Method for detecting demineralization of tooth structure
The optical method using structured light patterns addresses the challenge of standardizing and quantifying tooth demineralization by measuring light intensity and phase shifts, enabling accurate and sensitive early caries detection.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- IVOCLAR VIVADENT AG
- Filing Date
- 2022-04-23
- Publication Date
- 2026-06-05
AI Technical Summary
Current dental caries diagnosis methods, such as visual inspection and X-rays, lack standardization and cannot objectively quantify early tooth demineralization or tooth discoloration.
An optical method using structured light patterns to detect demineralization by measuring light intensity and phase shifts, enabling early imaging and quantification of morphological and chemical changes in tooth structure.
The method provides objective, quantifiable, and highly sensitive detection of demineralization, allowing for early caries diagnosis with depth sensitivity and standardizable data comparison.
Smart Images
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Abstract
Description
[Technical Field]
[0001] This invention relates to an optical method for detecting demineralization of tooth structure and a dental device for detecting demineralization of tooth structure. [Background technology]
[0002] Currently, dental caries is diagnosed purely visually, or using technical aids such as X-rays or autofluorescence of carious lesions. Visual diagnosis of caries depends on the experience of the treating dentist, making it unsuitable for standardization or qualitative stability, and it cannot be objectively quantified. Furthermore, it is impossible to quantitatively detect tooth discoloration at an early stage using these methods. [Overview of the Initiative] [Problems that the invention aims to solve]
[0003] Therefore, the technical problem of the present invention is to determine the area of tooth structure that corresponds to demineralization, which can occur during caries symptoms. [Means for solving the problem]
[0004] The aforementioned problems are solved by the subject matter of the independent claims. Technically preferred embodiments are the subject matter of the dependent claims, the detailed description of the invention, and the accompanying drawings.
[0005] According to a first aspect of the present invention, the above technical problems are solved by a method for detecting demineralization of tooth structure, comprising the steps of: irradiating tooth structure with a structured light pattern; detecting the light intensity and / or amplitude of the light pattern emitted from the volume of tooth structure; detecting the light intensity of the light pattern emitted from the volume of tooth structure; and determining demineralization of tooth structure based on the detected light intensity. This method makes it possible to achieve early imaging of morphological or chemical changes within tooth structure. Additionally, demodulation of the amplitude and / or phase of the intensity can be performed. In this method, the light intensity reflected from the tooth surface can also be detected. This method makes demineralization objective and quantifiable, achieving early detection and high sensitivity. In addition, depth sensitivity is achieved, thereby enabling the determination of demineralization within the volume of tooth structure. Comparability and standardization of the obtained datasets make it possible to quantify the diagnosis of early caries. This can be recorded in an objective manner.
[0006] In a technically preferred embodiment of this method, the fluorescence transition of the emitted light intensity and / or the elastic dispersion of the emitted light intensity are detected. The fluorescence transition of the reflected light intensity and / or the elastic dispersion of the reflected light intensity can also be detected. This achieves a technical advantage, for example, that demineralization can be determined with high accuracy.
[0007] In another preferred embodiment of this method, the irradiated structured light pattern has a stripe pattern, a dot pattern, a grid pattern, and / or a periodic structure. This achieves the technical advantage of enabling, for example, rapid and accurate detection of changes within tooth structure.
[0008] In another technically preferred embodiment of this method, multiple structured light patterns having different spatial frequencies are irradiated onto the tooth structure. This achieves the technical advantage that, by optimizing the spatial frequency of the incident light patterns, such as sinusoidal patterns, the sensitivity of the depth region to be measured is maximized, and depth resolution is performed.
[0009] In another technically preferred embodiment of this method, multiple structured light patterns, each having a different wavelength, are irradiated onto the tooth structure. This achieves the technical advantage of being able to obtain data on demineralization from different depths of tooth structure, and to additionally determine information regarding shape.
[0010] In another technically preferred embodiment of this method, tooth demineralization is also determined based on the phase shift between the irradiated light pattern and the emitted light pattern. Tooth demineralization can also be determined based on the phase shift between the irradiated light pattern and the reflected light pattern. This achieves the technical advantage of being able to determine demineralization more accurately, for example.
[0011] In another technically preferred embodiment of this method, the amplitude and phase shift of the intensity are spatially resolved and determined over a single surface region, and demineralization is spatially resolved and quantified or determined based on the said surface region. This achieves the technical advantage of being able to determine demineralization more accurately, for example, over the surface of tooth structure.
[0012] In another technically preferred embodiment of this method, demineralization and its layer thickness are determined using a model based on the detected light intensity. Demineralization or layer thickness can be determined using a model based on the detected light intensity, and further, for example, using analytical equations of the radiative transfer principle for layered geometry. This achieves the technical advantage of obtaining quantitative and therefore comparable numerical values for characterizing demineralization.
[0013] In another technically preferred embodiment of this method, the angle between the direction in which the light pattern is irradiated and the direction in which the light intensity of the light pattern is measured is from 0° to 45°. Thereby, for example, a technical advantage is achieved in that surface reflection can be prevented or reduced and demineralization can be detected extremely well.
[0014] In another technically preferred embodiment of this method, the spatial geometry of the dentin is additionally determined based on the reflected and / or emitted light pattern. Thereby, for example, a technical advantage is achieved in that the shape of the tooth or dentin can be additionally measured.
[0015] In another technically preferred embodiment of this method, the spatial geometry of the dentin is determined using a model from a plurality of reflected and / or emitted light patterns having different spatial frequencies. The determined spatial geometry can be used to more accurately quantify the demineralization of the dentin. Thereby, for example, a technical advantage is achieved in that the measurement accuracy of the spatial shape is increased.
[0016] According to a second aspect, there is provided a dental device for detecting demineralization of dentin, comprising: a projection device that irradiates a structured light pattern onto the dentin; a detection device that detects the light intensity and / or the amplitude of the intensity of the light pattern emitted from the volume of the dentin; and a determination device that determines the demineralization of the dentin based on the detected light intensity. Additionally, the detection device can be configured to detect the light intensity of the light pattern reflected from the surface.
[0017] In a technically preferred embodiment of this dental device, the projection device comprises a digital projector having a radiation source of multiple spectra. Thereby, for example, a technical advantage is achieved in that light patterns having different structures or light patterns of different wavelengths having spatially resolved and arbitrarily changeable light intensities can be irradiated.
[0018] In another technically preferred embodiment of this dental device, the detection device comprises an electronic camera. By doing so, for example, a technical advantage of being able to digitally detect an optical pattern quickly and effectively is achieved.
[0019] In another technically preferred embodiment of this dental device, the determination device is configured to determine the spatial geometry of dentin based on the emitted and / or reflected optical pattern. By doing so, for example, a technical advantage of additionally being able to detect the spatial shape of a tooth or dentin is achieved.
Brief Description of the Drawings
[0020] [Figure 1] It is an explanatory diagram schematically showing a dental device. [Figure 2] It is an explanatory diagram schematically showing different optical patterns and phase shifts when incident on dentin. [Figure 3] It is an explanatory diagram showing variously simulated cross-sectional states when different optical patterns are incident on dentin. [Figure 4] It is a block diagram of a method for detecting demineralization of dentin.
Embodiments for Carrying Out the Invention
[0021] In FIG. 1, a dental device 100 is schematically shown. The dental device 100 functions to detect demineralization of the dentin 101 of a tooth. The dental device 100 includes a projection device 109 that irradiates the dentin 101 with a structured optical pattern 103. The projection device 109 is constituted by, for example, a liquid crystal projector or a DLP projector (Digital Light Processing) equipped with a digital micromirror device (DMD).
[0022] Therefore, with an appropriate optical system and light source, a light pattern of any color and structure can be projected onto the tooth structure 101, for example, as a stripe pattern, a dot pattern, or a grid pattern. The light pattern 103 can have a variable periodic structure. However, other light patterns 103 that are generally appropriately structured can also be used.
[0023] In addition, the light pattern can be changed, and therefore multiple structured light patterns having different spatial frequencies or different wavelengths can be irradiated onto the tooth structure 101 in sequence. The reliability of this method can be increased by irradiating with multiple spectra. Since the magnitude of structural changes in the tooth structure 101 is initially small in early caries, it is preferable to use a small wavelength, i.e., blue light, to achieve the highest possible sensitivity.
[0024] The structured light pattern 103 collides with the tooth structure 101 in the oral cavity, penetrates into the tooth structure 101, and is emitted from the volume of the tooth structure 101. In this case, unlike directional reflection which satisfies the laws of reflection, it involves scattering (omnidirectional) light reflection. It is also possible that a portion of the light pattern 103 is reflected by the surface of the tooth structure 101.
[0025] During emission, elastic dispersion of the irradiated light pattern 103 is possible, in which case the wavelength of the light is maintained without change, or fluorescence emission occurs in which the wavelength of the light pattern 103 changes due to fluorescence transitions within the tooth structure 101. Fluorescence is the instantaneous emission of light immediately after the tooth structure is excited by light. In this case, the emitted photons are usually of lower energy than those absorbed beforehand. Therefore, in this case, inelastic dispersion is involved.
[0026] The optical detection device 111 operates to detect the light intensity of a light pattern 103 emitted from or reflected from the volume of tooth structure 101. The detection device 111 includes, for example, a digital camera having a CCD array or a CMOS array, and can acquire an image of the illuminated light pattern 103 by the digital camera. The optical detection device 111 generates a dataset that reproduces the light pattern emitted and / or reflected from tooth structure 101. Depending on the spatial frequency and the number of light wavelengths used, the measurement can be performed for, for example, several hundred ms. The angle between the direction 107-1 from which the light pattern 103 is illuminated and the direction 107-2 from which the light intensity of the light pattern 103 is measured can be, for example, 0° to 45°.
[0027] Within the detection device 111, fluorescence is detected by a CCD or CMOS camera, for example, by using a filter that suppresses elastic dispersion. In this case, spatially resolved and depth-selected fluorescence measurements can be performed in the volume of tooth structure, such as in the distribution of porphyrins, which enables additional characterization of early caries. In this case, for example, a light pattern having blue or red light is irradiated, and the backscattered radiation is measured in the red or infrared region.
[0028] The determination device 113, which has an electronic circuit, operates to determine the demineralization of tooth structure 101 based on the measured light intensity. Therefore, the determination device 113 includes, for example, a digital processor and digital memory such as random access memory (RAM). These allow it to process the dataset using an algorithm. By having the light pattern 103 penetrate the volume of tooth structure 101, it is possible to detect the characteristics of that volume, such as demineralization in the case of caries. To this end, the determination device 113 compares the intensity (amplitude of intensity), wavelength shift (fluorescence), or spatial phase shift of the emitted light pattern with the irradiated light pattern 103 for determination. If these values differ from those obtained for healthy tooth structure 101, demineralization can be concluded.
[0029] Figure 2 shows different light patterns 103-1,...103-3 and their respective phase shifts when entering the dentin 101. In the case of the uniform light pattern 105, since there is no reference structure, the phase shift is not detected.
[0030] The light pattern 103-1 is a first light pattern having a first spatial frequency F sfd , sfd , ,
[0033] , sfd , , sfd , , sfd , sfd , sfd , , ,
[0032] , sfd , sfd This light pattern is irradiated onto the dentin 101. The emitted light pattern 103-1 has a specific phase shift φ and an amplitude R of the changed intensity with respect to the irradiated light pattern sfd having.
[0031] The light pattern 103-2 is a second light pattern having a second spatial frequency F sfd higher than sfd This light pattern 103-2 also has a specific phase shift φ and an amplitude R of the changed intensity with respect to the irradiated light pattern sfd having.
[0032] The light pattern 103-3 is a third light pattern having a third spatial frequency F sfd higher than the first and second spatial frequencies F sfd This light pattern 103-3 also has a specific phase shift φ and an amplitude R of the changed intensity with respect to the irradiated light pattern sfd having. In the illustrated embodiment, as the spatial frequency F sfd of the light pattern 103 increases, the amplitude R sfd of the intensity decreases, and the phase shift φ increases as the spatial frequency F sfd of the light pattern 103 increases.
[0033] According to the degree of demineralization of the dentin, different values are measured for the phase shift φ and the amplitude R sfd of the intensity with respect to the spatial frequency F sfd If those values are different from the reference values obtained for healthy dentin 101, demineralization and lesions of the dentin 101 can be concluded.
[0034] Figure 3 shows different cross-sectional states when different light patterns 103 enter a modeled lesion within tooth structure 101. Signals are illustrated for different depths of tooth structure 101.
[0035] Measurement of emitted light in structured irradiation allows for the measurement of the amplitude R of the emitted intensity. sfd This enables spatially resolved determination of the phase shift φ. The amplitude R of the emitted intensity. sfd And the phase shift φ is generally related to the optical characteristics of a lesion, the absorption coefficient μ a , scattering coefficient μ s , influenced by the scattering phase function and refractive index n, particularly the optical transmission thickness μ s Affected by '*d, at which time μ s ' represents the effective scattering coefficient, and d represents the thickness of the lesion.
[0036] In the case of lesions with a greater thickness d, the spatial frequency F sfd Amplitude R of the emitted intensity sfd Another curve with a phase shift φ is shown. The light propagation of tooth structure 101 is similar to the optical properties of tooth structure 101 (absorption coefficient μ). a , scattering coefficient μ s It depends on the scattering phase function and refractive index. Scattering coefficient μ s This is increased compared to healthy enamel through initial demineralization. Thickness can be determined by modeling light propagation based on the radiative transfer equation for multilayer media.
[0037] Quantitative and spatially resolved measurements of the amplitude and phase shift of emitted and reflected intensities in the spatial frequency domain, using a model based on a solution of the radiative transfer principle, for example, the effective scattering coefficient μ s ' and absorption coefficient μ a Important numerical values related to light propagation, such as the effective scattering coefficient μ, can be determined. s ' correlates with the degree of demineralization, and the absorption coefficient μ a This correlates with tooth discoloration. Both parameters can be measured and recorded using this method.
[0038] Figure 4 shows a block diagram of a method for detecting demineralization of tooth structure 101. In step S101, a structured light pattern 103 is irradiated onto the tooth structure 101. In step S102, the light intensity of the light pattern 103 emitted from the volume of tooth structure 101 is detected. In step S103, demineralization of tooth structure 101 is determined based on the detected light intensity. Therefore, a comparison is performed between the emitted light intensity and a reference value. In addition to light intensity, the phase shift φ between the irradiated light pattern and the emitted light pattern can be determined. In this case as well, a comparison can be performed between the phase shift φ and a reference value.
[0039] This method enables highly sensitive, objective, and quantitative measurement of the degree of (de)mineralization of tooth structure 101 in three dimensions. Therefore, the method is extended, for example, to obtain information from the depth (volume) of tooth structure 101, using a stripe ray method (structured illumination image). In this case, a monochromatic, structured light pattern, for example, in the blue spectral region, can be used to illuminate the tooth structure 101, for example, using sinusoidal wave patterns of different spatial frequencies.
[0040] Light emitted from the volume of tooth structure 101 or reflected from its surface is captured by a camera. Amplitude and phase shift can be calculated from the dataset using an appropriate algorithm, for example, by N-phase projection or Fourier-based demodulation. Based on the calibration of the camera beam combined with phase encoding by active illumination, tooth topography can be calculated from the camera image (three-dimensional scan). In addition, volumetric intensity calibration can be performed using the reconstructed three-dimensional tooth topography, and thus a quantifiable amplitude diagram can be formed in addition to the previously used phase diagram. Therefore, the amplitude of emitted and reflected intensity can be determined at any image point depending on the irradiated spatial frequency, i.e., the stripe frequency. This corresponds to the optical transfer function of tooth structure 101, which depends on the microstructure. The microstructure causes light scattering and discoloration of tooth structure 101 in addition to the color base. As tooth structure 101 becomes more porous during caries, this can be demonstrated by changes in light scattering. Changes and depths of microstructure can be quantified using a model based on the optical transfer function.
[0041] Demineralization determination based on the aforementioned dataset can be performed using a model, based on an AI-driven method, or based on a multivariate classification method. For this method, calculations of optical transfer functions using the model are performed to create a classification index. This method allows for quantifiable measurements of the amplitude of emitted intensity and reflections on any geometry of the tooth structure 101.
[0042] All features described and illustrated in relation to individual embodiments of the present invention can be applied to the present invention in various combinations, thereby achieving effective advantages simultaneously.
[0043] All method steps can be performed using apparatus suitable for carrying out each method step. All functions performed by the feature in question can be method steps in this method.
[0044] The scope of protection of this invention is defined by the appended claims and is not limited by the features described or illustrated in this description. [Explanation of Symbols]
[0045] 100 dental devices 101 Tooth structure 103 Light Patterns 105 Uniform irradiation 107 directions 109 Projection device 111 Detection device 113 Judgment device
Claims
1. A method for detecting demineralization of tooth structure (101), comprising the steps of: irradiating tooth structure (101) with a structured light pattern (103) (S101); detecting the light intensity and / or amplitude of intensity (Rsfd) of the light pattern (103) emitted from the volume of tooth structure (101) (S102); determining the demineralization of tooth structure (101) based on the detected light intensity (S103); and further determining the demineralization by the phase shift (φsfd) between the irradiated light pattern (103) and the reflected light pattern (103).
2. The method according to claim 1, which detects the fluorescence transition of emitted light intensity and / or the elastic dispersion of emitted light intensity.
3. The method according to claim 1 or 2, wherein the irradiated structured light pattern is a stripe pattern, a dot pattern, a grid pattern, and / or a periodic structure.
4. The method according to claim 3, wherein multiple structured light patterns having different spatial frequencies are irradiated onto tooth structure (101).
5. The method according to claim 4, wherein multiple structured light patterns, each having a different wavelength of light, are irradiated onto tooth structure (101).
6. The method according to claim 1, wherein the amplitude of intensity (Rsfd) and the phase shift (φsfd) are spatially resolved and determined over a single surface region, and demineralization is spatially resolved and quantified, or determined based on the said surface region.
7. The method according to claim 6, wherein demineralization and its layer thickness are determined using a model based on the detected light intensity.
8. The method according to claim 1, wherein the angle between the direction (107-1) in which the light pattern (103) is irradiated and the direction (107-2) in which the light intensity of the light pattern is measured is 0° to 45°.
9. The method according to claim 8, wherein the spatial geometry of the tooth structure (101) is further determined based on the reflected and / or emitted light pattern (103).
10. The method according to claim 1, wherein the spatial geometry of tooth structure (101) is determined using a model from a plurality of reflected and / or emitted light patterns (103) each having a different spatial frequency.
11. A dental device (100) for detecting the demineralization of tooth structure (101), comprising: a projection device (109) that irradiates the tooth structure (101) with a structured light pattern (103); a detection device (111) that detects the light intensity and / or amplitude of intensity (Rsfd) of the light pattern (103) emitted from the volume of tooth structure (101); a determination device (113) that determines the demineralization of the tooth structure (101) based on the detected light intensity; and a device that further determines the demineralization by the phase shift (φsfd) between the irradiated light pattern (103) and the reflected light pattern (103).
12. The dental apparatus (100) according to claim 11, wherein the projection device (109) comprises a digital projector having multiple spectral radiation sources.
13. The dental apparatus (100) according to claim 11 or 12, wherein the detection device (111) is equipped with an electronic camera.
14. The dental device (100) according to claim 11, wherein the determination device (113) is configured to determine the spatial geometry of tooth structure (101) based on the emitted and / or reflected light pattern (103).