Subdividing a digital dentition model

• US 20040175671A1
• Filed: 03/15/2004
• Published: 09/09/2004
• Est. Priority Date: 06/20/1997
• Status: Active Grant

• Current Assignee: Align Technology Incorporated
• Original Assignee: Align Technology Incorporated
• Inventors: Chishti, Muhammad, Bala, Gregory P., Wen, Huafeng, Jones, Timothy N.
• Granted Patent: US 7,247,021 B2
• Time in Patent Office: Days
• US Class Current: 433/24
• CPC Class Codes: A61C 2007/004 Automatic construction of a set of axes for a tooth or a plurality of teeth
• CPC Class Codes: A61C 7/00 Orthodontics, i.e. obtaining or maintaining the desired position of teeth, e.g. by straightening, evening, regulating, separating, or by correcting malocclusions
• CPC Class Codes: A61C 7/002 Orthodontic computer assisted systems
• CPC Class Codes: A61C 9/00 Impression cups, i.e. impression trays; Impression methods computer-assisted sizing A61C13/0004; instruments for determining occlusion A61C19/05
• CPC Class Codes: A61C 9/0053 Optical means or methods, e.g. scanning the teeth by a laser or light beam

Abstract

A computer or other digital circuitry is used to assist in the creation of a digital model of an individual component, such as a tooth or gum tissue, in a patient'"'"'s dentition. The computer receives a data set that forms a three-dimensional (3D) representation of the patient'"'"'s dentition, applies a test to the data set to identify data elements that represent portions of the individual component, and creates a digital model of the individual component based upon the identified data elements. Many implementations require the computer to identify data elements representing a 2D cross-section of the dentition lying in a 2D plane that is roughly parallel to or roughly perpendicular to the dentition'"'"'s occlusal plane. The computer analyzes the 2D cross-section to identify dentition features that represent boundaries between individual dentition components.

Claims

1. A computer-implemented method for use in creating a digital model of an individual component of a patient'"'"'s dentition, the method comprising:

(a) receiving a data set that forms a three-dimensional (3D) representation of the patient'"'"'s dentition;

(b) applying a computer-implemented test to the data set to identify data elements that represent portions of an individual component of the patient'"'"'s dentition; and

(c) creating a digital model of the individual component based upon the identified data elements.

2. The method of claim 1, wherein the data set includes data taken from at least one of the following sources:

two-dimensional (2D) x-ray data and three-dimensional (3D) x-ray data.

3. The method of claim 1, wherein the data set includes data taken from at least one of the following sources:

computed tomography (CT) scan data and magnetic resonance imaging (MRI) scan data.

4. The method of claim 1, wherein the data set includes data taken from a photographic image of the patient'"'"'s dentition.

5. The method of claim 1, wherein some of the data is obtained by imaging a physical model of the patient'"'"'s teeth.

6. The method of claim 1, wherein some of the data is obtained by imaging the patient'"'"'s teeth directly.

7. The method of claim 1, wherein the data set forms a 3D volumetric representation of the patient'"'"'s dentition.

8. The method of claim 1, wherein the data set includes geometric surface data that forms a 3D geometric surface model of the patient'"'"'s dentition.

9. The method of claim 1, wherein the individual component is an individual tooth in the patient'"'"'s dentition.

10. The method of claim 1, wherein the individual component includes gum tissue found in the patient'"'"'s dentition.

11. The method of claim 1, wherein applying the computer-implemented test includes receiving information input by a human user to identify a boundary of the individual component to be modeled.

12. The method of claim 11, wherein receiving information includes receiving position data from a computer-implemented tool through which the human user identifies the boundary in a graphical representation of the patient'"'"'s dentition.

13. The method of claim 12, wherein the computer-implemented tool is a saw tool that allows the user to identify the boundary by defining a curve in the graphical representation that separates the data elements associated with the individual component from other elements of the data set.

14. The method of claim 12, wherein the computer-implemented tool is an eraser tool that allows the user to identify the boundary by erasing a portion of the graphical representation representing the boundary.

15. The method of claim 1, wherein receiving the data, applying the computer-implemented test, and creating the electronic model all are carried out by a computer without human intervention.

16. The method of claim 1, wherein applying the computer-implemented test includes automatically applying a rule to identify a boundary of the individual component to be modeled.

17. The method of claim 16, wherein the boundary includes a surface of a tooth.

18. The method of claim 16, wherein the boundary includes a gingival margin.

19. The method of claim 1, wherein applying the computer-implemented test includes identifying elements of the data set that represent a structural core of the individual component to be modeled and labeling those data elements as belonging to the individual component.

20. The method of claim 19, further comprising applying another computer-implemented test to identify elements of the data set that represent a structural core of another individual component of the dentition and labeling those data elements as belonging to the other individual component.

21. The method of claim 20, wherein applying the computer-implemented tests includes applying tests to link other elements of the data set to those representing the structural cores of the individual components and labeling the linked elements as belonging to the individual components to which they are linked.

22. The method of claim 21, wherein applying the tests to link other data elements to the structural cores of the individual components includes determining whether a data element already is labeled as belonging to one of the individual components.

23. The method of claim 1, wherein applying the computer implemented test includes identifying an initial 2D cross-section of the individual component having continuous latitudinal width, a relative minimum value of which occurs at an end of the initial cross-section.

24. The method of claim 23, wherein applying the computer-implemented test includes isolating portions of the data corresponding to the initial 2D cross-section of the individual component to be modeled.

25. The method of claim 24, wherein the received data includes 3D image data obtained by imaging the individual component volumetrically, and wherein isolating portions of the data corresponding to the initial 2D cross-section includes isolating elements of the 3D image data representing the initial 2D cross-section.

26. The method of claim 23, wherein applying the computer-implemented test includes applying a test to identify the end of the initial cross-section at which the relative minimum value of the latitudinal width occurs.

27. The method of claim 26, wherein applying the test to identify the end of the initial cross-section includes:

(a) establishing line segments within the initial cross-section, each of which is bounded at each end by an endpoint lying on a surface of the individual component, and each of which is roughly perpendicular to a latitudinal axis of the individual component;

(b) calculating a length for each line segment; and

(c) identifying elements of the data set that correspond to the endpoints of the line segment with the shortest length.

28. The method of claim 27, wherein applying the computer-implemented test also includes:

(a) isolating portions of the data set corresponding to other 2D cross-sectional of the individual component, all lying in planes parallel to the initial 2D cross-sectional;

(b) for each of the other cross-sections, identifying data elements that correspond to endpoints of a line segment representing an end of the cross-section; and

(c) defining a solid surface that contains all of the identified data elements.

29. The method of claim 28, further comprising labeling the solid surface as representing a surface of the individual component to be modeled.

30. The method of claim 28, further comprising using the data elements identified in the initial cross-section as guides for identifying the data elements in the other cross-sections.

31. The method of claim 26, wherein applying the test to identify the end of the initial cross-section includes first creating an initial curve that is roughly perpendicular to the latitudinal axis of the individual component and that is fitted between the surfaces of the 2D cross-section on which the endpoints of the line segments will lie.

32. The method of claim 31, wherein establishing the line segments includes first establishing a set of initial line segments that are roughly perpendicular to the curve and to the latitudinal axis and that have endpoints lying on the surfaces of the individual component.

33. The method of claim 32, wherein establishing the line segments also includes pivoting each initial line segment about a point at which the initial line segment intersects the curve until the initial line segment has its shortest possible length.

34. The method of claim 33, wherein establishing the line segments also includes:

(a) locating a midpoint for each of the initial line segments after pivoting; and

(b) creating a refined curve that passes through all of the midpoints.

35. The method of claim 34, wherein establishing the line segments also includes creating the line segments to be perpendicular to the refined curve.

36. The method of claim 31, wherein the individual component is a tooth and the curve is a portion of a larger curve fitted among the lingual and buccal surfaces of all teeth in a 2D cross-section of a tooth arch in which the tooth lies.

37. The method of claim 36, wherein the larger curve is a catenary.

38. The method of claim 36, wherein the larger curve is created by manipulating mathematical control points to fit the curve to the shape of the cross-section of the tooth arch.

39. The method of claim 27, wherein establishing the line segments includes first establishing an initial line segment by creating a line that intersects the initial 2D cross-section, such that the initial line segment has endpoints that lie on surfaces of the individual component.

40. The method of claim 39, wherein establishing the line segments also includes establishing at least one additional line segment parallel to and spaced a predetermined distance from a previously established line segment.

41. The method of claim 39, wherein establishing the line segments also includes, for each additional line segment, locating a midpoint of the additional line segment and pivoting the additional line segment about the midpoint until the additional line segment has its shortest possible length.

42. The method of claim 41, wherein establishing the line segments also includes limiting the rotation of each additional line segment to no more than a predetermined amount.

43. The method of claim 42, wherein the rotation of each additional line segment is limited to no more than approximately +/−

10°

.

44. The method of claim 41, wherein establishing the line segments also includes establishing a curve that is fitted among the midpoints of the additional line segments.

45. The method of claim 44, wherein establishing the line segments includes establishing the line segments to be perpendicular to the curve.

46. The method of claim 45, wherein establishing the line segments includes locating midpoints for each of the line segments and pivoting each line segment about its midpoint until the line segment has its shortest possible length.

47. The method of claim 23, wherein the individual component is a tooth and the relative minimum value of the initial 2D cross-section lies on an interproximal surface of the tooth.

48. The method of claim 47, wherein identifying the initial 2D cross-section includes isolating elements of the data set that correspond to 2D cross-sections of the tooth lying in parallel planes between the roots and the occlusal surface of the tooth.

49. The method of claim 48, wherein identifying the initial 2D cross-section also includes identifying adjacent ones of the 2D cross-sections in which the interproximal surface of the tooth is obscured by gum tissue in one of the adjacent cross-sections and is not obscured by gum tissue in the other adjacent cross-section.

50. The method of claim 49, wherein identifying the initial 2D cross-section also includes selecting as the initial 2D cross-section the adjacent cross-section in which the interproximal surface of the tooth is not obscured by gum tissue.

51. The method of claim 48, wherein identifying the initial 2D cross-section also includes, for each of the isolated cross-sections, establishing a contour line that outlines the shape of the dentition in that cross-section.

52. The method of claim 51, wherein identifying the initial 2D cross-section also includes applying a test to each of the isolated cross-sections to identify those cross-sections in which the interproximal surface of the tooth is not obscured by gum tissue.

53. The method of claim 52, wherein applying the test includes calculating the rate of curvature of the contour line.

54. The method of claim 52, wherein identifying the initial 2D cross-section includes selecting as the initial 2D cross-section the isolated cross-section that lies closest to the roots of the tooth and in which the interproximal surface of the tooth is not obscured by gum tissue.

55. The method of claim 23, wherein applying the computer-implemented test also includes identifying two elements of the data set that define endpoints of a line segment spanning the relative minimum width of the initial 2D cross-section.

56. The method of claim 55, wherein applying the computer-implemented test also includes defining, for each endpoint, a neighborhood containing a predetermined number of elements of the data set near the endpoint in the initial 2D cross-section.

57. The method of claim 56, wherein applying the computer-implemented test also includes identifying an additional 2D cross-section of the individual component in a plane parallel and adjacent to the initial 2D cross-section, where the additional 2D cross-section also has a continuous, latitudinal width with a relative minimum value occurring at one end of the cross-section.

58. The method of claim 57, wherein applying the computer-implemented test also includes identifying two elements of the data set that define endpoints of a line segment spanning the relative minimum width of the additional 2D cross-section by:

(a) defining two neighborhoods of data elements, each containing elements of the data set that are adjacent to the data elements contained in the neighborhoods defined for the initial 2D cross-section; and

(b) identifying one data element in each neighborhood that corresponds to one of the endpoints of the line segment spanning the relative minimum width of the additional 2D cross-section.

59. The method of claim 57, further comprising establishing a solid surface that is fitted among line segments spanning the relative minimum widths of the parallel 2D cross-sections.

60. The method of claim 59, wherein the individual component to be modeled is a tooth and the solid surface represents an interproximal surface of the tooth.

61. The method of claim 23, further comprising receiving information provided by a human user that identifies elements of the data set that correspond to the relative minimum width of the initial 2D cross-section.

62. The method of claim 61, further comprising displaying a graphical representation of the patient'"'"'s dentition in which the user identifies portions corresponding to the relative minimum width of the cross-section.

63. The method of claim 62, wherein the graphical representation is three dimensional.

64. The method of claim 62, wherein the graphical representation includes a 2D representation of the initial 2D cross-section.

65. The method of claim 64, further comprising receiving the information from an input device used by the human user to identify the relative minimum width of the initial 2D cross-section in the graphical representation.

66. The method of claim 64, wherein the initial 2D cross-section is one of many 2D cross-sections displayed to the human user.

67. The method of claim 64, further comprising receiving information from the human user identifying which of the displayed 2D cross-sections is the initial 2D cross-section.

68. A computer-implemented method for use in creating a digital model of a tooth in a patient'"'"'s dentition, the method comprising:

(a) receiving a three-dimensional (3D) data set representing the patient'"'"'s dentition;

(b) applying a computer-implemented test to identify data elements that represent an interproximal margin between two teeth in the dentition;

(c) applying another computer-implemented test to select data elements that lie on one side of the interproximal margin for inclusion in the digital model.

69. The method of claim 68, further comprising creating a set of 2D planes that intersect the dentition roughly perpendicular to an occlusal plane of the dentition, each 2D plane including data elements that form a 2D cross-section of the dentition.

70. The method of claim 69, further comprising identifying the 2D plane with the smallest cross-sectional area.

71. The method of claim 70, further comprising rotating the 2D plane with the smallest cross-sectional area to at least one other orientation to form at least one other 2D cross-section of the dentition.

72. The method of claim 71, further comprising selecting the orientation that gives the rotated plane its smallest possible cross-sectional area.

73. The method of claim 72, further comprising identifying data elements that represent the selected orientation of the rotated plane as lying on an interproximal margin.

74. The method of claim 71, wherein the plane is rotated about two orthogonal lines passing through its center point.

75. The method of claim 70, further comprising creating a set of additional 2D planes in the vicinity of the 2D plane with the smallest cross-sectional area.

76. The method of claim 75, further comprising identifying the plane in the set of additional planes that has the smallest cross-sectional area.

77. The method of claim 76, further comprising rotating the plane with the smallest cross-sectional area to at least one other orientation to form at least one other 2D cross-section of the dentition.

78. The method of claim 77, further comprising selecting the orientation that produces the 2D cross-section with the smallest possible area.

79. The method of claim 69, wherein creating a set of 2D planes includes creating an initial plane near one end of the dentition.

80. The method of claim 79, further comprising selecting a point in the dentition that is a predetermined distance from the initial plane and creating a second plane.

81. The method of claim 80, wherein the second plane is roughly parallel to the initial plane.

82. The method of claim 80, further comprising rotating the second plane to at least one additional orientation to form at least one additional 2D cross-section of the dentition.

83. The method of claim 82, further comprising selecting the orientation that produces the 2D cross-section with the smallest cross-sectional area.

84. The method of claim 82, further comprising selecting a point that is a predetermined distance from the second plane and creating a third plane that includes the selected point.

85. The method of claim 84, further comprising rotating the third plane to at least one other orientation to create at least one additional 2D cross-section of the dentition.

86. The method of claim 84, further comprising creating additional planes, each including a point that is a predetermined distance from a preceding plane, until the other end of the dentition is reached.

87. The method of claim 86, further comprising identifying at least one plane having a local minimum in cross-sectional area.

88. The method of claim 86, further comprising identifying a centerpoint of the cross-section in each of the planes and creating a curve that fits among the identified centerpoints.

89. The method of claim 88, further comprising creating a set of additional 2D planes along the curve, where the curve is roughly normal to each of the additional planes, and where each of the additional planes is roughly perpendicular to the occlusal plane.

90. The method of claim 89, further comprising identifying at least one of the additional planes that has a local minimum in cross-sectional area.

91. A computer-implemented method for use in creating a digital model of a tooth in a patient'"'"'s dentition, the method comprising:

(a) receiving a 3D dataset representing at least a portion of the patient'"'"'s dentition, including at least a portion of a tooth and gum tissue surrounding the tooth;

(b) applying a test to identify data elements lying on a gingival boundary that occurs where the tooth and the gum tissue meet; and

(c) applying a test to the data elements lying on the boundary to identify other data elements representing portions of the tooth.

92. The method of claim 91, wherein applying the test to identify data elements on the gingival boundary includes creating an initial 2D plane that intersects the dentition roughly perpendicular to an occlusal plane of the dentition and that includes data elements representing an initial cross-sectional surface of the dentition.

93. The method of claim 91, wherein applying the test to identify data elements on the gingival boundary includes creating a series of roughly parallel 2D planes, each intersecting the dentition roughly perpendicular to an occlusal plane of the dentition, and each including data elements that represent a cross-sectional surface of the dentition.

94. The method of claim 93, wherein the cross-sectional surface in each 2D plane includes two cusps that roughly identify the locations of the gingival boundary.