Patent Application
20210322138
The disclosure relates generally to intraoral imaging and more particularly to generating and conditioning a 3D model of patient dentition using combined results from intraoral scanning directly from the patient and from an impression.
Intraoral imaging has proven to have significant value as a tool with a diverse range of applications, including use as a diagnostic aid, use for treatment and restoration planning, and use in color shade matching, among other applications. Optical intraoral scans produce contours of dentition objects and are beneficial in improving visualization of teeth, gums, and other intra-oral structures. Surface contour information can be particularly useful for assessment of tooth condition and has recognized value for various types of dental procedures, such as for restorative dentistry.
For orthodontic and other restorative procedures, a model of patient dentition is generated, initially and at various stages of the process. A number of standardized metrics can then be applied to the models for comparison and to track overall progress of the treatment regimen.
In conventional practice, the generated model is formed from an impression obtained from the patient. This standard method is time consuming and can be uncomfortable for the patient, but has been perfected over a number of years so that the materials and methods used, in spite of some drawbacks, provide very suitable results for forming an accurate model of patient dentition.
Thanks to continuing improvement in image quality and response time, 3D intraoral scanners provide tools for acquisition of a digital model that can be readily obtained without the encumbrance of impression techniques and materials. Using the 3D intraoral scanner, a technician or practitioner can obtain accurate volume image information by carefully moving the scanner from tooth to tooth within the mouth of the patient, viewing a display and observing progress of the growing digital data that represents intraoral structures as a mesh or point cloud.
While 3D scanners are convenient and easy to use, however, there is some room for improvement. One particular shortcoming relates to the quality of imaging of localized areas such as the tooth margin. Accurate characterization of the tooth margin is significant for successful preparation and fitting, such as for a crown or implant. 3D intraoral scanners can fail to model the tooth margin to the practitioner's satisfaction, due to illumination constraints, limitations of the imaging optics, and other difficulties. Subgingival tissue can tend to obscure the margin, which is often effectively hidden beneath the soft tissue.
Another limitation of the 3D scanner relates to bite registration. Attempts to accurately characterize bite registration using intraoral scanning have proved disappointing.
Thus, it can be seen that there would be benefit to a digital imaging approach that more accurately characterizes the tooth margin and allows assessment of bite registration when forming a 3D model of patient dentition.
It is an object of the present disclosure to advance the art of diagnostic imaging and to address the need for improved 3-D intraoral imaging and scanning, particularly for portions of the teeth related to tooth margin and, in addition, to provide approaches for bite registration.
These objects are given only by way of illustrative example, and such objects may be exemplary of one or more embodiments of the invention. Other desirable objectives and advantages inherently achieved by the disclosed methods may occur or become apparent to those skilled in the art. The invention is defined by the appended claims.
According to an aspect of the present disclosure, there is provided a method for imaging a region of interest of patient dentition, the method executed at least in part by a computer system and comprising:
According to an alternate aspect of the present disclosure, there is provided a method for characterizing bite registration comprising:
The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of the embodiments of the invention, as illustrated in the accompanying drawings.
The elements of the drawings are not necessarily to scale relative to each other. Some exaggeration may be necessary in order to emphasize basic structural relationships or principles of operation. Some conventional components that would be needed for implementation of the described embodiments, such as support components used for providing power, for packaging, and for mounting and protecting system optics, for example, are not shown in the drawings in order to simplify description.
The following is a detailed description of the preferred embodiments, reference being made to the drawings in which the same reference numerals identify the same elements of structure in each of the several figures.
Where they are used in the context of the present disclosure, the terms “first”, “second”, and so on, do not necessarily denote any ordinal, sequential, or priority relation, but are simply used to more clearly distinguish one step, element, or set of elements from another, unless specified otherwise.
As used herein, the term “energizable” relates to a device or set of components that perform an indicated function upon receiving power and, optionally, upon receiving an enabling signal.
In the context of the present disclosure, the term “optics” is used generally to refer to lenses and other refractive, diffractive, and reflective components or apertures used for shaping and orienting a light beam. An individual component of this type is termed an optic.
In the context of the present disclosure, the term “scattered light” is used generally to include light that is reflected and backscattered from an object.
In the context of the present disclosure, the terms “viewer”, “operator”, and “user” are considered to be equivalent and refer to the viewing practitioner, technician, or other person who may operate a camera or scanner and may also view and manipulate an image, such as a dental image, on a display monitor. An “operator instruction” or “viewer instruction” is obtained from explicit commands entered by the viewer, such as by clicking a button on the camera or scanner or by using a computer mouse or by touch screen or keyboard entry.
In the context of the present disclosure, the phrase “in signal communication” indicates that two or more devices and/or components are capable of communicating with each other via signals that travel over some type of signal path. Signal communication may be wired or wireless. The signals may be communication, power, data, or energy signals. The signal paths may include physical, electrical, magnetic, electromagnetic, optical, wired, and/or wireless connections between the first device and/or component and second device and/or component. The signal paths may also include additional devices and/or components between the first device and/or component and second device and/or component.
In the context of the present disclosure, the term “camera” relates to a device that is enabled to acquire a reflectance, 2-D digital image from reflected visible or NIR light, such as structured light that is reflected from the surface of teeth and supporting structures.
The general term “scanner” relates to an optical system that projects a scanned light beam to the tooth surface and provides image content based on the resulting scattered or reflected light content. According to some intraoral imaging embodiments, the terms “camera” and “scanner” may be considered equivalent.
The term “set”, as used herein, refers to a non-empty set, as the concept of a collection of elements or members of a set is widely understood in elementary mathematics. The terms “subset” or “partial subset”, unless otherwise explicitly stated, are used herein to refer to a non-empty proper subset, that is, to a subset of the larger set, having one or more members. For a set S, a subset may comprise the complete set S. A “proper subset” of set S, however, is strictly contained in set S and excludes at least one member of set S. A “partition of a set” is a grouping of the set's elements into non-empty subsets so that every element is included in one and only one of the subsets. Two sets are “disjoint” when they have no element in common.
The term “subject” refers to the tooth or other portion of a patient that is being imaged and, in optical terms, can be considered equivalent to the “object” of the corresponding imaging system.
In the context of the present disclosure, the terms “viewer”, “operator”, and “user” are considered to be equivalent and refer to the viewing practitioner or other person who may acquire, view and manipulate a dental or medical image on a display monitor.
In the context of the present disclosure, the terms “point cloud”, “mesh”, “3D surface image”, and “surface image” are used equivalently to describe the digital model of the surface contour that can be formed using a scanner that obtains a series of reflectance images from intraoral or other surfaces. The surface image that provides the digital model is a composite image formed by stitching together individual scans successively acquired for adjacent surface features. Point cloud and mesh are convenient and similar storage and display structures representative of the surface image.
The schematic diagram of
In structured light imaging, a pattern of lines or other shapes is projected from illumination array 10 toward the surface of an object from a given angle. The projected pattern from the illuminated surface position is then viewed from another angle as a contour image, taking advantage of triangulation in order to analyze surface information based on the appearance of contour lines. Phase shifting, in which the projected pattern is incrementally shifted spatially for obtaining additional measurements at the new locations, is typically applied as part of structured light imaging, used in order to complete the contour mapping of the surface and to increase overall resolution in the contour image. By way of example and not limitation, use of structured light patterns for surface contour characterization is described in commonly assigned U.S. Patent Application Publications No. US2013/0120532 and No. US2013/0120533, both entitled “3D INTRAORAL MEASUREMENTS USING OPTICAL MULTILINE METHOD” and incorporated herein in their entirety.
By knowing the instantaneous position of the camera and the instantaneous position of the line of light or other illumination field within an object-relative coordinate system when the image was acquired, a computer and software can use triangulation methods to compute the coordinates of numerous illuminated surface points relative to a plane. As the plane is moved to intersect eventually with some or all of the surface of the object, the coordinates of an increasing number of points are accumulated. As a result of this image acquisition, a point cloud can be generated and used as the surface image to represent the extent of a surface within a volume. The points in the point cloud then represent actual, measured points on the three-dimensional surface of an object. A mesh can alternately be constructed from the same surface acquisition, represented as vertices for congruent polygonal faces (typically triangular faces) that characterize the surface shape. The full 3D digital model can then be formed by combining the surface contour information provided by the surface image in point cloud or mesh form with polychromatic image content obtained from a camera, such as camera 24 of
Polychromatic image content can be provided in a number of ways, including the use of a single monochrome imaging sensor with a succession of images obtained using illumination of different primary colors, one color at a time, for example. Alternately, a color imaging sensor could be used.
Image processing at control logic processor 80 can generate a digital contour surface model using line scan data from structured light imaging, or using point cloud or mesh data or other volume image data, including video image data. By way of example,
It should be noted that other types of reflectance imaging can be used for obtaining intraoral surface contour data used to form the digital model. Surface contour information can be obtained using time-of-flight imaging or range imaging methods, such as structure-from-motion processing, for example.
The conventional method for 3D modeling of teeth and gums of a patient's dentition is a dental impression, which provides a negative imprint of the intraoral features for the complete dental arch. The process of obtaining the impression body requires depositing a soft impression, putty-like material into the patient's mouth and instructing the patient to bite down and hold the bite position for a few minutes while the material hardens to an elastic solid state. Careful removal of the hardened impression material then obtains the physical impression or impression body as a negative imprint that can be used as a mold for forming a 3D model for the corresponding dental arch. While the process is not itself painful or invasive, it can be an unwelcome ordeal and uncomfortable to the patient. Impression techniques can be particularly accurate for reproducing complex curvatures and abrupt surface transitions such as at the tooth cervical margin.
The use of the 3D intraoral scanner or camera allows the practitioner to acquire 3D contour data for the patient without the need for impression materials and apparatus and without the complications and discomfort of conventional impression practice. However, as was noted previously in the background material, it can be difficult to obtain intraoral scan data that reliably and accurately characterizes the tooth margin. There may also be other specific areas of patient dentition, which may be highly patient-specific, for which direct intraoral imaging may not obtain sufficient data to meet the accuracy expectations of the practitioner for generating a 3D digital surface model. Imaging problems can result from insufficient light or excessive light. For example, it can be difficult to direct sufficient light to interproximal features or to obtain enough reflected light from these features for accurate identification of the surface contour. Too much reflected light, such as from a highly reflective ceramic material within the mouth, can also prevent accurate surface characterization. Embodiments of the present disclosure address shortcomings of conventional intraoral scanning that relate to 3D imaging of the tooth margin, and other specific areas, by combining the 3D contour data for the arch, acquired as the surface image from the intraoral scanner, with localized information obtained from scanning a partial impression, that is, an impression that is formed from only a portion of the dental arch.
As noted previously in the background material and shown in the exemplary images of
The logic flow diagram of
With the surface image generated, an optional ROI identification step S530 then identifies a region of interest (ROI) within the scanned content, as shown highlighted by outline in
Automated methods for ROI identification can use various segmentation or pattern-recognition utilities, for example.
Identification of the ROI by the operator or using automated pattern recognition is optional. The ROI can be identified in the surface image from the intraoral scan of the dental arch or, alternately, from the scanned impression acquired in subsequent step S540. According to an alternate embodiment of the present disclosure, the ROI can be defined by default, using the boundary of the scanned impression.
An impression that includes the margin or other ROI is obtained and scanned in an impression scanning step S540. A full impression of the complete dental arch is not needed; only a partial impression is used for this step. The partial impression includes the ROI and can further include sufficient neighboring features to facilitate subsequent registration processing. By way of example,
A registration step S550 then registers the scanned impression, or at least the portion of the scanned impression that includes the ROI, to the mesh or other type of surface image generated from the intraoral scan. Registration can use a feature matching algorithm or, alternatively, an iterative closest point (ICP) algorithm, or a combination of these two approaches, for example.
A merge step S560 then merges the contour data from the scanned impression of the ROI with the surface image formed from the intraoral scan. Where the ROI is clearly identified, merge step S560 can simply discard the identified nodes of the intraoral scan within the ROI region and substitute the corresponding points or nodes from the registered scanned impression. Where the ROI is only positionally identified, other substitution from the impression data can be performed. For example, nodes of the first model within a given distance of the ROI, such as within 100 microns, can be replaced by the impression data. Other methods for merger or combination of nodes can alternately be applied, including averaging, for example.
The resultant hybrid digital model can then be rendered to a display in a display step S570. The displayed 3D digital model can optionally indicate the region of interest, such as outlined or otherwise highlighted.
Previous description focused on using a hybrid scanning approach for localized ROI content. The Applicants have also found that complementing the intraoral scan with data from a scanned physical impression can also have value for improved imaging related to bite registration.
A physical impression of the bite surfaces, acquired at positions that cover only a portion of the intraoral cavity, is then obtained from the patient. For this step, it should be emphasized that only the occlusal surface is needed for the bite registration process of
With the occlusal surface impression or impressions obtained, an impression scanning step S1230 is then executed, in which the practitioner or technician scans each obtained occlusal impression using the intraoral scanner or other suitable scanning device, such as a desktop scanner, for example. The occlusion impression is formed from imprints of two facing or opposing bite surfaces, one maxillary, the other mandibular. A subsequent surface image generation step S1240 then generates a mesh, point cloud, or other type of surface image corresponding to the surface of the acquired occlusion impression. By way of example,
Still following the
Embodiments of the present disclosure include apparatus such as those shown in
Consistent with an embodiment of the present invention, a computer program utilizes stored instructions that perform on image data that is accessed from an electronic memory. As can be appreciated by those skilled in the image processing arts, a computer program for operating the imaging system in an embodiment of the present disclosure can be utilized by a suitable, general-purpose computer system operating as a CPU as described herein, such as a personal computer or workstation. However, many other types of computer systems can be used to execute the computer program of the present invention, including an arrangement of networked processors, for example. The computer program for performing the method of the present invention may be stored in a computer readable storage medium. This medium may comprise, for example; magnetic storage media such as a magnetic disk such as a hard drive or removable device or magnetic tape; optical storage media such as an optical disc, optical tape, or machine readable optical encoding; solid state electronic storage devices such as random access memory (RAM), or read only memory (ROM); or any other physical device or medium employed to store a computer program. The computer program for performing the method of the present disclosure may also be stored on computer readable storage medium that is connected to the image processor by way of the internet or other network or communication medium. Those skilled in the art will further readily recognize that the equivalent of such a computer program product may also be constructed in hardware.
It should be noted that the term “memory”, equivalent to “computer-accessible memory” in the context of the present disclosure, can refer to any type of temporary or more enduring data storage workspace used for storing and operating upon image data and accessible to a computer system, including a database, for example. The memory could be non-volatile, using, for example, a long-term storage medium such as magnetic or optical storage. Alternately, the memory could be of a more volatile nature, using an electronic circuit, such as random-access memory (RAM) that is used as a temporary buffer or workspace by a microprocessor or other control logic processor device. Display data, for example, is typically stored in a temporary storage buffer that is directly associated with a display device and is periodically refreshed as needed in order to provide displayed data. This temporary storage buffer is also considered to be a type of memory, as the term is used in the present disclosure. Memory is also used as the data workspace for executing and storing intermediate and final results of calculations and other processing. Computer-accessible memory can be volatile, non-volatile, or a hybrid combination of volatile and non-volatile types.
It will be understood that the computer program product of the present disclosure may make use of various image manipulation algorithms and processes that are well known. It will be further understood that the computer program product embodiment of the present disclosure may embody algorithms and processes not specifically shown or described herein that are useful for implementation. Such algorithms and processes may include conventional utilities that are within the ordinary skill of the image processing arts. Additional aspects of such algorithms and systems, and hardware and/or software for producing and otherwise processing the images or co-operating with the computer program product of the present disclosure, are not specifically shown or described herein and may be selected from such algorithms, systems, hardware, components and elements known in the art.
The invention has been described in detail and may have been described with particular reference to a suitable or presently preferred embodiment, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2018/101891 | 2/23/2018 | WO | 00 |
