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EP-4167125-B1 - 3D TEETH MODEL GUM LINE IDENTIFYING METHOD, SYSTEM AND APPARATUS, AND STORAGE MEDIUM

EP4167125B1EP 4167125 B1EP4167125 B1EP 4167125B1EP-4167125-B1

Inventors

  • WANG, YONG
  • FENG, Wei

Dates

Publication Date
20260506
Application Date
20201208

Claims (12)

  1. A computer-implemented method for identifying a gum line of a 3D tooth model, comprising: extracting a plurality of feature points from the 3D tooth model based on a geometric algorithm of curvature, pre-processing each of the feature points, and outputting a feature contour point group; obtaining a first fitting reference line from a pre-stored fitting reference line pool with the first fitting reference line being matched with a shape parameter of the 3D tooth model, comprising: identifying the shape parameter of the 3D tooth model, and determining a direction of the 3D tooth model according to the shape of the 3D tooth model; obtaining feature contour lines from the pre-stored fitting reference line pool with the feature contour lines having the same direction as feature contour of the 3D tooth model, based on the direction of the 3D tooth model; and screening and obtaining the first fitting reference line from the feature contour lines with the same-direction according to a pre-established coordinate system and a first threshold; performing an iterative operation on the first fitting reference line based on the feature contour point group, to generate an initial fitted line, wherein the iterative operation comprising: projecting points of the first fitting reference line to feature points, closest thereto, of the feature contour point group, and determining a projection error; cycling the projecting and the determining when the projection error is not less than a set threshold; and stopping the projecting when the projection error is less than a set threshold; and performing smoothing processing on the initial fitted line by using a dimensionality reduction algorithm, to output the gum line, characterizedin that, comprising: performing smoothing processing on the initial fitted line by using a principal component analysis method, and determining main direction points of the initial fitted line; and performing smooth connection on the main direction points of the initial fitted line subjected to the smoothing processing according to an interpolation spline, to output the gum line; wherein the geometric algorithm of curvature refers to a method to calculate a rotation rate of the tangential direction angle of a surface on the 3D tooth model to an arc length, and each of the feature points is characterized by a corresponding rotation rate.
  2. The method as claimed in claim 1, wherein the pre-processing comprises filtering processing or denoising processing; and the step of extracting a plurality of feature points from the 3D tooth model based on a geometric algorithm of curvature, pre-processing each of the feature points, and outputting a feature contour point group comprises: after identifying the shape parameter and a maximum bottom surface of the 3D tooth model, adjusting the 3D tooth model to a target position; extracting the plurality of feature points from the 3D tooth model at the target position by using the geometric algorithm of curvature, wherein the plurality of feature points are distributed in recessed and raised regions of the 3D tooth model; and performing filtering processing or denoising processing on the each of the extracted feature points, to generate the feature contour point group.
  3. The method as claimed in claim 2, wherein the step of after identifying the shape parameter and a maximum bottom surface of the 3D tooth model, adjusting the 3D tooth model to a target position comprises: acquiring the 3D tooth model, identifying the maximum bottom surface and the shape parameter of the 3D tooth model, and outputting a normal vector of the maximum bottom surface; rotating the 3D tooth model to a target plane according to the normal vector of the maximum bottom surface and a first preset normal vector; acquiring a contour of the 3D tooth model on the target plane, determining a skeleton curvilinear equation of a 3D tooth model according to the contour, and outputting a direction vector of the 3D tooth model based on the skeleton curvilinear equation; and rotating the 3D tooth model to the target position according to the direction vector of the 3D tooth model and a second preset normal vector.
  4. The method as claimed in claim 3, wherein the first preset normal vector is a corresponding normal vector of the 3D tooth model when the 3D tooth model is rotated to the target plane; and the second preset normal vector is a corresponding normal vector of the 3D tooth model when the 3D tooth model is rotated to the target position.
  5. The method as claimed in any one of claims 3-4, wherein the step of acquiring a contour of the 3D tooth model on the target plane, determining a skeleton curvilinear equation of a 3D tooth model according to the contour comprises: projecting the 3D tooth model to obtain the contour of the 3D tooth model; extracting a skeleton from the contour, and denoising the extracted skeleton to obtain the skeleton line, and determining the skeleton curvilinear equation based on the skeleton line.
  6. The method as claimed in any one of claims 3-5, wherein the step of adjusting the 3D tooth model to a target position comprises: obtaining a rotation angle and a rotation axis according to vector values before and after a rotation; rotating the 3D tooth model to a target plane according to the rotation angle and the rotation axis; obtaining another rotation angle and another rotation axis according to vector values before and after another rotation; rotating the 3D tooth model to the target position according to the another rotation angle and another rotation axis.
  7. The method as claimed in claim 1, wherein the step of screening and obtaining the first fitting reference line from the feature contour lines with the same-direction according to a pre-established coordinate system and a first threshold comprises: screening a reference line with a minimum deviation from the feature contour lines, to obtain the first fitting reference line, wherein the first threshold is a value representing the minimum deviation between matched feature contour lines and the 3D tooth model.
  8. The method as claimed in any one of claims 1 to 7, wherein the step of performing an iterative operation on the first fitting reference line based on the feature contour point group, to generate an initial fitted line comprises: performing geometric superposition on a centroid of the first fitting reference line and a centroid of the feature contour point group based on the pre-established coordinate system; and performing iterative fitting on the first fitting reference line and each of the feature points of the feature contour point group by using an approximate iterative algorithm, to generate the initial fitted line.
  9. The method as claimed in any one of claims1-8, wherein a direction of the first fitting reference line is the same as a direction of the feature contour point group such that the first fitting reference line covers a region of the feature contour point group.
  10. A data processing system for identifying a gum line of a 3D tooth model, comprising: an extraction module, configured to extract a plurality of feature points from the 3D tooth model based on a geometric algorithm of curvature, pre-process each of the feature points, and output a feature contour point group; a matching module, configured to obtain a first fitting reference line from a pre-stored fitting reference line pool with the first fitting reference line being matched with a shape parameter of the 3D tooth model; wherein the matching module comprises: a determination unit, configured to identify the shape parameter of the 3D tooth model, and determine a direction of the 3D tooth model according to the shape of the 3D tooth model; a matching unit, configured to obtain feature contour lines from the pre-stored fitting reference line pool with the feature contour lines having the same direction as feature contour of the 3D tooth model, based on the direction of the 3D tooth model; and a screening unit, configured to screen and obtain the first fitting reference line from the feature contour lines with the same-direction according to a pre-established coordinate system and a first threshold; an iteration module, configured to perform an iterative operation on the first fitting reference line based on the feature contour point group, to generate an initial fitted line, wherein the iterative operation comprises: projecting points of the first fitting reference line to feature points, closest thereto, of the feature contour point group, and determining a projection error; cycling the projecting and the determining when the projection error is not less than a set threshold; and stopping the projecting when the projection error is less than a set threshold; and an output module, configured to perform smoothing processing on the initial fitted line by using a dimensionality reduction algorithm, to output the gum line; characterized in that , the output module comprises: a smoothing unit, configured to perform smoothing processing on the initial fitted line by using a principal component analysis method, and determine main direction points of the initial fitted line, wherein the dimensionality reduction algorithm comprises the principal component analysis method; and a smooth unit, configured to perform smooth connection on the main direction points of the initial fitted line subjected to the smoothing processing according to an interpolation spline, to output the gum line; wherein the geometric algorithm of curvature refers to a method to calculate a rotation rate of the tangential direction angle of a surface on the 3D tooth model to an arc length, and the each of the feature points is characterized by a corresponding rotation rate.
  11. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of claims 1-9.
  12. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of claims 1-9 when executed by the computer.

Description

Cross-Reference to Related Disclosure The present disclosure is proposed based on Chinese Patent Application No. 202010634000.2 and filed on 02 July 2020, and claims priority to the Chinese Patent Application. Technical Field The present disclosure relates to the technical field of orthodontics, and in particular, to a method and system for identifying a gum line of a 3D tooth model, a device, and a storage medium. Background Term explanation: Invisible Orthodontic: refers to invisible orthodontics without brackets, and belongs to one type of orthodontics. With the development of scientific and technical information, technologies such as computer technology, manufacturing technology, digital modeling technology, material science, numerical control technology, etc. have rapidly developed and grew stronger, and these subjects merge with each other. In particular, the computer technology has been increasingly infiltrated into various aspects such as teaching, scientific research and clinical applications in various medical fields, and can achieve more progressive mutual cooperation. Moreover, with the development and popularity of measurement technology, people can conveniently acquire digitized tooth models, which plays an important role in the process of oral clinical diagnosis and treatment. The emergence and development of 3D printing technology has become one of the current hot topics, and applying the 3D printing technology to the medical field is also very common. 3D printing has been applied in the medical field for more than two decades, and is widely applied to operations such as oral planting, or thopaedics, and neurosurgery. Dental treatment is an unavoidable problem for most people. With the improvement of computer software and hardware technologies and the appearance of increasingly precise tooth data, people also turn their attention from traditional pure manual dental treatment to digitized dental treatment such as tooth diagnosis and treatment in the invisible orthodontic, so as to improve the safety and success rate of dental treatment with the help of priori knowledge provided by advanced digital technology. In the current application scenarios of tooth diagnosis and treatment in the invisible orthodontic, performing data processing on tooth models are all needed; however, data pre-processing of the tooth models occupies most of the time of 3D tooth printing work. In particular, in application scenarios of orthodontics, in addition to requiring to perform data pre-processing including placement, hollowing and Boolean operations on a tooth model, after printing is completed, it is also necessary to perform film pressing, and after the film pressing, manual cutting is required, or a gum line is manually drawn to supply to a CNC machine for cutting. This process needs to consume significant labor costs and significant workload. In order to increase the efficiency of the whole diagnosis and treatment process and enhance the user experience, it is necessary to shorten the data processing time of tooth model data. In addition, currently, an automatic processing flow of orthodontics is still in a blank stage in China, and therefore there is an urgent need to achieve automatic generation and processing flow of orthodontics according to technologies such as artificial intelligence algorithm, 3D printing and numerical control machining, so as to improve the working efficiency and competitiveness of the whole industry. Document CN104504693A discloses a method for obtaining a margin line of a tooth model, which generates a model by scanning, obtains feature points and generates feature lines by screening the feature points, determines an initial point of the margin line, and screens the desired margin line by screening the feature lines. Document KR101476715B1 discloses a transparent orthodontic device and a method for producing the same. The transparent orthodontic device comprises: an inserting orthodontic unit which is covered on a tooth group including tooth pocket grooves which are formed corresponding to an orthodontic shape; and a support unit which is extended from the inserting orthodontic unit to gums, wherein a removing handle is formed on the outer gums of the molar. Document CN108986123A discloses a method for segmenting a three-dimensional digital model of a jaw, comprising: obtaining a three-dimensional digital model of a first jaw; and segmenting each part of the first three-dimensional digital model of a jaw using a trained deep artificial neural network teeth. Regarding the current domestic technical problems of low degree of automation, poor efficiency and poor user experience during data processing of tooth models in an orthodontic automatic process, the technical solutions of some embodiments of the present disclosure take efficiency improvement as a basis, innovatively explore a combination of the dental field and the 3D printing technology, and integrate the digital 3D printing te