Method for scanning a user's dental arch

Abstract

A method for scanning a user's dental arch, the method comprising - a preliminary step of generating a reference representation, then - a plurality of cycles of the following steps a) to d): a) acquisition of an 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 all the elementary marked areas; c) determination and presentation of guidance information towards new acquisition conditions; d) movement of the acquisition device towards said new acquisition conditions.No figure for the abbreviation.

Description

Description Title of the invention: Method for scanning a dental arch of a user technical field

[0001] — The present invention relates to a method for scanning a dental arch of a user, and a device to implement such a process. Previous technique

[0002] It is common practice to perform a scan of a user's dental arches in order to to analyze his dental situation, especially before establishing orthodontic treatment donique. However, performing a scan of a user's dental arches requires the user to travel to a dental professional or that they transmit information, particularly images, to the healthcare professional dental. Performing a scan within a dental practice or more generally However, visiting a dental professional can incur significant costs. not only support but also stress for the user. Furthermore, image acquisition Dental procedures performed by the user themselves can lead to insufficient image quality or to incomplete content.

[0003] There is a need to facilitate the acquisition of a dental arch scan, in limiting the risk of an incomplete scan.

[0004] One aim of the invention is to meet this need. Summary of the invention

[0005] … The invention proposes a method for scanning a user's dental arch, the process comprising - a preliminary step of determining a representation of a dental arch of reference, called "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 acquisition device of images, preferably by the user; b) analysis of the updated image in order to identify the surface of the image ac- a custom-designed representation of the user's dental arch, called an "acquired 2D surface", then delimitation and marking of a surface of the corresponding reference representation to the acquired 2D surface, or "elementary marked area", and addition of the area marked elementary in a "marked zone of the representation of reference » grouping together all the areas, empty before the first said cycle marked elementary elements defined during 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) movement of 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. 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 care professional. 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. 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. Advantageously, the acquisition can be done in real time, with the updated images being extracted, for example, from a film. 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. 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. 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 which was used to acquire the updated images, of all the visual marks generated in all the preceding steps b). A visual mark preferably includes a graphic representation of the elementary marked area, for example a representation of the outline of the elementary area. marked commentary and / or a flat area of ​​a color and / or pattern within the limits of the marked elementary area. Acquisition is thus simplified. In particular, during real-time cycling, the screen displays a reference representation whose marked area fills in with each cycle, allowing the user to easily identify the unmarked area and position and orient the image acquisition device accordingly. Visual markers therefore provide preferred guidance information. 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. The reference representation can be generated. Alternatively, it can be selected, for example from a database. The reference representation can be two-dimensional. In a preferred implementation method, the reference representation is a three-dimensional digital model. By acquiring various updated images, the process allows different areas of this model to be marked 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, 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. In particular, the coverage threshold can be 90%, better 95%, or even better 99%. 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. In one particular embodiment, at step c), the percentage of coverage is presented to the user. The percentage of coverage can be presented in the form of a gauge, a digital display, a progress bar, objectives presented successively when a particular objective is reached, or simultaneously and presenting a A different display distinguishes between objectives achieved and those that remain to be achieved. For example, the objectives are "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", "acquisition with an orthodontic splint". 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 via a tablet or 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 with 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" arcade - representative of the "historical" arcades of a complex 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 - consisting of an assembly of tooth models according to an arrangement determined by analysis of one or more images analyzing 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 reference model observed 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, that is to say 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 step c), preferably at any step c), the acquisition device image provides variable information depending on a difference between the actual acquisition conditions and the new acquisition conditions, for example by emitting a sound signal or a visual indication, for example a flashing, which is all the more intense the smaller the differences are; the user thus knows advantageously whether the movement of the image acquisition device that he is making 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 cycling, we acquire - at least one updated image taken facing the user and / or at least one updated image taken to the user's right and / or at least one updated image taken to the user's left, preferably at least one updated image taken facing the user and at least one updated image taken to the user's right and at least one updated image taken to the user's left; and / or - at least one updated image taken from the user's perspective, and at least one updated image taken from above the user and / or at least one updated image taken from below the user, preferably at least one updated image taken from the user's perspective, at least one updated image taken from above the user, and at least one updated image taken from below the user; and / or - at least one updated image taken with mouth open and / or at least one updated image taken with 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; - we stop the cycling 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; - we compare the final model to another model representing the user's dental arch, for example to correct the final model or the other model, and / or we cut the final model into tooth models and, preferably, we move said tooth models; - the final model is compared to the reference model, and, preferably, this comparison is presented to the user, for example by superimposing, preferably by 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," which exhibits maximum concordance with the updated image under said virtual acquisition conditions; then - by projecting the acquired 2D surface onto the reference representation, following the observation direction of said reference representation under said virtual acquisition conditions; - the virtual acquisition conditions are determined by seeking to superimpose notable points of the dental arch represented on the updated image with the corresponding notable points of the reference representation. The invention also relates to: - a computer program, and in particular specialized software for mobile phones or tablets, 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. 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). The invention also relates to a device for implementing a method according to the invention, said device comprising: - optionally, a first computer including a first computer program comprising program code instructions to generate the reference representation or select the reference representation, for example in a database; - an image acquisition device for the implementation of steps a); - preferably, a screen for displaying guidance information during steps c); - a second computer, identical or different from the first computer, containing a second computer program including program code instructions for the execution of steps b) and c); - a third computer, identical or different from the first and / or second or- computer(s), comprising a third computer program including program code instructions for implementing 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 slice the final model into tooth models and, preferably, move said tooth models. 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. 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. 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 A "user" is a person for whom a process according to the invention is implemented. The term “dental professional” refers to any person qualified to provide dental care, which includes an orthodontist and a dentist. 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. 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. A retractor, or dental retractor, is a device designed to retract the lips. It has 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 observation of the teeth without obstruction from the lips. The teeth do not, however, rest on the retractor, so the user can, by turning their head relative to the retractor, modify which teeth are visible through the retractor opening. They can also modify 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 so that the distance between the upper and lower edges, and / or between the right and left edges, is constant.For example, spacers are described in PCT / EP2015 / 074896, US 6,923,761, or US 2004 / 0209225. According to the international convention of the International Dental Federation, each tooth in a dental arch has a predetermined number. 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". 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. Typically, a computer includes a processor, memory, a human-machine interface (typically 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. 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. By "model," we mean a three-dimensional digital model. A model consists of a set of voxels. A "tooth model" is a three-dimensional digital model of a tooth. A model of a dental arch can be segmented to define tooth models for at least some of the teeth, preferably for all the teeth represented in the arch model. These tooth models are therefore models within the arch model. 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. 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 of an arch model. One example of software that allows for manipulating tooth models and creating a treatment scenario is the Treat program, described on the page https.: / / en.wikipedia.org / wiki / Clear_alignersf#cite_note-invisalignsystem-10. 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. 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. 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. 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. The "marking" of a surface in 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." The "acquisition conditions" of an image specify the position and orientation within the 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. 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. 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. 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. 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. "First", "second", "third" and "fourth", "reference", "updated", "historical", "target" are used for clarity. "Vertical", "horizontal", "right", "left", "front" or "facing", "behind", "above", "below" refer to a user who is standing upright. "Comprising" or "containing" or "presenting" should be interpreted in a non-restrictive manner, unless otherwise indicated. Brief description of the drawings 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] [Fig.1] schematically represents a cycle of a process according to the invention; [Fig. 2] [Fig. 2] schematically represents a device according to the invention. [Fig. 3] [Fig. 3] represents the progressive coloring of a reference model. Detailed description Process A method for scanning a user's dental arch according to the invention comprises steps a) to d) as illustrated by [Fig.1]. Preferably, it also includes a preliminary step of determining a reference representation. Determining the reference representation may involve generating a representation, in particular a three-dimensional model. In another embodiment, determining the reference representation may consist of selecting a representation from a database. The reference representation is a model or image representing a reference dental arch. Preferably, the reference representation is a model, called a "reference model". 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. The reference representation can be representative of a population of individuals. In one embodiment, the reference representation is obtained by statistically processing a set of representations of historical arches from a population of historical individuals sharing one or more characteristics with the user, for example, grouping people of the same age group as the user or having 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 representations of historical arches. The reference representation can be, in particular, the model of a typodont. 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 fewer than 1,000,000 tooth models, referred to as "historical tooth models" torics”, 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 so as to create a dental arch model that presents maximum proximity to the arch shown on the analysis image, or "assembled model"; - optionally, replacing at least one optimal tooth model with another tooth model and returning to the previous step in order to maximize the concordance between the assembled model and the analysis image; - optionally, repeat the said analysis with another analysis image and, at the arrangement and / or replacement stage, seek maximum concordance with all the analysis images used. 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. 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. 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). After the reference representation has been made available, the process comprises a plurality of cycles of steps a) to d). 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. 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. 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. 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. We will now describe in detail an example of a cycle. In step 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. Preferably, the acquisition is carried out by the user himself. The updated image is preferably "extraoral", that is, without the camera lens being inserted into the user's mouth. 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. 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. In a preferred embodiment, the user uses a mobile phone that is free to move, meaning that its position and orientation can be freely determined, and in particular, that it is not attached to a support. The method according to the invention allows the user to be guided in taking pictures, so 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. 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 may also be immediate. immediately before step a), for example less than 5 minutes before step a). 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". The analysis can be done using classical segmentation methods. We then search for a part of the surface of the reference representation which corresponds to the acquired 2D surface. Preferably, said part results from a one-to-one relationship with the acquired 2D surface, that is to say that, for each acquired 2D surface, a unique part of the surface of the reference representation is defined. Preferably, said part is the result of a projection of the acquired 2D surface onto the reference representation. 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. A search for a view of the model in accordance with the updated image is described for example in European application no. 18 184486. 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. The portion of the reference representation surface corresponding to the acquired 2D surface is then marked. This is called the "elementary marked area." The "marked area" is 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 at the end of the first cycle, and is then completed with each subsequent cycle, as the acquisition device moves and new images are acquired. The "unmarked area," re- presenting the parts of the reference representation that correspond to regions of the dental arch that do not appear on any updated image, therefore reduces progressively. In step c), guidance information for the image acquisition device is determined and presented. 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. 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. 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. 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. Sensory information can be a vibration indicating, for example, to the user to stop a movement. 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. 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. Real-time cycling offers the advantage of immediately visualizing how the marked area expands. The progressive coloring of the representation of The reference is playful. In one embodiment, an objective can be set for the user, for example to encourage them to color the reference representation as quickly as possible, which further increases the playful aspect of acquiring the updated images. Preferably, the marked area is colored, preferably in a different color than 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). 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. 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. Steps b) and c) are implemented by a computer program. In step d), the user changes the position and / or orientation of the acquisition device according to the guidance information. Preferably, the cycle of steps a) to d) is repeated until a stopping criterion is reached. 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. 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. 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. 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 Have an orthodontic appliance made, preferably an orthodontic aligner. Device The invention also relates to a device for implementing a scanning method according to the invention. Such a device is shown schematically in [Fig.2]. A device 1 according to the invention comprises: - optionally, a first computer containing a first computer program including program code instructions to generate the reference representation: - an image acquisition device 10 for implementing steps a) of acquiring updated images 12, - a screen 14 for displaying guidance information 16 during steps c), - a second computer 18 comprising a second computer program including program code instructions for the execution of 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), containing a third computer program including program code instructions to generate 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 cut the final model into tooth models and, preferably, move said tooth models. 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. 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. 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. The device may include a memory for storing the updated images and / or video when the updated images are extracted from a video and / or a final model generated from the updated images. Examples 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. Specialized software is considered to implement a step if it performs it itself or if it communicates with a remote computer for this purpose. 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 user 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. 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. The specialized software then displays the reference model on the mobile phone screen and asks the user to film their brow bone. 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. 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". The acquired 2D surface is then projected onto the reference model. For this purpose, the Specialized software determines a direction that allows observation of the reference model in order to obtain a view virtually identical to the representation of the user's arch on the updated image. The acquired 2D surface is then projected onto the reference model along this direction, which makes it possible to identify 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. 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. In this example, the goal is to cover the entire reference model; that is, the marked area should encompass the entire surface of the reference model, as illustrated [Fig. 3] at time t. In one embodiment, however, the goal is to cover only 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. The specialized software then provides guidance information so that the user can position the mobile phone or tablet camera to reach the goal. In a preferred embodiment, specialized software visually marks the marked area, preferably by coloring it differently from the unmarked area. The user can thus 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. Fig. 3 illustrates different views of a reference model with 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). Before the first cycle, at time to, the marked area of ​​the reference model is the empty set. Each tooth model 30 can be colored when more than 80% of the tooth model surface is covered by the marked area of ​​the reference model, preferably when more than 90% of the tooth model surface is covered by the marked area of ​​the reference model, and even better when the entire surface of the The tooth model is covered by the marked area of ​​the reference model. The presentation of the 32 colored tooth models provides guidance information to the user. 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. 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. 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. 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. In the example of [Fig.3], at time t; 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. As is now clear, a device and a 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 needs to make an appointment with a dental care professional. Of course, the invention is not limited to the embodiments described and represented above. 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. The reference representation is not limited to a reference model. It can be a two-dimensional image, although a model is preferred.

Claims

Claims

1. A method of scanning a dental arch of a user, the method comprising - a preliminary step of determining a representation of an arcade reference dental representation, called “reference representation”, then - a plurality of cycles of steps a) to d) following: (a) acquisition, under acquisition conditions, of a two-dimensional image sional of said dental arch, or “updated image”, by means of an image acquisition device, by the user; b) analysis of the updated image in order to identify the surface of the updated image representing the user's dental arch, called " 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 elemental marked area in a “marked area of ​​reference representation” grouping the whole, empty before the first cycle, of the zones elementary markings defined during previous cycles; (c) determination and presentation to the user of information of guiding the acquisition device to new conditions acquisition adapted so that the next cycle increases the area marked with the reference representation; (d) moving the acquisition device to the said new acquisition conditions; the process comprising, after the last cycle, a final stage of ge- generation of a “final” three-dimensional model from said images updated.

2. A method according to claim |, wherein 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 being executed in real time real during the acquisition of said film, at least part of the guidance information being presented on a screen of said tablet or said telephone, respectively.

3. A method according to any preceding claim, in which the guidance information includes a presentation of the area marked on a screen of the image acquisition device in super- position with the reference representation in which the non-zone marked area has a different appearance than the marked area.

4. A method according to any preceding claim, in which the reference representation is: one or more illustrations, in 3D or 2D, of a dental arch, possibly truly photorealistic, or a “reference” model of an arcade "reference" - representative of the “historical” arcades of a group comprising more than 10 historical individuals, or - made up of assembling tooth models according to an arrangement determined by analysis of one or more arch analysis images user's dental.

5. A method according to the immediately preceding claim, in which, at step c) of any cycle, a view of the reference model observed along an observation direction oriented, relative to the reference model, substantially like the direction of acquisition of the image updated in step a) of said cycle, by relative to the user's dental arch, so that said view is substantially superimposable in register with said updated image.

6. A method according to any preceding claim, in which, at any step c), the image acquisition device provides variable information depending on a difference between the actual acquisition conditions and said new conditions acquisition.

7. A method according to any preceding claim, in which, for step a) of at least one cycle, the lips and / or the cheeks of the user's dental arch so as to expose the image acquisition device at least one tooth.

8. A method according to any preceding claim, in which, during cycling, we acquire - at least one updated image taken in front of the user and at least one updated image taken to the right of the user and at least one ac- taken to the left of the user; and / or at least one updated image taken facing the user and at least one updated image taken from above the user and at least one updated image taken from below the user; and / or - at least one updated image taken with the mouth open and at least one Updated image taken with mouth closed.

9. A method according to any preceding claim, in in which the user is more than 100 m from any healthcare professional dental.

10. A method according to any preceding claim, in which stops cycling when more than 50% of the surface of the representation- reference position are represented on at least one ac- technically.

11. A method according to any preceding claim, in in which the final model is compared to another model representing the user's dental arch and / or the final model is compared to the reference model, preferably we present this comparison to the user, for example by superimposing, preferably in register, the final model and the reference model.

12. A method according to any preceding claim, in which the guidance information includes sound information, a visual information, and / or sensory information.

13. A method according to any preceding claim, in which the reference representation is a model and we determine the surface of the reference representation corresponding to the 2D surface acquired - by seeking suitable virtual acquisition conditions for an acquisition of a view of the reference representation, called “image reference”, showing maximum concordance with the ac- realized under said virtual acquisition conditions; then - by projecting the acquired 2D surface onto the reference representation and following the direction of observation of said reference representation under the said virtual acquisition conditions.

14. | Method according to the preceding claim, in which the conditions virtual acquisitions are determined by seeking to superimpose notable points of the arcade represented in the updated image with the corresponding remarkable points of the representation of reference.

15. Device for implementing a method according to any one of the preceding claims, comprising - optionally, a first computer comprising a first computer program comprising code instructions program to generate the reference representation; - an image acquisition device for implementing the steps has); - preferably, a screen for the presentation of information from guidance during steps c); - a second computer, identical or different from the first computer, comprising a second computer program comprising program code instructions for carrying out steps b) and c); - a third computer, identical or different from the first and / or second computer(s), comprising a third computer program comprising program code instructions for implementing 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 comprising program code instructions for comparing the final model with another model representing the user's dental arch.