CN115937072A

CN115937072A - VTK-based oral guide plate initial extraction method

Info

Publication number: CN115937072A
Application number: CN202210563921.3A
Authority: CN
Inventors: 马海英; 李金舟; 曹东杰; 孙国荣; 黄双龙
Original assignee: Nantong University
Current assignee: Nantong University
Priority date: 2022-05-23
Filing date: 2022-05-23
Publication date: 2023-04-07

Abstract

The invention provides an oral cavity guide plate initial extraction method based on VTK, and belongs to the technical field of oral cavity image measurement, sleeve fusion, image area segmentation and three-dimensional data expansion of images. The problems of oral CT image and medical three-dimensional image measurement, tooth surface segmentation and oral guide plate extraction are solved. The technical scheme is as follows: the method comprises the following steps: s10, measuring distance and angle; s20, fusing the sleeve; s30, segmenting a tooth area; and S40, expanding the tooth area. The invention has the beneficial effects that: the invention carries out comparison analysis in algorithm aspect by a plurality of different methods; and in the aspect of image expansion, a vtkWarpVector method is used, and finally, 3D printing is performed on data after the tooth surface is expanded to obtain an initial sampling sample of the oral guide plate.

Description

Initial extraction method of oral cavity guide plate based on VTK

Technical Field

The invention relates to the technical field of oral cavity image measurement, sleeve fusion, image area segmentation and three-dimensional data expansion of images, in particular to an oral cavity guide plate initial extraction method based on VTK.

Background

With the increasing maturity of artificial intelligence technology, optical imaging technology, three-dimensional image processing technology, high-resolution CT scanning technology and computer software development technology and the continuous deepening of clinical analysis and experimental research of oral implantation, display and analysis of oral implantation operation environment, prediction and navigation of preoperative simulation scheme and extraction and manufacturing of three-dimensional digital oral guide plates become a great hotspot of new research fields, the technology development is not mature in China, but the demand of the oral implantation guide plates is not reduced. Important factors for the success of the oral implant operation include two aspects, on one hand, a scientific, reasonable and safe treatment scheme is established for a patient before the operation; and on the other hand, the simulation operation is carried out on the scheme to predict the result. The oral cavity guide plate extraction system has a good operation navigation function, is tested and tried out in a clinical operation to a certain extent, can ensure the safety and stability of the operation, and reduces the unknown property of the operation, thereby effectively improving the success rate of the planting operation.

Strict requirements are placed on the design and placement of the implant in the oral implant operation, the detection error of the distance between the implant and the neural tubes of the upper palate bone and the lower alveolar teeth is within 2 mm, the requirements on the assessment of the bone mass of the jaw bone defect and the position relation between the implant and the prosthesis are strict, and whether the operation can be smoothly completed depends on a planned scheme before the operation. Although the conventional radial apex and jaw bone curved surface lamina can provide a certain guidance for a clinician, the conventional X-ray film is a two-dimensional image with overlapped structures, the density resolution is low, and the local tissue structure is deformed and reduced to a certain extent under the influence of the shooting angle. In a word, according to preoperative planning and design of common X-ray film examination, accurate measurement and calculation cannot be performed on the density and the defect area of the jaw bone, so that a clinician sinks into a very passive situation in an oral implantation operation, not only an effective treatment effect cannot be achieved, but also the falling of an implant can be caused, even serious sequelae are generated, such as symptoms of adjacent tooth injury, lower lip numbness, jaw absorption, maxillary sinus infection and the like, and the organism injury and the psychological disorder of a patient are caused.

The previous implant operation has extremely strict requirements on the experience and technical level of doctors, the implant implantation needs to be designed by considering the bone density of local jawbone and the anatomical structure, and the artificial conclusion can be reached only after the bone-sticking film is turned over in the operation process. The designed implantation position and angle before the operation have certain deviation from the actual operation implantation position, which not only causes the failure of the operation, but also brings some sequelae. The minimally invasive implantation technology is widely adopted with the advantages that the precision of the implantation operation can be improved, the intraoperative hemorrhage can be reduced, the postoperative swelling can be reduced, the alveolar bone absorption can be avoided, the fear of the patient can be reduced, and the like. The use of the implant guide plate makes the operation possible without flap turning, and like some other operation guide plates, the implant guide plate is also an information carrier of the implant operation and a navigation tool in the operation.

Disclosure of Invention

The invention aims to provide a VTK-based oral cavity guide plate initial extraction method, wherein a surgical guide plate manufactured by a 3D printing technology can be used for designing and manufacturing the depth and the angle of an implant implanted into a jaw bone through a three-dimensional measurement technology, so that the important nerve and blood vessel structure in the jaw bone is prevented from being damaged, and even a young doctor of new duties can smoothly complete the implant surgery by using the surgical guide plate.

In order to achieve the purpose of the invention, the invention adopts the technical scheme that: a VTK-based oral cavity guide plate initial extraction method comprises the following steps:

and S10, measuring distance and angle. Measuring the distance between two teeth in the two-dimensional mandibular bone section data image by using the VtkDistanceWidgets; using vtkAngleWidget for measuring the angle between two rays (defined by three points); three-dimensional angle and distance measurements are achieved using vtkk widgetreflection.

And S20, fusing the sleeve. The method directly carries out fusion processing on the STL triangular surface data by utilizing a Boolean operation method, and can effectively solve the problem of time waste.

And S30, dividing the tooth area. The model is segmented according to a threshold value or other significant features of the model, the feature value of the model is generally set for segmentation or three-dimensional segmentation is carried out in a mouse interactive mode, and the model is segmented into a plurality of areas in a user-defined mode.

And S40, expanding the tooth area. VTK-based image dilation transforms merge two data sets with vector addition. The dilation region X ≦ B is a set of vector sums for all points in the triangular face, the two operands for vector addition come from set X and set B, respectively, and any possible set combination is chosen.

Further, the step S10 includes:

and S101, measuring two-dimensional distance. First, the user defines the settings (i.e. selects two endpoints) and then defines the way in which the mouse interacts (interactively moves the two endpoints), and some events using this Windows window require instantiation (NEW) of an instance of vtkDistanceWidget and its form of construction (subclass of vtkdistancerepetition). The event is realized by using two instances of the vtkHandleWidget, wherein the two instances are used for determining two endpoints of the measured area and inherit to a vtkAbstractWidge class;

and S102, measuring a two-dimensional angle. First, the user defines the settings (i.e., selects two endpoints and a center point) and then defines the manner in which the mouse interacts (interactively moves the two endpoints and the center point). To use some events of this Windows window, one instance of vtkAngleWidget and its form of construction (a subclass of vtkAngleRepression) need to be instantiated (NEW). These examples are used to locate these three points. Representations of these events are provided by vtkAngleRepression. By default, the widget will respond to the following VTK events (i.e., it monitors these events in the vtkrenderwindow interactor): leftbutton pressevent-add point or select handle, mousenoveeevent-locate second or third point, or move handle leftbutton releaseevent-release selected handle;

and S103, three-dimensional measurement. Such is used to define APIs and implement presentation forms for different types of widgets. Plug-in representation (vtkWidgetRegenation) is a type of vtkProp; meaning that they can be associated with the vtkrender end embedded in the scene, just like any other vtkkactor. However, vtkkwidgets registration also defines an API that enables it to pair with the vtkbastractwidget subclass, meaning that it can be driven by the widget, representing the widget when it responds to a registered event. The API defined herein should be viewed as a guide to the implementation of widgets and widget representations. The behavior of widgets is complex, the way in which the representation responds to registered widget events is also complex, and thus the API may vary from widget to reflect this complexity. vtkddistanceresentation 3D is for representing vtkddistancewidge. The representation includes one measurement line (axis) and two vtkholdlewidgets to place the endpoints of the line.

Further, the step S20 includes:

s201, the two STL data are respectively data A and data B, and the Boolean operation relation between the model A and the model B is derived from geometry and computer graphics:

AinB means the collective data of A inside data B, aoutB means the collective data of A outside data B, (AinB) ^-1 The difference set of the set data of the data A in the data B is shown, namely the result that all normal vectors of the triangular surface in the set data of the data A in the data B are in opposite directions. (BinA) ^-1 The difference set of the set data of the data B in the data A is shown, namely the result that all normal vectors of the triangle surfaces of the set data of the data B in the data A are in opposite directions. BoutA means aggregated data with B outside data a, and BinA means aggregated data with B inside data a.

S202, traversing each triangular surface vertex of the mandible model A and the mandible model B, finding out the maximum value and the minimum value of the x, y and z coordinates of the vertex in each triangular surface of each mandible model, and respectively recording the maximum value and the minimum valueIs XB _min 、XB _max 、YB _min 、 YB _max 、ZB _min 、ZB _max And XA _min 、XA _max 、YA _min 、YA _max 、ZA _min 、ZA _max If the coordinate data satisfies XA _max <XB _min Or XB _max <XA _min Or YA _max <YB _min Or YB _max <YA _min Or ZA _max <ZB _max Or ZB _max < ZA _min Under any one condition, the mandible model A and the mandible model B cannot be intersected, otherwise, the mandible model A and the mandible model B are intersected.

The positional relationship of each triangular surface data field obtained by dividing the surfaces of the mandible model a and the mandible model B by the intersection line S203 with respect to the other model has the intersection line as a boundary line, and the boundary is either outside the model a or inside the model B. The rounding problem to be faced in boolean operations is to determine the positional relationship of each region obtained by dividing one entity of the model mandible a and mandible model B along the intersection line with respect to the other entity. Therefore, to determine the position relationship of the triangular patch region obtained by dividing the intersection line of the mandible model a and the mandible model B with respect to another entity, a vertex can be found, the vertex is a non-intersection point of the triangular face, then the position relationship of the vertex with respect to another entity model is checked, and the position relationship of the region where the point is located and another entity model can be obtained from point to surface.

S204, the solution method of the intersection is realized by adopting an intersection solving algorithm of two triangles proposed by Tomas Moller. Two triangular surfaces T ₁ And T ₂ The vertexes are respectively

And &>

Triangular surface T ₁ And T ₂ The planes are respectively alpha and beta, and the plane beta equation is calculated: n is a radical of ₂ *X+d ₂ =0, where X is a point on the triangular face. />

From triangle T ₁ The directed distance to the plane β can be obtained by substituting the points into the plane equation:

if it is

Then T1 is on one side of β and there is no intersection. The same process is also performed for the triangular face T2. If->

Then the triangular faces will intersect. If the intersection areas formed by the triangular surfaces and the straight lines overlap each other, the triangular surfaces also intersect.

Further, the step S30 includes:

s301, firstly, determining plane coordinates. In principle, the coordinates can be determined arbitrarily, but in practical tests, suitable coordinates are selected according to different test models. Using the selected coordinates as (x) _o ，y _o ，z _o ) The coordinate is the central point of the cutting surface, can be set by self definition, and is selected from the inside of the tooth skeleton data of the lower jaw bone;

s302, determining a normal vector inside a tooth, and setting an angle for cutting a mandible through self definition according to the inclination degree of a tooth skeleton model, namely the direction when the data of the upper surface of the tooth are separated, wherein the normal vector of a cutting plane is provided with two methods: the first method is that the keyboard inputs rectangular coordinates; the second method is to set the polar coordinates; the comparison between the two is obviously that the form of the polar coordinate is more intuitive, but more choices are point methods of a space surface in the actual operation process of the code, namely the polar coordinate is converted into a rectangular coordinate through a certain formula;

s303, assuming that the polar coordinate of the normal vector is (r) ₀ ,ψ ₀ ,θ ₀ ) The transformation of the coordinates into rectangular coordinates can be done by equation (3), and the resulting new coordinates are set to (i) ₀ ，j ₀ ，k ₀ ) Namely, the coordinate is in the form of a normal vector of the converted tooth cutting surface, the direction of the tooth cutting surface is determined by the normal vector, and the cutting surface can be determined according to the space plane point normal equation (4) by the two conditions.

i ₀ (x-x _o )+j ₀ (y-y _o )+k ₀ (z-z _o )＝0 (4)

S304, after the tooth cutting plane is determined, the next key step is mapping of the cutting plane, namely solving the intersection of the cutting plane and the three-dimensional model, and adding the intersection part into the three-dimensional model. And (3) segmenting the three-dimensional model of the oral teeth by using the plane, obtaining two parts of the segmented oral teeth data after determining the normal vector of the cutting plane, coloring the surfaces of the teeth, and keeping the original model of the rest parts.

Further, the step S40 includes:

s401, addition of quantities (or set addition, such as (x, y, z) + (a, b, c) = (x + a, y + b, c + d)) merges the two data sets. Expansion zone

Is a set of vector sums of all points in the triangular surface, the two operands of vector addition are from set X and set B, respectively, and any possible combination of sets is chosen.

S402, a large amount of redundant operation exists in most of traditional image expansion processing, the larger the data volume of the triangular surface of the image is, the more complex the structural elements are, and the more obvious the result of the redundant operation is. The redundant operation comes from two places:

(1) And (5) performing expansion processing on the interior of the triangular surface image. The expansion operation is an incremental operation mode, when the expansion operation is performed on the regional three-dimensional volume data, the final result is influenced only by processing the image boundary, and the traditional expansion algorithm can operate the data in the image, so that a large amount of time is spent, and the efficiency of the algorithm is further reduced. In fact, the dilation algorithm may perform dilation operation on the boundary of the original image, and then combine with the original image;

2) The overlapping portions of adjacent triangular face dilation operations. And expansion operation of adjacent triangular surfaces has a large amount of triangular surface overlapping parts between the front operation and the rear operation, the more the triangular surfaces are, the larger the structural elements are, the more the mutual direct overlapping is, the more the execution time of the algorithm is, and the lower the efficiency is.

Compared with the prior art, the invention has the following beneficial effects:

(1) The initial extraction method of the oral cavity guide plate based on the VTK realizes the accurate measurement of the distance and the angle between the oral cavity CT image and the medical three-dimensional image, and the pre-operation simulation is more real by the Boolean fusion technology of the sleeve.

(2) The initial extraction method of the oral cavity guide plate based on the VTK provided by the invention has the advantages that the operation is simpler based on the planar three-dimensional image segmentation technology, the data conversion is not needed, and the image segmentation can be completed by setting the coordinates of the cutting surface and the normal vector of the cutting surface after the tooth data are read.

(3) The initial extraction method of the oral guide plate based on the VTK provided by the invention realizes the initial extraction of the oral guide plate by utilizing the three-dimensional image expansion technology, and is convenient for 3D physical printing.

(4) The invention finally realizes the initial extraction of the oral cavity guide plate by adopting an oral cavity image measuring technology, a sleeve fusion technology, an image area segmentation technology and an image three-dimensional data expansion technology, and realizes the measurement of mouse interactive two-dimensional and three-dimensional images in the aspect of measurement; in the aspect of sleeve fusion, the sleeve insertion of a user-defined area is realized by using a point pickup and Boolean operation method; the region segmentation aspect uses a planar interactive segmentation method.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

Fig. 1 is a flowchart of an initial extraction method of a VTK-based oral guide provided by the present invention.

FIG. 2 is a schematic view showing the measurement of the distance between the section of the mandible in the present invention.

FIG. 3 is a schematic view showing the measurement of the angle of the mandible section in the present invention.

Fig. 4 is a schematic diagram of three-dimensional oral distance measurement in the present invention.

Fig. 5 is a schematic diagram of the three-dimensional oral angle measurement of the present invention.

FIG. 6 is a schematic diagram of the Boolean union operation of the mandible and sleeve data in accordance with the present invention.

FIG. 7 is a schematic representation of the marking of the upper surface of a tooth in accordance with the present invention.

FIG. 8 is a schematic view of a tooth surface of the present invention.

Fig. 9 is a schematic view of the expansion treatment of the tooth surface in the present invention.

Fig. 10 is a schematic diagram of actual object printing of the mouthpiece in the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. Of course, the specific embodiments described herein are merely illustrative of the invention and are not intended to be limiting.

Example 1

Referring to fig. 1 to 10, the present embodiment provides a VTK-based oral guide initial extraction method, as shown in fig. 1, including the following steps:

And S30, dividing the tooth area. The model is segmented according to a threshold value or other remarkable characteristics of the model, the characteristic value of the model is usually set for segmentation or three-dimensional segmentation is carried out in a mouse interactive mode, and the model is segmented into a plurality of areas by user definition.

And S40, expanding the tooth area. VTK-based image dilation transforms merge two data sets with vector addition. The inflation region X ≧ B is the set of vector sums for all points in the triangular face, the two operands to vector addition come from set X and set B, respectively, and any possible combination of sets is chosen.

Preferably, the step S10 includes:

and S103, three-dimensional measurement. Such is used to define APIs and implement presentation forms for different types of widgets. Plug-in representation (vtkWidgetRegenation) is a type of vtkProp; meaning that they can be associated with the vtkrender end embedded in the scene just like any other vtkActor. However, vtkkwidgets registration also defines an API that enables it to pair with the vtkbastractwidget subclass, meaning that it can be driven by the widget, representing the widget when it responds to a registered event. The API defined herein should be viewed as a guide to the implementation of widgets and widget representations. The behavior of widgets is complex, the way in which the representation responds to registered widget events is also complex, and thus the API may vary from widget to reflect this complexity. vtkddistanceresentation 3D is for representing vtkddistancewidge. The representation includes one measurement line (axis) and two vtkholdlewidgets to place the endpoints of the line.

Preferably, the step S20 includes:

s201, the two STL data are data A and data B respectively, and are derived from geometry and computer graphics, and the Boolean operation relation between the model A and the model B is as follows:

AinB means the collective data of A inside data B, aoutB means the collective data of A outside data B, (AinB) ^-1 Representing the difference set of the set data of the data A inside the data B, i.e. all the triangular surfaces in the set data of the data A inside the data BThe normal vector of (a) is the result in the opposite direction. (BinA) ^-1 The difference set of the set data of the data B in the data A is shown, namely the result that all normal vectors of the triangular surface in the set data of the data B in the data A are in opposite directions. BoutA means aggregated data with B outside data a, and BinA means aggregated data with B inside data a.

S202, traversing each triangular surface vertex of the mandible model A and the mandible model B, finding out the maximum value and the minimum value of the x, y and z coordinates of the vertex in each triangular surface of each mandible model, and respectively recording the maximum value and the minimum value as XB _min 、XB _max 、YB _min 、 YB _max 、ZB _min 、ZB _max And XA _min 、XA _max 、YA _min 、YA _max 、ZA _min 、ZA _max If the coordinate data satisfies XA _max <XB _min Or XB _max <XA _min Or YA _max <YB _min Or YB _max <YA _min Or ZA _max <ZB _max Or ZB _max < ZA _min Under any one condition, the mandible model A and the mandible model B cannot be intersected, otherwise, the mandible model A and the mandible model B are intersected.

S204, the solving method of the intersection line is realized by adopting an intersection line solving algorithm of two triangles proposed by Tomas Moller. Two triangular surfaces T ₁ And T ₂ The vertexes are respectively

And &>

if it is

Then T1 is on one side of β and there is no intersection. The same applies to the triangular surface T2. If->

Preferably, the step S30 includes:

s301, firstly, determining plane coordinates. The coordinates can in principle be determined arbitrarily, but in the actual test they are determined from different test patternsAnd selecting proper coordinates. Using the selected coordinates as (x) _o ，y _o ，z _o ) The coordinate is the central point of the cutting surface, can be set by self definition, and is selected from the inside of the tooth skeleton data of the lower jaw bone;

s302, determining a normal vector inside a tooth, and according to the inclination degree of a tooth skeleton model, setting an angle for cutting a mandible through self definition, namely a direction when data of the upper surface of the tooth are separated, wherein the normal vector of a cutting plane is provided with two methods: the first method is that the keyboard inputs rectangular coordinates; the second method is to set the polar coordinates; the comparison between the two is obviously that the form of the polar coordinate is more intuitive, but more choices are point methods of a space surface in the actual operation process of the code, namely the polar coordinate is converted into a rectangular coordinate through a certain formula;

s303, assuming that the polar coordinate of the normal vector is (r) ₀ ,ψ ₀ ,θ ₀ ) The transformation of the coordinates into rectangular coordinates can be done by equation (3), and the resulting new coordinates are set to (i) ₀ ，j ₀ ，k ₀ ) Namely, the coordinate is in the form of a normal vector of the cutting surface of the converted tooth, the direction of the cutting surface of the tooth is determined by the normal vector, and the cutting surface can be determined according to the space plane point normal method (4) by the two conditions.

/>

S304, after the tooth cutting plane is determined, the next key step is mapping of the cutting surface, namely solving the intersection of the cutting surface and the three-dimensional model, and adding the intersection part into the three-dimensional model. And (3) segmenting the three-dimensional model of the oral teeth by using the plane, obtaining two parts of the segmented oral teeth data after determining the normal vector of the cutting plane, coloring the surfaces of the teeth, and keeping the original model of the rest parts.

Preferably, the step S40 includes:

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A VTK-based oral cavity guide plate initial extraction method is characterized by comprising the following steps:

s10, measuring the distance and the angle, namely measuring the distance between two teeth in the two-dimensional mandible section data image by using VtkDistanceWidgets; using vtkAngleWidget for measuring the angle between two rays; measuring three-dimensional angles and distances by using vtkWidgetReferentiation;

s20, sleeve fusion, namely directly carrying out fusion processing on the STL triangular surface data by utilizing a Boolean operation method;

s30, tooth area segmentation, namely segmenting according to a threshold value or other significant features of the model, setting a feature value of the model for segmentation or performing three-dimensional segmentation in a mouse interactive mode, and segmenting the model into a plurality of areas by user definition;

s40, expanding the tooth area, combining the two data sets by adopting vector addition based on VTK image expansion transformation, wherein the expansion area X ^ B is a set of vector sums of all points in the triangular surface, two operands of the vector addition are respectively from the set X and the set B, and any possible set combination is selected.

2. The VTK-based oral guide initial extraction method according to claim 1, wherein the step S10 comprises the steps of:

s101, two-dimensional distance measurement, namely, firstly, user self-defining setting is carried out, namely, two endpoints are selected, then a mouse interaction mode is defined, the two endpoints are interactively moved, and a vtkDistanceWidget instance and a vtkDistanceRepression subclass in a construction form are instantiated by using events of the Windows window; the event is realized by using two instances of the vtkHandleWidget, wherein the two instances are used for determining two endpoints of the measured area and inherit to a vtkAbstractWidge class;

s102, two-dimensional angle measurement, firstly, user-defined setting is carried out, namely two end points and a central point are selected, then a mouse interaction mode is defined, the two end points and the central point are interactively moved, some events of the Windows window are used, an instance of vtkAngleWidget and a construction form of the instance need to be instantiated, subclasses of vtkAngleRepression are used for positioning the three points, representation of the events is provided by vtkAngleRepression, and a widget monitors the events in vtkRenderWindowInteractor in response to the following VTK events by default: leftbutton pressevent-add point or select handle, mousenoveeevent-locate second or third point, or move handle leftbutton releaseevent-release selected handle;

s103, three-dimensional measurement, wherein the API is defined for different types of widgets and the representation form is realized, and plug-in representation (vtkWidgetReservation) is a type of vtkProp; meaning that they are associated with the vtkRenderer end embedded in the scene, just like any other vtkActor, vtkWidgetReservation also defines an API, which pairs with the vtkAbstractWidge subclass, which is driven by the widget and represents the widget when it responds to a registered event, where the defined API is considered as a guide for implementing the widget and its representation, which is complex in behavior, complex in the way it responds to registered widget events, different from widget to reflect this complexity, vtkDistanceReservation 3D is to represent vtkDisceWit, which comprises a measurement line and two vtkHandleWinds to place the end points of the line.

3. The VTK-based oral guide initial extraction method according to claim 1, wherein the step S20 comprises the steps of:

AinB means the collective data of data A inside data B, aoutB means the collective data of A outside data B, (AinB) ^-1 The difference set of the set data of the data A in the data B is represented, namely the result that all normal vectors of the triangular surface in the set data of the data A in the data B are in opposite directions; (BinA) ^-1 The difference set of the set data of the data B in the data A is represented, namely the result that all normal vectors of the triangular surface of the set data of the data B in the data A are in opposite directions; boutA means aggregated data with B outside data a, and BinA means aggregated data with B inside data a;

s202, traversing each triangular surface vertex of the mandible model A and the mandible model B, finding out the maximum value and the minimum value of the x, y and z coordinates of the vertex in each triangular surface of each mandible model, and respectively recording the maximum value and the minimum value as XB _min 、XB _max 、YB _min 、YB _max 、ZB _min 、ZB _max And XA _min 、XA _max 、YA _min 、YA _max 、ZA _min 、ZA _max If the coordinate data satisfies XA _max <XB _min Or XB _max <XA _min Or YA _max <YB _min Or YB _max <YA _min Or ZA _max <ZB _max Or ZB _max <ZA _min Under any one condition, the mandible model A and the mandible model B cannot be intersected, otherwise, the mandible model A and the mandible model B are intersected;

s203, the position relation of each triangular surface data domain obtained by dividing the surfaces of the lower jaw bone model A and the lower jaw bone model B by the intersection line is based on the intersection line as a boundary line, and the boundary is either outside the model A or inside the model B; the round-off problem to be faced in Boolean operation is to judge the position relation of each region obtained by dividing one entity in the model mandible A and the mandible model B along the intersecting line relative to the other entity; when the position relation of a triangular patch area obtained by dividing an intersecting line ring of a lower jaw bone model A and a lower jaw bone model B relative to another entity needs to be judged, a vertex is found, the vertex is a non-intersection point of a triangular surface, then the position relation of the vertex relative to the other entity model is checked, the position relation of the area where the point is located and the other entity model is obtained from point to surface, when the vertex is outside the other lower jaw bone entity model, the triangular surface is outside the other entity, and if the vertex is not outside the other entity, the triangular surface is inside the other entity;

s204, the solution method of the intersection line is realized by adopting an intersection line solving algorithm of two triangles proposed by Tomas Moller, and the two triangular surfaces T ₁ And T ₂ The vertexes are respectively

And &>

Triangular surface T ₁ And T ₂ The planes are respectively alpha and beta, and the plane beta equation is calculated: n is a radical of ₂ *X+d ₂ =0, wherein X is a point on the triangular face; />

From triangle T ₁ The directed distance to the plane β is obtained by substituting the points into the plane equation:

if it is

If the T1 is on one side of the beta, the intersection is avoided, and the triangular surface T2 is processed in the same way; if it is not

Then the triangular faces will intersect, and if the intersection areas formed by the triangular faces and the straight lines overlap, then the triangular faces will also intersect.

4. The VTK-based oral guide initial extraction method according to claim 1, wherein the step S30 comprises the steps of:

s301, firstly, determining plane coordinates, wherein the coordinates can be determined at will in principle, selecting proper coordinates according to different test models in actual test, and using (x) as the selected coordinates _o ，y _o ，z _o ) The coordinate is the central point of the cutting surface, is set by self-definition and is selected from the tooth skeleton data of the lower jaw bone;

s302, determining a normal vector inside a tooth, and according to the inclination degree of a tooth skeleton model, setting an angle for cutting a mandible through self definition, namely a direction when data of the upper surface of the tooth are separated, wherein the normal vector of a cutting plane is provided with two methods: the first method is that the keyboard inputs rectangular coordinates; the second method is to set the polar coordinates; the comparison between the two is obviously in a polar coordinate form, and a point method formula of a space surface is selected in the actual operation process of the code, namely the polar coordinate is converted into a rectangular coordinate through a certain formula;

s303, assuming that the polar coordinate of the normal vector is (r) ₀ ,ψ ₀ ,θ ₀ ) And the transformation of the coordinates into rectangular coordinates is accomplished by equation (3), resulting in new coordinates set as (i) ₀ ，j ₀ ，k ₀ ) That is, the coordinates are in the form of normal vectors of the converted tooth cutting surface, the direction of the tooth cutting surface is determined by the normal vectors, and the cutting surface is determined according to the space plane point normal equation (4) by the two conditions:

i ₀ (x-x _o )+j ₀ (y-y _o )+k ₀ (z-z _o )＝0 (4)

s304, after the tooth cutting plane is determined, the next step is mapping of the cutting plane, intersection of the cutting plane and the three-dimensional model is solved, the intersection part is added into the three-dimensional model, the three-dimensional model of the oral teeth is divided by the plane, when the normal vector of the cutting plane is determined, the two parts obtained after the oral teeth data are divided are obtained, the tooth surface is colored, and the rest parts keep original patterns.

5. The VTK-based oral guide initial extraction method according to claim 1, wherein the step S40 comprises the steps of:

s401, addition or aggregate addition of quantities, such as (X, y, z) + (a, B, c) = (X + a, y + B, c + d)) combines two data aggregates, the dilation region X ≦ B is a set of vector sums of all points in the triangular surface, the two operands of the vector addition are from set X and set B, respectively, and any possible aggregate combination is selected:

s402, redundant operation exists in the traditional image expansion processing, the larger the triangular surface data volume of an image is, the more complex the structural elements are, the more obvious the redundant operation result is, and the redundant operation comes from two places:

(1) For the expansion processing in the triangular surface image, the expansion operation is an increasing operation mode, when the expansion operation is carried out on the three-dimensional volume data of the area, the final result is influenced by the image boundary processing, and the expansion operation is carried out on the boundary of the original image by the expansion algorithm and then is combined with the original image;

the overlapping part of the expansion operation of the adjacent triangular surfaces, the expansion operation of the adjacent triangular surfaces and the triangular surface overlapping part between the front operation and the rear operation.