Intensity-based three-dimensional tooth structure estimation

Abstract

: The present invention relates to a computer-implemented method for intensity-based tooth structure estimation. The method comprises receiving a transfer function describing a relationship between a distance of a sensing head from a surface of an object and an illumination intensity of the surface of the object, wherein the sensing head comprises a light source configured for illuminating the surface of the object with light and a light sensor configured for receiving light that is reflected and / or emitted from the surface of the object in response to the illumination with the light, controlling the light source to illuminate a surface of a tooth in a mouth of a subject, receiving measurement data from the light sensor, the measurement data being indicative of an illumination intensity of the surface of the tooth, and determining a calculation result indicative of a distance of the surface of the tooth from the sensing head based on the measurement data.

Description

[0001] 2025PF00038

[0002] 1 29.09.2025

[0003] INTENSITY-BASED THREE-DIMENSIONAL TOOTH STRUCTURE ESTIMATION

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to a computer-implemented method for intensity-based tooth structure estimation, a data processing apparatus, an intra-oral camera system, a computer program, and a computer-readable storage medium.

[0006] BACKGROUND OF THE INVENTION

[0007] Intra-oral cameras or scanners are of interest as they can detect dental issues such as plaque, stains, gingivitis, tooth alignment and caries. Obtaining a three-dimensional (3D) structure of the teeth and dentition with such an intra-oral camera system may be valuable for a number of reasons: With the 3D structure of the mouth, teeth can be more easily segmented and recognized, and certain dental issues such as tooth alignment, cavities, tooth damage and gum retraction can be detected better from the 3D tooth structure. Further, adding also the 3D structure analysis of the gums can additionally give information on gingivitis, and depicting the 3D structure of the individual jaw gives a user a sense of high quality of the product. However, creating a 3D image with a 2D camera may be complicated. Typically, this can be done by acquiring multiple 2D images at known distances from the target and with predefined positions of image acquisition. In a simple intra-oral camera system, this exact location information is however not available. There is therefore a need for providing a method of estimating a 3D structure of the teeth based on a two-dimensional image of an intra-oral camera system.

[0008] SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide an improved method that solves at least a part of the problems of the state of the art of how to generate a three-dimensional model of the teeth and dentition with an intra-oral camera system.

[0010] The inventors of the present invention have developed a method that generates deep information using a two-dimensional image and therefore provides a three-dimensional model of the teeth and dentition, thereby significantly improving the reliability and accuracy of the detection of dental issues.

[0011] The object of the present invention is solved by the subject matter of the independent claims, wherein further embodiments are incorporated in the dependent claims.

[0012] The described embodiments pertain to a computer-implemented method for intensitybased tooth structure estimation, a data processing apparatus, an intra-oral camera system, a computer program, and a computer-readable storage medium. The embodiments described further may be combined in any possible way. Synergistic effects may arise from different combinations in various ways2025PF00038

[0013] 2 29.09.2025

[0014] of the embodiments described further although these combinations might not be described explicitly in detail.

[0015] Further on, it shall be noted that all embodiments of the present invention concerning a method might be carried out with the order of the steps as described, nevertheless this has not to be the only and essential order of the steps of the method. The herein presented methods can be carried out with another order of the disclosed steps without departing from the respective method, unless explicitly mentioned to the contrary hereinafter.

[0016] According to a first aspect of the invention, there is provided a computer-implemented method for intensity-based tooth structure estimation. The method comprises receiving a transfer function describing a relationship between a distance of a sensing head from a surface of an object and an illumination intensity of the surface of the object, wherein the sensing head comprises a light source configured for illuminating the surface of the object with light and a light sensor configured for receiving light that is reflected and / or emitted from the surface of the object in response to the illumination with the light, controlling the light source to illuminate a surface of a tooth in a mouth of a subject, receiving measurement data from the light sensor, the measurement data being indicative of an illumination intensity of the surface of the tooth, and determining a calculation result indicative of a distance of the surface of the tooth from the sensing head based on the measurement data.

[0017] In an intraoral camera system, light sources are available that are usually light emitting diodes (LEDs) with a specific light angle, i.e., the light beam of the LED diverges. This divergent behavior of the light beam causes the illumination intensity of an illuminated target to be dependent on the distance from the light source. Thus, also the image intensity of an image acquired with a light sensor or a camera of the illuminated target depends on the distance of the target from the light source.

[0018] Preferably, the light source and the light sensor are arranged in a common housing like a sensor head, which results in the distance of the target from the light source being essentially the same as the distance of the target from the light sensor.

[0019] The light that is reflected and / or emitted from the surface of the object in response to the illumination with the light includes light that is reflected or scattered from the surface of the object, and also fluorescence emission light that is emitted from the surface of the object in response to the illumination light that can be excitation light induced fluorescence.

[0020] This relationship of the image intensity and the distance of the sensor head from the target can be expressed in terms of a transfer function describing the distance of a target like a tooth, for example, from the sensor head of an intra-oral camera system. Having received or determined such a transfer function, the distance of each pixel of an image of a tooth can be estimated based on its image intensity, which builds a 3D structure of each image. It is noted that this approach may require a sufficiently homogeneous surface structure and therefore brightness of the surface of the tooth, as a varying reflectivity of the tooth may lead to erroneous results. In addition, it may be necessary to prevent light from external light sources reaching the tooth to be imaged. Having calculated the 3D structure of2025PF00038

[0021] 3 29.09.2025

[0022] one or more teeth visible in each image of a plurality of images of the dentition of a user or a patient, these images and the respective 3D structures can be combined for generating a 3D model of the dentition and the mouth of the user or patient. Combining this with an ideal jaw model to smoothen out spots with atypical reflections, which can be caused by lesions or stains, will deliver a 3D structure of the oral cavity. This 3D structure can be used to segment and recognize teeth and to give a personalized representation of the teeth. The ideal jaw model may be personalized overtime, making the 3D structure more accurate.

[0023] In an embodiment of the invention, the object is a tooth of the subject, a three-dimensional model of a tooth, a typodont, or an object having a surface with a reflectivity and / or fluorescence similar to the reflectivity and / or fluorescence of a tooth.

[0024] In order to generate the transfer function, it may be necessary to perform measurements providing the dependency of the image intensity from the distance between tooth and sensor head. These measurements can be performed with the tooth in the mouth of the subject, which can be a user or patient, for example, which would however require an additional distance sensor. Thus, it is preferred to determine the transfer function in advance utilizing a dedicated object having similar surface and therefore reflectivity properties like teeth. This object can be, for example, a model of a tooth, a typodont, or simply a target disk, for example. Further, more realistic models can be utilized like a typodont covered with auto-fluorescent plaque. However, it may be possible to determine the transfer function based on known reflectivity properties of teeth.

[0025] In an embodiment of the invention, the light source is configured to emit divergent light. This has the effect that the illumination intensity of the tooth decreases with an increasing distance from the light source.

[0026] In an embodiment of the invention, the light source is configured to emit light having an illumination intensity that is essentially homogeneous over an illumination area of the light source. This helps to reach a homogenous illumination of the surface of the tooth with the light from the light source. However, a known intensity profile of the light source may be corrected by taking the illumination angle into account, i.e. the deviation from the optical axis of the light source.

[0027] In an embodiment of the invention, the light sensor is an optical camera configured to receive a two-dimensional image of the surface of the tooth, and provide the two-dimensional image as the measurement data.

[0028] In an embodiment of the invention, the method further comprises smoothening the calculation result by applying a predefined smoothening algorithm. Thus, sharp edges and artifacts in the image can be eliminated, which may be due to stains or lesions on the tooth.

[0029] In an embodiment of the invention, the calculation result comprises a two-dimensional distance array of distance values of the surface of the tooth from the sensing head. Thus, a distance value can be assigned to each pixel of the image.

[0030] In an embodiment of the invention, the two-dimensional distance array is a first two-dimensional distance array of a first region of the mouth of the subject, and the method further comprises2025PF00038

[0031] 4 29.09.2025

[0032] stitching the first two-dimensional distance array of a first region of the mouth of the subject and at least one second two-dimensional distance array of a second region of the mouth of the subject, wherein the at least one second region is adjacent to the first region, thereby generating a three-dimensional model of the set of teeth of the subject. In this way, a complete 3D model of the dentition of the subject can be generated based on a plurality of images of individual teeth or groups of teeth.

[0033] In an embodiment of the invention, the method further comprises receiving a standard model of teeth representing an average set of teeth, comparing the three-dimensional model of the set of teeth of the subject with the standard model of teeth, thereby identifying a deviation in the three-dimensional model of the set of teeth of the subject from a shape of a realistic tooth surface, correcting the identified deviation, thereby generating a corrected three-dimensional model of the set of teeth of the subject, and outputting the corrected three-dimensional model of the set of teeth of the subject. Thus, it is possible to provide a corrected 3D structure of the teeth that is adapted to an average dentition, and which is corrected, for example, for artifacts due to stains or lesions.

[0034] In an embodiment of the invention, the method comprises further providing a plurality of standard models of teeth, and selecting, using an Al model, an appropriate standard model of teeth of the plurality of standard models of teeth based on the three-dimensional model of the set of teeth of the subject and / or an optical image of the teeth of the subject. These models may take into account the number of teeth present in the mouth of the subject, or may refer to the condition of the teeth.

[0035] In an embodiment of the invention, the light source comprises a plurality of LEDs each emitting light of a different wavelength, the light sensor is a multicolor camera like an RGB camera, the measurement data comprises an illumination intensity of the surface of the tooth for the respective wavelength of each of the plurality of LEDs, and determining the calculation result comprises determining a calculation result for the respective wavelength of each of the plurality of LEDs. This would provide in each color channel of the camera a different intensity profile which can be transferred for each channel in a distance array. In this way, three arrays are made of the same spot, which can also help to get rid of noise and deviating spots.

[0036] According to another aspect of the invention, there is provided a data processing apparatus for carrying out the steps of the method according to any one of the preceding embodiments.

[0037] According to another aspect of the invention, there is provided an intra-oral camera system comprising the data processing apparatus according to the preceding embodiment, and a sensing head, wherein the sensing head comprises a light source configured for illuminating the surface of an object and a light sensor configured for receiving light that is reflected from the surface of the object.

[0038] The object can be in particular a tooth in the mouth of a subject, or the object can be a dedicated model having a surface with a similar reflectivity as teeth.

[0039] According to another aspect of the invention, there is provided a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method according to any one of the preceding embodiments.2025PF00038

[0040] 5 29.09.2025

[0041] According to another aspect of the invention, there is provided a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to any one of the preceding embodiments.

[0042] Thus, the benefits provided by any of the above aspects equally apply to all of the other aspects and vice versa.

[0043] In summary, the invention relates to a computer-implemented method for intensity-based tooth structure estimation. The method comprises receiving a transfer function describing a relationship between a distance of a sensing head from a surface of an object and an illumination intensity of the surface of the object, wherein the sensing head comprises a light source configured for illuminating the surface of the object with light and a light sensor configured for receiving light that is reflected and / or emitted from the surface of the object in response to the illumination with the light, controlling the light source to illuminate a surface of a tooth in a mouth of a subject, receiving measurement data from the light sensor, the measurement data being indicative of an illumination intensity of the surface of the tooth, and determining a calculation result indicative of a distance of the surface of the tooth from the sensing head based on the measurement data.

[0044] One of the advantages of embodiments of the present invention of obtaining a three-dimensional structure of the teeth and dentition is that teeth can be more easily segmented and recognized, and certain dental issues such as tooth alignment, cavities, tooth damage and gum retraction can be detected better based on the 3D tooth structure. Further, adding also the 3D structure analysis of the gums can additionally give information on gingivitis, and depicting the 3D structure of the individual jaw gives a user a sense of high quality of the product.

[0045] These advantages are non-limiting and other advantages may be envisioned within the context of the present application.

[0046] The above aspects and embodiments will become apparent from and be elucidated with reference to the exemplary embodiments described hereinafter. Exemplary embodiments of the invention will be described in the following with reference to the following drawings:

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Fig. 1 shows a block diagram of a computer-implemented method for intensity-based tooth structure estimation according to an embodiment of the invention.

[0049] Fig. 2 shows a schematic setup of a sensor head comprising a light source and a light sensor according to an embodiment of the invention.

[0050] Fig. 3 shows a schematic setup of an intra-oral camera system according to an embodiment of the invention.

[0051] Fig. 4 shows a relation between distance and intensity of quantitative light-induced fluorescence images.2025PF00038

[0052] 6 29.09.2025

[0053] Fig. 5A shows a line plot of the intensity over a quantitative light-induced fluorescence image from a premolar on a typodont.

[0054] Fig. 5B shows the estimation of the distance from the camera using the transfer function between distance and intensity of the line plot of Fig. 5A.

[0055] DETAILED DESCRIPTION OF EMBODIMENTS

[0056] Fig. 1 shows a block diagram of a computer-implemented method for intensity-based tooth structure estimation according to an embodiment of the invention. The method comprises step S 110 of receiving a transfer function describing a relationship between a distance of a sensing head 100 from a surface of an object 130 and an illumination intensity of the surface of the object 130, wherein the sensing head 100 comprises a light source 110 configured for illuminating the surface of the object 130 with light 111 and a light sensor 120 configured for receiving light 111 that is reflected and / or emitted from the surface of the object 130 in response to the illumination with the light 111, and step S120 of controlling the light source 110 to illuminate a surface of a tooth 140 in a mouth of a subject. The method comprises further step SI 30 of receiving measurement data from the light sensor 120, the measurement data being indicative of an illumination intensity of the surface of the tooth 140, and step S 140 of determining a calculation result indicative of a distance of the surface of the tooth 140 from the sensing head 100 based on the measurement data.

[0057] Fig. 2 shows a schematic setup of a sensor head 100 comprising a light source 110 and a light sensor 120 according to an embodiment of the invention. In this embodiment, the sensing head 100 comprises two light sources 110, each emitting light 111. The light is divergent light, i.e., the illumination intensity decreases with increasing distance from the light source 110. Preferably, the light has an illumination intensity that is essentially homogeneous over an illumination area of the light source. If not homogeneous, there could still be a correction of the inhomogeneity of the light field using an algorithm. The light 111 is reflected back from the surface of an object 130 like a tooth 140, for example, and is detected by a light sensor 120. The light sensor 120 is preferably a camera comprising a plurality of pixels, thus providing a two-dimension image as measurement data. The intensity of light 111 detected in each pixel of the image acquired by the cameras corresponds to the illumination intensity of the respective depicted area of the object 130 or tooth 140, which in turn is dependent on the distance between the object 130 or tooth 140 and the light source 110. This dependency is described by the transfer function. Besides being a tooth 140 of a user, the object 130 can be a three-dimensional model of a tooth, a typodont, or an object having a surface with a reflectivity and / or fluorescence similar to the reflectivity and / or fluorescence of a tooth, for example.

[0058] Fig. 3 shows a schematic setup of an intra-oral camera system 200 according to an embodiment of the invention. The intra-oral camera system comprises the sensing head 100 as described with respect to Fig. 2, with a light source 110 configured for illuminating the surface of an object 130 and a light sensor 120 configured for receiving light that is reflected from the surface of the object 130, and in2025PF00038

[0059] 7 29.09.2025

[0060] addition a data processing apparatus 210. The data processing apparatus 210 is configured for carrying out the steps of the method as described with respect to Fig. 1 or any of the previously described embodiments.

[0061] Fig. 4 shows a transfer function, i.e., the relation between distance and intensity, of quantitative light-induced fluorescence (QLF) images from a flat target disk and a typodont with artificial red auto-fluorescent plaque (RAFP). In embodiments of the invention, the method uses this transfer function between intensity and distance, which can be measured for each specific design of a sensor head 100 of an intra-oral camera 200, to create an estimation of the 3D shape of the teeth. This could be acquired from QLF images but also from reflective images using white light or other types of light, e.g. colored light, infra-red (NIR), etc.

[0062] The method starts with the input of the transfer function of the image intensity with distance. This transfer function is best built with the same target as in the application, e.g. dentition, or something representing similar reflection or fluorescence conditions. The transfer function would be typically created before the solution is used by the user, but there may be embodiments that create the transfer function upon first use in the mouth of a user. For this the camera should be supplemented with a distance sensor. Fig. 4 shows two transfer functions. The smooth, lower curve gives the transfer function of a red target disk. While the upper curves is acquired utilizing a typodont covered with artificial red auto-fluorescent plaque.

[0063] With the transfer function each image or frame of a scan movie can be transferred from an intensity array to a distance array. With all these distance arrays combined a complete estimation of the 3D structure of the dentition can be built using algorithms to overlap and stitch the different distance arrays of different teeth.

[0064] Fig. 5A shows a line plot of the intensity over a quantitative light-induced fluorescence image crossing a premolar on a typodont. On the X-axis, the width position in the image is given in pixel numbers, and the Y-axis represents the measured intensity per pixel in arbitrary units. A low intensity corresponds to a high distance.

[0065] Fig. 5B shows the estimation of the distance from the camera using the transfer function between distance and intensity of the line plot of Fig. 5A. This graph is determined by using the measured line plot in Fig. 5A and the transfer function acquired earlier. Fig. 5B gives the distance of the surface of the typodont from the camera in millimeters in dependence on the pixel position, and therefore the tooth profile. This profile corresponds well to the real dimensions of the premolar in the typodont. For each image of a scan movie these distance profiles can be created, and a full 3D estimation of the dentition can be constructed.

[0066] To cope with noise there could be a simple smoothening algorithm to improve the final result. But there can also be intrinsic local differences in absorption or fluorescence, such as stains, white spots or fillings. To correct these deviations a standard 3D model of teeth standard providing a 3D shape of an average dentition can be used which represents the average dentition. The estimated 3D structure2025PF00038

[0067] 8 29.09.2025

[0068] can be adapted using this standard 3D model, correcting obvious deviations from realistic tooth surfaces. The embodiment could also use a series of standard models to have a model adapted to the personal situation of the user, e.g. a model without wisdom teeth, a model without the first premolars, a model with missing teeth, a model with worn teeth, a model with subtracted gums or a model with crowded teeth.

[0069] Al models may be used to first detect all such deviations independently from the 3D estimation based on the RGB images: e.g. stains, white spots, bright fluorescent spots and missing teeth can easily be recognized by a trained deep learning algorithm. This input could then serve to pick the best standard model, e.g. missing teeth, and to correct deviating absorption spots, e.g. stains.

[0070] When looking at reflections of illuminated teeth with a standard RGB camera some embodiments may use instead of white illumination sources different color illumination, such as red, green and blue LEDs. If the different color LEDs have different transfer functions for the intensity with distance, e.g. by adding different lenses on the LEDs, this would provide in each of the R, G and B channel of the camera a different intensity profile which can be transferred for each channel in a distance array. In this way three arrays are made of the same field of view, which can also help to get rid of noise and deviating spots.

[0071] Thus, embodiments of the present invention work for any imaging system with dedicated illumination, where the illumination has a predictive pattern of intensity with distance. Imaging systems could be (intra-oral) QLF cameras, normal (intraoral) cameras, NIR cameras etc.

[0072] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

[0073] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

[0074] It is to be understood that any of the previous steps described in relation to embodiments and / or training steps described above can be performed by a specific-purpose computer system or general-purpose computer system, or a computer-readable medium, or data carrier system configured to carry out any of the steps described previously. The computer system can include a set of software instructions that can be executed to cause the computer system to perform any of the methods or computer-based functions disclosed herein. The computer system may operate as a standalone device or may be connected, for example using a network, to other computer systems or peripheral devices. In embodiments, a computer system performs logical processing based on digital signals received via an analogue-to-digital converter.2025PF00038

[0075] 9 29.09.2025

[0076] However, all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system memories or registers or other such information storage devices. Portions of the present disclosure include processes and instructions that may be embodied in software, firmware, or hardware, and when embodied in software, may be downloaded to reside on and be operated from different platforms used by a variety of operating systems.

[0077] In a networked deployment, the computer system operates in the capacity of a server, or as a client user computer in a server-client user network environment, or as a peer computer system in a peer-to-peer or distributed network environment. The computer system can also be implemented as or incorporated into various devices, such as a server or another type of computer such as a workstation that includes a controller, a stationary computer, a mobile computer, a personal computer (PC), a laptop computer, a tablet computer, or any other machine capable of executing a set of software instructions sequentially or non-sequentially that specify actions to be taken by that machine. The computer system can be incorporated as an integrated system part of a larger system that includes additional devices. In an embodiment, the computer system can be implemented using electronic devices that provide voice, video, or data communication possibilities. Further, while the computer system is illustrated in the singular, the term “system” shall also be taken to include any collection of systems or sub-systems that individually or jointly execute a set or multiple sets, of software instructions to perform one or more computer functions.

[0078] The computer system may also include a processor. The processor executes instructions to implement some, or all aspects of methods and processes described herein. The processor is tangible and non-transitory. As used herein, the term “non-transitory” is to be interpreted not as an eternal characteristic of a state, but as a characteristic of a state that will last for a period. The term “non-transitory” specifically disavows fleeting characteristics such as characteristics of a carrier wave or signal or other forms that exist only transitorily in any place at any time. The processor is an article of manufacture and / or a machine component. The processor is configured to execute software instructions to perform functions as described in the various embodiments herein. The processor may be a general-purpose processor or may be part of an application specific integrated circuit (ASIC). The processor may also be a microprocessor, a microcomputer, a processor chip, a controller, a microcontroller, a digital signal processor (DSP), a state machine, or a programmable logic device, a logical circuit, including a programmable gate array (PGA), such as a field programmable gate array (FPGA), or another type of circuit that includes discrete gate and / or transistor logic. The processor may be a central processing unit (CPU), a graphics processing unit (GPU), or both. Additionally, any processor described herein may include multiple processors, parallel processors, or both. Multiple processors may be included in, or2025PF00038

[0079] 10 29.09.2025

[0080] coupled to, a single device or multiple devices. The processor can include one or more internal levels of cache, and a bus controller or bus interface unit to direct interaction with a bus. The term “processor” as used herein encompasses an electronic component able to execute a program or machine executable instruction. References to a computing device comprising “a processor” should be interpreted to include more than one processor or processing core, as in a multi -core processor. A processor may also refer to a collection of processors within a single computer system or distributed among multiple computer systems. The term computing device should also be interpreted to include a collection, or network, of computing devices each including a processor or processors. Programs have software instructions performed by one or multiple processors that may be within the same computing device or which may be distributed across multiple computing devices. Further, the software instructions, when executed by the processor, perform one or more steps of the methods and processes as described herein.

[0081] The computer system can further include a communications interface by way of which the computer system can connect to networks and receive data useful in executing the methods and system set out herein as well as transmitting information to other devices. The computer system further includes a video display unit as an output device by which information can be output, such as a liquid crystal display (LCD), an organic light emitting diode (OLED), a flat panel display, a solid-state display, or a cathode ray tube (CRT), for example. Additionally, the computer system includes an input device, such as a keyboard / virtual keyboard or touch-sensitive input screen or speech input with speech recognition, and a cursor control device, such as a mouse or touch-sensitive input screen or pad. The computer system also optionally includes a disk drive unit, a signal generation device, such as a speaker or remote control, and / or a network interface device.

[0082] The processes and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may also be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform one or more method steps. The structure for a variety of these systems is discussed in the description below. In addition, any programming language that is sufficient for achieving the techniques and implementations of the present disclosure may be used. In addition, the language used in the specification has been principally selected for readability and instructional purposes and may not have been selected to delineate or circumscribe the disclosed subject matter. Accordingly, the present disclosure is intended to be illustrative, and not limiting, of the scope of the concepts discussed herein.

[0083] In accordance with various embodiments of the present disclosure, the methods described herein may be implemented using a hardware computer system that executes software programs. Further, in an exemplary, non-limited embodiment, implementations can include distributed processing, component / object distributed processing, and parallel processing. Virtual computer system processing may implement one or more of the methods or functionalities as described herein, and a processor described herein may be used to support a virtual processing environment.2025PF00038

[0084] 11 29.09.2025

[0085] The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to fully describe all the elements and features of the disclosure described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure. Other embodiments may be utilized and derived from the disclosure, such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. Additionally, the illustrations are merely representational and may not be drawn to scale. Certain proportions within the illustrations may be exaggerated, while other proportions may be minimized. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive.2025PF00038

[0086] 12 29.09.2025

[0087] LIST OF REFERENCE SIGNS:

[0088] 100 sensing head

[0089] 110 light source

[0090] 111 light

[0091] 120 light sensor

[0092] 130 object

[0093] 140 tooth

[0094] 200 intra-oral camera system 210 data processing apparatus

Claims

2025PF0003829.09.2025CLAIMS:

1. A computer-implemented method for intensity-based tooth structure estimation, the method comprising:receiving (S 110) a transfer function describing a relationship between a distance of a sensing head (100) from a surface of an object (130) and an illumination intensity of the surface of the object (130), wherein the sensing head (100) comprises a light source (110) configured for illuminating the surface of the object (130) with light (111) and a light sensor (120) configured for receiving light (111) that is reflected and / or emitted from the surface of the object (130) in response to the illumination with the light (111);controlling (S120) the light source (110) to illuminate a surface of a tooth (140) in a mouth of a subject;receiving (S130) measurement data from the light sensor (120), the measurement data being indicative of an illumination intensity of the surface of the tooth (140); anddetermining (S 140) a calculation result indicative of a distance of the surface of the tooth (140) from the sensing head (100) based on the measurement data.

2. The method according to claim 1, wherein the object (130) is a tooth (140) of the subject, a three-dimensional model of a tooth, a typodont, or an object having a surface with a reflectivity and / or fluorescence similar to the reflectivity and / or fluorescence of a tooth.

3. The method according to any of the preceding claims, wherein the light source (110) is configured to emit divergent light.

4. The method according to any of the preceding claims, wherein the light source (110) is configured to emit light having an illumination intensity that is essentially homogeneous over an illumination area of the light source (110).

5. The method according to any of the preceding claims, wherein the light sensor (120) is an optical camera configured to receive a two-dimensional image of the surface of the tooth (140), and provide the two-dimensional image as the measurement data.

6. The method according to any of the preceding claims, wherein the method further comprises smoothening the calculation result by applying a predefined smoothening algorithm.2025PF0003814 29.09.20257. The method according to any of the preceding claims, wherein the calculation result comprises a two-dimensional distance array of distance values of the surface of the tooth (140) from the sensing head (100).

8. The method according to claim 7, wherein the two-dimensional distance array is a first two-dimensional distance array of a first region of the mouth of the subject, and wherein the method further comprises:stitching the first two-dimensional distance array of a first region of the mouth of the subject and at least one second two-dimensional distance array of a second region of the mouth of the subject, wherein the at least one second region is adjacent to the first region, thereby generating a three-dimensional model of the set of teeth of the subject.

9. The method according to claim 8, the method further comprising:receiving a standard model of teeth representing an average set of teeth;comparing the three-dimensional model of the set of teeth of the subject with the standard model of teeth, thereby identifying a deviation in the three-dimensional model of the set of teeth of the subject from a shape of a realistic tooth surface;correcting the identified deviation, thereby generating a corrected three-dimensional model of the set of teeth of the subject; andoutputting the corrected three-dimensional model of the set of teeth of the subject.

10. The method according to claim 9, further comprising:providing a plurality of standard models of teeth; andselecting, using an Al model, an appropriate standard model of teeth of the plurality of standard models of teeth based on the three-dimensional model of the set of teeth of the subject and / or an optical image of the teeth of the subject.

11. The method according to any of the preceding claims, wherein the light source (110) comprises a plurality of LEDs each emitting light of a different wavelength, the light sensor (120) is a multicolor camera, the measurement data comprises an illumination intensity of the surface of the tooth (140) for the respective wavelength of each of the plurality of LEDs; anddetermining the calculation result comprises determining a calculation result for the respective wavelength of each of the plurality of LEDs.

12. A data processing apparatus (210) for carrying out the steps of the method according to any one of claims 1 to 11.2025PF0003815 29.09.202513. An intra-oral camera system (200) comprisingthe data processing apparatus (210) according to claim 12, anda sensing head (100), wherein the sensing head (100) comprises a light source (110) configured for illuminating the surface of an object (130) and a light sensor (120) configured for receiving light that is reflected from the surface of the object (130).

14. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method according to any of claims 1 to 11.

15. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to any of claims 1 to 11.

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