WO2011054177A1

WO2011054177A1 - Method for designing middle stages of complete dental digital model

Info

Publication number: WO2011054177A1
Application number: PCT/CN2010/001737
Authority: WO
Inventors: 顾书华; 范然; 钮叶新; 杨峰; 金小刚
Original assignee: 常州高新技术产业开发区三维工业技术研究所有限公司; 常州雷卡牙科医疗科技有限公司
Priority date: 2009-11-04
Filing date: 2010-11-01
Publication date: 2011-05-12
Also published as: CN102073749B; CN102073749A

Abstract

A method for designing middle stages of a complete dental digital model, by reinforcing the anchorage in the actual orthodontic process, the method transforms the teeth that need to be orthodontic between the anchorage teeth and the moving teeth in the process of the designing of the model.

Description

Method for designing a digital model of the middle full jaw tooth

Technical field

The present invention relates to a method of designing a digital model for intermediate full jaw teeth. Background technique

The bracketless invisible appliance has become more and more popular in recent years due to its aesthetic, comfortable, hygienic, removable and convenient. The manufacturing method is as follows: (1) obtaining a high-precision digital model of the full-maxillary tooth by performing high-precision three-dimensional digital scanning and three-dimensional reconstruction of the model on the gingival or dental model; 2 correcting the digital model of the whole-collar tooth by computer-aided design The program design generates a series of intermediate digital models of the teeth that have been adjusted to the position of the teeth; 3 a series of intermediate full-toothed teeth entities are generated by rapid prototyping according to a series of intermediate digital models of teeth that are adjusted according to a series of tooth positions in 2 Model; 4 press the heated plastic sheet with a positive or negative pressure on the middle full jaw tooth solid model; '5 After cooling, the excess material is trimmed by trimming to obtain a series of bracketless invisible appliances. A key to this method of fabrication is the design of a series of intermediate full-tooth jaw models (digital models or solid models) with adjusted tooth positions. At present, computer-assisted design of a series of intermediate digital models of teeth with adjusted tooth position (see Bai Yuxing, Zhou Jiejun, etc.: Development and development of domestically-made bracketless orthodontic orthodontic treatment system. Beijing Stomatology. p89-92 , 96. ( 2004 ); Zhai Peng, Gao Hongtao, etc.: Computer-assisted gingival deformity correction technique. China Mechanical Engineering. P1637- 1640, 1653. ( 2004 ); Chinese Patent No.: ZL02117088. 6; Chinese application patent number: 200510025479. 5) , or by adjusting the physical reproduction of the tooth to design a series of intermediate full-toothed tooth solid model with adjusted tooth position (Chinese Patent Application No.: 200710018398. 1 ), all lack of consideration of the actual tooth between the teeth The anchorage, but simply adjusts all the teeth that need to be corrected from the initial state to the target state, resulting in the positional change of the teeth in the actual correction is far from the design position change, after a certain cumulative effect, The actual correction process is deviated from the pre-designed treatment process. Eventually, it was necessary to re-collect the patient's dental data, re-do all the design process, and add a lot of work. Summary of the invention

SUMMARY OF THE INVENTION The object of the present invention is to provide a method of designing a digital model of an intermediate full jaw tooth that overcomes the existing simple bracketless invisible appliance that is merely a simple subsection of the need to correct the tooth from an initial state to a target state. Insufficient solution, by strengthening the anchorage during the actual correction process, the teeth to be treated are converted between the anchoring teeth and the moving teeth, and a series of intermediate initial full jaw digital models are obtained according to the transformation. At the same time, the invention is also based on the mature digital three-dimensional grid processing algorithm, and utilizes the acceleration function of the graphics hardware to improve the speed and stability of processing the fine tooth digital model.

In order to achieve the above object, the present invention adopts a technical solution including the following five steps:

1. Interactively adjust the position of the teeth to capture the amount of movement of the tooth from the initial position to the target position. To achieve this, there are 3 sub-steps: building a local tooth movement, interactive motion, and adding key frames.

a) Establish a local coordinate system for the teeth

The three-dimensional data of the teeth is consistent with the whole digital model of the whole jaw. This allows the teeth to move and rotate only with reference to the overall coordinate system of the digital model of the whole jaw. This is not in line with the requirement of digital oral Sakisaki. The need to move and rotate itself.

Establishing a local coordinate system for each tooth allows each tooth to move and rotate relative to itself.

The specific steps to establish a local coordinate system for teeth are:

• Calculate the mean value of the dimensional data of the tooth's three-dimensional digital grid data (ie, the original x, y, and z coordinate values of the tooth), and z, which is the center point of the three-dimensional digital grid of the tooth.

• Calculate the covariance moments. Formula: co (X,Y) =

Where: and the average of the two coordinate directions representing X and Y are calculated by the previous steps. The formula: ^Cm * ⁿ = , ^C ''j = ^Dim^ Dimj )) is used to calculate the entire covariance matrix. The specific expansion is:

Co (x,x) co (x,y) cov(x,z)

C = co\(y,x) cov( ,y) cov y, z)

Cov(z,x) co (z,y) cov(z,z) Calculate the eigenvectors and eigenvalues of the covariance matrix C, sort according to the size of the eigenvalues _; define the eigenvalues according to the descending order of the eigenvalues The eigenvectors are the primary, secondary, and 3-axis. Through these three steps, the local coordinate system of a three-dimensional digital grid of teeth is calculated: the center point and three coordinate axes orthogonal to each other.

b) interactive motion operations

The movement of the teeth is interactively manipulated by motion controls around the teeth. The specific performance is as follows: Six control icons with two-way arrows are drawn around the teeth, which indicate the translation in the positive/negative direction of the main axis, the translation in the positive/negative direction of the secondary axis, the translation in the positive/negative direction of the 3 axes, and the rotation around the main axis. The positive direction rotates clockwise/counterclockwise, rotates clockwise/counterclockwise in the positive direction of the secondary axis, and rotates clockwise/counterclockwise around the positive direction of the 3 axes.

When the mouse drags and drops, the coordinates p (x, y, z) of the current point in the three-dimensional space of the screen point are calculated by picking up the current screen coordinate point and applying the OpenGL matrix.

Picking point 3D space coordinates p is used to compare the motion controls to see which motion control is acting. Calculate the motion of the tooth based on the motion meaning represented by the control and the distance the mouse moves on the screen.

c) Add keyframes

The key frame is defined as a snapshot of the state of the digital model of the full jaw tooth, in which several teeth move. Key frame addition is a key function in tooth position adjustment. The key path is used to strictly define the specific path of the tooth during the movement from the initial position to the target position to plan the movement path of the entire tooth. This is a complex case that can be handled by the present invention. One of the core technologies.

In order to achieve this, the tooth interactive position adjustment method provided by the present invention includes operations for saving current position to key frames and selection, deletion, and the like of key frames.

2. Smooth interpolation Decomposes the amount of tooth movement into a progressive movement step.

A suitable bracketless invisible appliance with a period of 2 weeks of action should have a maximum single-step movement of the corresponding tooth of 0. 5 mm. This value can be appropriately corrected according to the patient's age, tibial density and other factors. Therefore, the smoothing interpolation decomposition is performed in order to ensure that the single-step maximum motion of the teeth does not exceed 0.5.

Smooth interpolation decomposes the amount of tooth movement including two main steps: computer automatic interpolation and manual fine adjustment. a) Computer automatic interpolation

Computer automatic interpolation is based on satisfying three limit parameters: single step maximum translation, single step maximum rotation angle, single step maximum motion amount, and the method of automatically decomposing the motion amount into the initial progressive motion step. The specific implementation is:

Translational motion interpolation: direct linear interpolation The formula _Pi = p ₀ + - ( _Pd - A) is used to resolve the translational motion, where , ) is the coordinates of the initial position of the tooth, n

/ ^ is the coordinates of the tooth target position, and n is the total number of steps to be decomposed. • Rotational motion interpolation:

In order to overcome the problem of unsmoothing and universal locking caused by directly interpolating the angle, the present invention adopts a quaternion linear interpolation method of quaternion, which can smoothly interpolate between two quaternions and avoids the universal lock problem.

The formula ^ r / ( , ^", o = *(( ) ^_1 *V _{d is} used to calculate the spherical linear interpolation of the quaternion, where . and ^" are the rotation angle of the tooth at the initial position and the target position respectively. The value, t is the interpolation parameter, which is equivalent to the translation of the translational motion interpolation.

n

• Motion data verification: Motion data verification is to ensure that the single-step movement of a single tooth does not exceed the human body's tolerance. The bracketless invisible appliance prepared using this model is clinically safe and effective.

Select more than 4 (including 4) reference points on the tooth surface, calculate the amount of motion of these reference points in this single-step motion, and use the total amount of motion of all reference points not to exceed the single-step maximum motion amount as the initial progressive step of computer automatic interpolation. standard. The selection principle of the reference point is that the maximum amount of motion of the reference point between two adjacent steps can be as close as possible to the maximum amount of motion of the tooth. For example, according to the three coordinate axes of the local coordinate system of the teeth, the vertices at the two ends of the three coordinate axes are selected, that is, the six vertices from the distal end of the tooth center are used as reference points.

b) manual fine-tuning

Manual interactive fine-tuning gives the designer the opportunity to modify the initial progressive motion steps so that the motion data decomposition can be adjusted to the designer's needs to create progressive motion steps.

In order to achieve this, it is necessary to display the data automatically interpolated by the aforementioned computer to provide a modification interface.

The specific modification operation needs to go through the current step data modification, the current step motion data check, the precursor step data modification, the precursor step motion data check, the subsequent step data modification, the subsequent step motion data check and the like. The core idea is to ensure that the current and predecessor and subsequent single-step motion data meet the requirements of motion data verification when modifying the current single-step data to cause changes in the precursor and subsequent single-step data. 3. Based on the principle that the teeth to be treated are converted between the anchoring teeth and the moving teeth, the step of moving the teeth in step (2) is combined to obtain a series of intermediate initial full jaw digital models.

The digital model of the middle full jaw tooth corresponds to an appliance for the digital orthodontic method. The correction plan is to rationalize the various progressive steps of the tooth to be combined with the actual situation of the case into different intermediate initial full jaw digital models.

A basic orthodontic approach is to use all of the teeth to be treated with a head-to-head position adjustment. The digital full-tooth jaw digital model required for this treatment regimen is minimal, and the designed treatment cycle is also the shortest. However, due to the interaction of forces, the actual correction process tends to deviate from the design process. As a result, after a period of correction, the patient needs to re-acquire the full-maxillary tooth data, redesign the correction plan, and finally lead to a longer time to complete the entire correction process, and more manpower and material resources. This occurs at a very high frequency when the number of teeth to be corrected in the jaw is greater than the number of teeth that need not be corrected. This is the case with all the movements of the teeth using a corrective position adjustment scheme, mainly because the importance of anchorage during the actual treatment is not taken into account.

In order to strengthen the anchorage during the actual treatment, reduce the number of repeated jaw extraction models and repeat the treatment plan, the present invention provides an interface for combining the steps of the various progressive processes of the tooth, including adding an intermediate initial full-neck digital model, The intermediate initial full jaw digital model is deleted, and the operation of the single progressive motion step of the tooth to any intermediate initial full jaw digital model is placed.

The combination provided by the present invention is required to correct the interface of each progressive movement step of the tooth, and it should be ensured that the number of teeth in the initial digital model of the initial full-necked tooth is at least one and cannot exceed 15 at the same time. The number of teeth in each of the intermediate initial lock-in tooth digital models is preferably no more than 1/2 of the number of teeth to be treated, preferably no more than 1/3 of the number of teeth to be treated.

4. Install the accessories.

The attachments are primarily designed to enhance the force, handle some special tooth movements, and assist the appliance in the movement of the teeth. The elevation of the anterior teeth, the depression, the rotation of the cone or the prototype tooth, the closure of the gap in the case of extraction and the translation of the large distance of the teeth are the main applications requiring an accessory for assisted correction.

Attachment installation involves appliance attachment and tooth surface attachment installation. On the one hand, the doctor installs attachments on the surface of the teeth where the case needs to be attached according to the type and size of the attachment specified in the treatment plan. On the other hand, the appliance must contain an accessory containment compartment that can accommodate the accessory, and the accessory containment compartment tightly wraps the attachment mounted on the tooth, increasing the force exerted by the appliance on the tooth.

In order to achieve this, an attached three-dimensional digital grid and a three-dimensional digital grid of host teeth are required. The fusion is a Boolean merge operation. Guo Kaibo, Zhang Lichao, etc. The Boolean operation method based on intersecting loop detection proposed in the article "Implementation of Boolean Operation in STL Model" can be applied to the mesh of tooth model and accessory model. The specific implementation steps are as follows:

a) Read in two entities, topology reconstruction, establish connection relationships, and establish closed-surface information.

b) Intersect test, if there are patches, then turn c, no face will intersect, then turn ^

c) Find the intersection line and track the intersection line.

d) Perform a quadratic triangulation on the intersected triangles and use the intersection loop to divide the intersecting surfaces.

e) Judging the positional relationship of the sub-surface obtained by the split with respect to another entity.

f) Determine the inclusion relationship of all non-intersecting surfaces relative to another entity.

g) Boolean operations are implemented using Boolean operators.

5. Virtual gingival free deformation, generating a digital model of the middle full jaw tooth

Changes in the position of the teeth can cause changes in the gum tissue around the teeth. Gingival data obtained from the calculation of gingival deformation, which is more in line with tooth traction, can improve the comfort of the appliance during use and reduce the compression of the appliance on the gum tissue. At the same time, the process of deformation of the gums along with the movement of the teeth can improve the convenience of the doctor and the patient in the design of the treatment plan, and can intuitively show the entire treatment plan to the patient.

The virtual gingival free deformation is based on the tooth motion information in the correction program stage to calculate the deformation of the virtual gingival grid data, so that the middle full jaw tooth digital model contains the deformed gingival data.

To achieve this, the present invention employs a model free deformation algorithm based on the Laplacian operator. The virtual gums are divided into different deformation regions, and one deformation region includes a tooth adjacent to the gum region and the boundary of two adjacent teeth as a fixed boundary of the deformation region. Use the tooth movement frame to control the gum boundary, and then control the local area of the gum. The overall deformation of the gums is sequentially deformed by localized areas, and the gingival deformation is finally completed. DRAWINGS

Figure 1 Flow chart of the design of the middle maxillary tooth digital model

Figure 2 Digital model of the complete jaw of the complete tooth segmentation in the case of maxillary gap closure in the single-maxillary correction (including maxillofacial view, lip view, left cheek view, right buccal view)

Figure 3 Digital model of the full-maxillary teeth with position adjustment in the upper jaw correction closed single-maxillary correction case Figure 4 Intermediate initial 7 steps from the initial position to the final position in the upper jaw closure Full-necked tooth digital model (maxillofacial view)

Figure 5: The initial initial full-tooth digital model (right buccal) of the 7-step initial position to the final position in the case of maxillary gap closure

Figure 6. Attachment model on the left and right incisors in the digital initial model of the maxillary teeth in the upper jaw correction case

Figure 7: Setting the virtual gingival free deformation zone in the case of upper maxillary gap closure

Fig. 8 The triangular model of the middle full jaw tooth digital model in the seventh step of the upper jaw correction closed single jaw correction case

Figure 9 Clinical comparison before and after correction in the case of upper maxillary gap closure

detailed description

The invention is intended to be illustrative, and not to limit the scope of the invention.

Example 1 The generation of a digital model of a full-collar tooth in a case of maxillary gap closure in a single jaw correction.

The teeth to be corrected are the right canine (UR3), the right second incisor (UR2), the right incisor (UR1), the left incisor (UL1), the left second incisor (UL ² ), and the left canine (UL ³ ). ).

1. Open the computer software and import the digital model of the full-tooth jaw of the tooth segmentation repair that needs to close the gap, as shown in the attached figure: Figure 2 The digital model of the full-toothed tooth in the case of the upper jaw correction closed single-finger correction (including maxillofacial view, lip view, left cheek view, right buccal view).

2. By establishing the local motion system of the teeth, interactive motion operations, adding key frames, adjusting the position of the teeth, closing the gaps of the teeth, aligning them, and obtaining the amount of movement of the teeth from the initial position to the target position. For example, the figure shows: Figure 3 The digital model of the full-maxillary tooth that completes the position adjustment in the upper jaw correction closed single-jaw correction case.

3. Interactively set the smooth interpolation to decompose the maximum single-step movement of the tooth. 0. 5, the maximum rotation of the single step is 5 degrees, the maximum movement of the single step is 0. 5mm, and the interpolation is performed automatically by computer software to decompose the amount of movement of the teeth into a progressive movement step. And through manual fine-tuning, the progressive movement steps meet the designer's requirements.

4. On the basis of the progressive movement of the teeth in the third step, consider the anchorage effect in the actual correction, and the principle of the progressive movement of the teeth in step 3 in combination with the principle that the teeth to be treated are converted between the anchoring teeth and the moving teeth. , obtained a series of intermediate initial full jaw digital models in the correction process. As shown in the attached drawing: Figure 4 The initial initial full-tooth digital model (maxillofacial view) from the initial position to the final position in the upper maxillary gap closed single-maxillary correction case, Figure 5 Upper maxillary gap closed single-jaw correction From the most The initial initial full-tooth digital model (right buccal view) of the initial position to the final position of 7 steps, the change of the position of the teeth in the initial digital model of the initial full-tooth jaw in each step is shown in Table 7.

Table 1 shows the change of tooth position in the initial digital model of the initial full jaw tooth in the first step

Table 2, the second step of the intermediate initial full jaw digital model of the change in the position of the teeth

Table 3 shows the change of tooth position in the digital model of the initial initial maxillary teeth in the third step of Table 3.

Table 4 shows the change of tooth position in the digital model of the initial initial maxillary teeth in the fourth step of Table 4.

Table 5 shows the change of tooth position in the initial digital model of the initial full jaw tooth in the fifth step of Table 5.

Table 6 shows the change of tooth position in the initial initial full-tooth digital model in the sixth step

Table 7 shows the change of tooth position in the digital initial model of the initial initial maxillary teeth in the seventh step of Table 7.

5. Attach the attachment model for enhanced orthodontic force to the left and right incisors on the digital initial model of the initial full-maxillary teeth by attachment model positioning and Boolean merging. Figure 6 Upper maxillary gap closure single-jaw correction case In the example, the attachment model is mounted on the left and right second incisors in the middle initial full-maxillary tooth digital model.

6. When the tooth position changes, the virtual gingival free deformation area, when the tooth position changes, the virtual gingival tissue uses the Laplacian operator-based model free deformation algorithm to simulate the shape change of the actual gingival tissue, so that the post-production appliance conforms. Anatomical requirements, comfortable to wear. For example, the figure shows: Figure 7 The virtual jaw free deformation zone is set in the upper jaw correction closed single-jaw correction case.

7. Output a digital model of the middle full jaw tooth and save it as a triangular mesh model. As shown in the attached figure: Figure 8 The triangular model of the digital model of the middle full jaw tooth in the seventh step of the upper jaw correction.

Through a certain device, the digital model of the middle collar tooth is materialized, and based on the physical model of the middle full jaw tooth, a series of appliances are manufactured, and the patient achieves the orthodontic treatment by wearing these appliances. As shown in the attached drawing: Figure 9 Clinical comparison before and after correction in the case of upper maxillary gap closure. [Embodiment 2] The method of designing a digital model of the middle full jaw tooth of the present invention and the method of designing a digital model of the middle full jaw tooth in parallel are clinically compared.

Experiment: Ten patients with 3 jaws were selected, and 10 patients with a crowded jaw size of 4 mm were selected. Twenty patients were divided into two groups, each group consisting of 5 patients with interdental space and 5 patients with crowded jaws. For the first group of patients, the design of the intermediate maxillary tooth digital model according to the present invention is used to design and manufacture the appliance, and for the second group of patients, the intermediate full jaw tooth number is designed for the second group of patients. The method of the model is designed to produce an appliance. See Table 8 for the redesign of the two groups of patients during the correction process.

Table 8 Comparison of clinical application effects based on two methods for designing a digital model of the maxillary teeth in the middle

Through the above experiments, it can be obtained that the tooth correction is performed by using the method of the present invention, and the number of times of design re-design is zero, the correction time is greatly saved, the correction efficiency is improved, and the cost is saved.

Claims

Rights request

A method for designing a digital model of an intermediate full-toothed tooth, characterized in that the anchorage during an actual correction process is enhanced, and the tooth to be treated is converted between the anchoring tooth and the moving tooth during the design of the model, and according to the The transformation yields a series of intermediate initial full jaw digital models.

2. The method of designing an intermediate full-range tooth digital model according to claim 2, characterized in that the described tooth is converted between an anti-tooth and a moving tooth, wherein the number of moving teeth is at least one .

3. The method of designing a digital model of an intermediate full jaw tooth according to claim 2, characterized in that the described tooth is converted between an anti-tooth and a moving tooth, wherein the number of moving teeth is preferably not More than 15 pieces.

4. The method of designing a digital model of an intermediate full jaw tooth according to claim 2, characterized in that the described tooth is converted between the anchoring tooth and the moving tooth, wherein the number of moving teeth is preferably not More than 1/2 of the number of teeth to be treated.

5. The method of designing a digital model of an intermediate full jaw tooth according to claim 2, characterized in that the described tooth is converted between an anti-tooth and a moving tooth, wherein the number of moving teeth is preferably not More than 1/3 of the number of teeth to be treated.

6. Claim 1 The method of designing a digital model of the intermediate full jaw tooth is selected from the following steps:

(1) Determining the position of the tooth target for the complete maxillary tooth digital model of the tooth to be reconstructed and reconstructing, and interactively adjusting the position of the tooth to the target position to obtain the amount of movement of the tooth from the initial position to the target position;

(2) The amount of tooth movement in the smooth interpolation decomposition step (1) is a progressive motion step;

(3). Based on the principle that the tooth to be treated is converted between the anchoring tooth and the moving tooth, the step of moving the tooth in the step (2) is combined to obtain a series of intermediate initial full jaw digital model;

(4). Install attachments on the surface of the teeth to assist the correction;

(5) The free deformation of the virtual gingiva is performed according to the movement of the teeth in each of the intermediate initial full jaw digital models in step (3) to generate a digital model of the intermediate full jaw tooth.

7. The method of designing an intermediate fully locked tooth digital model of claim 6 wherein the described target position determining method comprises a plurality of key frames for determining a correction path.

8. The method of designing a digital model of an intermediate full jaw tooth according to claim 6, wherein the quaternary linear interpolation method based on the quaternion used in the described tooth motion amount decomposition comprises computer automatic interpolation. And interactive fine-tuning.

9. The method of designing a digital model of an intermediate full jaw tooth according to claim 6, wherein the attachment mounting method of the method comprises attachment mounting, positioning, ablation operation, and fusion of the attached three-dimensional mesh and the host tooth model.

10. A method of designing a digital model of an intermediate full jaw tooth as claimed in claim 6 wherein the described virtual gingival free deformation employs a Laplacian based mesh controlled free deformation method.

11. The method of designing a digital model of an intermediate full jaw tooth according to claim 6, wherein the intermediate digital model of the full jaw tooth comprises a mesh of the attachment and the fusion of the teeth and a mesh after the virtual gum is optimized.