PROCESS FOR DETERMINING A TOOTH COLOR

• US 20200132550A1
• Filed: 10/07/2019
• Published: 04/30/2020
• Est. Priority Date: 10/25/2018
• Status: Active Grant

• Current Assignee: Ivoclar Vivadent AG
• Original Assignee: Ivoclar Vivadent AG
• Inventors: Lerch, Stefan, Pulido Estepa, Jose Antonio
• Granted Patent: US 11,199,452 B2
• Time in Patent Office: Days
• CPC Class Codes: A61C 19/04 Measuring instruments specially adapted for dentistry A61C5/44 takes precedence; testing vitality of teeth A61B5/0534; radiation diagnosis specially adapted for dentistry A61B6/51
• CPC Class Codes: A61C 19/10 Supports for artificial teeth for transport or for comparison of the colour
• CPC Class Codes: A61C 5/00 Filling or capping teeth
• CPC Class Codes: G01J 3/463 Colour matching
• CPC Class Codes: G01J 3/508 measuring the colour of teeth
• CPC Class Codes: G01J 3/52 using colour charts

Abstract

A process for determining a tooth color of a filling or another restoration is provided which in particular is produced using composite materials, wherein at least one tooth is scanned or is visually detected. The process is characterized in that natural teeth are spectrally measured in advance, that the color values measured within a color space are classified into several, in particular four, categories which each form a color cloud extending in a three-dimensional fashion within the color space, which is done with the help of a structuring algorithm, in particular a Nearest Neighbour Algorithm, or a symmetry recognition algorithm, and that the tooth color of the filling is determined by means of evaluating to which category the tooth scanned has the smallest color distance, or to which color cloud the tooth scanned belongs.

Claims

1. A process for determining a tooth color of a filling or restoration comprising

electronically recording a color value of at least one tooth,

wherein natural teeth are spectrally measured in advance or in a first step to determine color values of the natural teeth,

wherein the measured color values of the natural teeth are classified into several categories within a color space,

wherein each of the several categories form a three-dimensional color cloud within the color space, which is performed with a structure-recognizing algorithm, and

wherein the tooth color of the filling or restoration is determined by evaluating to which of the several categories the recorded color value has the smallest color distance, or to which color cloud the recorded color value belongs.

2. The process according to claim 1,

wherein the filling or restoration is produced using composite materials,

wherein the at least one tooth is are scanned to determine the color value, and

wherein the several categories comprise four categories.

3. The process according to claim 1,

wherein the determined tooth color is used for the filling or the restoration.

4. The process according to claim 1,

wherein the natural teeth are selected from a multitude of at least 20 different existing natural teeth, independently of the restoration or filling to be color-matched.

5. The process according to claim 1,

wherein based on the spectral measurement, one point within the color space is determined for each of the natural teeth, and

wherein, based on the points determined for each of the natural teeth measured, a convex envelope is determined within the color space, to which the color value points of all of the natural teeth measured belong.

6. The process according to claim 5,

wherein a structure, a grid or a mesh, made up of uniformly distributed points is placed over the color space, and, based on initial categories, evaluating which initial category is closest to some O point or initial point, category boundaries between individual categories are iteratively determined as surfaces extending in a three-dimensional fashion.

7. The process according to claim 1,

wherein the classification into categories is performed based on the largest number of neighboring points,

wherein each category corresponds to one natural tooth.

8. The process according to claim 7,

wherein a Euclidian distance is used as the measurement of the color distance.

9. The process according to claim 1,

wherein the algorithm is a Nearest Neighbour Algorithm or one symmetry-recognition algorithm.

10. The process according to claim 1,

Wherein, for determining the categories, random initial categories are first selected,

wherein entropy of categorisation is calculated as a measurement of quality over the entire color space, and

wherein, with the help of the Nearest Neighbour Algorithm comprising a K Nearest Neighbour Algorithm, and pre-determining the number of categories, optimum category boundaries are iteratively determined.

11. The process according to claim 10,

wherein the number of categories is first determined to be a specific value by way of trial, and

wherein a maximum permissible color distance value is determined, and

wherein the number of categories is increased if the color distance value is exceeded in the worst case.

12. The process according to claim 11,

wherein the specific value comprises 4, and

wherein the maximum permissible color distance value comprises E=5.8.

13. The process according to claim 11,

wherein the specific value comprises 4,

wherein a second maximum permissible color distance value is determined, and

wherein the number of categories is reduced if the color distance value is undercut in a worst case.

14. The process according to claim 13,

wherein the second maximum permissible color distance value comprises E=3.

15. The process for determining a tooth color of a filling, an inlay or an onlay which is produced using composite materials comprising

scanning or visually detecting at least one tooth,

spectrally measuring, in advance, natural teeth to provide color values within a color space classified into several categories which each form a color space extending in a three-dimensional fashion within the color space, which is done with a structure-recognizing algorithm, and

determining the tooth color of the filling, inlay or onlay by evaluating to which center of the color cloud of one of the categories the tooth has the slightest color distance,

wherein the color value centers were determined in advance.

16. The process according to claim 15,

wherein the several categories comprise four categories.

17. The process according to claim 15,

wherein four color clouds are formed corresponding to the categories, and

wherein the centers of each of the four color clouds are situated at the following position:

18. An apparatus comprising

at least one processor,

a memory operatively coupled to the at least one processor and storing computer readable instructions, that when executed cause the apparatus to:

receive measured color values from a plurality of natural teeth,

classify the color values of the plurality of measured teeth into several categories within a color space,

wherein each of the several categories form a three-dimensional color cloud within the color space using a structure-recognizing algorithm,

wherein the several categories provide a set of color values for a set of tooth coloring materials.

19. The apparatus according to claim 18, further comprising

a connection to a spectrophotometer.

20. A computer implemented method for determining color values of dental materials comprising;

spectrally measuring a plurality of natural teeth to determine color values of the natural teeth,

classifying the measured color values of the natural teeth into several categories within a color space,

wherein each of the several categories form a three-dimensional color cloud within the color space, and

wherein the several categories provide a set of color values for a set of dental materials or tooth coloring materials.

21. The computer implemented method according to claim 20,

wherein the forming of the three-dimensional color cloud is done with a structure-recognizing algorithm.

22. The computer implemented method according to claim 20, further comprising

determining which dental material or tooth coloring material most closely matches a patient'"'"'s tooth for which a dental restoration is being made.

23. A set of dental materials comprising

a set of different colored dental materials having color values determined using the method of

spectrally measuring a plurality of natural teeth to determine color values of the natural teeth,

classifying the measured color values of the natural teeth into several categories within a color space,

wherein each of the several categories form a three-dimensional color cloud within the color space, and

wherein the several categories provide a set of color values for the set of different colored dental materials.