application.
Referring to fig. 1, a schematic flow chart of a process data optimization method 100 for a shell-shaped dental appliance manufacturing process based on a hot-pressing film forming technique according to an embodiment of the present application is shown.
In 101, a first set of process data is acquired.
The first set of process data is process data of a shell-shaped dental appliance manufacturing process based on a hot-pressing film forming technology, and may include: a digital model of the male mold, material properties of the male mold, thickness of the diaphragm, material properties of the diaphragm, heating temperature of the diaphragm, and pressure of the squeeze film, among others.
In 103, a first shell-like dental instrument geometry is calculated based on the first set of process data.
In one embodiment, a finite element analysis of the manufacturing process of the shell-like dental instrument may be performed using a finite element method based on the first set of process data to obtain a first shell-like dental instrument finite element model comprising data representing the geometry of the shell-like dental instrument. The geometry of the shell-like dental instrument comprised by the first shell-like dental instrument finite element model may be referred to as the first shell-like dental instrument geometry.
Referring to FIG. 2, a schematic flow chart diagram of a finite element analysis method 200 of a shell-like dental instrument fabrication process in one embodiment of the present application is schematically illustrated. In one embodiment, the method may be used to perform a finite element analysis of a manufacturing process of a shell-like dental instrument based on the first set of process data obtained in 101 to obtain a finite element model of the first shell-like dental instrument.
In some embodiments, the finite element analysis may be performed in steps of film heating, film lamination, die cooling, and die cutting to simplify the calculations.
In one embodiment, the finite element analysis may be performed using ANSYS LS-DYNA software. However, it is understood that in addition to this, finite element analysis of the shell-like dental instrument fabrication process may be performed using any other suitable software, such as ANSYS, NASTRAN, CATIA, FEPG, SciFEA, JiFEX, KMAS, FELAC, DYNAFORM, LS-DYNA, ABAQUS, HyperWorks, etc.
In 201, process data is acquired.
In some embodiments, the process data may include: a finite element model of the diaphragm, a finite element model of the dental cast, a finite element model of the heating device, a finite element model of the forming base, a forming pressure, a female die cooling temperature, and the like. In the present application, in most cases, the "dental mold" and the "male mold" can be substituted for each other. Wherein, in the process of the film pressing process, the dental cast is fixed on the forming base.
In some embodiments, the finite element model of the diaphragm may include physical parameters of the diaphragm material, such as density, poisson's ratio, modulus of elasticity, yield strength, thermal conductivity, specific heat capacity, coefficient of linear expansion, viscoelastic parameters, and the like. Some physical parameters of the membrane may change with temperature, for example, table 1 below shows the temperature-dependent parameters of one membrane material in one embodiment of the present application.
Temperature of Poisson ratio Modulus of elasticity Yield strength
23℃ 0.38 2200MPa 53MPa
40℃ 0.38 1510MPa 50.2MPa
60℃ 0.40 1348MPa 39.6MPa
70℃ 0.41 1136MPa 29.5MPa
TABLE 1
In some embodiments, a geometric model of the diaphragm may be defined directly in the finite element simulation system, i.e., its two-dimensional shape is defined and given a certain thickness, and then mesh-divided based on the geometric model to obtain a finite element model of the diaphragm.
In other embodiments, a file in a format such as IGES, STP or STL of the diaphragm may be directly introduced as the geometric model.
In one embodiment, to simplify the calculation, the shell cells may be sampled to mesh the diaphragm.
The finite element model of the heating device may include physical parameters of the heating device, such as emissivity, convective heat transfer coefficient, etc.
In some embodiments, a file in the format of IGES, STP or STL of the heating device may be directly imported as its geometric model, and then mesh-divided based on the geometric model to obtain a finite element model of the heating device.
In some embodiments, the finite element model of the dental model may include physical parameters of the dental model material, such as emissivity, convective heat transfer coefficient, and the like.
In some embodiments, a file in an IGES, STP, STL, or the like format of the dental model may be directly imported as a geometric model thereof, and then mesh division is performed based on the geometric model to obtain a finite element model of the dental model.
In some embodiments, an adaptive approach may be used to mesh the cast such that the meshing where the geometric curvature is larger is finer than the meshing where the geometric curvature is smaller.
In some embodiments, the finite element model of the shaped base may include physical parameters of the shaped base, such as specific heat capacity, thermal conductivity, and convective heat transfer coefficient, among others.
In some embodiments, a file in an IGES, STP, STL, or the like format of the forming base may be directly imported as a geometric model thereof, and then mesh division is performed based on the geometric model to obtain a finite element model of the forming base.
In 203, a film heating simulation is performed.
In one embodiment, the heating of the membrane may be subjected to a finite element analysis based on the finite element model of the membrane and the finite element model of the heating device to obtain a finite element model of the heated membrane.
In some embodiments, boundary conditions for the film heating simulation may include: limiting the freedom degree of the edge node of the diaphragm; the relative position relationship between the heating device and the membrane; and the temperature of the heating device, etc.
In some embodiments, the membrane is always held by the membrane clamp to the pressing device during the heating or even the lamination process, so that the point where the membrane contacts the inside of the membrane clamp can be taken as an edge node and its degree of freedom is limited.
In some embodiments, to simplify the simulation operation, it may be assumed that the heating device is constant temperature.
In still other embodiments, the simulation of the heating of the membrane may also include a simulation of the heating device warming process and temperature fluctuations.
In some embodiments, the finite element model of the heated diaphragm may include a temperature field, a stress field, and a deformation condition of the heated diaphragm.
In some embodiments, the ambient initial temperature field may be used as one of the initial conditions for the membrane heating finite element simulation.
Because many commercial software integrate basic dynamics simulation operation module at present, and the simulation operation mode can vary widely according to specific situations and requirements, the specific operation equation is not explained here. For the specific implementation of the film heating simulation, reference may be made to "finite element analysis and simulation research of temperature field in the heating process of polymer sheet" published by white reflection.
In 205, a lamination molding simulation is performed.
In one embodiment, the die press may be subjected to finite element analysis based on the finite element model of the heated diaphragm and the finite element model of the dental model obtained in 203 to obtain a finite element model of the female die before cooling.
Because the film pressing forming process generally only needs a few seconds, in order to simplify the operation, the temperature field of the film sheet can be assumed to be kept unchanged in the whole film pressing forming process.
In some embodiments, the boundary conditions of the lamination molding simulation may include: limiting the degree of freedom of the diaphragm edge node; molding pressure; the geometry of the dental cast; and the position of the cast.
At 207, a negative mold cooling simulation is performed.
In one embodiment, the cooling of the female mold may be subjected to a finite element analysis based on the finite element model of the female mold before cooling, the finite element model of the dental mold, and the finite element model of the forming base obtained in 205, to obtain a finite element model of the female mold after cooling.
In one embodiment, to simplify the calculation, the effect of the dental cast and the forming base on the cooling of the female mold may be mainly considered in the female mold cooling simulation, and the effect of other parts of the shell-like dental apparatus manufacturing device on the cooling of the female mold is ignored.
In some embodiments, the negative mold cooling simulation boundary conditions may include: limiting the freedom degree of the edge node of the diaphragm; and cooling the ambient temperature.
In one embodiment, the finite element model of the cooled cavity block may include the cooled cavity block geometry, thickness distribution, and stress distribution.
Since heat conduction and convection heat transfer play a dominant role during the cavity cooling process, while heat radiation is of a more limited role, in order to simplify the operation, in one embodiment, the effects of heat radiation can be ignored when performing the cavity cooling finite element analysis.
At 209, a negative die cut simulation is performed.
In one embodiment, the die cut may be subjected to a finite element analysis based on the finite element model of the cooled die and the cut line obtained in 207 to obtain a finite element model of the shell-like dental appliance.
In one embodiment, the trim line includes a boundary line of the shell-like dental implement.
In some embodiments, the trim line may be defined manually by the user. In still other embodiments, the trim line may also be automatically defined by the computer according to certain rules.
In some embodiments, the trim line may also include the boundary line of other structures on the shell-like dental implement, such as cutouts that mate with attachments on the teeth.
In some embodiments, the negative die-cut simulation boundary conditions may include degrees of freedom that limit fiducials.
In some embodiments, the reference points may be selected as close as possible to each other, for example, three reference points may be selected on the female mold corresponding to the same tooth.
In some embodiments, the finite element model of the shell dental appliance may include the geometry, stress distribution, and thickness distribution of the shell dental appliance.
Based on the first set of process data obtained in 101, a first shell dental instrument geometry may be obtained using a finite element analysis method 200 of a shell dental instrument fabrication process in one embodiment of the present application.
Referring again to fig. 1, at 105, the first set of process data is modified based on the first shell-shaped dental instrument geometry to at least partially offset deviations between the first shell-shaped dental instrument geometry and the design caused by elasto-plastic deformation or rebound deformation in the hot-press film forming process to obtain a second set of process data. "design" refers to an ideal shell-like dental appliance designed to closely follow the intended tooth layout.
In one embodiment, the modification to the first set of process data is primarily to at least partially offset a deviation of the bow width of the first shell-like dental instrument geometry from the design bow width. "design arch width" refers to the arch width of an ideal shell-like dental appliance designed to closely follow the intended tooth layout.
In one embodiment, the arch width may be the linear distance from the cusp of one canine tooth to the cusp of another canine tooth. For a shell-like dental instrument, the arch width may be the linear distance from the location corresponding to the cusp of one canine tooth to the location corresponding to the cusp of another canine tooth.
In yet another embodiment, the arch width may be a linear distance from a mesial buccal cusp of one first molar to a mesial buccal cusp of another first molar. For a shell-like dental appliance, the arch width may be a linear distance from a location corresponding to a mesial-buccal cusp of one first molar to a location corresponding to a mesial-buccal cusp of another first molar.
In yet another embodiment, the arch width may be a linear distance from a distal buccal cusp of one second molar to a distal buccal cusp of another second molar. For a shell-like dental appliance, the arch width may be a linear distance from the location of the distal buccal cusp for one second molar to the location of the distal buccal cusp corresponding to another second molar.
In one embodiment, the arch width of the first shell dental appliance finite element model obtained in the shell dental appliance fabrication process finite element analysis method 200 may be compared to the design arch width and process data of the first set of process data relating to the arch width of the shell dental appliance may be modified based on the comparison to obtain a second set of process data such that the arch width of the shell dental appliance fabricated based on the second set of process data is closer to the design arch width.
In one embodiment, means of varying the arch width of the shell-like dental appliance include, but are not limited to: varying the arch width (or arch) of the dental cast, varying the initial temperature of the dental cast during the lamination process, varying the initial temperature of the base during the lamination process, varying the pressure-time profile during the lamination process, and any combination thereof.
It is understood that changing the arch width of the cast can directly change the arch width of the shell-like dental appliance.
The initial temperature of the dental model and the base in the film pressing process is changed (for example, the initial temperature is preheated), so that the deformation influence between the diaphragm and the dental model caused by temperature reduction can be reduced.
The pressure-time curve in the film pressing process is changed, so that the pressure relief process is relatively smooth, and the rebound deformation caused by sudden pressure relief can be reduced to a certain extent.
The above example is based on comparing the calculated bow width/bow of the shell-like dental instrument with the design bow width/bow, and adjusting and optimizing the process data. In a further embodiment, the process data can also be modified and optimized in accordance with the calculated movement effect on the teeth.
For example, in one embodiment, the effect of the shell dental appliance moving teeth may be calculated based on the first shell dental appliance finite element model obtained in the finite element analysis method 200 of the shell dental appliance fabrication process and the process data modified based thereon to change the arch width of the shell dental appliance.
Referring to fig. 3, a schematic flow chart of a method 300 for verifying orthodontic appliances based on computer finite element analysis in one embodiment of the present application is shown.
In 301, a finite element model of a dental jaw is acquired.
The dental jaw can be either the upper jaw or the lower jaw.
The dental jaw may be a full or partial dental jaw depending on the appliance to be tested.
The finite element models of the jaw may include finite element models of a plurality of teeth of the dentition, a periodontal ligament finite element model, and an alveolar bone finite element model.
In one embodiment, a geometric model of the teeth, periodontal ligament, and alveolar bone of a patient's jaw can be obtained by CT scanning.
In the case of performing correction using a shell-shaped orthodontic appliance (e.g., an invisible appliance), the correction generally needs to be divided into a plurality of successive stages (e.g., 20 to 40 successive stages), each stage corresponding to one shell-shaped orthodontic appliance. However, the jaw of each stage is different, for example, the arrangement of teeth is different in each stage, and the orientation of the cavity of alveolar bone for accommodating the tooth root may be different in each stage. In order to verify a shell-like orthodontic appliance at a certain stage, it is necessary to obtain a geometric model of the jaw at the beginning of the stage.
In one embodiment, the periodontal membrane thickness is assumed to be constant and fixed relative to the root and alveolar bone interface, thus allowing the orientation of the alveolar bone cavity that receives the root to be determined based on the current tooth placement. If the outer contour of the alveolar bone is not changed, a geometric model of the dental jaw can be obtained. If the layout of the teeth at the beginning of each stage is assumed to be consistent with the design, the geometric model of the jaw at the beginning of any stage can be obtained by the method. Methods for obtaining the tooth layout at each stage are well known in the art and will not be described herein.
In a further embodiment, the geometric model of the jaws at the end of a certain stage obtained by analyzing the effect of the shell-like orthodontic appliance in a finite element method can be used as the geometric model of the jaws at the beginning of the next stage.
In one embodiment, the thickness of the periodontal ligament can be set empirically to obtain a geometric model of the periodontal ligament. For example, the thickness of the periodontal ligament may be set to 0.25 to 0.38 mm.
After the geometric model of the dental jaw is obtained, it can be gridded.
In one embodiment, the material model of the teeth may be an elastic plastic or rigid material model.
If an elastic-plastic material model is adopted, the tooth deformation is small in the correction process, and the strain amount of plastic deformation cannot be achieved, so that the plastic deformation can not be considered. In one example, the modulus of elasticity of the material model of the tooth may be set to a value between 15000 and 25000MPa, such as 20000 MPa. In one example, the Poisson's ratio of the material model of the teeth may be set to a value between 0.15 and 0.4, such as 0.3.
The properties of periodontal ligament mainly include almost incompressible. In one embodiment, the modulus of elasticity of the material model of the periodontal ligament may be set to a value between 0.05 and 70MPa, such as 0.68 MPa. When the poisson's ratio is 0.5, the material is incompressible. In one example, the Poisson's ratio of the material model of the periodontal ligament can be set to a value between 0.4 and 0.49, such as 0.45, making it almost incompressible.
In one embodiment, the material model of the alveolar bone may employ an elastic-plastic or rigid material model, and plastic deformation may not be considered, similar to the case of teeth.
In one example, the modulus of elasticity of the material model of the alveolar bone may be set to a value between 12000 and 15000MPa, such as 13700 MPa. In one example, the Poisson's ratio of the material model of the alveolar bone may be set to a value between 0.2 and 0.4, such as 0.3.
In the course of actual orthodontic treatment, alveolar bone at the orthodontic tooth may be osteoclastically broken. Therefore, when one correction stage is completed, the shell-shaped orthodontic appliance worn on the dentition is less stressed, and accordingly, the shell-shaped orthodontic appliance is less deformed. Since the finite element model of alveolar bone in one embodiment of the present application does not include the characteristic of osteoclastogenesis, when the finite element model of the shell-shaped orthodontic appliance is worn on the finite element model of the jaw and reaches equilibrium, the stress of the finite element model of the shell-shaped orthodontic appliance is large, and accordingly, the deformation of the finite element model of the shell-shaped orthodontic appliance is large. That is, this may cause a gap between the corrected tooth layout obtained through finite element analysis and the actual corrected tooth layout.
In one example, in order to compensate for the deviation due to the fact that the alveolar bone finite element model does not have the osteoclastogenesis characteristic to some extent, the elastic modulus of the material of the alveolar bone finite element model may be reduced to be lower than the actual elastic modulus of the alveolar bone.
In one embodiment, to simplify the calculation, the relative freedom of the contact surface of the finite element model of the tooth and the finite element model of the periodontal ligament can be constrained, i.e. the contact surface of the tooth root and the periodontal ligament is set not to be displaced relatively. In one embodiment, the contact surfaces of the finite element model of the tooth and the finite element model of the periodontal ligament may be made to share a node, thereby limiting the relative degrees of freedom of the two contact surfaces.
Similarly, in one embodiment, to simplify the calculations, the relative degrees of freedom of the interface of the alveolar bone finite element model and the periodontal ligament finite element model can be constrained, i.e., the interface of the alveolar bone and the periodontal ligament is set to be free from relative displacement. In one embodiment, the contact surfaces of the bone finite element model and the periodontal ligament finite element model can share a node, thereby limiting the relative freedom of the contact surfaces.
Based on the geometric models, the material models and the constraint conditions of the teeth, the periodontal ligament and the alveolar bone, the finite element model of the jaw can be obtained.
In 303, a finite element model of the orthodontic appliance is obtained.
In one embodiment, a finite element model of the orthodontic appliance may be obtained based on the finite element analysis method 200 of the shell-like dental appliance fabrication process.
In 305, a finite element model of the orthodontic appliance is worn on the finite element model of the jaw and subjected to a finite element analysis.
In one embodiment, the finite element model of the orthodontic appliance is worn on the finite element model of the jaw, that is, the finite element model of the jaw and the finite element model of the orthodontic appliance are constrained and combined, and the problem of rigid-flexible coupling dynamic contact as a nonlinear structure can be solved.
In one embodiment, the degrees of freedom of the finite element models of the teeth may be restricted first in the finite element models of the jaws, and the restrictions on the degrees of freedom of the finite element models of the teeth may be released after the finite element model of the orthodontic appliance is worn on the finite element models of the jaws. This simplifies the calculation of wearing a finite element model of an orthodontic appliance on a finite element model of the jaw.
Taking the shell-shaped orthodontic appliance as an example, in one embodiment, three points which are not on the same straight line can be randomly selected on the position of the finite element model of the shell-shaped orthodontic appliance corresponding to each tooth, and the three points are set to be in rigid connection, namely, six degrees of freedom of each connected node are completely synchronous and have no relative deformation with each other. This may make the calculation of the finite element analysis more stable.
Then, one can randomly select a point (which is not present in the penetrating interference of the tooth) on the site of the finite element model of the shell-like orthodontic appliance corresponding to each tooth, apply full constraint of six degrees of freedom to the points, or define only the rotational degrees of freedom of the points in all directions. This may also make the calculation of the finite element analysis more stable.
The mutual position of the inner surface of the finite element model of the shell-like orthodontic appliance and the outer surface of the finite element model of the tooth may then be defined in a manner of initial conditions, for example, by performing a preliminary form fit using a best fit alignment algorithm, or by moving the inner surface of the finite element model of the shell-like orthodontic appliance to the outer surface of the finite element model of the tooth by means of a finite element preprocessing tool.
The finite element model of the shell orthodontic appliance is then subjected to a constant load in a direction (e.g., normal to the outer surface of the dentition) using an explicit algorithm. After establishing the initial contact, the previously applied load is slowly unloaded using an explicit algorithm.
After contact establishment is completed by using an explicit algorithm, releasing all contact constraints on the shell-shaped orthodontic appliance, and then performing stress redistribution calculation by using an implicit algorithm to eliminate unreal stress concentration caused by the constraints, so as to obtain a finite element model of the shell-shaped orthodontic appliance worn on the dental jaw, wherein the finite element model includes but is not limited to the geometric form and the stress distribution of the shell-shaped orthodontic appliance worn on the dentition.
At this time, the limitation of the degree of freedom of the finite element model of the tooth can be released to perform the finite element analysis of the movement of the tooth under the action of the shell-shaped orthodontic appliance.
In one embodiment, the contact between teeth and shell orthodontic appliances may be provided as non-adhesive, slidable, frictional, non-penetrating contact types/characteristics.
In one embodiment, the contact between the tooth and the periodontal ligament, and between the periodontal ligament and the alveolar bone, may be provided as a adhesively bonded, non-slidable, non-releasable, non-penetrating contact type/feature. Further, in one embodiment, the tooth may be made to share a node with the periodontal ligament, which shares a node with the alveolar bone.
In one embodiment, a finite element node can be arbitrarily selected on the finite element model of the alveolar bone at a position not in contact with the finite element model of the periodontal ligament, and full constraint of six degrees of freedom (the alveolar bone can be deformed but is not displaced as a whole) is applied to the node as one of boundary conditions of finite element analysis on tooth movement.
In one embodiment, a finite element node can be arbitrarily selected on the finite element model of the tooth at a position without contact with the shell-shaped orthodontic appliance, and the node is rigidly connected with the origin of the local coordinate system of the tooth, so that the local coordinate system of the tooth moves along with the movement of the tooth.
In one embodiment, a threshold may be set when the force fluctuations across the finite element model of the shell orthodontic appliance are less than the threshold and held for a period of time that is considered to be equilibrium. The new layout of the teeth at this time can be used as the orthodontic effect which can be achieved by the shell-shaped orthodontic appliance, namely, the layout of the teeth after the shell-shaped orthodontic appliance is fully worn.
In 307, the orthodontic appliance is verified based on the finite element analysis results.
In one embodiment, the new layout of teeth obtained in 305 may be compared to the designed layout of teeth, and if the difference (including distance and angle) between the two meets predetermined requirements, the orthodontic appliance is deemed to be acceptable, and otherwise, the orthodontic appliance is deemed to be unacceptable.
In one embodiment, a tooth position deviation threshold and a lower match rate limit may be preset. When the new tooth layout is compared with the designed tooth layout, if the range of the form matching area smaller than the tooth position deviation threshold value is larger than the lower limit of the matching rate, the orthodontic appliance is qualified.
In one embodiment, the tooth position deviation threshold may be set to 0.1mm and the lower match rate limit may be set to 90%.
The method 300 for inspecting an orthodontic appliance based on computer finite element analysis can also be used for inspecting a shell-shaped dental retainer, for example, a finite element model of the shell-shaped dental retainer can be worn on a finite element model of a jaw, the influence on teeth can be analyzed by the finite element analysis, and if the shell-shaped dental retainer moves beyond a predetermined range due to rebound of an expansion arch, the shell-shaped dental retainer is considered to be unqualified.
In one embodiment, the first set of process data may be modified based on the verification obtained in 307 to at least partially offset deviations in the shell-like dental instrument geometry from the design caused by elasto-plastic deformation in the thermoforming process, thereby improving the orthodontic effect.
Referring again to fig. 1, at 107, a shell-shaped dental appliance is fabricated based on the second set of process data.
In one embodiment, a shell-like dental instrument may be fabricated based on the second set of process data, provided that the second set of process data modified based on the first set of process data is acceptable.
It can be understood that 101-105 of the optimization method 100 for the process data of the shell-shaped dental instrument based on the hot-pressing film forming process can be executed in a circulating manner until qualified process data is obtained.
Although the above embodiments have described the Method for inspecting an orthodontic appliance according to the present invention by taking Finite element analysis as an example, it is understood that the Finite element Method is only one of numerical calculation methods of a multi-mesh model, and may be implemented by sampling a Finite Volume Method (Finite Volume Method), a Finite Difference Method (Finite Difference Method), a region decomposition Method, a Finite point Method, a boundary element Method, and the like, in addition to the Finite element Method.
The technological data optimization method of the shell-shaped dental appliance manufacturing process based on the hot-pressing film forming technology enables optimization to be carried out in the design stage before appliance manufacturing, so that correction efficiency is improved, and economic benefits are improved.
While various aspects and embodiments of the disclosure are disclosed herein, other aspects and embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification. The various aspects and embodiments disclosed herein are for purposes of illustration only and are not intended to be limiting. The scope and spirit of the application are to be determined only by the claims appended hereto.
Likewise, the various diagrams may illustrate an exemplary architecture or other configuration of the disclosed methods and systems that is useful for understanding the features and functionality that may be included in the disclosed methods and systems. The claimed subject matter is not limited to the exemplary architectures or configurations shown, but rather, the desired features can be implemented using a variety of alternative architectures and configurations. In addition, to the extent that flow diagrams, functional descriptions, and method claims do not follow, the order in which the blocks are presented should not be limited to the various embodiments which perform the recited functions in the same order, unless the context clearly dictates otherwise.
Unless otherwise expressly stated, the terms and phrases used herein, and variations thereof, are to be construed as open-ended as opposed to limiting. In some instances, the presence of an extensible term or phrases such as "one or more," "at least," "but not limited to," or other similar terms should not be construed as intended or required to imply a narrowing in instances where such extensible terms may not be present.

Claims (14)

1. A process data optimization method for a shell-shaped dental instrument manufacturing process based on a hot-pressing film forming technology comprises the following steps:
acquiring a first set of process data of a shell-shaped dental instrument manufacturing process based on a hot-pressing film forming technology;
calculating a first shell-like dental instrument geometry based on the first set of process data; and
modifying the first set of process data based on the first shell-like dental instrument geometry to at least partially offset deviations of the first shell-like dental instrument geometry from a design caused by elasto-plastic deformation in the shell-like dental instrument fabrication process, resulting in a second set of process data.
2. The method for optimizing process data of a shell-shaped dental instrument manufacturing process based on a hot-pressing film forming technology according to claim 1, further comprising: fabricating a shell-shaped dental appliance based on the second set of process data.
3. The method of claim 1, wherein the modification of the first set of process data is a modification of at least one of the following process data: the method comprises the following steps of forming a convex mold, wherein the convex mold is fixed on a base in the film pressing process.
4. A method of optimizing process data for a shell-type dental instrument fabrication process based on hot-embossing film formation as claimed in claim 1, wherein the modification of the first set of process data is primarily to at least partially offset the deviation of the bow width of the first shell-type dental instrument geometry from the design bow width.
5. The method of claim 1, wherein the shell dental instrument manufacturing process is simulated and calculated using a multi-grid model calculation method based on the first set of process data to obtain a first shell dental instrument multi-grid digital model comprising the first shell dental instrument geometry.
6. The method for optimizing process data of a shell-shaped dental instrument manufacturing process based on the thermoforming technique according to claim 5, further comprising:
acquiring a multi-grid digital model of a jaw, wherein the multi-grid digital model of the jaw comprises a multi-grid digital model of a plurality of teeth of the jaw, a periodontal ligament multi-grid digital model and an alveolar bone multi-grid digital model; and
the first shell-shaped dental instrument multi-grid digital model is worn on the multi-grid digital model of the dental jaw and is calculated by using a multi-grid model calculation method, and a calculation result comprising at least one of the following is obtained: a new layout of the multi-mesh digital model of the plurality of teeth achieved under the action of the multi-mesh digital model of the first shell-like dental appliance;
wherein the modification to the first set of process data is based on the calculated results.
7. The method for optimizing process data of a shell-shaped dental instrument manufacturing process based on the hot-pressing film forming technology as claimed in claim 6, wherein the periodontal ligament multi-mesh digital model covers root portions of the multi-mesh digital models of the plurality of teeth, and the alveolar bone multi-mesh digital model covers the periodontal ligament multi-mesh digital model.
8. The method of claim 7, wherein the periodontal ligament multi-grid digital model and the multi-grid digital models of the teeth have a limited degree of freedom relative to a node on a contact surface between the two.
9. The method of claim 8, wherein the periodontal ligament multi-grid digital model and the multi-grid digital models of the teeth share a node on a contact surface.
10. The method of claim 7, wherein the periodontal ligament multi-grid digital model and the alveolar bone multi-grid digital model have a limited degree of freedom relative to a node on a contact surface.
11. A method of optimizing process data for a shell-like dental instrument manufacturing process based on hot-lamination film formation as claimed in claim 10, wherein the periodontal ligament multi-grid digital model and the alveolar bone multi-grid digital model share a node on the interface.
12. The method of claim 6, wherein after the first shell-shaped dental apparatus multi-grid digital model is worn on the multi-grid digital model of the dental jaw, the fluctuation of the interaction force between the first shell-shaped dental apparatus multi-grid digital model and the multi-grid digital model of the dental jaw is less than a predetermined value and is kept for a predetermined period of time, and then the layout of the multi-grid digital model of the plurality of teeth is used as the new layout.
13. The method of claim 6, wherein the modification of the first set of process data is based on a comparison of a new layout and a design layout of the multi-grid digital model of the plurality of teeth.
14. The method for optimizing process data of a shell-shaped dental instrument manufacturing process based on the thermoforming technique according to claim 5 or 6, wherein the multi-mesh digital model is a finite element model and the multi-mesh model calculation method is a finite element analysis method.
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