Dental prostheses are typically manufactured at specialized dental laboratories that employ computer-aided design (CAD) and computer-aided manufacturing (CAM) milling systems to produce dental prostheses according to patient-specific specifications provided by dentists. In a typical work flow, information about the oral situation of a patient is received from a dentist, the dental laboratory designs the dental prosthesis, and the prosthesis is manufactured using a mill or other fabrication system. When making use of CAD design and CAM manufacturing in dentistry, a digital model of the patient's dentition is required as an input to the process. One technique to generate a digital model includes CT scanning physical dental impressions. Physical dental impressions can include, for example, a rigid frame, handle region, impression material, and mesh. The physical dental impressions can also additionally include a higher radiodensity material arranged in the rigid frame. The presence of the higher radiodensity material can cause CT reconstruction artifacts in regions between the higher radiodensity material using conventional scanning techniques. Due to these reconstruction artifacts, CT scanning of impressions containing higher radiodensity material such as steel wires is typically avoided. Where some conventional techniques attempt to preprocess x-ray projections to eliminate the higher radiodensity material, the techniques can increase CT reconstruction time and still leave artifacts that distort digital model dental regions.
Disclosed is a method of CT scanning a physical dental impression. The method can include arranging a physical dental impression comprising a higher radiodensity material in a CT scanner so that a transverse axis of the physical dental impression is non-perpendicular with respect to an axis of rotation.
Also disclosed is a method of CT scanning a physical dental impression that includes arranging a physical dental impression comprising a higher radiodensity material so that the transverse axis is non-parallel with respect to the one or more x-ray paths at any given position around an axis of rotation.
For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods, apparatus, and systems should not be construed as being limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods, apparatus, and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present or problems be solved.
Although the operations of some of the disclosed embodiments are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods. Additionally, the description sometimes uses terms like “provide” or “achieve” to describe the disclosed methods. The actual operations that correspond to these terms may vary depending on the particular implementation and are readily discernible by one of ordinary skill in the art.
As used in this application and in the claims, the singular forms “a,” “an,” and “the” include the plural forms unless the context clearly dictates otherwise. Additionally, the term “includes” means “comprises.” Further, the terms “coupled” and “associated” generally mean electrically, electromagnetically, and/or physically (e.g., mechanically or chemically) coupled or linked and does not exclude the presence of intermediate elements between the coupled or associated items absent specific contrary language.
In some examples, values, procedures, or apparatus may be referred to as “lowest,” “best,” “minimum,” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many alternatives can be made, and such selections need not be better, smaller, or otherwise preferable to other selections.
In the following description, certain terms may be used such as “up,” “down,” “upper,” “lower,” “horizontal,” “vertical,” “left,” “right,” and the like. These terms are used, where applicable, to provide some clarity of description when dealing with relative relationships. But, these terms are not intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” surface can become a “lower” surface simply by turning the object over. Nevertheless, it is still the same object.
As noted above, in a typical work flow, information about the oral situation of a patient is received from a dentist, the dental laboratory designs the dental prosthesis, and the prosthesis is manufactured using a mill or other fabrication system. When making use of CAD design and CAM manufacturing in dentistry, a digital model of the patient's dentition is required as an input to the process. Despite the rise of intraoral scanning technology, the prevalent method of acquisition of digital model data is still scanning a stone model cast from a physical negative impression of the patient's dentition.
A physical negative impression of the patient's dentition is typically obtained by the use of a dental impression tray containing impression material. An example of an impression tray is shown in
For example, in
As noted above, in a conventional workflow, a physical dental impression formed in the manner described above would be used to cast a model of the patient's dentition formed of stone, polymeric, or other suitable material. The cast model would then be scanned using a laser scanner in order to obtain a digital model. The digital model would then be used to design one or more restorations, or for other purposes. This conventional workflow creates potential sources of error or inaccuracy that would be avoided by alternative methods or alternative workflows that avoided the step of forming the case model and, instead, proceeded directly from the physical impression to a digital model.
In one embodiment of the present method, a computed tomography (CT) scanner uses x-rays to make a detailed image of a physical impression. A plurality of such images are then combined to form a 3D model of the patient's dentition. A schematic diagram of an example of a CT scanning system 140 is shown in
An example of a suitable scanning system 140 includes a Nikon Model XTH 255 CT Scanner (Metrology) which is commercially available from Nikon Corporation. The example scanning system includes a 225 kV microfocus x-ray source with a 3 μm focal spot size to provide high performance image acquisition and volume processing. The processor 150 may include a storage medium that is configured with instructions to manage the data collected by the scanning system. A particular scanning system is described for illustrative purposes; any type/brand of CT scanning system can be utilized.
One example of CT scanning is described in U.S. Patent Application No. US20180132982A1 to Nikolskiy et al., which is hereby incorporated in its entirety by reference. As noted above, during operation of the scanning system 140, the impression 146 is located between the x-ray source 142 and the x-ray detector 148. A series of images of the impression 146 are collected by the processor 150 as the impression 146 is rotated in place between the source 142 and the detector 146. An example of a single image 160 is shown in
The plurality of images 160 of the impression 146 are generated by and stored within a storage medium contained within the processor 150 of the scanning system 140, where they may be used by software contained within the processor to perform additional operations. For example, in an embodiment, the plurality of images 160 undergo tomographic reconstruction in order to generate a 3D virtual image 170 (see
In some embodiments, an impression such as a triple tray impression or any other type of impression can contain material having a higher radiodensity material that can cause distortions after CT reconstruction.
Disclosed is a method of CT scanning a physical dental impression that can include arranging a physical dental impression having a higher radiodensity material in a CT scanner to minimize x-rays intersecting the higher radiodensity material more than once in some embodiments. A method of CT scanning a physical dental impression can include arranging a physical dental impression having a higher radiodensity material in a CT scanner so that a transverse axis of the physical dental impression is non-perpendicular with respect to an axis of rotation in some embodiments. A method of CT scanning a physical dental impression, can include arranging a physical dental impression having a higher radiodensity material so that the transverse axis is non-parallel with respect to the one or more x-ray paths at any given position around an axis of rotation in some embodiments. In some embodiments, the physical dental impression can be a triple-tray impression. Other types of physical dental impressions can be used as well.
Radiodensity indicates a material's opacity to x-rays. In some embodiments, radiodensity can be quantified according to the Hounsfield scale and expressed in Hounsfield Units (HU). For example, distilled water can have a radiodensity of 0 HU, and air can have a radiodensity of −1000 HU. In some embodiments, the higher radiodensity material 512 can include one or more materials having a radiodensity of +5,000 HU and above, for example. Some materials having a radiodensity of at least +5,000 HU can include, for example, steel, copper, silver, gold, and/or brass. In some embodiments, the steel can be stainless steel. In some embodiments, the higher radiodensity material 512 can include dental cement, whole/pieces of dental restoration parts such as whole or parts of crowns and/or other dental restoration parts. In some embodiments, the higher radiodensity material 512 can include dental cement, for example. In some embodiments, the rigid frame 102 itself can be made partly or entirely of higher radiodensity material. In some embodiments, the handle 106 can also be partly or entirely out of a higher radiodensity material. For example, in some embodiments, the rigid frame 102 itself can be made partly or entirely out of steel and/or other materials having a radiodensity of at least +5,000HU. In some embodiments, the handle 106 can also be partly or entirely out of steel and/or other materials having a radiodensity of at least +5,000 HU. Other materials having a radiodensity of at least +5,000 HU can be determined by those skilled in the art.
Rigid frame 102, handle 106, and mesh 104 can be made of any material, such as, for example, plastic material. The impression material 503 can be made of any suitable impression material including but not limited to polyvinyl siloxane (pvs), alginate, etc. The higher radiodensity material 512 can be made of material having a greater radiodensity than the impression material 503 in some embodiments. In some embodiments, the higher radiodensity material 512 can have a greater radiodensity than the rigid frame 102, handle 106, and/or the mesh 104. In some embodiments, the impression material 503, rigid frame 102, handle 106, and/or mesh 104 can have radiodensities below +5,000 HU. In some embodiments, the higher radiodensity material 512 can be at least one wire, for example. In some embodiments, the higher radiodensity material 512 can include metal with a radiodensity of at least +5,000 HU, for example, or other any other higher radiodensity material having a radiodensity of at least +5,000 HU.
In some embodiments, arranging the physical dental impression includes arranging the physical dental impression 500 between an x-ray source 142 and an x-ray detector 148. This can expose the physical dental impression 500 to x-rays generated by the x-ray source 142. The physical dental impression 500 can be attached to a holding device 566 as illustrated in the example of
In some embodiments, the holding device 566 can connect with the handle 106 of the physical dental impression 500 to hold the physical dental impression 500 at a particular arrangement and orientation. However, the holding device 566 can hold the physical dental impression 500 on any suitable region of the physical dental impression 500. The holding device 566 with the physical dental impression 500 can be placed on the rotating platform 568. The x-ray source 142 can optionally be placed or mounted to an optional stand 562. Rotating platform 568 can rotate either clockwise or counterclockwise. The optional stand 562 and rotating platform 568 can be on a CT scanner base 564 in some embodiments, for example. Once scanning is complete, the holding device 566 with the physical dental impression 500 can be removed from the rotating platform 568 and/or the physical dental impression 500 can be removed from the holding device 566 in some embodiments for example. These elements can be configured in other arrangements, and are shown as configured for illustrative purposes.
Conventionally, the physical dental impression tray 501 with impression material and one or more dentition regions (impression material and dentition regions not shown for clarity) is scanned so that the longitudinal axis 502 is upright or vertical toward an axis of rotation 528 as illustrated in
In some embodiments, the physical dental impression 500 can be arranged to minimize reconstruction artifacts. For example, the physical dental impression 500 can be arranged to minimize the number of intersection points between one or more x-rays or one or more x-ray paths and the higher radiodensity material 512. In some embodiments, physical dental impression 500 can be arranged to minimize the number of multiple intersection points between one or more x-rays or one or more x-ray paths and the higher radiodensity material 512. In some embodiments, the physical dental impression 500 with the higher radiodensity material 512 can be arranged in a CT scanner to minimize x-rays or x-ray paths intersecting the higher radiodensity material more than once. In some embodiments, the physical dental impression 500 can be arranged in a CT scanner to be angled with respect to the axis of rotation 528 to minimize intersection points between the higher radiodensity material and one or more x-ray paths 520.
In some embodiments, the physical dental impression 500 can be arranged in a CT scanner to be angled with respect to the axis of rotation 528 to minimize intersection points between the higher radiodensity material 512 and one or more x-ray paths 520. For example, the transverse axis 504 can be oriented toward a direction parallel to the axis of rotation 528. For example, the physical dental impression 500 can be arranged so that a transverse angle 552 between the transverse axis 504 and the axis of rotation 528 is minimized in some embodiments. In some embodiments, for example, the transverse angle 552 can be reduced as much as possible based on physical/space constraints, obstacles, and/or other scanning limitations that may hinder or prevent the physical dental impression 500 from rotating or the CT scanner from obtaining a scan. In some embodiments, the transverse angle 552 is the angle formed between the portions of the transverse axis 504 and the axis of rotation 528 above their intersection point, or the angle formed between the portions of the axes furthest from rotating platform 568 at any rotational position. The physical dental impression 500 can be arranged so that the transverse axis 504 is non-perpendicular with the axis of rotation 528 in some embodiments. For example, the physical dental impression 500 can be arranged so that the transverse angle 552 is less than 90 degrees in some embodiments. In some embodiments, the transverse angle 552 can be in the range of 0 to less than 90 degrees (including zero degrees). The physical dental impression 500 can be arranged so that the transverse axis 504 is parallel with the axis of rotation 528 in some embodiments. The physical dental impression 500 can be arranged so that the axis of rotation 528 as illustrated in the figure is oriented transversely across the physical dental impression 500. In some embodiments, the physical dental impression 500 can be arranged so that axis of rotation 528 is oriented transversely over roughly a centroid of the physical dental impression 500, or across a dentition region of the physical dental impression 500, for example. However, the physical dental impression 500 can be arranged to have any axis of rotation 528.
In some embodiments, the axis of rotation 528 is not parallel to the one or more x-ray paths 520. In some embodiments, the axis of rotation 528 is perpendicular to at least one of the one or more x-ray paths 520.
In the example illustrated in the figure, the physical dental impression 500 is arranged so that the longitudinal axis 502 is initially oriented toward the detector 148 and/or is approximately orthogonal to the x-ray detector 148. The top region 554 of the physical dental impression 500 can be initially oriented toward the detector, for example. Although the physical dental impression 500 is illustrated in the figure with the longitudinal axis 502 oriented in the horizontal direction from the x-ray source 142 to the detector 148, the longitudinal axis 502 can be initially oriented in any horizontal direction. In some embodiments, the physical dental impression 500 can be arranged such that the longitudinal axis 502 is non-parallel with the axis of rotation 528. In some embodiments, the physical dental impression 500 can be arranged so that the longitudinal axis 502 is perpendicular to the axis of rotation 528.
In some instances, it may be challenging to arrange the physical dental impression 500 so that the transverse axis 504 is parallel with the axis of rotation 528. This can be due to space restrictions or obstacles that can impede rotation of the physical dental impression 500 in that arrangement and/or limit scanning. In some embodiments, the physical dental impression 500 can be arranged to minimize reconstruction artifacts by angling the physical dental impression 500 as much as possible during scanning. For example,
As illustrated in the example of
In some embodiments, the physical dental impression 500 can be arranged with the shorter side 574 of the higher radiodensity material 512 above the longer side 572 of the higher radiodensity material 512 to reduce or minimize the number of x-rays or x-ray paths intersecting the higher radiodensity material 512 at multiple points. For example, as illustrated in
At least one advantage of many of one or more features described in the present disclosure can include for example allowing CT scanning of physical dental impressions with higher radiodensity material, not significantly increasing CT processing time, and removing or reducing artifacts of the higher radiodensity material on reconstructed teeth.
The above descriptions of the scanning system and the algorithms used to perform the scanning, imaging, and reconstruction are not intended to suggest any limitation as to scope of use or functionality. For example, the computing environment used to perform these functions can be any of a variety of computing devices (e.g., desktop computer, laptop computer, server computer, tablet computer, gaming system, mobile device, programmable automation controller, etc.) that can be incorporated into a computing system comprising one or more computing devices.
For example, a computing environment may include one or more processing units and memory. The processing units execute computer-executable instructions. A processing unit can be a central processing unit (CPU), a processor in an application-specific integrated circuit (ASIC), or any other type of processor. In a multi-processing system, multiple processing units execute computer-executable instructions to increase processing power. For example, a representative computing environment may include a central processing unit as well as a graphics processing unit or co-processing unit. The tangible memory may be volatile memory (e.g., registers, cache, RAM), non-volatile memory (e.g., ROM, EEPROM, flash memory, etc.), or some combination of the two, accessible by the processing unit(s). The memory stores software implementing one or more innovations described herein, in the form of computer-executable instructions suitable for execution by the processing unit(s).
A computing system may have additional features. For example, in some embodiments, the computing environment includes storage, one or more input devices, one or more output devices, and one or more communication connections. An interconnection mechanism such as a bus, controller, or network, interconnects the components of the computing environment. Typically, operating system software provides an operating environment for other software executing in the computing environment, and coordinates activities of the components of the computing environment.
The tangible storage may be removable or non-removable, and includes magnetic or optical media such as magnetic disks, magnetic tapes or cassettes, CD-ROMs, DVDs, or any other medium that can be used to store information in a non-transitory way and can be accessed within the computing environment. The storage stores instructions for the software implementing one or more innovations described herein.
The input device(s) may be, for example: a touch input device, such as a keyboard, mouse, pen, or trackball; a voice input device; a scanning device; any of various sensors; another device that provides input to the computing environment; or combinations thereof. For video encoding, the input device(s) may be a camera, video card, TV tuner card, or similar device that accepts video input in analog or digital form, or a CD-ROM or CD-RW that reads video samples into the computing environment. The output device(s) may be a display, printer, speaker, CD-writer, or another device that provides output from the computing environment.
The communication connection(s) enable communication over a communication medium to another computing entity. The communication medium conveys information, such as computer-executable instructions, audio or video input or output, or other data in a modulated data signal. A modulated data signal is a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media can use an electrical, optical, RF, or other carrier.
In view of the many possible embodiments to which the principles of the disclosure may be applied, it should be recognized that the illustrated embodiments are only examples and should not be taken as limiting the scope of the disclosure. Rather, the scope of the invention is defined by all that comes within the scope and spirit of the following claims.