CN104392492A - Computer interaction type method for segmenting single tooth crown from three-dimensional jaw model - Google Patents

Abstract

The invention discloses a computer interaction type method for segmenting a single tooth crown from a three-dimensional jaw model. The method includes the steps: reading and visually displaying the three-dimensional jaw grid model; detecting anatomic characteristic points and an occlusion plane of upper teeth of a jaw in the three-dimensional jaw grid model; assigning constraint points of harmonic fields of the three-dimensional jaw grid model; calculating the harmonic fields according to constraint conditions to obtain a tooth crown segmenting border line; performing grid cutting according to the obtained tooth crown segmenting border line to obtain a tooth crown model. By the method, a tooth segmenting border can be accurately obtained, the method is simple to use, and a user interactively determines two border points on a visual view of the jaw model for a single tooth to be separated, so that the tooth crown grid model of the tooth can be accurately obtained. The method has important significance for dental orthodontics, virtual jaw surgery simulation and the like.

Description

A method for computer-interactive segmentation of single tooth crowns from Dental cast

FIELD

[0001] The present invention relates to a method of interactive computer single tooth dental crown from three-dimensional model divided.

Background technique

[0002] With the development of 3D acquisition technology, dental three-dimensional model is widely used in dentistry related areas such as oral medicine, forensic medicine, anthropology and archeology. For dental segmentation model, the classification of treatment is treatment planning, virtual surgery and other dental integral part of virtual reality applications.

[0003] Currently automatic mesh segmentation method for the crown is difficult to get an accurate model, robustness is not strong. While interactive segmentation method may utilize a priori knowledge of the person, the operation fully reflect the user's intention, but the methods generally require the user to specify a number of points along the boundary line dividing the expected crown, this tedious, time-consuming step clearly inconsistent with the intelligent identification. Either conventional method requires a lot of manual interaction to determine the boundaries, time-consuming, or not accurate crown segmentation results, poor robustness. Therefore, accurate and precise separation of the intelligent object is a model of all the challenging crown from dental crown edge mesh contains complex information.

SUMMARY

[0004] The present invention solves the technical problem, the prior art for less than the above, there is provided a single tooth crown segmentation method of interactive computer three-dimensional model from a dental cast.

[0005] To solve the above technical problem, the technical solution employed in the present invention is: A three-dimensional model divided from a single-tooth dental crown computer interactive method, comprising the steps of:

[0006] 1) reads and visualizing dental 3D mesh model;

[0007] 2) detecting the three-dimensional mesh model of dental anatomical feature point on teeth and dental occlusal plane;

[0008] 3) three constraint points specify the harmonic field of dental mesh model;

[0009] 4) The constraint points is calculated harmonic field, obtaining a crown division boundary line;

[0010] 5) in accordance with the cutting crown mesh division boundary line acquired, to give the crown model.

[0011] step 2), using the acquired tooth on dental anatomical feature point information and the curvature of the apex of the watershed method of dental 3D mesh model, using the anatomical feature point determination occlusal plane.

[0012] step 3) in order to specify a target crown located near the teeth and at a constraint point is located at the distal teeth, respectively.

[0013] step 4), the harmonic field calculation process is as follows: set of dental 3D mesh model has m nodes, n-constraint points, solving AO = b, the resulting solution is the dental 3D mesh corresponding to each vertex of the model harmonic field value; wherein,

, Li "is mXm order Laplace matrix,

, (I, j) GE, 0 San i, j San m-1, E is a dental 3D mesh model in the set of edges;

Or if Vi 'at the point of a concave, Vi-dimensional coordinate values ​​at the dental model mesh points i, F for dental 3D mesh model average side length, © is a constant;

»C the elements Cu = 1, p San San remainder 0,0 ml, p is the number of points in the r constraint dental 3D mesh model is, r = 0, 1, ••• n-1; w = 1000.

»B 'values ​​of G in each element {0, 0.5, 1}.

[0014] step 4), the obtaining of a crown division boundary line process: several pieces of extracted contour as a candidate set from the boundary line harmonic field, select the highest score as a candidate boundaries ring tooth crown crown division boundary line.

[0015] said n points comprises the anatomic constraint point Laid diagnostic step 2) obtained in step 3) and the two constraint points around a series of constraints specified does not belong to the target point B of the crown; the constraint the method of determining the point B is as follows: find all anatomical feature points of the projected points on the occlusal plane, is located to find the occlusal plane, and a straight line passing through the projection point; normal to the occlusal plane of the track, the the linear translation toward the bottom of dental a distance, the distance is set from the bottom to the crown dental cusp 2/3 times the vertical distance; obtaining intersection of the line with the dental model, the intersection is the set of B.

[0016] step 4), the crown after acquiring the division boundary line, optimizing the crown division boundary line, the optimization process is as follows: calculate a boundary line dividing points scalar field as a crown, each point unit normal vector corresponding to the scalar value for that point B near the lingual side of the dot per unit dot product of vectors, including the concept can be seen by the dot product, the scalar field range is [-1, 1]; select is greater than the threshold value square of the scalar field value of the threshold, the crown division boundary line into two parts near and near labial lingual, lingual portion near discarded, retention portion near the lip border line; then, in close spline configuration on a plane near the lingual side of the dental surface, near the plane defined by the lip border line reserved two endpoints and near the lingual side B 1 point determination, the spline as a new near lingual crown boundary line; Finally, the crown after the complete boundary near the lip portion side of the boundary line and a new boundary line near lingual crown combined to become a boundary line dividing optimization.

[0017] Compared with the prior art, the present invention has beneficial effects: the present invention, only a small amount of user interaction, will be able to obtain accurate crown model with the boundary information, robust, time saving, easy to operate easy to realize; using the method disclosed in the present invention, the dividing boundary can be accurately obtained teeth, and simple to use: for single tooth to be separated, usually only user visualized dental model view interactive two boundary points determined , grid model can accurately obtain the crown of the tooth. The present invention has important implications for orthodontics, dental surgery virtual simulation.

BRIEF DESCRIPTION

[0018] FIG. 1 is a flowchart separated from the upper crown mesh model of the present invention;

[0019] anatomical feature points of each tooth on dental schematic FIG. 2 of the present invention is used;

[0020] FIG. 3 is not intended to calculate the desired harmonic field constraint points;

[0021] FIG. 4 is a schematic view of the resulting harmonic field calculation results and their contours;

[0022] FIG 5A is a schematic view of a boundary line dividing the need to optimize the crown;

[0023] FIG 5B is a side near the lip line and configured retained after the separation of the tongue near the plane schematic side borderlines dependence;

[0024] FIG 5C is a schematic view of the boundary line is divided into a crown optimized, including nearly tongue side borderlines new configuration;

[0025] The picture shows the division boundary line in accordance with a crown mesh cutting, the final result of the separation of single tooth crowns.

Detailed ways

[0026] DETAILED DESCRIPTION The present invention is described in detail as follows:

[0027] 1, interactive method of separating from the upper crown mesh model according to the present invention, comprising the steps of: a visual display and read dental 3D mesh model; 2 automatically detects edentulous anatomical feature points and the occlusal plane of the teeth; 3 designated by the user constraint points of the grid model harmonic field; 4 calculates harmonic field the constraint points, obtaining a boundary line dividing the crown; 5, if necessary, to optimize the boundary line; 6 in accordance with obtaining a boundary line mesh cut to obtain crown model.

[0028] 1. Read in and visualizing dental 3D mesh model

[0029] Loading dental generic mesh model from the data file, the three-dimensional mesh model can capture devices (such as scanners) obtained can also be obtained from the reconstructed CBCT and other medical picture sequence. Later by a general purpose computer graphics visualization platform (e.g., the OpenGL) visual display, the user can use the device model mouse, keyboard or the like in a computer for interactive operations (e.g., zoom, rotate, pan, etc. setpoint).

[0030] The automatic detection of anatomical characteristic points upper teeth and dental plane

[0031] The use of curvature information and related algorithms vertices on the mesh model (e.g. watershed algorithm), to obtain a smooth anatomical feature point information on the crown. For example, two endpoints on the incisors crest shown in FIG. 2A, FIG 2B 1 cuspidal points (cusps) on canine shown, two sharp points (tongue shown on the premolars to Figure 2C, buccal cusp) and FIG. 2D 4 cuspidal points (distal buccal cusp of the upper molars shown, the distal tip of the tongue, near the tip of the tongue, mesial buccal cusp).

[0032] After determining good feature points, along the occlusal plane may also be determined. The present invention employs a common definition, i.e. two adjacent points incisor, first molar on the left side and the right side near the tip of the tongue near the tip of the tongue of the first molar to determine the three co-occlusal plane.

[0033] 3. The user specifies the constraint points of the grid model harmonic field

[0034] In the present invention, an interactive design environment, the user can use a mouse, keyboard, freely selected (by rotation, translation, scaling) visualizations suitable dental model and view selected arbitrarily selected grid vertex on the model and to obtain the coordinates. In the present invention, the user needs to specify two constraint points are located near the teeth and at the distal target crown. Tooth shown in FIG. 3 is a graphical view of a left first premolar of the lower jaw, wherein the pellets ① shows the identification requirements of this invention, the user can specify a constraint point.

[0035] The constraint point calculating harmonic field, obtaining a crown division boundary line

[0036] In the present invention, we will look for a boundary line dividing the problem into the computing grid surface harmonic field and select an article which contours resolve the problem.

[0037] Solving mesh surface harmonic field solving the Poisson equation A〇 i.e. = 0 (A behalf discrete Laplacian) mathematically. The least square method may be solved using the Poisson equation, then the original equation is converted to the form AO = b, and

[0039] where L is the Laplacian matrix, if there are m nodes in the mesh, L is the order matrix mXm, for 0 ^ i, j ^ m-1,

[0041] wherein, E is a dental 3D mesh model in the set of edges; "Laplacian is the weight for the harmonic field distribution has an important influence. Here we use

[0042]

If Vi or Vj is at the pits

[0043] Representative division boundary to capture the mesh surface recessed region, where Vi is the coordinate value at the point i, F represents the average side length, © a small constant (e.g., 0.001).

[0044] C and b 'are representative of field harmonic constraint matrices and vectors. If there are n m constraint points on the grid nodes, and the C b 'can be expressed as follows:

[0046] w is a big factor, where a value of 1000. For the first i (i = 0, 1, ... n-1) th constraint points, which number in the grid is P (P San San square m-1), the elements in the cip C = 1, the remaining 0 . b 'values ​​of the elements h G {square, square. 5, 1}, i.e., the value h 0,0. 5, or 1, corresponding to the value of the i-th constraint points. By solving large sparse coefficients AO = b equation solution kit is obtained, i.e. the corresponding values ​​of the vertices of each harmonic field with a matrix of linear equations.

[0047] In order harmonic field than using separate crown, in addition to two constraint points specified by the user (referred to as U, which corresponds to the value of 0.5 h), the rest of the constraint points acquired by the system automatically. They are characteristic points on the crown determined in step 2 (denoted is F, the corresponding value of h 1), and a series of constraint around the target point does not belong to the crown (referred to as B, the corresponding value of h 0). 3 as an example, where the identified ② and ③ respectively represent F ball and B.

[0048] We use the following method to determine B: B is determined by the intersection point of the straight line and a series of dental grid model. These lines respectively, after initialization of the nip point F of each point on the projection plane, and located on the occlusal plane. Then, we occlusal plane along the normal trajectory as, respectively, toward their bottom pan dental a distance. This distance is generally set to 2/3 the length of our times from the point to the bottom tip of the crown dental vertical distance.

[0049] for solving linear equations AO = b harmonic field specified constraint is later obtained corresponding to each node on the mesh harmonic field scalar value. We use several pieces of contours extracted from the harmonic field line set as candidate boundaries. Figure 4 shows the harmonic field contour and a target crown pieces under the given constraints. Finally, we use the scores to select the way best candidate boundary line as a boundary dividing boundary crown ring.

[0050] 5. If necessary, the resulting optimization of the boundary 4

[0051] If the target for tooth lingual obvious boundary (shown in FIG. 5), it is necessary for the boundary lines 4, the necessary optimization. First, we calculate a scalar field for the point boundary line. Unit normal vector of the scalar field, each point corresponding to the scalar value for that point B near the lingual side of the dot product of vectors point average unit normal, a concept known dot product, the value of the scalar field domain [-1,1]; select a certain threshold value greater than the square of the scalar field value of the threshold, it will be near the boundary line into two parts near the labial and lingual, lingual portion near we abandoned, leaving the rest near a boundary line portion of the labial side (e.g., FIG. 5B curved portion with respect to FIG. 5A, the reservation it). Then, we close the spline configuration (e.g., FIG. 5C with respect to FIG. 5B, the curved portion which it is added) near a specific plane dental lingual surface, the spline as a new near-lingual crown boundary line. This plane is determined only by the endpoints 1:02 near the reserved line and the B side of the lip near the lingual side (e.g., Figure 5B with respect to the plane of FIG. 5A, the they are added). Finally, both sides (i.e., near and near labial lingual) obtained in step 2 before the boundary lines combine into a complete crown optimized division boundary line.

[0052] 6. The mesh boundary line cut in accordance with the acquired model obtained crown

After the [0053] crown satisfactory division boundary line, we use a method of cutting the target grid is separated from the dental crown. The specific method is the distance of the mesh vertices calculated for each point adjacent to the boundary line. By using the local distance field, even if the division boundary line can not be completely attached to the dental surface of the grid (e.g., near the lingual side of the newly constructed spline boundary lines), grid cutting can be performed smoothly. FIG ® crown model shows the cut according to the boundary line.

Claims (7)

A three-dimensional model is divided from the single-tooth dental crown interactive computer method comprising the following steps: 1) reading and visualizing a three-dimensional dental model mesh; 2) detecting the three-dimensional dental cast grid model of dental anatomical feature points on the tooth and the occlusal plane; 3) specify the constraint of dental point of the 3D mesh model harmonic field; 4) is calculated according to the harmonic field constraint points, obtaining a boundary line dividing the crown; 5) in accordance with a boundary line dividing the acquired crown mesh cut to obtain crown model.

According to claim dividing three-dimensional model from the single-tooth dental crown computer interactive method of claim 1 wherein 2) said step of using the curvature information on vertices dental 3D mesh model and watershed method for obtaining dental anatomical feature points on the teeth, with the occlusal plane determined anatomical feature point.

3. From the three-dimensional model into single tooth dental crown interactive computer method, wherein according to claim 2, in the step 3), to specify a target located near the crown of the teeth, respectively and a distal teeth located at the point of constraint.

4. From the three-dimensional model into single tooth dental crown interactive computer method, wherein according to claim 3, said step 4), the harmonic field calculation process is as follows: set of dental 3D mesh model has m nodes, constraint point [eta], solving ΑΦ = b, the resulting solution is the harmonic field value of each vertex of the mesh model corresponding to the three-dimensional dental cast; wherein,

^? ^ '' A

Lij is the Laplacian matrix mXm order, (i, j) e E, 0 San i, j San m-1, i PE dental 3D mesh model is a set of edges;

If Vi or \ at a concave point, Vi-dimensional coordinate values ​​at the dental model mesh points i, F for dental 3D mesh model average side length of constant square;

C 1 = the elements, the remainder being 0,0 San San p m-1, p is the number of points in the r constraint 3D mesh model in the dental,

The value of each element e {0, 0.5, 1}.

According to claim dividing three-dimensional model from the single-tooth dental crown computer interactive method of claim 4 wherein said step 4), the process of obtaining a crown division boundary line is: from the harmonic field extracted several pieces of contour boundary line as a candidate set, select a highest score as candidate boundaries crown crown ring division boundary line.

6. The computer-interactive method of dividing a single tooth from dental crown 4 or three-dimensional model according to claim 5, wherein said η anatomical constraints, VIP points comprising the step 2) obtained in point , step 3) of the two specified points and a set of constraint around the crown does not belong to the target point B constraints; method of determining the constraint point B as follows: find all anatomical feature points of the projected points on the occlusal plane, , locate the occlusal plane, and a straight line passing through the projection point; occlusal plane normal to the trajectory, the linear translation toward the bottom of dental a distance, the distance is set from the crown cusp 2/3 the vertical distance to the bottom of dental; obtaining the point of intersection of the straight line and dental 3D mesh model, the intersection is the set Β.

7. Dental cast from the interactive computer method of dividing a single tooth crown according to claim 6, wherein,) in step 4, after acquiring the division boundary line of the crown, optimize the dental crown division boundary line, the optimization process is as follows: each point of a boundary line dividing crown calculating a scalar field, each point corresponding to a scalar value for the average unit normal vector and the unit normal vector of the point B near the lingual side of the point dot product of the dot product of the concept can be seen, the range of the scalar field is [selected, 1]; greater than a selected threshold value square of the scalar field value of the threshold, the division boundary line into crown near the labial and portions near two lingual, lingual portion near discard reserved line side near the lip portion; then, a spline configuration on a plane close to the near-lingual surface of the dental, the near side of the plane defined by the lip retained two endpoints, and B is near the lingual side of the boundary of one point is determined, the spline as a new boundary line near lingual crown; Finally, the near-side boundary portion of the lip and the new boundary line after almost a complete crown lingual crown boundary line combination, be optimized Cut boundary line.