Intraoral scanning system that removes excessive materials from intraoral scans

Patent metadata

Field	Value
Publication number	US-11928832-B2
Application number	US-202217895002-A
Country	US
Kind code	B2
Filing date	Aug 24, 2022
Priority date	May 2, 2019
Publication date	Mar 12, 2024
Grant date	Mar 12, 2024

Abstract

An intraoral scanning system comprises an intraoral scanner and a computing device. The computing device receives intraoral scans of a dental site from the intraoral scanner, the intraoral scans comprising at least a first intraoral scan and a second intraoral scan. The computing device determines, for each point in the second intraoral scan based on a first comparison of the first intraoral scan to the second intraoral scan, whether the point is a back-face point or an uncovered point. The computing device determines a region comprising a plurality of points in the second intraoral scan that are uncovered points, determines whether the region satisfies one or more removal criteria, and removes the region from the second intraoral scan responsive to determining that the region satisfies the one or more removal criteria.

First claim

What is claimed is:

1. An intraoral scanning system, comprising:
an intraoral scanner; and
a computing device operatively connected to the intraoral scanner, wherein the computing device is to:
receive a plurality of intraoral scans of a dental site from the intraoral scanner, the plurality of intraoral scans comprising at least a first intraoral scan and a second intraoral scan;
determine, for each point in the second intraoral scan based on a first comparison of the first intraoral scan to the second intraoral scan, whether the point is a back-face point that is behind a corresponding point in the first intraoral scan when viewed from a first viewing direction, wherein points in the second intraoral scan that are not behind corresponding points in the first intraoral scan are uncovered points;
determine a region comprising a plurality of points in the second intraoral scan that are uncovered points;
determine whether the region satisfies one or more removal criteria; and
remove the region from the second intraoral scan responsive to determining that the region satisfies the one or more removal criteria.

2. The intraoral scanning system of claim 1 , wherein the computing device is further to:
determine, for each point in the second intraoral scan based on the first comparison of the first intraoral scan to the second intraoral scan, whether a surface normal at the point is co-directional with the first viewing direction associated with the first intraoral scan, wherein points in the second intraoral scan that have a surface normal that is co-directional with the first viewing direction are back-face points;
wherein the determined region comprises a plurality of points in the second intraoral scan that are both back-face points and uncovered points.

3. The intraoral scanning system of claim 2 , wherein the one or more removal criteria comprises a threshold number of points in the region that are both back-face points and uncovered points, and wherein the computing device is further to:
determine a number of points in the region that are both back-face points and uncovered points;
determine that the number of points in the region that are both back-face points and uncovered points exceeds the threshold number of points; and
determine that the region satisfies the one or more removal criteria.

4. The intraoral scanning system of claim 1 , wherein the one or more removal criteria comprises a moving tissue boundary condition, and wherein the computing device is further to:
determine that the region bounds moving tissue; and
determine that the region satisfies the one or more removal criteria.

5. The intraoral scanning system of claim 1 , wherein the one or more removal criteria comprises an empty space boundary condition, and wherein the computing device is further to:
determine a size of a perimeter of the region;
determine a length of a portion of the perimeter that bounds empty space;
determine a ratio of the length to the size;
determine that the ratio exceeds a ratio threshold, wherein the empty space boundary condition comprises the ratio threshold; and
determine that the region satisfies the one or more removal criteria.

6. The intraoral scanning system of claim 1 , wherein points in the second intraoral scan that are behind corresponding points in the first intraoral scan are covered points, and wherein the computing device is further to:
determine, for each point in the second intraoral scan, whether the point is an uncovered point that is proximate to a covered point, wherein uncovered points that are proximate to covered points are identified as proximity area points, wherein the region further comprises one or more proximity area points.

7. The intraoral scanning system of claim 6 , wherein the computing device is further to:
compute a surface normal for each proximity area point;
determine proximity area points having a surface normal that is orthogonal to the first viewing direction; and
identify proximity area points having a surface normal that is orthogonal to the first viewing direction as orthogonal proximity area points, wherein the orthogonal proximity area points are excluded from the region.

8. The intraoral scanning system of claim 6 , wherein the one or more removal criteria comprises a threshold number of points, wherein the computing device is further to:
determine a first number of points in the region that are proximity area points;
determine a second number or points in the region that are uncovered points;
determine a sum of the first number of points and the second number of points;
determine that the sum of the first number of points and the second number of points exceeds the threshold number of points; and
determine that the region satisfies the one or more removal criteria.

9. The intraoral scanning system of claim 1 , wherein the first intraoral scan is associated with a first scan capture direction, and wherein the computing device is further to:
determine a first scan direction for the first intraoral scan, wherein the first scan direction represents the first viewing direction for the first comparison between the first intraoral scan and the second intraoral scan;
determine whether a first difference between the first scan direction and the first scan capture direction exceeds a difference threshold; and
rasterize the first intraoral scan along the first scan direction responsive to determining that the first difference exceeds the difference threshold.

10. The intraoral scanning system of claim 9 , wherein the first intraoral scan comprises a first height map, wherein the first scan direction is represented by a first vector, and wherein rasterizing the first intraoral scan along the first scan direction comprises:
converting the first height map into a three-dimensional surface; and
projecting the three-dimensional surface onto a plane, wherein the first vector is normal to the plane.

11. The intraoral scanning system of claim 1 , wherein the computing device is further to:
determine a first scan direction for the first intraoral scan, wherein the first scan direction represents the first viewing direction for the first comparison between the first intraoral scan and the second intraoral scan, and wherein determining the first scan direction comprises:
determining a first plurality of surface normals for a first surface of the first intraoral scan, wherein each of the first plurality of surface normals is associated with a respective point on the first surface;
determining a first average of the first plurality of surface normals; and
determining a first vector based on the first average, wherein the first vector represents the first scan direction.

12. The intraoral scanning system of claim 1 , wherein the first intraoral scan comprises a first height map, and wherein the computing device is further to:
perform image in-painting on the first height map.

13. The intraoral scanning system of claim 1 , wherein the first intraoral scan has a first boundary and the second intraoral scan has a second boundary, and wherein the computing device is further to:
determine a region of the second boundary that does not overlap with the first boundary; and
identify points in the second intraoral scan that are within the region as out-of-bounds points.

14. The intraoral scanning system of claim 1 , wherein the plurality of intraoral scans further comprises a third intraoral scan, and wherein the computing device is further to:
determine, for each point in the second intraoral scan based on a second comparison between the third intraoral scan and the

Assignees

• Align Technology Inc

Inventors

• Minchenkov Mikhail
• Agniashvili Pavel
• Kryzhanovskiy Konstantin
• Chelishchev Evgeniy
• Kurilova Tatiana

Classifications

• G06T7/55 Primary

  from multiple images · CPC title

• A61C9/0053

  Optical means or methods, e.g. scanning the teeth by a laser or light beam · CPC title

• A61C13/0004

  Computer-assisted sizing or machining of dental prostheses · CPC title

• G06T7/0014

  using an image reference approach · CPC title

• G06T17/20

  Finite element generation, e.g. wire-frame surface description, {tesselation} · CPC title