METHOD FOR SCANNING A USER'S TOOTHBOARD

Description

technical field

[0001] The present invention relates to a method for scanning a user's dental arch, and a device for implementing such a method. Previous technique

[0002] It is common practice to scan a patient's dental arches to analyze their dental health, particularly before orthodontic treatment. However, obtaining a dental scan requires the patient to visit a dental professional or provide information, especially images, to the dental professional. Having a scan done at a dental office or other dental practice can be costly and stressful for the patient. Furthermore, self-recording dental images can result in poor image quality or incomplete information.

[0003] D1 discloses a device and method for semi-automatic learning of scanning a dental arch, where the learner is warned when deviating from the ideal trajectory.

[0004] There is a need to facilitate the acquisition of a dental arch scan, while limiting the risk of an incomplete scan.

[0005] One goal of the invention is to address this need. Description of the invention Résumé of the invention

[0006] The invention proposes a method for scanning a user's dental arch, the method comprising a preliminary step of determining a representation of a reference dental arch, called the "reference representation", then a plurality of cycles of the following steps a) to d): a) acquisition, under acquisition conditions, of a two-dimensional image of said dental arch, or "updated image", by means of an image acquisition device, preferably by the user; b) analysis of the updated image so as to identify the surface of the updated image representing the user's dental arch, called the "acquired 2D surface", then delimitation and marking of a surface of the reference representation corresponding to the acquired 2D surface, or "elementary marked area", and addition of the elementary marked area in a "marked area of ​​the reference representation" grouping together the set, empty before the first said cycle, of the elementary marked areas defined during the previous cycles;c) determining and presenting to the user guidance information for the acquisition device towards new acquisition conditions adapted so that the next cycle increases the marked area of ​​the reference representation; d) moving the acquisition device towards said new acquisition conditions; the process preferably comprising, after the last cycle, a final step of generating a final three-dimensional model from said updated images.

[0007] The generation of the final model can be carried out by the image acquisition device or by a computer remote from the image acquisition device and to which all the updated images acquired have been transmitted, preferably a computer of a dental professional.

[0008] As will be seen in more detail later in the description, a scanning process according to the invention leads quickly and easily to a set of updated images sufficient to produce a complete final model of the dental arch.

[0009] Furthermore, the user does not need to visit a dental professional, nor is the user supervised by a dental professional, to acquire the updated images. Thanks to the guidance system, the updated images can be acquired under precise acquisition conditions without any special training.

[0010] Advantageously, the acquisition can be done in real time, with the updated images being extracted, for example, from a film.

[0011] Preferably, in step c), the guidance information is displayed on a screen, preferably on the screen of the image acquisition device. The image acquisition device may be, in particular, a mobile phone or a tablet, preferably a mobile phone.

[0012] Guidance information can include, in particular, auditory, visual, and / or tactile information. This allows guidance information to be adapted to any user. Preferably, guidance information includes several different types of information, ideally stimulating multiple senses, thus facilitating communication with the user.

[0013] In a preferred embodiment of the invention, the marking comprises, for each step b), a visual marking of the surface of the reference representation, and each step c) comprises a presentation, preferably to the user, preferably on a screen, preferably on a screen of a user's mobile phone used to acquire the updated images, of all the visual marks generated in all the preceding steps b).

[0014] A visual mark preferably includes a graphic representation of the elementary marked area, for example a representation of the outline of the elementary marked area and / or a flat area of ​​a color and / or a pattern within the limits of the elementary marked area.

[0015] Acquisition is thus simplified. In particular, during real-time cycling, the screen displays a reference representation whose marked area is completed as the cycles progress, allowing the user to easily identify the unmarked area, and to position and orient the image acquisition device accordingly.

[0016] Conversely, during real-time cycling, the screen can display a reference representation whose unmarked area disappears with each cycle. Preferably, however, the screen continues to display at least the contours of the dental arch.

[0017] Visual markers thus constitute a preferred form of guidance information.

[0018] The guidance information may include supplementary information, supplementary information corresponding to information other than that intended to indicate a positioning of the acquisition device, supplementary information may for example indicate to the user to put on or take off an orthodontic splint, to open or close the mouth, and / or to use a retractor or on the contrary to remove it.

[0019] The reference representation can be generated. Alternatively, it can be selected, for example from a database.

[0020] The reference representation can be two-dimensional. In a preferred embodiment, the reference representation is a three-dimensional digital model. The process allows, by acquiring different updated images, for marking different areas of this model until a coverage threshold is reached, or preferably until the entire model is marked. The updated images then advantageously "cover" a majority of the model's surface, or preferably the entire surface of the model, and allow, for example, the creation of a final model representing the user's dental arch with high precision. The final model can be created by a computer belonging to the dental professional to whom the updated images are transmitted, or by the image acquisition device.

[0021] In particular, the coverage threshold can be 90%, better 95%, or even better 99%.

[0022] The process may include, at the end of each cycle, comparing the percentage of the marked area's surface area relative to the total model area, called the "coverage percentage," with the coverage threshold. If the coverage percentage is greater than the threshold, the final model generation step is performed; otherwise, a new cycle begins.

[0023] In one particular embodiment, at step c), the percentage of coverage is presented to the user.

[0024] The percentage of coverage can be presented as a gauge, a digital display, a progress bar, or objectives presented sequentially when a particular objective is achieved, or simultaneously with a different display distinguishing between achieved objectives and those remaining to be achieved. For example, the objectives might be "acquisition of molars," "acquisition of incisors," "acquisition of more than 10% of the model," "acquisition of more than 25% of the model," "acquisition of more than 40% of the model," "acquisition of more than 50% of the model," "acquisition of more than 75% of the model," "acquisition of more than 85% of the model," "acquisition of right-side view," "acquisition of left-side view," "acquisition of top view," "acquisition of bottom view," "acquisition of a closed-mouth view," "acquisition of an open-mouth view," or "acquisition with an orthodontic aligner."

[0025] A method according to the invention may also include one or more of the following optional features: the updated images of the successive cycles are extracted from a film acquired by the user by a tablet or a mobile phone, said cycles preferably being executed in real time during the acquisition of said film, at least part of the guidance information preferably being presented on a screen of said tablet or said phone, respectively; the guidance information includes a presentation of the marked area on a screen of the image acquisition device, preferably superimposed on the reference representation in which the unmarked area has an appearance, preferably a color, different from the marked area;the reference representation is a "reference" model of a "reference" arch representative of the "historical" arches of a set comprising more than 10, more than 100, more than 1,000, more than 10,000 and / or less than 1,000,000 historical individuals, or constituted by assembling tooth models according to an arrangement determined by analysis of one or more images of analysis of the user's dental arch, preferably acquired with the image acquisition device one or more illustrations, in 3D or 2D, of a dental arch, possibly photorealistic;at step c) of any cycle, a view of the observed reference model is presented along an observation direction oriented, with respect to the reference model, as the acquisition direction of the updated image at step a) of said cycle, with respect to the user's dental arch, i.e. substantially oriented as the direction of the optical axis of the camera or camera during said acquisition, so that said view is substantially superimposable in register with said updated image; at a step c), preferably at any step c), the image acquisition device provides variable information as a function of a difference between the actual acquisition conditions and said new acquisition conditions, for example by emitting an audible signal or a visual indication, for example a blink, the intensity of which is greater the smaller said differences are;The user thus advantageously knows whether the movement of the image acquisition device that he performs is more or less effective in reaching the new acquisition conditions; for step a) of at least one cycle, preferably for any step a), the lips and / or cheeks of the user's dental arch are separated, preferably using a retractor, so as to expose at least one tooth to the image acquisition device, for example to fully expose the extrados of an incisor and / or at least partially the extrados of a molar;During the cycling process, at least one updated image taken facing the user is acquired, and / or at least one updated image taken to the right of the user, and / or at least one updated image taken to the left of the user, preferably at least one updated image taken facing the user and at least one updated image taken to the right of the user and at least one updated image taken to the left of the user; and / or at least one updated image taken facing the user on the one hand and at least one updated image taken from above relative to the user and / or at least one updated image taken from below relative to the user, on the other hand, preferably at least one updated image taken facing the user and at least one updated image taken from above relative to the user and at least one updated image taken from below relative to the user;and / or at least one updated image taken with the mouth open and / or at least one updated image taken with the mouth closed; the user is at a distance, preferably more than 100 m or more than 1 km and / or less than 1000 km from any dental care professional, in particular any orthodontist; the cycling is stopped when more than 50%, more than 70%, more than 90%, preferably 100% of the surface of the reference representation are 'covered' by the acquired updated images, i.e., are represented on at least one updated image; the final model is compared to another model representing the user's dental arch, for example to correct the final model or the other model, and / or the final model is cut into tooth models and, preferably, said tooth models are moved;The final model is compared to the reference model, and preferably this comparison is presented to the user, for example by superimposing, preferably in a register, the final model and the reference model; the reference representation is a three-dimensional model and the surface of the reference representation corresponding to the acquired 2D surface is determined by searching for suitable virtual acquisition conditions for acquiring a view of the reference representation, called the "reference image", showing maximum concordance with the updated image in said virtual acquisition conditions; then by projecting the acquired 2D surface onto the reference representation, following the observation direction of said reference representation in said virtual acquisition conditions;The virtual acquisition conditions are determined by attempting to superimpose notable points of the dental arch represented on the updated image with the corresponding notable points of the reference representation.

[0026] The invention also relates to: a computer program, and in particular specialized software for mobile phone or tablet, or "app", comprising program code instructions for the execution of one or more steps of a process according to the invention, preferably for all steps b) to c) when said program is executed by a computer, a computer medium on which such a program is recorded, for example a memory or a CD-ROM.

[0027] Preferably, when the computer program is specialized software for mobile phone or tablet, the computer program includes instructions for executing step a), preferably even more for executing all steps a) to c).

[0028] The invention also relates to a device for implementing a method according to the invention, said device comprising: Optionally, a first computer with a first computer program including program code instructions to generate the reference representation or select the reference representation, for example from a database; an image acquisition device for carrying out steps a); preferably, a screen for displaying guidance information during steps c); a second computer, identical or different from the first computer, with a second computer program including program code instructions for carrying out steps b) and c); a third computer, identical or different from the first and / or second computer(s), with a third computer program including program code instructions for carrying out the final step of generating the final model of the user's dental arch from the updated images;preferably, a fourth computer, identical or different from the first and / or second and / or third computer(s), comprising a fourth computer program including program code instructions to compare the final model to another model representing the user's dental arch and / or to slice the final model into tooth models and, preferably, to move said tooth models.

[0029] Preferably, the screen and / or the first computer and / or the second computer and / or the third computer and / or the fourth computer is / are integrated into the acquisition device. Preferably, the image acquisition device is a mobile phone or a tablet. Preferably, the screen is the screen of the mobile phone or tablet, respectively.

[0030] The user can then easily, without third-party intervention, and in particular without the intervention of a dental professional, using a simple mobile phone or tablet, acquire good quality dental images that together fully represent the reference representation.

[0031] The device may also include means of communication, in particular allowing the sending of the updated image(s) and / or the receiving of the reference representation. Definitions

[0032] A "user" is a person for whom a process according to the invention is implemented.

[0033] The term “dental professional” refers to any person qualified to provide dental care, which includes an orthodontist and a dentist.

[0034] The "closed mouth" position is the occlusal position in which the user's upper and lower teeth are in contact. An "open mouth" position is a position in which the user's upper and lower teeth are not in contact, preferably the position of a fully open mouth.

[0035] By "arch" or "dental arch" we mean all or part of a dental arch, preferably comprising at least 2, preferably at least 3, preferably at least 4 teeth.

[0036] A retractor, or dental retractor, is a device designed to retract the lips. It consists of an upper and lower rim, and / or a right and left rim, extending around a retractor opening and intended to be inserted between the teeth and lips. In the working position, the user's lips rest on these rims, so that the teeth are visible through the retractor opening. A retractor thus allows the teeth to be observed without being obstructed by the lips. However, the teeth do not rest on the retractor, so the user can, by turning their head relative to the retractor, change which teeth are visible through the retractor opening. They can also change the spacing between their dental arches. In particular, a retractor does not press on the teeth to separate the two jaws from each other, but rather on the lips.In one embodiment, a retractor is configured to elastically separate the upper and lower lips so as to expose the teeth visible through the retractor opening. In another embodiment, a retractor is configured such that the distance between the upper and lower edges, and / or between the right and left edges, is constant. Retractors are described, for example, in PCT / EP2015 / 074896, US 6,923,761, or US 2004 / 0209225.

[0037] According to the international convention of the International Dental Federation, each tooth in a dental arch has a predetermined number.

[0038] A "notable point" is a point on an arch, tooth, arch pattern or tooth pattern that can be identified, for example the apex of the tooth or the tip of a cusp, an interdental contact point, i.e. of a tooth with an adjacent tooth, for example a mesial or distal point on the incisal edge of a tooth, or a point at the center of the crown of the tooth, or "barycenter".

[0039] The term "computer" refers to a computing unit, which includes a set of multiple machines with computing capabilities. This unit can be integrated into a mobile phone, a PC, or a server, such as a server located remotely from the user, like the cloud, or a computer at a dental practice. Both mobile phones and computers have communication capabilities to exchange information.

[0040] Typically, a computer includes a processor, memory, a human-machine interface (HMI) which typically includes a screen, and a communication module for internet, Wi-Fi, Bluetooth®, or telephone network connections. Software configured to implement a method of the invention is loaded into the computer's memory. The computer can also be connected to a printer.

[0041] The method according to the invention (excluding the operations of acquiring and moving the image acquisition device) is implemented by computer, preferably exclusively by computer.

[0042] By "model," we mean a three-dimensional digital model. A model consists of a set of voxels.

[0043] A "tooth model" is a three-dimensional digital model of a tooth. A dental arch model can be segmented to define tooth models for at least some of the teeth, preferably for all the teeth represented in the arch model. Tooth models are therefore models within the arch model.

[0044] A "model of an arch" is a model representing at least part of a dental arch, preferably at least 2, preferably at least 3, preferably at least 4 teeth.

[0045] The "slicing" of an arch model into "tooth models" is an operation that allows for the delimitation and autonomy of the tooth representations (tooth models) within the arch model. Computer tools exist for manipulating the tooth models within an arch model. One example of software that allows for manipulating tooth models and creating a treatment plan is the Treat program, described on the page https: / / en.wikipedia.org / wiki / Clear _ aligners#cite _ note-invisalignsystem-10.

[0046] By "image," we mean a two-dimensional image, such as a photograph or a still from a film. An image is made up of pixels. A "film" is considered to be a collection of photographs.

[0047] By "image of an arch", or "model of an arch", or "reference representation" of a dental arch, we mean a representation of all or part of said arch, preferably representing at least 2 teeth, preferably at least 4 teeth.

[0048] The term "match" or "fit" between two objects, for example between the representations of a dental arch in two images, refers to a measure of the difference, or "distance," between these two objects. A match is maximal ("best fit") when this difference is minimal, particularly when the two images represent essentially the same elements in the same way, that is, in such a way that the representations of the elements in these two images are essentially superimposable in terms of register.

[0049] A superposition of two images is "in register" when the outlines of representations of physical elements in the first image overlap with the outlines of said physical elements in the second image. The superposition thus appears realistic.

[0050] The "marking" of a surface on a reference representation consists of storing sufficient data in a computer system to specifically reconstruct that surface. The boundaries of this surface can be represented on the reference representation in such a way that the user can visualize them. This marking is then described as "visual."

[0051] The "acquisition conditions" of an image specify the position and orientation in space of an image acquisition device relative to the user's teeth (actual acquisition conditions) or to a model of the user's teeth (virtual acquisition conditions), and preferably the calibration of this acquisition device. Acquisition conditions are said to be "virtual" or "theoretical" when they correspond to a simulation in which the acquisition device would be in said acquisition conditions (theoretical positioning and, preferably, calibration of the acquisition device) relative to a model.

[0052] Particularly in virtual acquisition conditions of a reference image, the acquisition device can also be described as "virtual". The image is in fact acquired by a fictitious acquisition device, having the characteristics of the "real" acquisition device used to acquire the real images, and in particular the updated images.

[0053] The calibration of a scanning device consists of all the values ​​of its calibration parameters. A calibration parameter is an intrinsic parameter of the scanning device (unlike its position and orientation) whose value influences the acquired image. Preferably, calibration parameters are chosen from the group formed by aperture, exposure time, focal length, and ISO sensitivity.

[0054] Statistical processing is a process that, when applied to a set of data, allows us to determine characteristics specific to that set, such as a mean, standard deviation, or median value. Statistical processing tools are well known to those skilled in the art.

[0055] An "illustration" has no physical reality. It can be a symbolic or schematic representation comprising a set of geometric shapes, a 2D or 3D digital drawing.

[0056] "First", "second", "third" and "fourth", "reference", "updated", "historical", "target" are used for clarity.

[0057] "Vertical", "horizontal", "right", "left", "front" or "facing", "behind", "above", "below" refer to a user who is standing upright.

[0058] "Comprising" or "comprising" or "presenting" should be interpreted in a non-restrictive manner, unless otherwise indicated. Brief description of the drawings

[0059] Other features and advantages of the invention will become apparent upon reading the detailed description that follows and examining the attached drawing in which: [ Fig 1 ] there figure 1 schematically represents a cycle of a process according to the invention; [ Fig 2 ] there figure 2 schematically represents a device according to the invention [ Fig 3 ] there figure 3 represents the progressive coloring of a reference model. Detailed description Process

[0060] A method for scanning a user's dental arch according to the invention comprises steps a) to d) as illustrated by the figure 1 .

[0061] Preferably, it also includes a preliminary step of determining a reference representation.

[0062] Determining the reference representation may involve generating a representation, in particular a three-dimensional model.

[0063] In another embodiment, determining the reference representation may consist of selecting a representation from a database.

[0064] The reference representation is a model or image representing a reference dental arch. Preferably, the reference representation is a model, called a "reference model".

[0065] The reference representation can depict a standard reference dental arch and be used for different users, possibly even for any user. However, the reference representation preferably depicts a reference dental arch whose shape closely resembles that of the user, thus improving the accuracy of the procedure.

[0066] The reference representation can be representative of a population of individuals.

[0067] In one embodiment, the reference representation is obtained by statistically processing a set of historical archway representations from a population of historical individuals who share one or more characteristics with the user, for example, grouping people of the same age group as the user or who have suffered from the same pathology as the user. The statistical processing may, for example, consist of determining a reference representation that minimizes the differences in shape with the historical archway representations.

[0068] The reference representation can be, in particular, the model of a typodont.

[0069] The reference representation can be obtained by arranging historical tooth models in a pattern corresponding to one or more "analytical" images of the user's dental arch, preferably taken with the user's mobile phone. Specifically, the following steps can be taken: creation of a historical library containing more than 1,000, preferably more than 10,000 and / or less than 1,000,000 tooth models, referred to as "historical tooth models", and preferably assigning a tooth number to each historical tooth model; analysis of at least one "analysis image" of the dental arch, for example by means of a deep learning device, preferably a neural network, so as to determine at least one area of ​​the analysis image representing a tooth, or "analysis tooth area", and preferably the number of said tooth; for each analysis tooth area determined in the previous step, search, in the historical library, for a historical tooth model exhibiting maximum shape proximity to the analysis tooth area, or "optimal tooth model", and preferably having the same tooth number as the tooth represented on the analysis tooth area;arrangement of all optimal tooth models to create a dental arch model that is as close as possible to the arch shown in the analysis image, or "assembled model"; optionally, replacement of at least one optimal tooth model with another tooth model and return to the previous step to maximize the match between the assembled model and the analysis image; optionally, repeating said analysis with another analysis image and, at the arrangement and / or replacement step, seeking maximum match with all the analysis images used.

[0070] A method for generating a reference representation in the form of a model by arranging historical tooth models is described in particular in European application no. 18 184486.

[0071] The reference representation can be generated by the imaging device, particularly from images of the user's dental arch taken with the imaging device. It can also be generated by another device, for example, a computer used by the dental professional.

[0072] The reference representation can be stored in memory or in the cloud, accessible via digital communication means. It is made accessible to the computer that implements steps b) and c).

[0073] After the reference representation has been made available, the process comprises a plurality of cycles of steps a) to d).

[0074] The time interval between two successive cycles is preferably less than 5 minutes, 1 minute, 30 seconds, or 1 second. Preferably, the user acquires updated images in real time, preferably by filming their dental arch, and steps b) to d) are immediately performed for each updated image. The marking, preferably visual, of the reference representation is thus performed in real time, and the user is guided during the filming process.

[0075] Preferably, a cycle is performed for at least one updated image taken facing the user, at least one updated image taken to the right of the user and at least one updated image taken to the left of the user.

[0076] Preferably, a cycle is performed for at least one updated image taken with the mouth open and for at least one updated image taken with the mouth closed.

[0077] During the first cycle, the reference representation is partially marked in step b). The marking of the reference representation is then completed in each subsequent cycle.

[0078] We will now describe in detail an example of a cycle.

[0079] At the stage a) An updated image, preferably a photograph, representing a user's dental arch is acquired using an image acquisition device. Preferably, a film is acquired with the image acquisition device, and the updated image is extracted from the film.

[0080] In one particular embodiment, a step a) involves acquiring a plurality of updated images, preferably photographs, representing a user's dental arch, using an image acquisition device, the plurality of images being able to be extracted from a film.

[0081] Preferably, the acquisition is carried out by the user himself.

[0082] The updated image is preferably "extraoral", that is, without the camera lens being inserted into the user's mouth.

[0083] The image acquisition device may be in particular a mobile phone, a tablet, a camera or a computer, the image acquisition device being preferably a mobile phone or a tablet, in particular so that the user can acquire up-to-date images anywhere, and in particular outside the office of a dental professional, for example more than 1 km from the office of a dental professional.

[0084] In one embodiment, the user uses a mobile phone and a mount to which the mobile phone is removably attached, the mount being held against the user during the acquisition of all refreshed images. In particular, the mount may be of the type described in PCT / EP2021 / 068702, EP17306361, PCT / EP2019 / 079565, PCT / EP2022 / 053847 or FR2113577.

[0085] In a preferred embodiment, the user uses a free-standing mobile phone, meaning one whose position and orientation they can freely determine, and in particular, one not attached to a support. The method according to the invention allows the user to be guided in their shooting, so that guidance by means of a support is not necessary. Preferably, the image acquisition device is not in contact with the user's mouth, either directly or via a support for the image acquisition device.

[0086] The time interval between the preliminary step of generating the reference representation and step a) is preferably less than 4 weeks, 2 weeks, or 1 week, particularly when said generation is performed from analysis images of the user's dental arch. The preliminary step can also be immediately before step a), for example, less than 5 minutes before step a).

[0087] In step b), the updated image is analyzed in such a way as to identify, in the updated image, a surface representing, at least partially, the user's dental arch, called the "acquired 2D surface".

[0088] When a plurality of updated images is acquired in step a) which precedes step b), each updated image of the plurality of updated images is analyzed so as to identify, in each updated image, an acquired 2D surface.

[0089] The analysis can be done using classical segmentation methods.

[0090] We then search for a part of the surface of the reference representation that corresponds to the acquired 2D surface. Preferably, this part results from a one-to-one relationship with the acquired 2D surface, that is to say, for each acquired 2D surface, a unique part of the surface of the reference representation is defined.

[0091] Preferably, said part is the result of a projection of the acquired 2D surface onto the reference representation.

[0092] In a preferred embodiment, the reference representation is a model. We then seek a view of the model that corresponds to the updated image, that is, one that represents the modeled arcade substantially like the updated image. In other words, we seek suitable virtual acquisition conditions for acquiring a view of the model that exhibits maximum concordance with the updated image under these virtual acquisition conditions. These virtual acquisition conditions can be determined by finding the virtual acquisition conditions that allow us to superimpose notable points on the updated image onto corresponding notable points on the model, preferably using an optimization algorithm.

[0093] A search for a view of the model in accordance with the updated image is described for example in European application no. 18 184486.

[0094] The view and the updated image can then be substantially superimposed on each other in register. This register superposition of the model view and the updated image defines a region of the view that is covered by, or covers, the acquired 2D surface. The boundaries of this region can be projected onto the model. They then delimit the portion of the reference representation's surface that corresponds to the acquired 2D surface. This portion is the result of projecting the acquired 2D surface onto the reference representation along the model's viewing direction, in which the view represents the model.

[0095] The portion of the reference image corresponding to the acquired 2D surface is then marked. This is called the "elementary marked area." The term "marked area" refers to the union of all the elementary marked areas defined during the cycling process. The marked area, initially empty before the first cycle, therefore contains one elementary marked area after the first cycle, and is then completed with each subsequent cycle, as the acquisition device moves and new images are acquired. The "unmarked area," representing the portions of the reference image that correspond to regions of the dental arch not appearing on any updated image, thus gradually decreases.

[0096] In step c), We determine and present guidance information for the image acquisition device.

[0097] The guidance information is useful information to help the user move the image acquisition device so that, in the next cycle, the updated acquired image represents a new acquired 2D surface that allows the marked area to be completed, i.e., that leads to an elementary marked area at least partly outside the marked area defined at the end of step b) of the current cycle.

[0098] The guidance information informs the user about the parts of their dental arch for which they still need to acquire one or more updated images. It guides them in orienting and / or positioning the acquisition device to achieve the desired acquisition.

[0099] In one embodiment, the computer implementing step c) determines, for example by random search or with an optimization algorithm, the new acquisition conditions for the next cycle, such that the new 2D surface acquired under these new acquisition conditions maximizes the increase in the marked area of ​​the reference representation. These new acquisition conditions can be described as new "target" acquisition conditions.

[0100] Guidance information may include visual, auditory, and / or tactile information. For example, guidance information may include audio instructions telling the user to move the acquisition device closer to or further from their teeth, to shift the acquisition device to the right or left, to rotate the acquisition device around the dental arch, to open or close their mouth, or to open or close their jaw.

[0101] Sensory information can be a vibration indicating, for example, to the user to stop a movement.

[0102] Preferably, in step c), visual guidance information is presented, preferably on a screen, preferably on a screen of the image acquisition device, preferably on a mobile phone or tablet screen.

[0103] In one embodiment, the marked area and, preferably, the unmarked area are displayed. This display allows for quick and efficient user guidance. This guidance, which gives the user considerable freedom, is intuitive, so the user does not need prior training.

[0104] Real-time cycling offers the advantage of immediately visualizing how the marked area expands. The progressive coloring of the reference representation is engaging. In one embodiment, a goal can be set for the user, for example, to encourage them to color the reference representation as quickly as possible, further enhancing the fun aspect of acquiring updated images.

[0105] Preferably, the marked area is colored, preferably in a different color from the unmarked area. Preferably, the outlines of the elementary marked areas are not specifically represented, only the outline of the marked area being shown if necessary. The marking in step b) is then, preferably, a visual marking consisting of extending the colored marked area so that it incorporates the elementary marked area defined in said step b).

[0106] A colouring of the marked area, and preferably a display of the unmarked area, allows the user to be indirectly informed how to move the image acquisition device so as to acquire, during the next cycle, an updated image representing a part of the dental arch corresponding to an uncoloured area and therefore to an unmarked area of ​​the reference representation.

[0107] Equivalent to progressively coloring the marked area, it is possible to progressively erase the unmarked area. On the screen, these two solutions are similar, with erasing an area being its coloring in the background color.

[0108] The guidance information can be determined based on the acquisition conditions of the updated image acquired in the previous step a) and the unmarked area.

[0109] Determining the guidance information based on the unmarked area, or equivalently, the marked area, implies that the guidance information is not solely dependent on the position of the imaging device in space. It depends on what the imaging device has observed so far, and therefore not only on the position of the imaging device in space, but also on the orientation of the imaging device's lens relative to the dental arch during image acquisition.

[0110] A representation of the trajectory of the image acquisition device, as described in US2020193871A1, does not depend on the marked area, but only on the position of the image acquisition device in space.

[0111] Steps b) and c) are implemented by a computer program.

[0112] In step d),The user changes the position and / or orientation of the acquisition device according to the guidance information.

[0113] Preferably, the cycle of steps a) to d) is repeated until a stopping criterion is reached.

[0114] The stopping criterion can be a ratio of the area of ​​the marked surface to the area of ​​the surface of the reference representation. In particular, steps a) to d) can be repeated until said ratio is greater than 50%, preferably greater than 75%, preferably greater than 80%, preferably greater than 90%, preferably greater than 95%, preferably 100%, that is to say until the reference representation no longer contains any unmarked area.

[0115] The scanning process according to the invention finally includes, after stopping the cycling of a) to d), a step of generating a 3D model from the updated images acquired during the different cycles.

[0116] Preferably, at the end of the cycling of steps a) to d), the process includes a step of sending the updated images acquired during the different cycles and / or a model generated from the updated images acquired during the different cycles, preferably to a dental care professional.

[0117] The model can be used in particular for a dental professional to make a diagnosis, or even to design an orthodontic treatment plan, or even to have an orthodontic appliance made, preferably an orthodontic splint. Device

[0118] The invention also relates to a device for implementing a scanning method according to the invention. Such a device is shown schematically in the diagram. figure 2 .

[0119] A device 1 according to the invention comprises: optionally, a first computer comprising a first computer program including program code instructions for generating the reference representation; an image acquisition device 10 for implementing steps a) of acquiring updated images 12, a screen 14 for presenting guidance information 16 during steps c), a second computer 18 comprising a second computer program including program code instructions for executing steps b) and c), the second computer 18 receiving a reference model 20 stored in a database 22, preferably, a third computer, identical or different from the first and / or second computer(s), comprising a third computer program including program code instructions for generating a final model of the user's dental arch from the updated images;preferably, a fourth computer, identical or different from the first and / or second and / or third computer(s), comprising a fourth computer program including program code instructions to compare the final model to another model representing the user's dental arch and / or to slice the final model into tooth models and, preferably, to move said tooth models.

[0120] Preferably, the screen and / or the first computer and / or the second computer and / or the third computer and / or the fourth computer is / are integrated into the image acquisition device.

[0121] Preferably, the image acquisition device is a mobile phone or tablet with a camera and screen, the first computer program and / or the second computer program and / or the third computer program and / or the fourth computer program being loaded onto the mobile phone or tablet, preferably in the form of specialized software.

[0122] The device may include means of communication enabling the sending of updated images and / or video when the updated images are extracted from a video and / or a final model generated from the updated images at the end of the cycles of steps a) to d) and / or enabling the reception of the reference representation before the first cycle.

[0123] The device may include memory for storing updated images and / or video when updated images are extracted from a video and / or a final model generated from the updated images. Example

[0124] A user wishes to obtain a model of at least one of their dental arches without having to visit a dental professional, for example, to have their teeth checked. They launch specialized software, or an "application," on their mobile phone or tablet to implement the process according to the invention.

[0125] Specialized software is considered to implement a step if it performs it itself or if it communicates with a remote computer for this purpose.

[0126] In the preliminary stage, the specialized software may ask the user to acquire analytical images, preferably by taking some photos or a video, to determine the characteristics of one of their dental arches. The software then selects a reference representation from a database, in the form of a reference model depicting a reference arch with identical or similar characteristics. Specifically, an analysis of the photos, possibly extracted from the video, allows the general shape of the arch to be determined. The reference model could be a model of a typical tooth, for example, with the same width as the user's arch.

[0127] Alternatively, the reference model can be a model of a standard typodont usable for a category of users, or even a universal typodont, usable regardless of the user.

[0128] The specialized software then displays the reference model on the mobile phone screen and asks the user to film their brow bone.

[0129] In step a), in selfie mode and preferably without using a support, the user films their eyebrow. Ideally, however, they use a retractor, particularly to separate the corners of their lips to film the teeth at the back of their mouth and / or to separate their upper and lower lips to clearly expose the incisors, preferably until the surrounding gum tissue is visible. The updated images are stills extracted from the video, preferably at regular time intervals.

[0130] In step b), each updated image of the film is analyzed by the specialized software to identify whether it represents a part of the dental arch. The analysis makes it possible, if so, to identify a part of the updated image, possibly in several pieces, that represents the dental arch, that is to say, to identify an "acquired 2D surface".

[0131] The acquired 2D surface is then projected onto the reference model. To this end, the specialized software determines a direction that allows observation of the reference model, providing a view virtually identical to the representation of the user's dental arch in the updated image. The acquired 2D surface is then projected onto the reference model along this direction, allowing the identification of a portion of the reference model's surface that represents the same parts of the reference arch as those of the user's arch represented by the acquired 2D surface.

[0132] This portion of the reference model's surface, or "marked elementary zone," is then added to the marked zone of the reference model, which is the union of all the elementary zones marked during previous cycles. At any given time, the specialized software can thus indicate the unmarked zone, for which at least one updated image still needs to be taken and analyzed.

[0133] In this example, the goal is to cover the entire reference model; that is, the goal is for the marked area to consist of the entire surface of the reference model, as illustrated. figure 3at time tf. In one embodiment, however, the purpose of the method is only to cover a portion of the surface of the reference model, and more generally of the reference representation. This portion can be made identifiable on the reference model, for example by tracing its outline. Alternatively, only this portion can be displayed on the mobile phone or tablet screen.

[0134] The specialized software then provides guidance information so that the user can position the mobile phone or tablet camera to reach the goal.

[0135] In a preferred embodiment, specialized software visually marks the marked area, preferably by coloring it differently from the unmarked area. The user can then immediately see the unmarked area and position the camera accordingly. Because the coloring is real-time, the user receives immediate feedback on the accuracy of the camera's positioning and can adjust it accordingly.

[0136] There figure 3 illustrates different views of a reference model including a visual mark constituting the guidance information over time t, the reference model 20 being composed of tooth models 30 being progressively colored according to the image acquisitions made during the implementation of step cycles a) to d).

[0137] Before the first cycle, at time t 0, the marked area of ​​the reference model is the empty set.

[0138] Each tooth model 30 can be colored when more than 80% of the tooth model's surface is covered by the marked area of ​​the reference model, preferably when more than 90% of the tooth model's surface is covered by the marked area of ​​the reference model, and even better when the entire surface of the tooth model is covered by the marked area of ​​the reference model. The presentation of the colored tooth models 32 provides guidance information to the user.

[0139] A tooth model can be partially colored, with the coloring corresponding to the areas of the tooth model covered by the marked area of ​​the reference model. This allows the user to easily orient the imaging device to capture an area of ​​the tooth model not covered by the marked area of ​​the reference model. Additional guidance information can be provided, either alternatively or, preferably, in addition to the visual marking.

[0140] In one embodiment, the specialized software determines new "target" acquisition conditions for the camera, i.e., conditions that would lead to the largest acquired 2D area or the largest elementary marked area—that is, new acquisition conditions that are particularly efficient for covering the surface of the reference model as quickly as possible. Preferably, the specialized software guides the user toward the new target acquisition conditions, for example, by different coloring of a region of the reference model, or by displaying an arrow indicating a desired camera movement, or by emitting a sound signal that becomes louder or higher-pitched as the camera approaches the new target acquisition conditions.

[0141] When the goal is reached, for example because the entire surface of the reference model is covered by the marked area, the stopping criterion is met. A message can be sent to the user to inform them of this, so that they can end the video.

[0142] The specialized software then has enough updated images to generate an "updated" model of the user's dental arch. The final model can be generated directly from the updated images, similar to a 3D scan. It can also result from the deformation of another model, such as the reference model, with the deformation guided so that the final model corresponds as closely as possible to the updated images.

[0143] In the example of the figure 3, at time tf all the tooth models are colored indicating to the user that the last cycle of steps a) to d) has been carried out and that the final step of generating a final three-dimensional model from the updated images can be carried out.

[0144] As is now clear, a device and method according to the invention advantageously increase user autonomy and improve the quality and content of images acquired by a user with no particular knowledge in the dental field. They advantageously allow for the remote creation of a 3D model of a user's dental arch. They thus greatly facilitate the remote determination of orthodontic treatment, without the user needing to schedule an appointment with a dental professional.

[0145] Of course, the invention is not limited to the embodiments described and represented above.

[0146] In particular, the invention is not limited by the use of the final model. The latter can, for example, be used to establish a diagnosis, develop an orthodontic treatment plan, or fabricate an orthodontic aligner. Specifically, the final model can represent only an area of ​​interest for analyzing the user's dental situation or determining orthodontic treatment; for example, an area where hygiene is to be assessed, a risk of relapse in a particular area of ​​the user's dental arch, or an area for which the user and / or a dental professional wishes to plan potential cosmetic treatment.

[0147] The reference representation is not limited to a reference model. It can be a two-dimensional image, although a model is preferred.

[0148] In a particular embodiment of the invention, step d) of the scanning process is optional, the scanning process comprising: a preliminary step of determining a representation of a reference dental arch, called the "reference representation", then a plurality of cycles of the following steps a) to c): a) acquisition, under acquisition conditions, of a two-dimensional image of said dental arch, or "updated image", by means of an image acquisition device, by the user; b) analysis of the updated image so as to identify the surface of the updated image representing the user's dental arch, called the "acquired 2D surface", then delimitation and marking of a surface of the reference representation corresponding to the acquired 2D surface, or "elementary marked area", and addition of the elementary marked area in a "marked area of ​​the reference representation" grouping together the set, empty before the first cycle, of the elementary marked areas defined during the previous cycles;c) determination and presentation to the user of guidance information for the acquisition device towards new acquisition conditions adapted so that the next cycle increases the marked area of ​​the reference representation; d) preferably, movement of the acquisition device towards said new acquisition conditions; the process includes, after the last cycle, a final step of generating a "final" three-dimensional model from said updated images.

[0149] Of course, the process may also include one or more of the optional features described above which are compatible with an optional step d).

Claims

1. Method for scanning a dental arch of a user, the method comprising - a prior step of determining a representation of a reference dental arch, referred to as a "reference representation", then - a plurality of cycles of the following steps a) to c), preferably steps a) to d): a) acquiring, by the user, under acquisition conditions, a two-dimensional image of said dental arch, or "updated image", by means of an image acquisition apparatus (10); b) analyzing the updated image so as to identify the surface of the updated image representing the dental arch of the user, referred to as the "acquired 2D surface", then outlining and labeling a surface of the reference representation that corresponds to the acquired 2D surface, or "elementary labeled region", and adding the elementary labeled region to a "labeled region of the reference representation" that brings together all the elementary labeled regions defined during the previous cycles, which were empty prior to the first cycle; c) determining and displaying to the user guide information (16) for guiding the acquisition apparatus toward new acquisition conditions suitable for the next cycle to increase the labeled region of the reference representation; d) preferably, moving the acquisition apparatus toward said new acquisition conditions; the method comprising, after the last cycle, a final step of generating a "final" three-dimensional model from said updated images (12).

2. Method according to claim 1, wherein the updated images of successive cycles are extracted from a video acquired by the user via a tablet or a cell phone, said cycles being executed in real time during the acquisition of said video, at least part of the guide information being displayed on a screen of said tablet or said phone, respectively.

3. Method according to any one of the preceding claims, wherein the guide information comprises a display of the labeled region on a screen of the image acquisition apparatus superimposed on the reference representation, wherein the unlabeled region has an appearance that is different from the labeled region.

4. Method according to any one of the preceding claims, wherein the reference representation is: one or more 3D or 2D illustrations of a dental arch, optionally photorealistic illustrations, or a "reference" model of a "reference" arch - representative of the "historic" arches of a set comprising more than 10 historic individuals, or - formed by assembling tooth models in an arrangement determined by analysis of one or more analysis images of the dental arch of the user.

5. Method according to the immediately preceding claim, wherein, in step c) of any cycle, a view is displayed of the reference model observed along a direction of observation that is oriented, with respect to the reference model, substantially like the direction of acquisition of the image updated in step a) of said cycle, with respect to the dental arch of the user, so that said view is substantially superimposable in alignment with said updated image.

6. Method according to any one of the preceding claims, wherein, in any step c), the image acquisition apparatus provides variable information depending on a difference between the actual acquisition conditions and said new acquisition conditions.

7. Method according to any one of the preceding claims, wherein, for step a) of at least one cycle, the lips and / or cheeks are moved away from the dental arch of the user so as to expose at least one tooth to the image acquisition apparatus.

8. Method according to any one of the preceding claims, wherein, during the cycles, the following are acquired: - at least one updated image taken facing the user, at least one updated image taken to the right of the user and at least one updated image taken to the left of the user; and / or at least one updated image taken facing the user, at least one updated image taken from above with respect to the user and at least one updated image taken from below with respect to the user; and / or - at least one updated image taken with the mouth open and at least one updated image taken with the mouth closed.

9. Method according to any one of the preceding claims, wherein the user is more than 100 m from any dental care professional.

10. Method according to any one of the preceding claims, wherein the cycles are stopped when more than 50% of the surface of the reference representation is represented on at least one updated image.

11. Method according to any one of the preceding claims, wherein the final model is compared with another model representing the dental arch of the user and / or the final model is compared with the reference model, this comparison is preferably displayed to the user, for example by superimposing, preferably in alignment, the final model and the reference model.

12. Method according to any one of the preceding claims, wherein the guide information comprises sound information, visual information, and / or sensitive information.

13. Method according to any one of the preceding claims, wherein the reference representation is a model and the surface of the reference representation that corresponds to the acquired 2D surface is determined - by searching for suitable virtual acquisition conditions for acquiring a view of the reference representation, referred to as the "reference image", that best matches the image updated under said virtual acquisition conditions; then - by projecting the acquired 2D surface onto the reference representation along the direction of observation of said reference representation under said virtual acquisition conditions.

14. Method according to the preceding claim, wherein the virtual acquisition conditions are determined by seeking to superimpose noteworthy points of the arch represented in the updated image on the corresponding noteworthy points of the reference representation.

15. Device for carrying out a method according to any one of the preceding claims, comprising - optionally, a first computer comprising a first computer program comprising program code instructions for generating the reference representation; - an image acquisition apparatus (10) for carrying out steps a); - preferably, a screen (14) for displaying guide information (16) during steps c); - a second computer (18), identical to or different from the first computer, comprising a second computer program comprising program code instructions for executing steps b) and c); - a third computer, identical to or different from the first and / or second computer(s), comprising a third computer program comprising program code instructions for carrying out the final step of generating the final model of the dental arch of the user from the updated images (12); - preferably, a fourth computer, identical to or different from the first and / or second and / or third computer(s), comprising a fourth computer program comprising program code instructions for comparing the final model with another model representing the dental arch of the user.