Device for detecting bacterial biofilm on tooth surface

Abstract

The present invention provides a device for detecting a bacterial biofilm on a tooth surface, the device comprising a light source for illuminating a tooth surface having a bacterial biofilm thereon, the light source being operable in a first mode and a second mode different from the first mode. The apparatus also includes a sensor to determine whether the apparatus is operating in a first mode or a second mode; and a light detector for detecting light reflected by the tooth surface and / or bacterial biofilm in a first mode and in a second mode to generate first reflection data and second reflection data, respectively. The device is configured to detect the bacterial biofilm by interpreting the second reflectance data using the first reflectance data as reference data to separate bacterial reflectance data indicating only light interaction with the bacterial biofilm.

Description

Technical Field

[0001] The present invention relates to a device for detecting bacterial biofilms on tooth surfaces, and in particular, although not exclusively, to a device for detecting bacterial biofilms on tooth surfaces by analyzing the interaction of light with the bacterial biofilms and tooth surfaces. Background Art

[0002] According to the Global Burden of Disease Study 2019, oral diseases affect nearly 3.5 billion people globally, and the most common disease is dental caries or tooth decay. Dental caries occur due to the accumulation and formation of bacterial biofilms or dental plaque on tooth surfaces, which over time convert sugars into acids that damage the tooth surface.

[0003] The presence of bacterial biofilms increases the likelihood of gum inflammation or gingivitis, and long-term gingivitis can lead to periodontitis, an inflammatory disease that causes permanent and irreversible damage to both soft and hard oral tissues. In its most severe form, periodontitis causes the gums to recede from the teeth and supporting bone structure, resulting in bone tissue loss and ultimately tooth loosening and loss. Periodontitis is the sixth most prevalent disease in the world and is preventable if treated early before the onset of the disease.

[0004] In fact, most oral diseases are preventable in their early stages, and the burden of oral diseases can be reduced by accessing oral health services, practicing good oral hygiene, having adequate exposure to fluoride, and following a balanced diet low in sugar.

[0005] Therefore, the ability to detect biofilms with a sensor system can guide users to brush their teeth in a targeted manner and promote good oral hygiene compliance.

[0006] Traditional biofilm detection methods rely on detecting and analyzing the fluorescence emitted by certain bacterial compounds under specific illumination (such as ultraviolet or blue light). However, this method has many drawbacks. First, the sensitivity of this fluorescence-based method is limited by the amount of fluorescent compounds and the light capture ability and sensitivity of the sensor system. Second, the intrinsic fluorescence signals of oral bacteria are different from each other, so it is difficult to correlate the detected fluorescence intensity with the number of bacteria present. Third, the fluorescence signals of some bacterial species overlap with the fluorescence of the teeth themselves, increasing the difficulty of detecting these types of bacterial biofilms. Finally, to improve sensitivity, traditional biofilm detection methods usually use additional fluorescent dyes or contrast agents, so they are cumbersome and complex to use.

[0007] Accordingly, there is a desire to provide an improved apparatus and method for detecting bacterial biofilms that do not suffer from the above disadvantages. Additionally, it may be advantageous to use the same apparatus / method to detect defects in the tooth structure, such as pits, fissures, and cracks in addition to bacterial biofilms. In fact, early detection of such defects in the tooth structure can allow users to monitor their dental condition and seek dental treatment with early intervention.

[0008] In view of the above considerations, the present invention has been designed. Summary of the Invention

[0009] In a first aspect, there is provided an apparatus for detecting bacterial biofilms on a tooth surface, the apparatus comprising:

[0010] a light source for irradiating the tooth surface having a bacterial biofilm thereon, the light source being operable in a first mode and a second mode different from the first mode;

[0011] a sensor for determining whether the apparatus is operating in the first mode or the second mode;

[0012] a light detector for detecting light reflected by the tooth surface and / or the bacterial biofilm in the first mode and in the second mode to respectively generate first reflection data and second reflection data; and

[0013] wherein the apparatus is configured to detect the bacterial biofilm by using the first reflection data as reference data to interpret the second reflection data to isolate the bacterial reflection data that only indicates the light interaction with the bacterial biofilm.

[0014] Advantageously, the apparatus does not rely on detecting and analyzing fluorescence emitted by bacteria under specific irradiation conditions, but generates and analyzes different types of reflection data that indicate the interaction (refraction / reflection / scattering) of light with different optical media on and in the user's teeth.

[0015] Typically, human teeth consist of multiple layers. The outer layer is enamel, and beneath it is dentin that surrounds the dental pulp. Here, the tooth surface refers to the outer surface of the tooth (preferably not surrounded by the gum). For healthy teeth, the tooth surface will be provided by enamel. However, if the tooth has a structural anomaly such that the enamel is severely interrupted, for example, by a cavity, then a portion of the underlying dentin layer can provide the tooth surface at the abnormal location. Due to the multi-layered structure, a tooth having a biofilm on its tooth surface includes multiple optical interfaces. First, there is an interface between the biofilm and the tooth surface environment (hereinafter simply referred to as the environment-biofilm interface). Next is the biofilm-tooth surface interface (which may be a biofilm-enamel or biofilm-dentin interface depending on whether the enamel is damaged). Assuming the enamel is substantially undamaged, the next interface is the enamel-dentin interface. Finally, there is the dentin-pulp interface. Depending on the wavelength of light and the optical properties of these layers, light emitted by a light source can be reflected / refracted at all or some of these optical interfaces, and it can be scattered / absorbed by some or all of the layers within the tooth.

[0016] The tooth surface having a bacterial biofilm thereon refers to the situation where the bacterial biofilm at least partially covers the tooth surface (i.e., the outer surface of the tooth). Depending on the user's dental hygiene, the extent to which the biofilm covers the tooth surface may vary.

[0017] To detect the biofilm on the tooth surface, the device needs to analyze bacterial reflection data that only indicates the interaction of light with the biofilm. Such bacterial reflection data can be the product of light reflected at the environment-biofilm interface and scattered by bacteria in the biofilm. However, in practice, it may be difficult to directly collect bacterial reflection data independently of other types of reflection data, such as data that is the product of light reflected from other optical interfaces in the tooth. Conveniently, the present device solves this problem through its dual-mode operation.

[0018] These two modes are different from each other because each mode provides suitable conditions for the interaction of light with different optical interfaces on the user's teeth.

[0019] The first mode is used to measure some or all of the optical interfaces on a tooth that include a biofilm, excluding the environment-biofilm interface. For example, the first mode can be used to measure all or some of the following interfaces: biofilm-tooth surface, enamel-dentin, dentin-pulp. To achieve this, the first mode is configured such that the refractive index contrast between the biofilm and the environment is not sufficient to cause reflection / refraction at the environment-biofilm interface. This allows light to pass largely uninterrupted from the environment to the biofilm to interact more significantly with some or all of the remaining optical interfaces. Thus, the environment in this mode is chosen to have a refractive index similar to that of the biofilm, i.e., approximately 1.33. For example, the environment can be water, which also has a refractive index of approximately 1.33. However, media other than water can be used to achieve the same effect as long as they have a refractive index similar enough to the biofilm. For example, the environment in the first mode can have a refractive index in the range of 1.20 to 1.46 (including the endpoints), such as 1.26 to 1.40 (including the endpoints). When the environment is water or another liquid, the first mode is called the wet mode. The first reflection data generated in this mode are characteristic of the tooth structure, such as including pits, cavities, fissures, cracks, etc.

[0020] In contrast, the second mode is used to measure the optical interfaces, including the environment-biofilm interface. For example, in addition to the environment-biofilm interface, the second mode can be used to measure all or some of the following interfaces: biofilm-tooth surface, enamel-dentin, dentin-pulp. To achieve this, the second mode is configured such that the refractive index contrast between the biofilm and the environment is sufficient to cause reflection / refraction at the environment-biofilm interface. For example, the environment can be air, which has a refractive index of approximately 1.00. However, media other than air can be used to achieve the same effect as long as they have a sufficiently different refractive index and can cause light to refract from the environment to the biofilm and vice versa (e.g., such that light does not experience total internal reflection). For example, the environment in the second mode can have a refractive index in the range from 0.90 to 1.10 (including the endpoints), such as from 0.95 to 1.05 (including the endpoints). When the environment is air or another gas, the first mode is called the dry mode. The second reflection data generated in this mode include the tooth structure as well as features characteristic of the presence and structure of the biofilm.

[0021] By using the first reflection data as reference data to interpret the second reflection data, the device can separate the contributions within the second reflection data that are due to the interaction of light with the environment-biofilm interface. This is how the bacterial reflection data is obtained to detect biofilms. Using the first reflection data as reference data to interpret the second reflection data involves computationally analyzing the two types of data together. For example, the first reflection data can be subtracted from the second reflection data or the first reflection data can be superimposed on the second reflection data (using mathematical operations) in order to computationally obtain a new set of data (different from the first and second reflection data), namely the bacterial reflection data.

[0022] Optional features will be discussed below. These can be used individually or in combination, unless such a combination is clearly not allowed or explicitly avoided.

[0023] The device can be a dental probe.

[0024] Optionally, the device can be used only in a first (e.g., wet) mode to detect structural abnormalities in the tooth surface, such as pits, fissures, cracks, cavities, etc. This is because, as described above, the first mode can be used to measure all or some of the following optical interfaces: biofilm-tooth surface, enamel-dentin, dentin-pulp.

[0025] Optionally, the first mode can be a wet mode, the second mode can be a dry mode, and the sensor used to determine whether the device is operating in the first mode or the second mode can be a submersion sensor. When the environment used in the first (wet) mode is a liquid, such as water, and the environment used in the second (dry) mode is a gas, such as air, the submersion sensor can determine in which mode the device is operating by determining the presence of liquid in the environment.

[0026] Optionally, the submersion sensor can be based on an optical sensor or an electrical sensor. When the submersion sensor is based on an optical sensor, it can determine whether the device is operating in the wet mode or the dry mode by monitoring a selected optical path in the device environment and detecting the presence of liquid (e.g., water) when the optical path changes. Alternatively, when the submersion sensor is an electrical sensor, it can determine whether the device is operating in the wet mode or the dry mode by detecting a change in the conductivity of the device environment. For example, the submersion sensor can be resistance-based or transistor-based.

[0027] Optionally, the light source may be configured to irradiate the tooth surface with light from the visible or near-infrared part of the electromagnetic spectrum. That is, the light source may be configured to irradiate the tooth surface with light having a wavelength in the range of 380 nm to 2500 nm (including the endpoints). Conveniently, this relatively wide wavelength range may allow for greater design and / or manufacturing flexibility, for example by ensuring that the device can perform its function well using a wide range of light sources and / or light detectors. Preferably, the light source may be configured to irradiate the tooth surface with light having a wavelength in the range of 500 nm to 900 nm, such as about 650 nm. Conveniently, by using light within this range, light absorption by the user's teeth can be reduced. Thus, the light emitted by the light source interacts with the tooth surface and different optical interfaces on the tooth mainly through reflection, refraction, and transmission. In addition, light detectors configured to detect light within this range are generally low-cost and widely available.

[0028] Optionally, the light source may be a laser diode.

[0029] Optionally, the light detector may be a two-dimensional 2D light detector. For example, the light detector may be based on a CCD imaging sensor or a CMOS imaging sensor. Preferably, the light detector has characteristics (such as resolution and / or pixel size) that allow it to successfully detect a biofilm layer with a thickness of 10 - 30 μm. Specifically, a biofilm layer with a thickness of 10 - 30 μm may cause the light reflected at the environment-biofilm interface to be detected on the light detector, at a distance between 15 μm and 40 μm from the light reflected at the biofilm-tooth surface interface. For example, the light detector may have a resolution in the range of 0.3 - 2.0 megapixels (including the endpoints), such as a resolution of 0.3 megapixels or 1.2 megapixels. The light detector may have a pixel size in the range from 1 μm by 1 μm to 5 μm by 5 μm (including the endpoints), such as 3 μm by 3 μm.

[0030] The device may include a lens located upstream of the light detector such that the reflected light incident on the light detector first passes through the lens and then irradiates the light detector. The lens may be a magnifying lens for magnifying the distance between different parts of the reflected light to assist in detecting and distinguishing them on the light detector.

[0031] The first, second, and / or bacterial reflection data may include the position on the light detector where the reflected light is detected. When the light detector is a 2D light detector, the position may be in the form of 2D coordinates. The first, second, and / or bacterial reflection data may also include the electromagnetic intensity values of the light detected at different positions on the light detector. This may be helpful when analyzing complex reflection and / or scattering patterns detected by the light detector.

[0032] The device may also include a memory for storing the reflected data and / or sensor output. Conveniently, this may allow the device to store the user's oral history, including for example the presence and / or location of biofilm and / or structural abnormalities detected on their teeth. For example, over time this may be useful in monitoring the user's oral health.

[0033] Optionally, the device may further include a processor communicatively connected to:

[0034] a light detector to receive reflected data therefrom; and

[0035] a sensor to determine whether the received reflected data is first reflected data or second reflected data;

[0036] wherein the processor is configured to use the first reflected data as reference data to interpret the second reflected data to isolate bacterial reflected data.

[0037] Optionally, the processor may further be configured to analyze the bacterial reflected data to determine properties of the detected bacterial biofilm. For example, the processor may be configured to determine properties such as microbial density / microbial activity, microbial type, and / or bacterial biofilm thickness on the tooth surface.

[0038] Similarly, when the device is used only in a first (e.g., wet) mode to detect structural abnormalities on the tooth surface, the processor may be configured to determine properties of the tooth structure. For example, the processor may be configured to determine the thickness of the enamel and / or properties of the detected structural abnormalities, such as size, shape, and / or topology.

[0039] In a second aspect, there is provided a head for an electric toothbrush, the head including the device of the first aspect.

[0040] In a third aspect, there is provided an electric toothbrush including:

[0041] a head and a body portion; and

[0042] the device of the first aspect.

[0043] Optionally, the light source, light detector, and sensor of the device may be provided in the head of the electric toothbrush. The processor may also be provided in the head, or alternatively, it may be provided in the body portion.

[0044] In a fourth aspect, there is provided a method of detecting a bacterial biofilm on a tooth surface using the device of the first aspect, the method including:

[0045] determining whether the device is operating in a first mode or a second mode;

[0046] Irradiate the tooth surface with light from a light source;

[0047] Detect the light reflected by the biofilm and / or the tooth surface to generate first / second reflection data;

[0048] Detect the bacterial biofilm by interpreting the second reflection data using the first reflection data as reference data to isolate the bacterial reflection data that only indicates the light interaction with the bacterial biofilm.

[0049] Optionally, the method may further include the step of analyzing the bacterial reflection data to determine the properties of the detected bacterial biofilm, such as the microbial density / microbial activity, microbial type, and / or thickness of the bacterial biofilm on the tooth surface.

[0050] The method may include the step of analyzing the first reflection data to determine the properties of the tooth structure, such as the thickness of the enamel and / or the properties of the detected structural abnormalities, such as size, shape, and / or topology.

[0051] Optionally, the method may include one or more calibration steps after determining that the device is operating in the first mode. For example, when the environment in the first mode is liquid, the light source and / or the light detector may be sealed in a light-transmissive housing to prevent damage due to liquid exposure. Before reaching the biofilm-tooth surface interface (and the optional light detector), the light emitted by the light source will interact with the light-transmissive housing and will thus be reflected and refracted as specified by the refractive index of the housing. Therefore, one or more calibration steps after determining that the device is operating in the wet mode may be adjusted for these interactions of the light with the housing so as not to compromise the quality of the first reflection data. Brief Description of the Drawings

[0052] Embodiments and experiments illustrating the principles of the present invention will now be discussed with reference to the accompanying drawings, wherein:

[0053] Figure 1 A device for detecting a bacterial biofilm on a tooth surface is schematically shown;

[0054] Figures 2A to 2B A schematic illustration of Figure 1 An experimental setup simulating the performance of the device in the first mode;

[0055] Figures 3A to 3B A schematic illustration of Figures 2A to 2B The experimental setup, which simulates Figure 1 The performance of the device in the second mode; and

[0056] Figure 4 A schematic illustration of the steps of a method for detecting a bacterial biofilm on a tooth surface using the Figure 1 device. Detailed Embodiments

[0057] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying drawings. Further aspects and embodiments will be apparent to those skilled in the art.

[0058] As is well known, when light impinges on an optical medium, it is reflected, absorbed, or refracted (in varying proportions). For light that is reflected and refracted at an interface, two conditions need to be met. First, the light must impinge on the interface at an angle other than 90 degrees and other than zero degrees. Second, at the optical frequency of the light, the refractive indices of the media on either side of the interface need to be sufficiently different, i.e., there needs to be a non-negligible refractive index contrast. The presence of inhomogeneities and / or rough surface topologies in one of the optical media causes the light to scatter in different directions. The present invention makes use of these principles.

[0059] Reference Figure 1 There is described a device for detecting a bacterial biofilm on a tooth surface according to an embodiment of the present invention. Device 10 includes a light source 11 for irradiating the tooth surface, a sensor 12 for determining whether the light source 11 is operating in a first mode or a second mode, and a light detector 12. The light detector 12 detects light reflected by the tooth surface and / or the bacterial biofilm in the first mode and in the second mode to respectively generate first reflection data and second reflection data.

[0060] In this example, the light source 11 is configured to irradiate the tooth surface with light from the visible or near-infrared portion of the electromagnetic spectrum, i.e., light having a wavelength in the range from 380 nm to 2500 nm (including the endpoints). Specifically, the light source 11 may be configured to irradiate the tooth surface with light having a wavelength in the range from 500 nm to 900 nm, for example, about 650 nm. The light source 11 may be a laser diode, such as a commercial laser diode module from Continental Electronics TM of TM .

[0061] In this example, the first mode is the wet mode, and the environment on the tooth surface is a liquid with a refractive index similar to that of a biofilm. Since bacterial biofilms are mainly composed of proteins and polymeric substances secreted by bacteria and water, their refractive index is usually similar to that of water, i.e., about 1.33. Therefore, the refractive index of the environment in the wet mode can be in the range of 1.20 to 1.46 (including the endpoints), for example, 1.26 to 1.40 (including the endpoints), to minimize the refractive index contrast at the environment-biofilm interface. In this example, the environment in the wet mode is water. The second mode is the dry mode, and the environment is a gas with a refractive index in the range of 0.90 to 1.10 (including the endpoints), for example, 0.95 to 1.05 (including the endpoints), to enhance the refractive index contrast at the environment-biofilm interface. Specifically, in this example, the environment is air with a refractive index of about 1.00.

[0062] In this example, sensor 13 is an immersion sensor, such as an optical immersion sensor or an electrical immersion sensor. When the immersion sensor 13 is an optical sensor, when the optical path changes, it determines whether the device is operating in the wet mode or the dry mode by monitoring a selected optical path in the device environment and detecting the presence of a liquid (such as water). An example of an optical sensor is the commercial LUP series compact leak detection sensor TM manufactured by Daitron TM . Alternatively, when the immersion sensor 13 is an electrical sensor, it determines whether the device is operating in the wet mode or the dry mode by detecting a change in the conductivity of the device environment. For example, the electrical immersion sensor can be a resistance-based sensor, such as the commercial Grove–Water Sensor TM from Seeed Studio TM , or a transistor-based sensor, such as the commercial simple water detection sensor with digital output TM from Adafruit TM .

[0063] The light detector 12 is a two-dimensional 2D light detector. For example, the light detector can be a CCD imaging sensor-based or a CMOS imaging sensor-based, such as the commercial Mira030-1RM2WP TM from AMS OSRAM TM or the AR0134CSSM25SUEA0-DRBR1 TM from ONSEMI TM。The characteristics of the light detector, such as overall size, pixel size, sensitivity, and dynamic range, affect its resolution and the quality of the reflected data it can generate (e.g., detail / granularity). Preferably, the light detector has characteristics that allow it to successfully detect a biofilm layer with a thickness of 10 - 30 μm. Specifically, a biofilm layer with a thickness of 10 - 30 μm can cause the light reflected at the environment-biofilm interface to be detected on the light detector, at a distance between 15 and 40 μm from the light reflected at the biofilm-tooth surface interface. For example, the light detector 12 can be selected to have a resolution in the range of 0.3 - 2.0 megapixels, such as a resolution of 0.3 megapixels or 1.2 megapixels. The light detector can have a pixel size in the range from 1 μm by 1 μm to 5 μm by 5 μm (including the endpoints), such as 3 μm by 3 μm.

[0064] The apparatus 10 can optionally include a lens (not shown) located upstream of the light detector 12, such that the reflected light incident on the light detector first passes through the lens and then irradiates the light detector. The lens can be a magnifying lens for magnifying the distance between different parts of the reflected light to assist in detecting and distinguishing them on the light detector.

[0065] In this example, the first, second, and bacterial reflected data generated by the light detector 12 include the positions on the light detector where the reflected light is detected. These positions are in the form of 2D coordinates. The reflected (first, second, and bacterial) data can also include the electromagnetic intensity values of the light detected at different positions on the light detector 12.

[0066] To reduce the risk of damage due to exposure to liquid in the wet mode, the light source 11 and the light detector 12 are sealed within a waterproof, light-transmissive housing (not shown).

[0067] Once the light detector 12 has generated the first and second reflected data, the processor 14 of the apparatus 10 uses the first reflected data as reference data to interpret the second reflected data to isolate the bacterial reflected data that only indicates the light interaction with the bacterial biofilm. For example, the processor 14 can analyze the first and second reflected data together, and by performing mathematical operations, it can isolate the bacterial reflected data. For example, the processor can mathematically subtract the first reflected data from the second reflected data to obtain a new data set, which is the bacterial reflected data.

[0068] Figure 1 The apparatus 10 optionally includes a memory 15 for storing the reflected data and / or sensor outputs. Conveniently, this can allow the apparatus to store the history of the user's oral health, including, for example, the presence and / or location of biofilm and / or structural abnormalities detected on their teeth. For example, over time, this can be useful in monitoring the user's oral health.

[0069] Next, the simulated performance of the device 10 in the first (wet) mode will be discussed with reference to Figures 2A-2B the experimental setup 100 shown in Figure 1 . The experimental setup 100 includes a light source 11, a light detector 12 as a 2D light detector, and a sensor 13 as an immersion sensor. The environment 20 is water with a refractive index of approximately 1.33. The light source 11 irradiates the enamel layer 18 and the dentin layer 17 beneath the enamel layer. The enamel layer 18 has a refractive index of approximately 1.62, while the dentin layer has a refractive index of approximately 1.54. Figure 2A and 2B the tooth surface of Figure 2B is entirely provided by the top surface of the enamel layer 18. The enamel layer 18 in

[0070] includes structural anomalies 23, such as voids or caries, which have their own optical properties different from those of the enamel / biofilm. The structural anomalies can also include a relatively rough topology. The tooth surface has a bacterial biofilm 19 located thereon. That is, the bacterial biofilm at least partially covers the tooth surface. The bacterial biofilm contains bacteria 21. Figures 2A-2B shown in

[0071] In use, the light source 11 emits light 22 from the visible or near-infrared portion of the electromagnetic spectrum (light with a wavelength in the range of 380 nm to 2500 nm (including the endpoints), for example 650 nm) to irradiate the biofilm 19 and the tooth surface. Since the refractive indices of both water and the biofilm are approximately 1.33, the emitted light 22 passes through the environment-biofilm interface 24 with substantially no interruption, without being reflected or refracted from the biofilm 19 through the biofilm 19 (as Figure 2A shown in Figure 2A . When the emitted light 22 reaches the biofilm-tooth surface interface 25, a portion 22b of it is reflected from the tooth surface and reaches the light detector 12. The remaining light is refracted at the biofilm-tooth surface interface 25 and enters the enamel layer 18. Then, the light reaches the enamel-dentin interface 26, and a portion 22c of it is reflected from the surface of the dentin layer 17. Then, the reflected portion of the light 22c propagates to the light detector 12 by refraction at the tooth surface-biofilm interface 25. A portion of the emitted light 22 may be refracted at the enamel-dentin interface 26 and propagate through the dentin layer 17. However, for simplicity, this is not shown in

[0072] From Figure 2AAs can be seen, a portion 22b of the light reflected at the biofilm-tooth surface interface 25 irradiates the light detector 12 at a position different from that of a portion 22c of the light reflected at the enamel-dentin interface 26. The positions (e.g., 2D coordinates) at which different portions of light irradiate the light detector are included in the first reflection data. By calculating the distance between these two different positions and using the laws of geometric optics and trigonometric formulas, the distance between the biofilm-tooth surface interface 25 and the enamel-dentin interface 26 can be calculated, which corresponds to the thickness of the enamel layer 18. This helps to evaluate the health of the enamel layer 18.

[0073] Reference Figure 2B , the enamel layer 18 includes a structural anomaly 23. Figure 2B shows how the emitted light 22 interacts with the structural anomaly. At the biofilm-tooth surface interface 25 at the location of the structural anomaly 23, a portion 22d of the emitted light 22 is scattered away from the structural anomaly and irradiates the light detection 12 at multiple different positions. Similar to above, the properties of the anomaly can be determined by analyzing the first reflection data. For example, the detection pattern of the scattered light 22d (e.g., the position of the scattered light irradiating the light detector 12 and / or the electromagnetic intensity at each position on the detector) can be used to determine the properties of the anomaly, such as its size and / or topology. It is noted that outside the location of the anomaly 23, the light interacts with the biofilm-enamel interface 25 and the enamel-dentin interface 26 in the manner Figure 2A shown. However, for clarity, the portions of the light 22b and 22c reflected from the enamel layer 18 and the dentin layer 17 respectively are omitted in Fig. 2b. For clarity, the light propagating through the enamel layer 18 is also not shown in Figure 2B .

[0074] Next, with reference to Figures 3A-3B the experimental setup 100 shown, the simulated performance of the device 10 in the second (dry) mode is discussed. Figure 1 The experimental setup of Figures 3A-3B is the same as that of Figures 2A-2B . In the example of Figures 3A-3B , the environment 20 is air with a refractive index of approximately 1.00. The enamel layer 18 is not interrupted by any structural anomalies and provides the tooth surface. In use, the light source 11 emits light 22 from the visible or near-infrared portion of the electromagnetic spectrum to irradiate the biofilm 19 and the tooth surface. Since the refractive indices of air (approximately 1.00) and the biofilm (approximately 1.33) differ significantly, the emitted light 22 is reflected and refracted at the environment-biofilm interface 24.

[0075] Figure 3A and 3B show different aspects of the interaction of the emitted light 22 with the multi-layer stack including the environment 20, the biofilm layer 19, the enamel layer 18, and the dentin layer 17. Specifically,Figure 3A shows light interacting with the environment-biofilm interface 24 and the biofilm-tooth surface interface 25, while Figure 3B shows light interacting with the bacteria 21 within the biofilm 19.

[0076] Reference Figure 3A , a portion 22a of the emitted light 22 is reflected at the environment-biofilm interface 24 and irradiates the light detector 12. A portion 22b of the remaining light refracts and propagates through the biofilm 19, reaching the biofilm-tooth surface interface 25, where some is reflected by refraction at the biofilm-environment interface 24 and propagates to the light detector 12. Some of the emitted light 22 may refract at the biofilm-tooth surface interface 25 and / or the enamel-dentin interface 26. However, for simplicity, this is not shown in Figures 3A-3B . The light detector 12 detects the reflected portions of the light 22a, 22b and generates second (dry) reflection data. Similarly to above, by calculating the distance between the positions on the light detector 12 where the two portions of light 22a, 22b have been detected, and by using the laws of geometric optics and trigonometric formulas, the thickness of the biofilm layer 19 can be determined.

[0077] Reference Figure 3B , a portion of the emitted light 22 refracts at the environment-biofilm interface 24 and propagates through the biofilm layer 19. As the light propagates through the biofilm, the light interacts with the bacteria 21 within the biofilm 19 and scatters from them. Then, multiple scattered portions of the light 22e are detected by the light detector 12, thereby forming a scattering pattern (e.g., in the form of 2D coordinates of the light irradiating the light detector and / or the electromagnetic intensity at the position where the light is detected) recorded in the second (dry) reflection data. From such a pattern in the second reflection data, properties of the biofilm can be inferred, including bacterial density, bacterial activity, and bacterial type. This is because the scattering pattern will reveal the shape and size as well as the number of bacteria that scatter the light, which can be correlated with the type and density of the bacteria. The more bacteria 21 there are in the biofilm 19, the more light will be scattered when passing through the biofilm, which will be detected by the light detector 12.

[0078] Next, with reference to Figure 4 is described a method of detecting a bacterial biofilm on a tooth surface using the Figure 1 device. In a first step S1, the immersion sensor 13 determines whether the device 10 is operating in a first (wet) mode or a second (dry) mode. Next, in S2, the light source 11 irradiates the tooth surface. Then, the light detector 12 detects the light reflected by the biofilm and / or the tooth surface to generate first / second reflection data in S3. In S4 and S5, the processor 14 separates the bacterial reflection data that only indicates the light interaction with the bacterial biofilm by interpreting the second reflection data using the first reflection data as reference data, thereby detecting the bacterial biofilm.

[0079] The method may include a plurality of optional steps. Some or all of these steps may be performed by the processor 14. First, after determining that the device 10 is operating in the wet mode (S1), the method may include one or more calibration steps (not shown). The calibration step(s) may be used to calibrate the optical interaction (reflection / refraction) of the transmissive housing of the sealed light source 11 and the light detector 12. This is to ensure that the (first / second / bacterial) reflection data does not include the effects due to the interaction of light with the housing, which would reduce the quality of the reflection data and thus the accuracy of the method.

[0080] The method may further include the optional step S6: analyzing the bacterial reflection data to determine the properties of the detected biofilm, such as the microbial density / microbial activity, microbial type, and / or thickness of the bacterial biofilm on the tooth surface. For example, such properties may be determined in the manner described in Figure 3B the reference.

[0081] Similarly, the properties of the tooth structure, such as the enamel thickness and / or the size / topology of structural abnormalities on the tooth surface, may be determined by analyzing the first (wet) reflection data. For example, this may be achieved in the manner described in Figure 2B the reference.

[0082] The features disclosed in the foregoing description, or in the following claims, or in the drawings, expressed in their specific forms or in terms of means for performing the disclosed functions, or in terms of methods or processes for obtaining the disclosed results, may, where appropriate, be used alone or in any combination of these features to implement the invention in its different forms.

[0083] Although the invention has been described in connection with the above exemplary embodiments, many equivalent modifications and variations will be apparent to those skilled in the art when the present disclosure is given. Therefore, the above exemplary embodiments of the invention are considered illustrative and not restrictive. Various changes may be made to the described embodiments without departing from the spirit and scope of the invention.

[0084] For the avoidance of any doubt, any theoretical explanations provided herein are for the purpose of enhancing the reader's understanding. The inventors do not wish to be bound by any of these theoretical explanations.

[0085] Any section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described.

[0086] Throughout the specification, including the claims which follow, unless the context requires otherwise, the words "comprise" and "include" and variations thereof will be understood to imply the inclusion of stated integers or steps or groups of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0087] It must be noted that, as used in the specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another embodiment includes from one particular value and / or to another particular value. Similarly, when values are expressed as approximations by use of the antecedent "about", it will be understood that the particular value forms another embodiment. The term "about" associated with a numerical value is optional and means, for example, + / - 10%.

Claims

1. An apparatus for detecting bacterial biofilms on tooth surfaces, the apparatus comprising: A light source for irradiating a tooth surface having a bacterial biofilm thereon, the light source being operable in a first mode and a second mode different from the first mode; A sensor for determining whether the apparatus is operating in the first mode or the second mode; A light detector for detecting light reflected by the tooth surface and / or the bacterial biofilm in the first mode and in the second mode to respectively generate first reflection data and second reflection data; And Wherein the apparatus is configured to interpret the second reflection data by using the first reflection data as reference data to isolate bacterial reflection data that only indicates light interaction with the bacterial biofilm, thereby detecting the bacterial biofilm.

2. The device according to claim 1, wherein, The first mode is a wet mode, the second mode is a dry mode, and the sensor for determining whether the apparatus is operating in the first mode or the second mode is an immersion sensor.

3. The device according to claim 2, wherein The immersion sensor is based on an optical sensor or an electrical sensor.

4. The apparatus according to any one of the preceding claims, wherein, The light source is configured to irradiate the tooth surface with light from the visible or near-infrared portion of the electromagnetic spectrum.

5. The apparatus according to any one of the preceding claims, wherein, The light source is a laser diode.

6. The device according to any one of the preceding claims, wherein The light detector is a two-dimensional 2D light detector.

7. The apparatus according to any one of the preceding claims, wherein, The light detector is based on a CCD imaging sensor or a CMOS imaging sensor.

8. The apparatus according to any one of the preceding claims, further comprising a processor communicatively connected to: The light detector to receive reflection data therefrom; and The sensor to determine whether the received reflection data is first reflection data or second reflection data; Among them, The processor is configured to interpret the second reflection data by using the first reflection data as reference data to isolate the bacterial reflection data.

9. The apparatus according to claim 8, wherein The processor is further configured to analyze the bacterial reflection data to determine the properties of the detected bacterial biofilm.

10. A head for an electric toothbrush, the head comprising the apparatus according to any one of the preceding claims.

11. An electric toothbrush, comprising: A head and a body portion; And The apparatus according to any one of claims 1 to 9.

12. The electric toothbrush according to claim 11, wherein, The light source, the light detector, and the sensor of the apparatus are provided in the head of the electric toothbrush.

13. A method for detecting bacterial biofilms on tooth surfaces using the apparatus according to any one of claims 1 to 9, the method comprising: Determining whether the apparatus is operating in the first mode or the second mode; Irradiating the tooth surface with light from the light source; Detecting light reflected by the biofilm and / or the tooth surface to generate first / second reflection data; Detecting the bacterial biofilm by interpreting the second reflection data by using the first reflection data as reference data to isolate bacterial reflection data that only indicates light interaction with the bacterial biofilm.

14. The method according to claim 13, further comprising the step of analyzing the bacterial reflection data to determine the properties of the detected bacterial biofilm.

15. The method according to claim 13 or 14, comprising one or more calibration steps after determining that the apparatus is operating in the first mode.

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