Oral cavity analysis device

Abstract

An apparatus and method for providing classification of tooth surface materials by using measured reflectance values of light within a particular band of light. In particular, at least two light reflection measurements within an optical wavelength band of 550 nm to 650 nm can be obtained, and wherein a characteristic value proportional to the difference or ratio of these measurements is calculated. This directly or indirectly provides an indication of the sign representing the slope of the reflectance spectrum within the band, and this has been experimentally determined as a reliable discriminating factor of healthy (absence of dental caries) and unhealthy enamel (presence of dental caries).

Description

Technical Field

[0001] The invention relates to a device for oral cavity analysis, in particular dental analysis. Background Art

[0002] Oral examinations may be performed for a variety of purposes, including for the detection of dental caries.

[0003] Dental caries is a well-known disease that affects more than half of the adult population. Especially when detected at an early stage, dental caries is still reversible. Therefore, there is a clinical need to detect dental caries in people so that if caries is found, the patient can be advised to improve their oral hygiene habits or be treated by a dentist.

[0004] Oral examination for caries is usually performed by a dentist through manual inspection.

[0005] It would be advantageous to provide a system that could at least partially automate the process of detecting caries. Summary of the invention

[0006] The present invention is defined by the claims.

[0007] One aspect of the present invention is a dental analysis device. The dental analysis device includes: a multi-frequency optical measurement device, including a light generator and a light detector, the light generator is used to illuminate the tooth surface with light during use, and the light detector is used to detect the reflection of light from the tooth surface during use. The light generator can be operable to selectively generate light output in each of a plurality of different wavelength bands. Additionally or alternatively, the light detector can be operable to differentially detect light at each of the plurality of wavelength bands. The dental analysis device also includes a processor unit, which includes one or more processors. The processor unit is suitable for controlling the optical measurement device to obtain a spectral measurement set, which includes at least two reflection intensity measurements at two different and non-overlapping wavelength sub-bands, each sub-band being in the range of 550nm to 650nm.

[0008] The processor unit is further adapted to calculate a characteristic value based on at least two reflection intensity measurements, wherein the characteristic value is proportional to the difference between the at least two reflection intensity measurements or to the ratio of the at least two reflection intensity measurements, whereby in either case the characteristic value provides a direct or indirect indication of the sign of the slope of the reflection spectrum of the sampling surface between the respective wavelengths of the at least two measurements.

[0009] The processor unit is further adapted to determine a classification of healthy tooth enamel versus unhealthy tooth enamel based on the characteristic values.

[0010] The processor unit is further adapted to generate an output from the processor unit indicative of the classification. This may be a data output, a signal output and / or a user perceptible output.

[0011] The device provided is based on the concept of applying spectral analysis to the surface of a tooth to classify the state of the enamel and thereby determine (automatically or by a dentist) the presence or absence of caries or any other oral pathology. More specifically, it is proposed to use diffuse reflectance spectroscopy technology, in which diffuse reflected light is detected and analyzed. This is in sharp contrast to techniques that, for example, use detection of surface fluorescence in response to optical illumination and techniques that rely on the use of coherent light. The use of diffuse reflected light relaxes the technical requirements for the light generator and the light detector, which means that, for example, a standard LED-based light generator can be used, and / or a simple set of one or more photodiodes or a camera chip can be used as a light detector.

[0012] The reader will also note that the classification is derived from the relative relationship between multiple reflection intensity measurements and does not depend on the measurement of absolute reflection intensity measurements, but only on relative intensity measurements. This also greatly relaxes the technical restrictions on the detector used.

[0013] As will be explained more clearly later in this document with reference to the illustrative drawings, the principles of the present invention rely on the inventors' recognition that when the reflectance intensity spectrum is measured over a wavelength range spanning approximately from 550nm to 650nm, healthy enamel (i.e., enamel without caries) very reliably exhibits its reflectance spectrum curve having a negative gradient, while unhealthy enamel (i.e., enamel with caries) very reliably exhibits its reflectance spectrum curve having a positive gradient. It was this discovery that led the inventors to further recognize that this allows the enamel to be classified as healthy or unhealthy based on the relative relationship between (at least) two reflectance intensity measurements at different points across this indicative range of the reflectance intensity spectrum. This can be the difference between the first measurement and the second measurement, or it can be the ratio between the first measurement and the second measurement. Either will generate an indication as to whether the sign of the reflectance spectrum curve over the relevant range 550-650 is negative or positive, and from this derive a classification of the enamel.

[0014] It has been found that dental caries can be detected optically in the above described manner at a relatively early stage, before irreversible cavities are formed, thereby enabling the disease to be treated at an early stage.

[0015] In some embodiments, the characteristic value is proportional to a ratio of a reflection intensity measurement at a lower wavelength of the at least two measurement wavelengths to an intensity measurement at a higher wavelength of the at least two measurement wavelengths. In this case, the processor unit: determines a classification of healthy enamel in response to the characteristic value being greater than or equal to 1; and determines a classification of unhealthy enamel in response to the characteristic value being less than 1.

[0016] In another set of embodiments, the characteristic value is proportional to a value obtained by subtracting an intensity measurement of a higher of the at least two measured wavelengths from an intensity measurement of a lower of the at least two measured wavelengths. In this case, the processor unit: determines a classification of healthy tooth enamel in response to a positive characteristic value; and determines a classification of unhealthy tooth enamel in response to a negative characteristic value.

[0017] In some embodiments, calculating the characteristic value includes calculating an estimate of the gradient of the slope of the reflectance spectrum of the sample surface between the corresponding wavelengths of the two measurements. For example, this can be based on calculating the difference between at least two reflection intensity measurements mentioned above and dividing by the difference in wavelengths corresponding to each measurement. In some embodiments, a series (more than two) of reflection intensity measurements can be obtained, and wherein the gradient is calculated based on the series of measurements. There are known methods for calculating gradient values ​​from a series of sample measurements.

[0018] In some embodiments, the at least two measurements include a first reflection intensity measurement within a wavelength sub-band of 550-600 nm, and a second intensity measurement within a wavelength sub-band between 600-650 nm. This will produce, for example, a slope gradient value for the spectrum centered around 600 nm. As will be explained later, this is the best spectral point to detect the gradient, as it can be reliably expected to be negative for healthy enamel and non-negative for unhealthy enamel.

[0019] In some embodiments, calculating the characteristic value includes calculating a ratio of at least two reflection intensity measurements, and wherein a first reflection intensity measurement of the at least two reflection intensity measurements is within a wavelength sub-band corresponding to green light, and a second reflection intensity measurement of the at least two reflection intensity measurements is within a wavelength sub-band corresponding to red light. Thus, a ratio of green to red reflection intensities is measured. As will be explained later, it can be reliably expected that for unhealthy enamel, this ratio is less than 1, while for healthy enamel, this ratio is greater than 1.

[0020] In some embodiments, the light generator includes one or more LEDs.

[0021] In some embodiments, the light detector comprises a camera.

[0022] In some embodiments, the light detector includes one or more photodiodes.

[0023] In some embodiments, the light detector includes at least one photodiode array.

[0024] In some embodiments, the output comprises a data output or a signal output.

[0025] In some embodiments, the output comprises a data output, and wherein the device further comprises a wireless communication module for transmitting the data output to an auxiliary computing device.

[0026] In some embodiments, the output comprises a user-perceptible output, such as a visual output or an acoustic output, generated by controlling a user output element.

[0027] In some embodiments, the device is an oral care device and further comprises an oral care apparatus adapted to perform an oral care function.

[0028] In some embodiments, the device is a toothbrush.

[0029] In some embodiments, the device is a mouthpiece device.

[0030] In some embodiments, the device includes an arrangement of cleaning elements for brushing the teeth during use.

[0031] In some embodiments, the device is an oral irrigator. In some embodiments, the device is an electric flossing device, such as an air flossing device or a liquid flossing device.

[0032] Another aspect of the invention is a method of optical analysis. The method includes controlling a multi-frequency optical measurement device, the multi-frequency optical measurement device including a light generator for illuminating a tooth surface with light during use and a light detector for detecting reflection of light from the tooth surface during use. The light generator is operable to selectively generate light output in each of a plurality of different wavelength bands, and / or the light detector is operable to differentially detect light at each of a plurality of wavelength bands. The method includes:

[0033] controlling an optical measurement device to acquire a set of spectral measurements comprising at least two reflection intensity measurements at two distinct and non-overlapping wavelength sub-bands, each sub-band being within a range of 550 nm to 650 nm;

[0034] calculating a characteristic value based on the at least two reflection intensity measurements, wherein the characteristic value is proportional to a difference between the at least two reflection intensity measurements or proportional to a ratio of the at least two reflection intensity measurements, such that the characteristic value provides a direct or indirect indication of the sign of a slope of a reflection spectrum of the sampled surface between corresponding wavelengths of the at least two measurements;

[0035] Determining a classification of healthy tooth enamel versus unhealthy tooth enamel based on the characteristic values; and

[0036] Produces output indicating classification.

[0037] In some embodiments, the method further comprises the step of positioning the multi-frequency optical measurement device within the oral cavity of the user such that the light generator and the light detector are in optical communication with the tooth surface.

[0038] Any optional features described above in relation to the dental analysis device aspect of the invention may also be applied to the method aspect to provide embodiments of the method aspect of the invention.

[0039] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] For a better understanding of the invention, and to more clearly illustrate how the invention may be put into practice, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0041] Figure 1 A block diagram showing components of an oral analysis device according to one or more embodiments of the present invention;

[0042] Figure 2 The steps of a method according to one or more embodiments are summarized;

[0043] Figure 3 shows experimentally obtained optical reflectance spectra of a sample set of ten different tooth surfaces, all with healthy enamel (caries-free); and

[0044] Figure 4 Optical reflectance spectra of a sample set with ten different tooth surfaces obtained experimentally are shown, including a single spectrum of a tooth with healthy enamel and nine spectra of different corresponding tooth surfaces with unhealthy enamel (having caries or enamel in the early starting stages of caries). DETAILED DESCRIPTION

[0045] The present invention will be described with reference to the accompanying drawings.

[0046] It should be understood that although the detailed description and specific examples illustrate exemplary embodiments of the device, system and method, these descriptions and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the device, system and method of the present invention will be better understood from the following description, the attached claims and the accompanying drawings. It should be understood that these drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

[0047] The present invention provides an apparatus and method for providing a classification of tooth surface materials using measured reflectance values ​​of light within a specific light band, which the inventors have found to be a particularly reliable predictor of the presence or absence of oral caries. Specifically, at least two light reflectance measurements can be obtained within a light wavelength band of 550nm to 650nm, and a characteristic value proportional to the difference or ratio of these measurements is calculated. This effectively provides an indication of the sign of the slope of the reflectance spectrum within this band, either directly or indirectly, and this has been experimentally determined to be a reliable distinguishing factor between healthy and unhealthy tooth enamel.

[0048] Thus, the concept of the present invention is based on a spectroscopic analysis system. Generally speaking, the system is designed to illuminate a surface with light having a specific intensity-wavelength relationship and determine whether a change in the intensity-wavelength relationship is found in the reflected light received from the spectroscopic analysis system. The intensity-wavelength relationship simply means a specific wavelength-intensity spectrum or composition of the light.

[0049] Embodiments may specifically rely on detection of diffuse light (diffuse reflectance spectroscopy). In this way, embodiments of the invention may be distinguished from systems that rely on detection of fluorescence or on the use of coherent light. According to embodiments of the invention, incoherent light may be generated and used (ie detected).

[0050] Embodiments of the present invention provide for detecting at least one characteristic of an oral cavity feature by illuminating the oral cavity feature with light, and a change in the intensity-wavelength relationship for the light may be used as a measure of the characteristic.

[0051] Figure 1 The components of an example device according to one or more embodiments are summarized in block diagram form.Before further explanation in the form of an example embodiment, the device features will be briefly described.

[0052] The apparatus comprises a multi-frequency optical measurement device 14, which in turn comprises a light generator 16 and a light detector 18. As schematically illustrated, the light generator 16 is used to (during operation) illuminate a tooth surface 20 with light. A light generator is sometimes referred to in the art as a light engine, and may comprise a light supply unit for supplying light for delivery to the oral cavity of a subject. The light detector is used to detect reflection of the same light from the tooth surface 20 during operation.

[0053] The light generator may include one or more light sources, such as LEDs. The light generator may include one or more optical processing components, such as a luminescent converter and / or a light guide.

[0054] To perform the analysis, light generator 16 may be configured to be operable to selectively generate light output within each of a plurality of different wavelength bands, and / or light detector 18 may be configured to be operable to differentially detect light at each of a plurality of wavelength bands.

[0055] A processor unit 30 is also provided which is adapted to execute a processing method associated with the data 24 acquired by the optical measuring device 14 and the steps of which will be described below. Figure 1 A processor is shown separate from the optical measuring device 14, but both may be integrated in a single unit, for example housed by a housing of a single device. However, the processor unit may even be separate from the optical measuring device 14, for example both being communicatively connected.

[0056] The processor unit 30 is adapted to control the optical measurement device to acquire a set of spectral measurements 24 comprising at least two reflection intensity measurements at two different and non-overlapping wavelength sub-bands, each sub-band being in the range of 550 nm to 650 nm.

[0057] The processor unit 30 is further adapted to calculate a characteristic value from at least two reflection intensity measurements, wherein the characteristic value is proportional to the difference between the at least two reflection intensity measurements or proportional to the ratio of the at least two reflection intensity measurements. In this way, the characteristic value can be understood as providing a direct or indirect indicator of the sign of the slope of the reflection spectrum of the sample surface between the corresponding wavelengths of the at least two measurements. This will be explained more clearly later with reference to the accompanying drawings.

[0058] The processor unit 30 is further adapted to determine a classification 34 of healthy tooth enamel versus unhealthy tooth enamel based on the characteristic values.

[0059] The processor unit 30 is further adapted to generate an output indicative of a classification 34 from the processor unit.

[0060] As previously indicated, the same inventive concept can also be embodied in the form of a method rather than an apparatus. To illustrate this more clearly, Figure 2 The steps of a method according to one or more embodiments of the same inventive concept are summarized. The steps of the method will be summarized in summary form, and the details will become more clear through the rest of the disclosure.

[0061] The method 40 includes controlling a multi-frequency optical measurement device 14, such as the devices already described, which includes a light generator 16 for illuminating a tooth surface 20 with light during use, and a light detector 18 for detecting reflection of light from the tooth surface during use. As previously described, the light generator may be operable to selectively generate light output in each of a plurality of different wavelength bands, and / or the light detector 18 may be operable to differentially detect light at each of the plurality of wavelength bands.

[0062] The method 40 comprises at least the following steps:

[0063] receiving 42 a spectral measurement set 24 from an optical measurement device 14, the spectral measurement set comprising at least two reflection intensity measurements at two different and non-overlapping wavelength sub-bands, each sub-band being within a range of 550 nm to 650 nm;

[0064] calculating 44 a characteristic value based on the at least two reflection intensity measurements, wherein the characteristic value is proportional to a difference between the at least two reflection intensity measurements or proportional to a ratio of the at least two reflection intensity measurements, such that the characteristic value provides a direct or indirect indication of the sign of a slope of a reflection spectrum of the sample surface between respective wavelengths of the at least two measurements;

[0065] determining 46 a classification 34 of healthy tooth enamel versus unhealthy tooth enamel based on the characteristic value; and

[0066] An output indicative of the classification is generated 48 .

[0067] The method may be partially or fully computer-implemented.The method may be performed by a processing unit, such as the processing unit 30 already described.

[0068] In some embodiments, the method may further include the step of positioning the multi-frequency optical measurement device 14 within the oral cavity of the user so that the light generator and the light detector are in optical communication with the tooth surface 20. In this case, this step of the method will be performed, for example, by a human operator (or a robot operator). In the former case, this step of the method will not be computer-implemented. However, in the latter case, this step may be implemented by a computer by issuing control instructions to such a robot.

[0069] The present invention may also be implemented in a computer program product comprising code means which, when run on a processor or a computer, are configured to cause the processor or the computer to perform a method according to any example or embodiment outlined in the present disclosure or according to any claim of the present patent application.

[0070] Embodiments of the present invention also relate to an oral inspection device configured to be at least partially positioned in an oral cavity of a subject for inspection purposes, the oral inspection device comprising the light engine as mentioned, and also to an oral inspection system comprising such an oral inspection device.

[0071] Embodiments of the present invention also relate to an inspection system capable of inspecting tissue types and communicating inspection results to a person.

[0072] The light source may comprise at least one LED. Where the light source comprises a plurality of LEDs, the LEDs may be positioned in the device in any configuration as required. The plurality of LEDs may for example be provided as one or more LED arrays.

[0073] As mentioned above, the light detector is adapted to measure the intensity of light reflected by the tooth surface at two or more wavelengths.

[0074] For this purpose, the light detector may include one or more photodiodes.

[0075] For this purpose, the light detector may additionally or alternatively comprise a camera or a camera chip.

[0076] From the foregoing it will be apparent that the inventive concepts may be implemented using simple, readily available and low cost light generating and detecting components and that this may be aided by data analysis methods that rely on relative rather than absolute values ​​of two or more spectral intensity measurements.

[0077] Output 34 may include, for example, a data output and / or a signal output carrying digital information representative of the classification.

[0078] The output may additionally or alternatively include a user perceptible output, such as a visual output or an acoustic output, an output generated by controlling a user output element. The user output element may be a sensory output element.

[0079] The device may also advantageously include a wireless communication module for transmitting data or signal output to an auxiliary computing device.

[0080] The auxiliary computing device may be an external device or system separate from the oral examination device. The auxiliary computing device may include components for generating a user-perceivable output indicating the information transmitted thereto, i.e., the classification 34. For example, the auxiliary computing device may be a mobile computing device, such as a smartphone or a tablet computer.

[0081] It should be noted that embodiments of the present invention may be advantageously used with both humans and animals, and use of the term "subject" may be understood to include non-human animals as well as humans.

[0082] Having now generally described the features of apparatus and methods embodying the concepts of the present invention, the details of data processing and analysis will now be explained in more depth.

[0083] As already explained previously, in the embodiments, several different wavelengths of light are measured to infer the presence of tooth material affected by caries. Affected tissue shows different optical reflections compared to healthy tissue. In addition, enamel and dentin show different optical properties. Generally speaking, caries are first visible in the enamel.

[0084] For illustration, now refer to Figure 3 and Figure 4 .

[0085] Figure 3 The optical reflectance spectra 62 of a sample set of ten different tooth surfaces obtained experimentally, all with healthy enamel (no caries), are shown. It can be seen that all spectra follow very similar curve shapes and trajectories. The peaks of all spectra are located at approximately the same wavelength, i.e., at approximately 550 nm.

[0086] For the purposes of the present invention, it is most important to realize that within the 550-650 nm sub-band, the slope of the spectral curve is negative, with a peak occurring at approximately 550 nm.

[0087] Figure 4 The experimental data of the comparison of unhealthy enamel are shown. Figure 3 An example spectrum 62a from the represented experiment is shown at Figure 4 on the same set of axes in . Figure 4 Also shown is a set of nine reflectance spectra 64 obtained in the experiment from nine different tooth surfaces, each tooth surface including unhealthy enamel affected by caries. It can be seen that the peaks in the case of unhealthy enamel can actually be different and this reflects that the severity of caries is different and the impact on the tooth material can present different specific characteristics. However, it can be observed that a very reliable characteristic of all spectra is that between 550nm and 650nm, the slope of the reflectance spectrum is positive.

[0088] from Figure 3 and Figure 4 From these data, presented in summary form, it can be concluded that a set of spectral measurements indicating, directly or indirectly, a negative slope of the reflectance spectrum at any point or sub-segment, or the entire band, within the wavelength range of 550 nm to 650 nm can be considered as indicative of healthy enamel, not affected by caries.

[0089] From this observation, a variety of specific methods can exploit the identified significant characteristics of the reflectance spectrum for deriving differential detection of the presence of diseased and non-diseased enamel.

[0090] One approach is to derive an (approximate) value of the slope at some point or subsection of the relevant band 550nm-650nm, for example at some point in the middle of the band, at or near 600nm. This can be achieved with at least two reflection intensity measurements, but more reflection intensity measurements can also be used if practical and if necessary. Another approach is to take the difference of the reflection intensity values ​​at two wavelengths within the band. Another approach is to take the ratio of the reflection intensity values ​​at two wavelengths within the band.

[0091] Taking these values ​​in reverse order, in the case of a ratio, the characteristic value derived by the processor unit 30 from the at least two reflection intensity measurements is proportional to the ratio of the reflection intensity measurement at the lower of the at least two measurement wavelengths to the intensity measurement at the higher of the at least two measurement wavelengths. In this case, the processor unit 30: determines the classification of healthy tooth enamel in response to the characteristic value being greater than or equal to 1; and determines the classification of unhealthy tooth enamel in response to the characteristic value being less than 1.

[0092] In the second option (the difference case) outlined above, the characteristic value derived by the processor unit 30 from the at least two reflected intensity measurements is proportional to the intensity measurement at the higher of the at least two measured wavelengths minus the intensity measurement at the lower of the at least two measured wavelengths. In this case, the processor unit 30: determines a classification of healthy enamel in response to the characteristic value being positive; and determines a classification of unhealthy enamel in response to the characteristic value being negative.

[0093] In the first case outlined above, the calculation of the characteristic value by the processing unit 30 comprises calculating an estimate of the gradient of the slope of the reflection spectrum of the sample surface between the corresponding wavelengths of the two measurements. For example, this can be based on calculating the difference between at least two reflection intensity measurements and dividing by the difference in the wavelength to which each measurement corresponds.

[0094] In any of the above options, the at least two reflection intensity measurements obtained using the optical measurement device may include a first reflection intensity measurement within a wavelength sub-band of 550-600 nm and a second intensity measurement within a wavelength sub-band between 600-650 nm. This, for example, obtains a slope value of the spectrum at a position centered around 600 nm.

[0095] In fact, as a more general principle, an advantageous embodiment includes determining an estimate of the gradient of the slope of the reflection spectrum of the sampling surface over a sub-segment of wavelength 550-650nm, the sub-segment being centered at 600nm. In other words, an advantageous embodiment includes determining an estimate of the gradient of the slope of the reflection spectrum of the sampling surface at or near a wavelength of 600nm.

[0096] For example, the slope at 600 nm can be measured by using a multi-spectral light generator, which includes, for example, two or more light sources, generating light in the spectral ranges of 550-600 nm and 600-650 nm, respectively, and measuring the reflected intensity obtained for each sub-band. In this case, a detector having only a single detection band (i.e., without spectral discrimination) can be provided. The single detection band can, for example, be roughly located in the red region. It can be a band of 550-650 nm. It can be a wider band than this. It can be configured to detect any visible light. However, the use of a spectrally discriminating light detector is not excluded in this case and is also an option.

[0097] For example, light sources with different spectral outputs may be operated sequentially, thereby eliminating the need to separate the detected reflected spectrum into spectral components; no spectral discrimination needs to be performed on the detection side.

[0098] This may require a one-time relative calibration for the light sources of different frequencies in the light generator, with the calibration factor defining the relative light output intensities of the light sources of different frequencies in the light generator. In this way, when a single detector detects the intensity for each light source, any baseline differences in emission intensity (represented by the calibration factor) can be ignored when calculating the characteristic value, for example by adjusting one or both of the measured intensity values, or adjusting the overall characteristic value.

[0099] Alternatively, in case a multi-frequency discriminating detector is used, the ratio of the sensitivities of different detection bands of such a detector may be determined as calibration factors, eg a one-time relative calibration factor for the green and red sensitive pixels of a camera.

[0100] Of course, the skilled reader will immediately recognize that rather than generating the two light outputs in time sequence, the two light outputs may be generated simultaneously and a spectrally discriminating detector used that is capable of providing separate intensity measurements for the two spectral sub-bands.

[0101] It will also be appreciated that instead of using two different light sources with different spectral output characteristics in the light generator, a single light source may be used having a broadband output spanning at least part of the range of 550-650nm, and wherein this is used in combination with a multi-spectral detector capable of differentially detecting intensities within two or more different non-overlapping sub-ranges within said at least part of the overall range.

[0102] It will also be immediately appreciated that the principles described above can be extended to measure more than two data points (ie, more than two wavelengths).

[0103] In some examples, more than two spectral intensity measurements may be obtained, where the additional measurements beyond the two may all be within the same 550-650nm range, or may be partially or entirely outside the 550-650nm range. For example, reflection intensity measurements may be acquired at 550nm, 600nm, and 700nm, respectively. For example, this may be achieved using three light sources emitting at 550nm, 600nm, and 700nm, respectively. This configuration is suitable for measuring intensity values ​​within the spectral region 550nm–700nm. A reflection maximum above 650nm always indicates that the enamel is affected.

[0104] Another possibility that has not yet been mentioned is to calculate the characteristic value as a ratio of at least two reflection intensity measurements, and wherein a first of the at least two reflection intensity measurements is measured within a wavelength sub-band corresponding to green light, and a second of the at least two reflection intensity measurements is measured within a wavelength sub-band corresponding to red light. This may be referred to simply as a "green-red ratio," or G / R intensity ratio. This actually represents a subclass of the more general example group already described, which takes the ratio of two reflection intensity measurements, since both green and red cover an area within the range of 550nm-650nm. Thus, in this case, the processor unit may determine a classification of healthy enamel in response to a G / R ratio being greater than or equal to one, and may determine a classification of unhealthy enamel in response to a G / R ratio being less than one.

[0105] Through two illustrative examples, from the experimental data, the following criteria can be derived to distinguish healthy enamel (H) from carious enamel (C)

[0106]

[0107] Table 1

[0108] Of course, for the slope at 600 nm, the more general criteria remain consistent with what is stated in the table, i.e., if the slope is less than zero, then the enamel can be classified as healthy, and if the slope is greater than zero, then the enamel can be classified as unhealthy (enamel with caries).

[0109] In some embodiments, the characteristic values ​​can be monitored over time to detect changes in the state of the enamel. Specifically, the ratio, difference, or slope values ​​can be recorded in a data set associated with the subject along with a timestamp, and the historical values ​​can then be monitored and trended. If the ratio, difference, or slope moves further toward the classification of unhealthy enamel, it can be communicated to the patient to prompt them to change their diet or cleaning habits; and if the ratio, difference, or slope moves further toward the healthy range, it can be communicated to the patient to confirm that they continue their current cleaning or eating habits.

[0110] For example, it is advantageous that the device includes storage capacity and software so that trends can be calculated based on the recorded historical data. Alternatively, the historical data may be stored in an external or remote data repository, such as a memory module of a mobile computing device communicatively connected to the analysis device or a cloud-based data repository.

[0111] In some embodiments, measurement and classification may be performed on a plurality of teeth in the mouth, and the results for each tooth may be recorded in the dataset for the patient along with an identifier of the tooth to which each classification corresponds.

[0112] In some examples, a caries risk score can be estimated based on caries progression (size of caries spots and growth of spots). In some examples, federated learning can be used, whereby brushing data from many users can be used and combined with inspection data from dentists and dental treatments to improve the accuracy of the risk score over time.

[0113] In some embodiments, the optical analysis apparatus may further include a position sensor for sensing at least the location of the optical measurement device within the oral cavity when acquiring each spectral measurement set. In this way, the oral cavity position and corresponding classification associated with each measurement set may be automatically detected and recorded.

[0114] As mentioned above, in some embodiments, the test results can be transmitted to an auxiliary computing device, such as a mobile computing device, such as a smart phone, tablet computer, etc., so that the results can be communicated to a person such as a dentist or other dental professional. Such communication can be carried out over a long distance (such as via the Internet) or a significantly shorter distance.

[0115] The oral analysis device may comprise a battery for providing power for driving the light generator, the detector and the processor. According to another possibility, the oral examination device may be connectable to a mains power supply.

[0116] In some embodiments, the oral analysis device may be an oral care device, which also includes an oral care device adapted to perform an oral care function. For example, the device may be a toothbrush or a mouthpiece, which includes an arrangement of cleaning elements for brushing teeth during use. The oral analysis device may, for example, be included in the brush head of a toothbrush, but may alternatively be included in the handle of a toothbrush. For example, it may also be incorporated into a dental drill or an air-jet toothbrush device.

[0117] In many cases, during normal inspection of a subject's oral cavity by a person such as a dental professional, a light source is used to illuminate the oral cavity with visible light. According to some embodiments, the light generator can be used for a dual purpose, namely to illuminate the oral cavity to provide visibility for the dental professional. Thus, the light can be visible light, the function of which is to ensure that the oral cavity or at least a portion of the oral cavity is illuminated so that the person can clearly see the teeth, gums and / or other oral features to be inspected. In addition, the light can play a role in the operation of the optical measurement device.

[0118] The embodiments of the present invention described above employ processor units. The processor unit may typically include a single processor or multiple processors. It may be located in a single containing device, structure or unit, or it may be distributed between multiple different devices, structures or units. Therefore, references to the processor unit are adapted or configured to perform specific steps or tasks, which may correspond to the steps or tasks performed by any one or more of the multiple processing components individually or in combination. The technician will understand how to implement such distributed processor units. The processor unit may include a communication module or input / output for receiving data and outputting data to other components.

[0119] The one or more processors of the processor unit can be implemented in a variety of ways using software and / or hardware to perform the various functions required. The processors are typically implemented in the form of one or more microprocessors that can be programmed using software (e.g., microcode) to perform the required functions. The processors can be implemented as dedicated hardware for performing some functions and as a combination of one or more programmed microprocessors and associated circuits for performing other functions.

[0120] Examples of circuits that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field programmable gate arrays (FPGAs).

[0121] In various implementations, the processor may be associated with one or more storage media, such as volatile and non-volatile computer memory, such as RAM, PROM, EPROM, and EEPROM. The storage media may be encoded with one or more programs that, when executed on one or more processors and / or controllers, perform the desired functions. The various storage media may be fixed within the processor or controller, or may be removable so that one or more programs stored thereon may be loaded into the processor.

[0122] Variations to the disclosed embodiments may be understood and implemented by those skilled in the art in practicing the claimed invention by studying the drawings, the disclosure and the appended claims. 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.

[0123] A single processor or other unit may fulfill the functions of several items recited in the claims.

[0124] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0125] The computer program may be stored / distributed on a suitable medium, such as optical storage media or solid-state media provided with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0126] If the term "suitable for" is used in the claims or the specification, it should be noted that the term "suitable for" is intended to be equivalent to the term "configured to".

[0127] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A dental analysis device comprising: A multi-frequency optical measurement device comprising a light generator for illuminating a tooth surface with light during use and a light detector for detecting reflection of the light from the tooth surface during use, wherein the light generator is operable to selectively generate light output within each of a plurality of different wavelength bands, and / or the light detector is operable to differentially detect light at each of the plurality of wavelength bands; as well as Processor unit for: controlling the optical measurement device to acquire a set of spectral measurements, the set of spectral measurements comprising at least two reflection intensity measurements at two different and non-overlapping wavelength sub-bands, each sub-band being in the range of 550 nm to 650 nm; calculating a characteristic value based on the at least two reflection intensity measurements, wherein the characteristic value is proportional to a difference between the at least two reflection intensity measurements or the characteristic value is proportional to a ratio of the at least two reflection intensity measurements, such that the characteristic value provides a direct or indirect indication of the sign of a slope of a reflection spectrum of the sample surface between respective wavelengths of the at least two measurements; determining a classification of healthy tooth enamel versus unhealthy tooth enamel based on the characteristic value; as well as An output indicative of the classification is generated from the processor unit.

2. An apparatus according to claim 1, wherein the characteristic value is proportional to the ratio of the reflection intensity measurement of the lower wavelength of the at least two measurement wavelengths to the intensity measurement of the higher wavelength of the at least two measurement wavelengths, and wherein the processor unit: determines the classification of healthy enamel in response to the characteristic value being greater than or equal to 1; and determines the classification of unhealthy enamel in response to the characteristic value being less than or equal to 1.

3. An apparatus according to claim 1 or 2, wherein the characteristic value is proportional to a value obtained by subtracting an intensity measurement of a higher wavelength of the at least two measuring wavelengths from an intensity measurement of a lower wavelength of the at least two measuring wavelengths, and wherein the processor unit: determines a classification of healthy enamel in response to a positive characteristic value; and determines a classification of unhealthy enamel in response to a negative characteristic value.

4. An apparatus according to claim 3, wherein calculating the characteristic value includes calculating an estimate of the gradient of the slope of the reflection spectrum of the sampling surface between the corresponding wavelengths of the two measurements, for example based on calculating the difference between the at least two reflection intensity measurements and dividing by the difference in the wavelength to which each measurement corresponds.

5. The apparatus according to any one of claims 1 to 4, wherein the at least two measurements comprise a first reflected intensity measurement within a wavelength sub-band of 550-600 nm and a second intensity measurement within a wavelength sub-band between 600-650 nm.

6. An apparatus according to any one of claims 1-5, wherein calculating the characteristic value includes calculating a ratio of the at least two reflection intensity measurements, and wherein a first reflection intensity measurement of the at least two reflection intensity measurements is within a wavelength sub-band corresponding to green light, and a second reflection intensity measurement of the at least two reflection intensity measurements is within a wavelength sub-band corresponding to red light.

7. The device of any one of claims 1-6, wherein the light generator comprises one or more LEDs.

8. The device of any one of claims 1-7, wherein the light detector comprises a camera.

9. The apparatus according to any one of claims 1 to 8, wherein the output comprises a data output or a signal output.

10. The apparatus of claim 9, wherein the output comprises a data output, and wherein the apparatus further comprises a wireless communication module for transmitting the data output to an auxiliary computing device.

11. The apparatus according to any one of claims 1 to 10, wherein the output comprises an output perceivable by a user, such as a visual output or an acoustic output, an output generated by controlling a user output element.

12. The device of any one of claims 1-11, wherein the device is an oral care device and further comprises an oral care implement adapted to perform an oral care function.

13. A device according to claim 12, wherein the device is a toothbrush or a mouthpiece comprising an arrangement of cleaning elements for brushing the teeth during use.

14. An optical analysis method, wherein the method comprises controlling a multi-frequency optical measurement device, the multi-frequency optical measurement device comprising a light generator for illuminating a tooth surface with light during use and a light detector for detecting reflection of the light from the tooth surface during use, wherein the light generator is operable to selectively generate light output within each of a plurality of different wavelength bands, and / or the light detector is operable to differentially detect light at each of the plurality of wavelength bands; The method comprises: controlling the optical measurement device to acquire a set of spectral measurements, the set of spectral measurements comprising at least two reflection intensity measurements at two different and non-overlapping wavelength sub-bands, each sub-band being in the range of 550 nm to 650 nm; calculating a characteristic value based on the at least two reflection intensity measurements, wherein the characteristic value is proportional to a difference between the at least two reflection intensity measurements, or proportional to a ratio of the at least two reflection intensity measurements, such that the characteristic value provides a direct or indirect indication of the sign of a slope of a reflection spectrum of the sample surface between respective wavelengths of the at least two measurements; determining a classification of healthy tooth enamel versus unhealthy tooth enamel based on the characteristic value; and An output is generated that is indicative of the classification.

15. The method of claim 14, further comprising the step of positioning the multi-frequency optical measurement device within the oral cavity of a user such that the light generator and the light detector are in optical communication with a tooth surface.

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