WO2017029670A1

WO2017029670A1 - Intra-oral mapping of edentulous or partially edentulous mouth cavities

Info

Publication number: WO2017029670A1
Application number: PCT/IL2016/050902
Authority: WO
Inventors: Alexander ENTELIS; Moshe Goldstein; Assaf Halevy; Roei YIFTAH
Original assignee: Optical Metrology Ltd.
Priority date: 2015-08-17
Filing date: 2016-08-17
Publication date: 2017-02-23

Abstract

A system for generating three-dimensional mapping of an edentulous or partially edentulous mouth, using an intraoral apparatus comprising specially-designed scan bodies, a plurality of cameras and optionally, one or more light sources. The scan bodies used for this purpose differ from those described in the prior art in that they not only reflect radiation that impinges on them, but that they are either self-illuminated, such as by use of an internal light source, or that they emit radiation in response to externally applied radiation that impinges on them, or a combination of more than one of these effects. The scan bodies have a predetermined geometry, both shape and dimensions, and a surface design which may be generated by engraving, by marking, or by color, that allows easy identification of their precise position and orientation within the intraoral cavity. The light source need not have a patterned emission.

Description

INTRA-ORAL MAPPING OF EDENTULOUS OR PARTIALLY EDENTULOUS MOUTH CAVITIES

FIELD OF THE INVENTION

The present invention relates to the field of optical intra-oral mapping, especially of an edentulous or partially edentulous mouth cavity.

BACKGROUND

Intraoral scanners are commercially available today from a number of vendors; these scanners use various different optical designs and techniques, such as structured light projection, confocal scanning, active wavefront sampling, and stereoscopy. All use handheld devices with limited fields of view. To capture the intraoral cavity, the dentist moves the scanner inside the patient's mouth and the data from different regions is stitched together to get three-dimensional data of the oral cavity. In edentulous cases the stitching process is inaccurate because of lack of data features on soft tissue for the stitching process.

There is no currently available method that has the high level of accuracy required for non-contact, intraoral scanning of a screw-retained, implant-based restoration. However, accurate three-dimensional intraoral mapping of an edentulous or partially edentulous mouth cavity containing dental implants is essential for teeth-restoration purposes. It is necessary to precisely determine the implants' location and spatial orientation with respect to the gingiva (gums).

Previous work in the field has focused on the techniques of three-dimensional mapping of mouth cavities consisting mainly of teeth, either natural or artificial. Solutions of this problem are more general than for the situation in which the mouth cavity lacks most if not all of its teeth. Accurate non-contact measurement solutions for edentulous patients are not currently available. Instead, for such cases a dental impression of the edentulous intraoral cavity is typically taken using impression material and a gypsum model is created from it. This model can then be scanned using various available scanning techniques and the scan output, in the form of a digital data file, is used for design and manufacture of the required dental restoration. As stated above, prior art systems deal with the situations where the mouth contains teeth, at least to some extent. Exact dimensions and locations of the teeth within the mouth are generally unknown and the prior art methods suggest ways to extract this information, usually by optical means, with the best possible precision.

Different methods are described in US 2015/0079534 to Tsuji et al. for "Apparatus for Imaging Dental Arch in Oral Cavity" and in US 2010/0239136 to Gandyra et al. for "Device for Determining the 3D Coordinates of an Object, in particular of a Tooth", which describe solutions which include a plurality of projectors that project light patterns on the intraoral cavity and teeth, and a plurality of cameras to detect these light patterns as they reflect off the measured objects. However, these solutions are not simple to implement since designing projectors capable of generating the required light patterns within the mouth cavity having the required quality is problematic, due to the sizes and the number of the required optical, electrical, and mechanical elements needed to provide the resolution required.

In International Published Patent Application No. WO 2013/149346 to Trispera Dental Inc. for "Intraoral Imaging Apparatus", there is described the use of a single projector for projecting an orientation point onto a surface of the oral cavity. This application focusses on the geometry of the data acquisition elements with respect to the suggested apparatus. However, using only a single orientation light point could be insufficient when the goal is to retrieve all the information needed for mapping the intraoral cavity.

The projection devices mentioned in the prior art usually constitute a light source, a pattern generator, and a projection lens or interference filter that projects stripes of different colors toward an object undergoing three-dimensional mapping, such as suggested in the technique described in in US patent application 2007/0299338 to G.R. Stevick, for "Method and Apparatus for Dynamic Space-time Imaging System". These projector devices are usually placed inside the mouth, where space is naturally limited. In this prior art, the use of such projecting devices is mandatory. This follows, since by analyzing how projected patterns are bent and modified after their reflection off a measured object, it is possible to extract the object's geometrical shape and its dimensions. Moreover, because of fundamental optical limitations, it is also difficult using current technologies to create projected light patterns with acceptable properties through the entire focus range needed to map the whole intraoral cavity.

In US patent Application No. 2012/126475 to C.S. Thomsen, for "Dental Abutment for Oral Scanning" and in US patent Application No. 2014/0377714 to D. Jahn for "Scan Body for determination of Positioning and Orientation of a Dental Implant", there are described scan bodies having predetermined geometrical sizes and shapes, which are fitted into dental implants, and which can be scanned by an intra-oral scanner to determine the position and orientation of the scan bodies in real space, and hence to define the pose of the implant itself. The proposed scan-body designs by Thomsen and Jahn can be scanned using intra-oral scanners, but they are passive elements that only reflect radiation that impinges on them, causing the intra oral scanner that measures them to rely on sophisticated illumination and/or acquisition techniques to retrieve three-dimensional information. As stated above, these techniques are difficult to implement in the restricted intraoral volume. Therefore, such methods do not provide accurate enough results for multi-unit implant-based restoration. Moreover, when scanning with an intraoral scanner wand, the dentist moves the scanner in the mouth where the three-dimensional information is captured during the scan and stitched together to create the full three- dimensional image. The stitching operation is typically based on image features that allow adding images together one by one to create an entire map of the desired area. When there are not enough features, or the features are not sharp enough, inaccuracy in the final three-dimensional image results. This is a further reason why in edentulous or partially-edentulous cases there is not enough accuracy for multi-unit implant based restorations. The information between implants does not have enough features, as it contains mostly data of the soft tissue of the gum.

Therefore, there exists a need for an accurate three-dimensional, non-contact measurement method for determining the features of an edentulous or partially edentulous mouth cavity containing dental implants, which overcomes at least some of the disadvantages of prior art systems and methods.

The disclosures of each of the publications mentioned in this section and in other sections of the specification are hereby incorporated by reference, each in its entirety. SUMMARY

The present disclosure describes new exemplary systems and methods for generating three-dimensional mapping of an edentulous or partially edentulous mouth, using an intraoral apparatus comprising specially-designed scan bodies, a plurality of cameras and optionally, one or more light sources. The scan bodies used for this purpose differ from those described in the prior art in that they not only reflect radiation that impinges on them, but that they are either self-illuminated, such as by use of an internal light source, or that they emit radiation in response to externally applied radiation that impinges on them, or a combination of more than one of these effects. The scan bodies have a predetermined geometry, both shape and dimensions, and a surface design which may be generated by engraving, by marking, or by color, or by any other pattern method or geometry that can enable the spatial and orientational position of the scan body to be determined, such that it allows precise extraction of their position and orientation within the intraoral cavity, and therefore the position and orientation of the dental implant. Moreover, each scan body model may contain unique coding that links it to a specific dental implant type and model. This can be done by writing various symbols and signs on the scan body such as letters and/or numbers, or in QR code, or by using different colors, or material composition, or engraving on each scan body type, or altering the scan bodies dimensions, sizes, and geometry, all for the purpose of allowing visual identification of the dental implant type.

The scan bodies are positioned within the dental implants and then a plurality of synchronized image-capturing devices in the scanning apparatus, such as individual cameras or camera arrays, image the scan bodies, the images covering the intraoral cavity under investigation. The image-capturing devices can be either static or be moved in order to register images from various positions and locations within the mouth. Image- processing algorithms allow reconstruction of a three-dimensional map of the intraoral cavity from a plurality of two-dimensional images taken using the image-capturing devices. The output of the apparatus consists of digital data files that include the exact location, orientation, and type of the dental implants positioned in the mouth, combined with digital files containing three-dimensional information of the gum, neighboring teeth, and any other features in the mouth, built from a plurality of captured images of the system.

As stated above, the scan bodies emit or reflect a predetermined pattern of light, with known dimensional parameters and with known characteristics, such that the pose of the scan body and hence of the implant can be determined from the light emitted from the scan body. There is therefore no need to use additional projection devices providing the complex illumination methods discussed in the prior art, such as projected light patterns, formed using different electro-optical methods and devices. By eliminating the need for various projection devices, the present system greatly simplifies the method of generating images containing sufficient information to allow three-dimensional data retrieval. Furthermore, marking the scan bodies with high quality active patterns enables simplification of the intraoral system by reducing the illumination element complexity and hence obtaining more accurate results, and in a simpler illumination system. Moreover this technique enables reduction of the size of the system and its integration into a tray shaped unit that can easily fit in to the patient mouth.

However, although the scan bodies of the present disclosure have their optimal usefulness in that they reduce the complexity of the illumination system, it is to be understood that the proposed scan bodies can also be used with intraoral scanners that use patterned illumination. The pattern scan body will allow increased precision of the patterned illumination intraoral scanner for extraction of the scan body position and orientation within the intraoral cavity. Since the positional relationship between the illumination pattern and the reflection pattern is unknown and arbitrary, since the illumination system can be moved relative to the oral cavity, the co-ordinate system of the patterned illumination must be associated with that of the patterned reflected light. This can be done for instance by using a series of differing illumination patterns, whose mutual relationship is known, and signal processing the images of the reflections from the scan body for each of the series, in order to define the spatial relationship between the two patterned coordinate systems - the illumination and the scan body surface. Additionally, the system described in this disclosure is not limited to intraoral mapping of the mouth cavity, and can also be used to scan models of the intraoral cavity, such as gypsum models.

Furthermore, it is to be understood that throughout this disclosure, and as claimed, the term pose is intended to mean the spatial position and the angular orientation of the scan body or implant.

There is thus provided in accordance with an exemplary implementation of the devices described in this disclosure, a system for determining the pose of a dental implant in a subject's oral cavity or on a model of a subject's oral cavity, the system comprising:

(i) an imaging system comprising a camera system for three dimensional scanning of the oral cavity,

(ii) a scan body mounted on the dental implant, the scan body having a known spatial relation to the dental implant, and

(iii) an image processing system using images obtained from the camera system to determine the pose of the scan body,

wherein the scan body has a surface having a predetermined pattern, such that the image processing system can use images generated by the camera system of the predetermined pattern to extract the pose of the scan body.

In such a system, the predetermined pattern may include the dimensions of the pattern or of its features. Furthermore, the predetermined pattern may be formed by features on the surface of the scan body, or it may comprise regions of different reflectivity on the surface of the scan body, and the camera system may then utilize non-patterned illumination of the oral cavity. Alternatively, the scan body may be internally illuminated, and the features may be transparent regions formed in a known pattern on the surface of the scan body.

In any of the above described systems, the scan body may have a surface pattern formed by at least one of engraving, marking or color. Alternatively, the scan body may be coated with or may comprise a luminescent material. Such a luminescent material may be a photo-luminescent, fluorescent, or phosphorescent material. According to further implementations of the above described systems, the scan body may further comprise a coded inscription that defines the dental implant to which it is attached. Additionally, the imaging system and the at least one light source may be incorporated within a tray housing adapted to cover a dental arch of the subject.

According to a different implementation of the above referenced systems, the imaging system may alternatively comprise at least one light source emitting non-patterned illumination.

Finally in any of the above described systems involving reflection from the surface of the scan body, the predetermined patterns may be regions of different reflectivity on the surface of the scan body, and the camera system may utilize patterned illumination of the oral cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features of the invention result from the claims as well as from the subsequent detailed description of exemplary implementations of the invention, which is illustrated by means of the drawings, in which:

FIG. 1 shows examples of scan bodies as described in the present disclosure;

FIG. 2 shows a partially edentulous dental arch without (left) and with {right} scan bodies mounted into dental implants;

FIG. 3 shows the apparatus fully covering the dental arch (left) and with a cross section of the apparatus and dental arch {right}; and

FIG, 4 shows the detailed cross section depicted in Fig. 3, containing the apparatus main parts, the dental arch, and scan bodies. DETAILED DESCRIPTION

This detailed description shows an exemplary intraoral scanning system for capturing three-dimensional information of mouth cavities, especially of an edentulous or partially edentulous mouth cavity for implant based restorations. The system contains an intraoral optical tray with one or more cameras and light sources, a processing unit, and some examples of novel scan bodies, as described hereinbelow in this detailed description section.

These novel scan bodies are mounted inside the intraoral cavity for the purpose of three- dimensional mapping of the position, orientation, and type of the dental implants. The scan bodies emit internally generated electro-magnetic radiation or transmit such illumination, or reflect incident illumination coded by reflection off the predetermined patterned surface of the scan bodies. In a first implementation, the system uses a light source, such as a laser or a LED, mounted within a specially-designed scan body that has easily-identified visual features, such as engraving on the scan body. The engraving can use alternating opaque and transparent material, or a grid-like structure design, or any similar coded surface. In another implementation, the scan body is made of, or is coated with, luminescent material, such as photoluminescent, fluorescent, or phosphorescent material. This feature can be used together with special features such as specific dimensions, unique engraving, or the like. In another alternative embodiment, light can be guided into the scan body, such as from its upper surface, and transmitted through its side walls for imaging using image-capturing devices. Alternatively, the scan body can be an optically passive element, composed of, or coated with, a material that reflects electro-magnetic radiation. In this case, in contrast to what is known in the art, imaging of any special markings, engravings, color pattern or visual structure is used to identify the scan body position, orientation, and type.

The exact construction of the scan body, which can include its dimensions, material composition, color, coating, surface properties, and internal structure, may be selected to assist in retrieving from the captured images, as much information as possible on the position, orientation and type of the dental implant on which the scan body is mounted. Reference is now made to Fig. 1, which illustrates schematically various exemplary scan bodies of the type described in this disclosure. Each scan body 100 has a screw thread 101 on its base, for mounting on the dental implant and an example optical feature 102. The samples in Fig. 1 show a cylindrical construction, but it is to be understood that any predetermined shape can be used, provided that that geometry can be handled by the image-processing software of the system. The exact shape of the scan body and the shape and nature of the optical features 102, such as are shown in the drawings of some examples of scan bodies in Fig. 1, can assist in extracting the seat position, orientation vector and rotation angle, all of which are crucial for engaging scan bodies, which provide information about rotation of the scan body around the implant center axis. Engaging scan bodies are used usually when the location of a single dental implant located next to one or more teeth is to be determined.

Fig. 2 shows on the left side drawing, a schematic representation of a partially edentulous mandible 200 with dental implants, 201, while the right side drawing of Fig. 2 shows the same mandible with scan bodies 202 screwed into the dental implants.

Fig. 3 shows schematic illustrations of an intraoral system scanning apparatus, positioned inside the patient's mouth after the scan bodies have been mounted in the dental implants, such that images of the mouth cavity can be captured. The left image of Fig. 3 shows the apparatus 300 covering the entire dental arch 301, of which only its end is shown, and the right image of Fig. 3 also includes a cross sectional view 302 of the apparatus, which is shown in more detail in Fig. 4. According to these illustrations the apparatus maps only the upper or lower dental arches in a single acquisition process that includes registering a plurality of images, but it is possible to capture both dental arches simultaneously during a single acquisition process, by using a double facing scanning apparatus.

Figure 4 presents, as described above, a cross section of the apparatus 400 and dental arch, with scan bodies 401 constructed according to the present application, mounted on it. The apparatus includes a plurality of image-capturing devices 402, and a plurality of illuminating sources 403. The illuminating sources can be such as to generate non- patterned illumination, use of which is enabled by the scan bodies of the present disclosure.

The intraoral system contains an array of image-capturing devices 402 that are pre- calibrated in respect to each other in orientation and position, such that the imaged information which they receive can be used by the processing unit in constructing a composite three dimensional image of the position and orientation of all of the relevant imaged features in the field of view of the array. The system may capture information synchronously by multiple cameras to prevent any impact on the result by system, patient or doctor movement.

The processing unit, (not shown in Fig. 4) which can incorporated in a computer or a dedicated hardware unit, processes the data and creates data output, digital files of implants position, intraoral situation of the gum, neighboring teeth, and any other features of interest.

It is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.

Claims

CLAIMS We claim:

1. A system for determining the pose of a dental implant in a subject's oral cavity or on a model of a subject's oral cavity, said system comprising:

an imaging system comprising a camera system for three dimensional scanning of said oral cavity;

a scan body mounted on said dental implant, said scan body having a known spatial relation to said dental implant; and

an image processing system using images obtained from said camera system to determine the pose of said scan body,

wherein said scan body has a surface having a predetermined pattern, such that said image processing system can use images generated by said camera system of said predetermined pattern to extract the pose of said scan body.

2. A system according to claim 1 wherein said predetermined pattern includes the dimensions of the pattern or of its features.

3. A system according to either of the previous claims, wherein said predetermined pattern is formed by features on the surface of said scan body.

4. A system according to any of the previous claims, wherein said predetermined pattern comprises regions of different reflectivity on said surface of said scan body, and said camera system utilizes non-patterned illumination of said oral cavity.

5. A system according to any of claims 1 to 3, wherein said scan body is internally illuminated, and said features are transparent regions formed in a known pattern on the surface of said scan body.

6. A system according to any of the previous claims, wherein said scan body has a surface pattern formed by at least one of engraving, marking or color.

7. A system according to claim 1 wherein said scan body is coated with or comprises a luminescent material.

8. A system according to claim 7 wherein said luminescent material is a photo- luminescent, fluorescent, or phosphorescent material.

9. A system according to any of the previous claims, wherein said scan body further comprises a coded inscription that defines the dental implant to which it is attached.

10. A system according to any of the previous claims, wherein said imaging system comprises at least one light source emitting non-patterned illumination.

11. A system according to any of the previous claims, wherein said imaging system and said at least one light source are incorporated within a tray housing adapted to cover a dental arch of the subject.

12. A system according to any of claims 1 to 3, wherein said predetermined patterns are regions of different reflectivity on said surface of said scan body, and said camera system utilizes patterned illumination of said oral cavity.