Optical caries diagnostic device and method of operating the optical caries diagnostic device

Abstract

To provide an optical caries diagnostic instrument and optical caries diagnostic method capable of quantitatively acquiring hardness of teeth by a single device for quantitatively diagnosing a progression degree of the caries, and a caries diagnostic system including them.SOLUTION: An optical caries diagnostic instrument includes an indenter having optical transparency and a tapered shape and coming into contact with an object, a light source for emitting light to the indenter, a light receiving element for receiving the light reflected from a tip of the indenter, and a lens disposed at such a position that the tip of the indenter and a light receiving surface of the light receiving element have an imaging relation to each other. The wavelength of the light emitted from the light source is 500 nm or less and an incident angle of the light emitted from the light source entering the tip of the indenter is 70° or less.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an optical caries diagnostic device and an optical caries diagnostic method capable of diagnosing caries, and a caries diagnostic system including them. [Background technology]

[0002] Dental health has a large impact on overall health, and caries prevention and appropriate treatment are social requirements. It is known that there is a strong correlation between the number of remaining teeth and the onset of dementia, particularly in the elderly, and maintaining dental health is said to be effective in preventing dementia. If the onset of dementia can be reduced through caries prevention and appropriate treatment, it is expected that nursing care costs will be significantly reduced.

[0003] When dental hard tissues (enamel, dentin) are affected by caries, they are demineralized and defects occur. Mild cases, such as white spots on the enamel, are monitored over time, but as the condition progresses, it becomes necessary to remove the affected parts. In conventional caries diagnosis and treatment, the distinction between caries and sound teeth and the selection of treatment methods are currently dependent on the senses of dental caregivers. For example, the distinction between caries and sound teeth is performed using dental probes and staining solutions, relying on the senses of dental caregivers, and is not based on quantitative indicators. In addition, the selection of caries to be removed is largely dependent on the senses of the dental caregivers' fingers. As a result, there are many cases where teeth that do not actually need to be removed are removed, and there is a demand for technology that can diagnose the extent of caries progression without being influenced by the experience of dental caregivers.

[0004] In addition, to halt the progression of dental caries, medications such as fluoride are applied, but it is necessary to accurately know the extent of dental caries progression in order to quantitatively evaluate the degree of dental caries progression and apply the optimal medication.

[0005] In particular, the incidence rate of root caries, which is caries at the root of the teeth, exceeds 50% among elderly people, but a method for quantitatively evaluating the progression of root caries has not been established. In particular, it is extremely difficult to diagnose the intermediate state between cases that should be removed and cases where preventive treatment is sufficient, so there is a need to improve the technology for diagnosing the progression of caries.

[0006] As a technique for diagnosing dental caries, dental caries diagnostic devices such as those disclosed in Patent Documents 1 and 2 are known, but it is difficult to quantitatively evaluate the degree of progression of dental caries using these devices.

[0007] In addition, in the "hardness measurement indenter and hardness measurement method using the same" disclosed in Patent Document 3, a quantitative hardness measurement is attempted, but there is a problem that multiple steps and devices are required, such as a step of applying paint to the surface of the conical indenter and a need for microscopic observation after measurement, and the measurement order is complicated.

[0008] Patent Document 4 discloses a caries diagnostic device that attempts to quantitatively diagnose caries by receiving light from a light source reflected by an indenter; however, this is only capable of obtaining information on relative tooth hardness; the specific hardness of the tooth must be correlated with another index such as Knoop hardness, and it is not possible to obtain quantitative tooth hardness using a single device. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2008-29412 A [Patent Document 2] JP 2010-252911 A [Patent Document 3] JP 2011-112629 A [Patent Document 4] International Publication No. 2020 / 080219 Brochure Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the above, and an object of the present invention is to provide an optical caries diagnostic device and an optical caries diagnostic method that can quantitatively obtain tooth hardness using a single device in order to quantitatively diagnose the degree of caries progression, as well as a caries diagnostic system including them. [Means for solving the problem]

[0011] The optical caries diagnostic device according to the embodiment of the present invention has a light-transmitting and tapered shape, and includes an indenter that contacts an object, a light source that emits light to the indenter, a light-receiving element that receives light reflected from the tip of the indenter, and a lens that is positioned so that the tip of the indenter and the light-receiving surface of the light-receiving element are in an image-forming relationship with each other, and the wavelength of the light emitted from the light source is 500 nm or less, and the angle of incidence of the light emitted from the light source on the tip of the indenter is 70° or less. With this configuration, the optical caries diagnostic device according to the embodiment of the present invention can quantitatively obtain tooth hardness with one device by comparing a light-receiving image obtained by contacting the indenter with a metal hardness standard piece with a light-receiving image obtained by contacting the indenter with a tooth.

[0012] The light receiving element preferably includes unit cells arranged two-dimensionally.

[0013] It is preferable to have a beam splitter disposed on the optical path between the indenter and the light source and on the optical path between the indenter and the light receiving element.

[0014] It is preferable that the apparatus further includes a pressure sensor, and that the light receiving element captures an image when the pressure with which the indenter contacts the object reaches a predetermined value.

[0015] It is preferable to obtain a differential intensity image by subtracting the light receiving intensity of the light receiving element when the tip of the indenter is in contact with the object from the light receiving intensity of the light receiving element when the tip of the indenter is not in contact with anything (non-contact). In this case, it is preferable to binarize the differential intensity image using a predetermined value as a threshold. Furthermore, in this case, it is preferable to issue an error signal when the ratio of the length of the major axis to the length of the minor axis of the outline of the differential intensity image obtained by binarization ((length of major axis) / (length of minor axis)) is equal to or greater than a predetermined value.

[0016] When binarizing, it is preferable to obtain the area of ​​the region exceeding the threshold value.

[0017] It is preferable that the indenter further has a housing, and the indenter is detachable from the housing.

[0018] An optical caries diagnosis method according to an embodiment of the present invention includes the steps of preparing the optical caries diagnostic device described above, contacting the tip of an indenter with an object having a known hardness, receiving light emitted from a light source and reflected from the tip of the indenter with a light receiving element while the tip of the indenter is in contact with the object having a known hardness to obtain a first captured image, contacting the tip of the indenter with the tooth to be diagnosed, receiving light emitted from a light source and reflected from the tip of the indenter with a light receiving element while the tip of the indenter is in contact with the tooth to be diagnosed to obtain a second captured image, and comparing the first captured image with the second captured image to determine the hardness of the tooth to be diagnosed from the hardness of the object having a known hardness.

[0019] It is preferable that the method further comprises a step of receiving light emitted from a light source and reflected from the tip of the indenter with a light receiving element and capturing an image in a state where the tip of the indenter is not in contact with anything (non-contact).

[0020] A caries diagnosis system according to an embodiment of the present invention includes the optical caries diagnostic meter described above, and has an information terminal device connected via a wired or wireless connection, and optical caries diagnosis information (measured by the optical caries diagnostic meter described above) stored in the information terminal device.

[0021] It is preferable that the information terminal device further stores caries diagnosis information measured by a device other than the optical caries diagnostic device. Effect of the Invention

[0022] According to the optical caries diagnostic device and optical caries diagnostic method of the present invention, and the caries diagnostic system including them, tooth hardness can be quantitatively measured by one device, and the degree of caries progression can be quantitatively diagnosed. By using the optical caries diagnostic device of the present invention, tooth hardness can be measured in a minimally invasive manner that places less strain on the patient. [Brief description of the drawings]

[0023] [Figure 1] 1 is a graph showing the relationship between the wavelength of incident light and the reflectance from the tip of an indenter when the indenter is in contact with a gold reference piece. [Diagram 2] 1 is a graph showing the relationship between the wavelength of incident light and the reflectance from the tip of an indenter when the indenter is in contact with a copper reference piece. [Diagram 3] 1 is a graph showing the relationship between the wavelength of incident light and the reflectance from the tip of an indenter when the indenter is in contact with a brass reference piece. [Figure 4] 1 is a graph showing the relationship between the angle of incidence and the reflectance from the tip of an indenter when the indenter is placed in contact with a gold reference piece and light with a wavelength of 625 nm is incident on the indenter. [Diagram 5] 1 is a graph showing the relationship between the angle of incidence and the reflectance from the tip of an indenter when the indenter is placed in contact with a gold reference piece and light with a wavelength of 455 nm is incident on the indenter. [Figure 6] 1 is a cross-sectional view of an indenter according to an embodiment of the present invention when the indenter contacts an object. [Figure 7] 1 is a cross-sectional view of an optical caries diagnostic device according to one embodiment of the present invention. [Figure 8] FIG. 2 illustrates a side view of an indenter according to an embodiment of the present invention. [Figure 9] 9 shows a plan view seen from the opposite side to the tip of the indenter shown in FIG. 8. [Figure 10]FIG. 4 illustrates a side view of an indenter according to another embodiment of the present invention. [Figure 11] 13 is a graph showing the relationship between time and contact pressure. [Figure 12] 8 illustrates another cross-sectional view of the optical caries diagnostic device shown in FIG. 7. [Figure 13] This is an image of reflected light from the tip of the indenter when the tip of the indenter is not in contact with anything (non-contact). [Figure 14] 13 is a captured image of light reflected from the tip of the indenter when the tip of the indenter is in contact with an object. [Figure 15] 15 is a difference intensity image obtained by subtracting the captured image shown in FIG. 14 from the captured image shown in FIG. [Figure 16] 16 is a binarized difference intensity image obtained by binarizing the difference intensity image shown in FIG. 15. [Figure 17] 1 is a schematic diagram showing the tip of an indenter perpendicularly contacting an object. [Figure 18] 1 is a schematic diagram showing a state where the tip of an indenter comes into contact with an object in a non-perpendicular manner. [Figure 19] 1 shows a captured image obtained in Example 1. [Figure 20] 1 is a captured image obtained in Comparative Example 1. [Figure 21] 11 is a captured image obtained in Example 2. [Figure 22] 13 is a captured image obtained in Comparative Example 2. [Diagram 23] 11 is a captured image obtained in Example 3. [Figure 24] 13 is a captured image obtained in Comparative Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The present invention will be described in more detail below based on the embodiments, but the present invention is not limited to the following embodiments, and can be modified as long as it satisfies the purpose described above and below, and all of these are included in the technical scope of the present invention. For convenience, hatching and component symbols may be omitted, but in such cases, the specification and other drawings should be referred to. Also, the dimensions of each component in the drawings may differ from the actual dimensions.

[0025] 1. Optical caries diagnostic device An optical caries diagnostic device according to an embodiment of the present invention has optical transparency and a tapered shape, and comprises an indenter for contacting an object, a light source for emitting light to the indenter, a light receiving element for receiving light reflected from the tip of the indenter, and a lens positioned so that the tip of the indenter and the light receiving surface of the light receiving element are in an imaging relationship with each other, wherein the wavelength of the light emitted from the light source is 500 nm or less, and the angle of incidence of the light emitted from the light source on the tip of the indenter is 70° or less.

[0026] The inventors have found that by bringing the indenter of the optical caries diagnostic device having the above-mentioned configuration into contact with a metal reference piece having a known hardness, irradiating the indenter with light, and receiving the light reflected from the tip of the indenter with a light receiving element, it is possible to obtain a received light image of the metal reference piece having a known hardness. Since it is now possible to obtain a received light image of the metal reference piece having a known hardness, it is possible to quantitatively obtain the hardness of the tooth from the hardness of the reference piece by bringing the same indenter as that brought into contact with the reference piece into contact with a tooth and similarly obtaining a received light image.

[0027] With reference to Figs. 1 to 5, a description will be given of how a light-receiving image of a metal reference piece having a known hardness can be obtained. Fig. 1 is a graph showing the relationship between the wavelength of incident light and the reflectance from the tip of an indenter when an indenter made of glass (Schott, N-BK7) is placed on a gold reference piece (Yamamoto Scientific Tool Research Co., Ltd., HMV30) and the reflectance from the tip of the indenter of light incident from a light source is measured. Fig. 2 is a graph showing the relationship between the wavelength of incident light and the reflectance from the tip of an indenter when an indenter made of glass (Schott, N-BK7) is placed on a copper reference piece (Yamamoto Scientific Tool Research Co., Ltd., HMV40) and the reflectance from the tip of the indenter of light incident from a light source is measured. Fig. 3 is a graph showing the relationship between the wavelength of incident light and the reflectance from the tip of an indenter when a glass (Schott, N-BK7) indenter is placed on a brass (70% copper, 30% zinc) standard piece (Yamamoto Scientific Tool Research Co., Ltd., HMV100) and the reflectance from the tip of the indenter of light incident from a light source is measured. Fig. 4 is a graph showing the relationship between the wavelength of incident light and the reflectance from the tip of an indenter when a glass (Schott, N-BK7) indenter is placed on a gold standard piece (Yamamoto Scientific Tool Research Co., Ltd., HMV30) and the reflectance from the tip of the indenter of light incident from a light source is measured. 625 5 is a graph showing the relationship between the angle of incidence to the tip of the indenter and the reflectance from the tip of the indenter when light of wavelength 100 nm is incident on the indenter. 455 1 is a graph showing the relationship between the angle of incidence to the tip of the indenter and the reflectance from the tip of the indenter when nm light is incident on the indenter.

[0028] 1 to 3, when the indenter is placed against gold, copper, and brass reference blocks, the reflectance decreases when the wavelength of the light incident on the indenter is 500 nm or less. Also, from Figs. 4 and 5, when light with a wavelength of 625 nm is incident on the indenter, the reflectance hardly changes in the range of incident angles from 0 to 90°, whereas when light with a wavelength of 455 nm is incident on the indenter, the reflectance changes little. Shooting It can be seen that the reflectance decreases when the incident angle is 70° or less.

[0029] As shown in Fig. 6, when the indenter 20 comes into contact with the object 100, a certain area of ​​the tip 21 of the indenter 20 comes into contact with the surface of the object 100 depending on the hardness of the object 100. This area is proportional to the hardness of the object 100, and the softer the object 100, the larger the area. When light is incident on the indenter 20 as in the case of incident light 11 in Fig. 6, even if the object 100 is a metal reference piece, the light is reflected at the portion S1 of the tip 21 of the indenter 20 that comes into contact with the surface of the object 100 with the reflectance as shown in Figs. 1 to 5, and total reflection occurs at the portion S2 of the tip 21 of the indenter 20 that does not come into contact with anything. Therefore, since the reflectance of the portion S1 of the tip 21 of the indenter 20 that comes into contact with the surface of the object 100 is low, that is, the wavelength of the light emitted from the light source 10 is 500 nm or less, and the incident angle θ at which the light is incident on the tip 21 of the indenter 20 is 100 nm or less, the reflectance of the light is 100 nm or less. i When the angle is 70° or less, it is possible to detect the contrast with the total reflection of the portion S2 of the tip 21 of the indenter 20 that is not in contact with anything, and to obtain information on the area of ​​the portion S1 of the tip 21 of the indenter 20 that is in contact with the surface of the object 100. This makes it possible to obtain the hardness of the object 100, which is proportional to this area.

[0030] Next, the same indenter 20 as that in contact with the reference piece is brought into contact with a tooth and a received image is obtained in the same manner, thereby obtaining information on the area of ​​the portion of the tip 21 of the indenter 20 in contact with the tooth surface when in contact with the tooth. Since the reference piece has a known hardness, by comparing the information on the area of ​​the indenter 20 in contact with the reference piece and the information on the area of ​​the indenter 20 in contact with the tooth, the tooth hardness can be quantitatively obtained with one device.

[0031] An optical caries diagnostic device according to one embodiment of the present invention will be described with reference to Figs. 7 to 12. Fig. 7 shows a cross-sectional view of an optical caries diagnostic device according to one embodiment of the present invention. Fig. 8 shows a side view of an indenter according to one embodiment of the present invention, and Fig. 9 shows a plan view of the indenter as viewed from the opposite side to the tip of the indenter shown in Fig. 8. Fig. 10 shows a side view of an indenter according to another embodiment of the present invention. Fig. 11 is a graph showing the relationship between time and contact pressure when an optical caries diagnostic device according to one embodiment of the present invention is contacted with an object. Fig. 12 shows another cross-sectional view of the optical caries diagnostic device shown in Fig. 7.

[0032] As shown in Fig. 7, the optical caries diagnostic device 1 according to one embodiment of the present invention has a tapered shape and is optically transparent, and includes an indenter 20 that contacts an object 100, a light source 10 that emits light to the indenter 20, a light receiving element 30 that receives light reflected from the tip 21 of the indenter 20, and a lens 40 that is disposed at a position where the tip 21 of the indenter 20 and the light receiving surface of the light receiving element 30 are in an image-forming relationship with each other, and is characterized in that the wavelength of the light emitted from the light source 10 is 500 nm or less, and the angle of incidence of the light emitted from the light source 10 on the tip 21 of the indenter 20 is 70° or less. With this configuration, the optical caries diagnostic device 1 can quantitatively obtain the hardness of a tooth with a single device by comparing a light receiving image obtained by bringing the indenter 20 into contact with a metal hardness standard piece with a light receiving image obtained by bringing the indenter 20 into contact with a tooth.

[0033] As shown in Fig. 8, tip 21 of indenter 20 is reduced in diameter so as to have a tapered shape. A preferred shape of tip 21 of indenter 20 is generally pyramidal, examples of which include the cone shown in Fig. 8 as well as a polygonal pyramid. Of these, tip 21 of indenter 20 is preferably a cone or a quadrangular pyramid. Tip 21 has apex 22. When tip 21 is a cone or a polygonal pyramid, apex 22 is the apex thereof.

[0034] As shown in FIG. 9, the shape of the surface of the indenter 20 opposite the top 22 (hereinafter sometimes referred to as the bottom surface) may be circular, or, although not shown, may be polygonal or any other shape.

[0035] As shown in Figures 8 and 9, the indenter 20 has a central axis c connecting the centroid O of the bottom surface (the center of a circle in the case of Figures 8 and 9) and the apex 22, and the tip 21 has an angle θ. The angle θ is the angle between opposing generatrix lines when the tip 21 of the indenter 20 is a cone, and is the angle between opposing faces when the tip 21 of the indenter 20 is a quadrangular pyramid. When light from the light source 10 is incident parallel to the central axis c of the indenter 20 as the incident light 11 shown in Figure 8, the angle between the incident light 11 and the generatrix line of the tip 21 is equal to θ / 2. The angle of incidence θ of the incident light 11 iis the angle between the perpendicular line p to the generating line and the incident light 11, so θ / 2 and θ i The sum of this is 90°.

[0036] The size of the bottom surface of the indenter 20 is not particularly limited as long as it can be inserted into the oral cavity without any problems and can abut against the object 100, but the diameter or major axis is preferably 3 mm or less, and more preferably 2 mm or less.

[0037] As shown in FIG. 10, the tip 21 of the indenter 20 may have a R portion that is not sharp but has a certain degree of roundness. By having the R portion, there is an advantage that the indenter 20 is less likely to break and the subject is less likely to feel pain. On the other hand, if the R portion is too rounded, it becomes difficult to abut against the object 100 or it may have a negative effect on the detection of reflected light, so the curvature radius r of the R portion may be appropriately determined so as to satisfy the above conditions. Specifically, the curvature radius r of the R portion is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 30 μm or more. In addition, the curvature radius r of the R portion is preferably 500 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less.

[0038] The indenter 20 has optical transparency. Since the indenter 20 has optical transparency, light incident from the bottom side of the indenter 20 can reach the tip 21 of the indenter 20, and light reflected at the tip 21 can pass through the indenter 20 and reach the light receiving element 30. The material for forming the indenter 20 is not particularly limited as long as it has optical transparency, and can be appropriately selected from glass, minerals, resin materials, and the like. Specifically, examples of the material include glass such as glass and organic glass; natural minerals such as sapphire and ruby; artificial minerals; and resin materials such as acrylic resin, polycarbonate resin, polyester resin, and polyvinyl chloride resin. Among these, the indenter 20 may be made of a material whose refractive index and hardness are optimal for the conditions of the object to be measured.

[0039] As shown in Fig. 7, the optical caries diagnostic device 1 according to one embodiment of the present invention has a lens 40 arranged at a position where the tip 21 of the indenter 20 and the light receiving surface of the light receiving element 30 are in an imaging relationship with each other. This makes it possible to accurately observe the difference in contrast between areas of weak and strong reflected light. Furthermore, there is an advantage that there is less variation in the calibration of the measured value compared to a method that simply measures the reflected light intensity.

[0040] The wavelength of the light emitted from the light source 10 is 500 nm or less, and the incident angle θ at which the light emitted from the light source 10 is incident on the tip 21 of the indenter 20 i is 70° or less. As a result, even if the object 100 is a metal reference piece, the reflectance of the portion where the tip 21 of the indenter 20 contacts the object 100 can be reduced, and the contrast with the total reflection of the portion where the tip 21 does not contact anything can be detected. The wavelength of the light emitted from the light source 10 is more preferably 480 nm or less, further preferably 450 nm or less, and may be 420 nm or less. The light emitted from the light source 10 is preferably 400 nm or more.

[0041] The light source 10 is not particularly limited, but may be a semiconductor laser, a light emitting diode, or the like. These are suitable because they can obtain light of a specific wavelength and are easy to separate from unnecessary light. Among them, a semiconductor laser is preferred because it has directionality.

[0042] As described above, the angle θ of the tip 21 and the angle of incidence are expressed as θ / 2+θ i = 90° and the incidence angle θ i is 70° or less, so when the shape of indenter 20 is a cone as shown in Figures 8 to 10, angle θ of tip 21 is 40° or more. The angle θ of tip 21 is more preferably 45° or more, and further preferably 48° or more. Moreover, angle θ of tip 21 is preferably 100° or less, more preferably 90° or less, and further preferably 80° or less, and may be 60° or less, or 55° or less.

[0043] Although the preferable angle θ of tip 21 has been explained above using a conical shape as an example, the same explanation can be applied to the case where tip 21 of indenter 20 has a shape other than a cone.

[0044] As shown in Fig. 7, it is preferable that the light emitted from the light source 10 enters the indenter 20 from the bottom side of the indenter 20 and reaches the tip 21 of the indenter 20 as shown by the optical path P1. It is preferable that the light that reaches the tip 21 of the indenter 20 is reflected at the tip 21 as shown by the optical path P2, passes through the lens 40 as shown by the optical path P3, and is received by the light receiving element 30. In Fig. 7, the light source 10 and the light receiving element 30 are arranged in positions where the optical path from the light source 10 to the tip 21 of the indenter 20 and the optical path from the tip 21 to the light receiving element 30 are not parallel, so the optical paths P2 and P3 that are not parallel to each other are shown. However, when the light receiving element 30 is arranged in the same direction as the light source 10 with respect to the tip 21 of the indenter 20, the optical paths P2 and P3 can be arranged in a straight line parallel to each other.

[0045] The light receiving element 30 preferably includes unit cells arranged two-dimensionally. The unit cells arranged two-dimensionally may be solid-state imaging elements (image sensors), CDC image sensors, CMOS image sensors, etc. Among them, CMOS image sensors are preferred because they are relatively inexpensive, consume little power, and are suitable for portable use.

[0046] The optical caries diagnostic instrument 1 according to the embodiment of the present invention preferably further includes a beam splitter 50 arranged on the optical path P1 between the indenter 20 and the light source 10 and on the optical path between the indenter 20 and the light receiving element 30. By arranging the beam splitter 50, it becomes possible for the optical path from the indenter 20 to the light receiving element 30 to have an optical path (optical path P3) that is not parallel to the optical path P1 from the light source 10 to the indenter 20 as shown in FIG. 7, and the degree of freedom of the optical caries diagnostic instrument 1 is improved. As a result, it is possible to make the optical caries diagnostic instrument 1 into a shape that allows the indenter 20 side of the optical caries diagnostic instrument 1 to be easily inserted into the oral cavity while the other end is held and operated. In addition, in order to increase the S / N ratio of the received light image, the reflectance of the beam splitter 50 is preferably 52% or more, more preferably 55%, and even more preferably 60% or more.

[0047] Alternatively, although not shown, the optical caries diagnostic device 1 according to the embodiment of the present invention may have a mirror arranged on the optical path P1 between the indenter 20 and the light source 10, and on the optical path between the indenter 20 and the light receiving element 30. When the light receiving element 30 is arranged on the opposite side of the indenter 20 to the light source 10, and the optical path from the indenter 20 to the light receiving element 30 is parallel to the optical path P1 from the light source 10 to the indenter 20, the reflected light from the indenter 20 can be reflected by the mirror and received by the light receiving element 30.

[0048] It is preferable that the optical caries diagnostic device 1 according to the embodiment of the present invention further includes a pressure sensor 71, and the light receiving element 30 captures an image when the pressure with which the indenter 20 contacts the object 100 reaches a predetermined value. This makes it possible to measure the hardness of the object 100 when the indenter 20 contacts the object 100 with a constant pressure, and enables quantitative measurement regardless of the skill of the operator.

[0049] Fig. 11 shows a graph showing the relationship between time and contact pressure. In Fig. 11, assuming that the predetermined contact pressure is S, an image is captured at timing T. Since the indenter 20 is brought into contact with the object 100 by the operator, it is inevitable that the contact pressure will change over time. However, by capturing an image at the timing of the predetermined contact pressure, it is possible to capture reflected light at a constant contact pressure. The predetermined value of the contact pressure is appropriately determined depending on the conditions of the object 100, but is preferably 3N or less, more preferably 2.5N or less, even more preferably 2N or less, and is preferably 0.1N or more, more preferably 0.5N or more, even more preferably 0.8N or more.

[0050] Although not shown, the optical caries diagnostic device 1 according to the embodiment of the present invention may further have a switch in addition to the pressure sensor 71, and the light receiving element 30 may capture an image in response to a signal from the switch. By capturing an image in response to a signal from the switch, it becomes possible to capture an image at any time even when the tip 21 of the indenter 20 is not in contact with anything (non-contact) and there is no signal from the pressure sensor 71.

[0051] The optical caries diagnostic device 1 according to the embodiment of the present invention may further include a filter 60. By setting the wavelength of light that can pass through the filter 60 to the wavelength of light emitted by the light source 10, it is possible to eliminate the influence of light other than the light emitted from the light source 10, such as the influence of an indoor fluorescent lamp or a dental lighting device, and to increase the S / N ratio of the captured image.

[0052] The optical caries diagnostic device 1 according to the embodiment of the present invention may be further housed in a housing 80. For example, as shown in Fig. 7, an optical path P1 from the light source 10 to the tip 21 of the indenter 20, an optical path P2 from the tip 21 of the indenter 20 to the beam splitter 50, and an optical path P3 from the beam splitter 50 to the light receiving element 30 are disposed in the housing 80, and the indenter 20 can be attached to an opening provided in the housing 80.

[0053] The indenter 20 is preferably detachable from the opening of the housing 80. The indenter 20 can be disinfected or sterilized before measurement, the indenter 20 can be replaced depending on the patient, or an optimal indenter 20 can be used depending on the condition of the target object 100. The indenter 20 can also be replaced periodically as a consumable part, or can be disposable after each use. In this case, it is preferable that the distances of the optical paths P1, P2, and P3 do not change every time a measurement is performed. Therefore, it is preferable that the housing 80 has a fixing part such as a stopper that fixes the indenter 20 in the opening where the indenter 20 is attached and detached. Since the distances of the optical paths P1, P2, and P3 are constant, the indenter 20 can be replaced without changing the imaging relationship, and stable imaging is possible.

[0054] A part of the housing 80 may be attached to a handle 90 having a cavity for accommodating the housing 80. As shown in Fig. 12, in one embodiment, the housing 80 can be attached to the handle 90 by fitting a rotation shaft 72 provided on the outside of the housing 80 into a shaft hole provided in the handle 90. When the tip 21 of the indenter 20 abuts against the target object 100, the housing 80 rotates about the rotation shaft 72, and the force generated at this time can be detected by the pressure sensor 71.

[0055] In order to quantitatively obtain the hardness measurement value, it is preferable that the area of ​​the region where the reflected light is weak is measured under certain conditions. For this purpose, the optical caries diagnostic device 1 according to the embodiment of the present invention can have the following image processing steps.

[0056] The image processing process according to the embodiment of the present invention will be described with reference to Figs. 13 to 18. Fig. 13 is a captured image of reflected light from the tip 21 of the indenter 20 when the tip 21 of the indenter 20 is not in contact with anything (non-contact). Fig. 14 is a captured image of reflected light from the tip 21 of the indenter 20 when the tip 21 of the indenter 20 is in contact with the object 100. Fig. 15 is a differential intensity image obtained by subtracting the captured image shown in Fig. 14 from the captured image shown in Fig. 13. Fig. 16 is a binarized differential intensity image obtained by binarizing the differential intensity image shown in Fig. 15. Fig. 17 is a schematic diagram of the tip 21 of the indenter 20 in contact with the object 100 perpendicularly, and Fig. 18 is a schematic diagram of the tip 21 of the indenter 20 in contact with the object 100 deviating from perpendicularly.

[0057] [Difference intensity image acquisition process] A differential intensity image (FIG. 15) is obtained by subtracting an intensity image (FIG. 14) captured by the light receiving element 30 of the reflected light when the tip 21 of the indenter 20 is in contact with the object 100 from an intensity image (FIG. 13) captured by the light receiving element 30 of the reflected light when the tip 21 of the indenter 20 is not in contact. By subtracting this, it is possible to eliminate variations in reflection due to individual differences in the indenter 20 and contributions other than the reflected light to be observed. In the above image processing process, the same indenter 20 is used, and images are captured under the same other imaging conditions.

[0058] [Binarization process of difference intensity image] The differential intensity image obtained above is binarized with a predetermined value as a threshold. At this time, the optical caries diagnostic device 1 according to the embodiment of the present invention can issue an error signal under the following conditions. When the tip 21 of the indenter 20 is brought into contact with the object 100, it is preferable that the central axis c of the indenter 20 is brought into contact as perpendicularly as possible with the surface of the object 100 as shown in FIG. 17, but this may not always be at a right angle depending on the unevenness of the surface of the object 100 and the skill of the operator. If the contact angle between the central axis c and the surface of the object 100 deviates from the perpendicular, the outer diameter of the area where the reflected light is weak deviates from a circular shape as shown in FIG. 18. If this happens, the captured image obtained will contain information other than hardness, so if the major axis L of the outer shape of the differential intensity image (binarized differential intensity image) exceeds the threshold, the major axis L of the outer shape of the differential intensity image (binarized differential intensity image) exceeds the threshold.m Length and minor axis L s The ratio of the length of the major axis L m length) / (minor axis L s It is preferable to generate an error signal when the length of the sigma-based ...

[0059] [Process of obtaining the area of ​​the binary difference intensity image] The area of ​​the binarized difference intensity image obtained through the above process is obtained. The area reflects the hardness of the object 100. If the object is hard, the area is small, and if the object is soft, the area is large.

[0060] 2. Optical caries diagnosis method An optical caries diagnosis method according to an embodiment of the present invention includes the steps of preparing the optical caries diagnostic device 1, bringing the tip 21 of the indenter 20 into contact with an object having a known hardness, receiving light emitted from the light source 10 and reflected from the tip 21 of the indenter 20 with the light receiving element 30 while the tip 21 of the indenter 20 is in contact with the object having a known hardness, and acquiring a first captured image, bringing the tip 21 of the indenter 20 into contact with the tooth to be diagnosed, receiving light emitted from the light source 10 and reflected from the tip 21 of the indenter 20 with the light receiving element 30 while the tip 21 of the indenter 20 is in contact with the tooth to be diagnosed, and acquiring a second captured image, and comparing the first captured image with the second captured image to determine the hardness of the tooth to be diagnosed from the hardness of the object having a known hardness. In the optical caries diagnostic device 1 according to the embodiment of the present invention, the reflectance of the portion of the tip 21 of the indenter 20 in contact with the surface of the object 100 is low, whether the object 100 is a metal reference piece or a tooth. In other words, the wavelength of the light emitted from the light source 10 is 500 nm or less, and the angle of incidence θ at which the light is incident on the tip 21 of the indenter 20 is 500 nm or less. iWhen the angle is 70° or less, the contrast with the total reflection of the part of the tip 21 of the indenter 20 that is not in contact with anything can be detected, and information on the area of ​​the part of the tip 21 of the indenter 20 that is in contact with the surface of the object can be obtained. If a metal reference piece having a known Knoop hardness, for example, is used as the object having a known hardness, a calibration curve can be obtained from the Knoop hardness and the area of ​​the weak light receiving intensity in the first captured image. Based on this calibration curve, the Knoop hardness of the tooth to be diagnosed can be obtained from the area of ​​the weak light receiving intensity in the second captured image.

[0061] The object having a known hardness may have any value of hardness such as Vickers hardness, Mohs hardness, Rockwell hardness, Brinell hardness, etc., other than Knoop hardness. The object having a known hardness is preferably a metal reference piece. In the case of a metal reference piece, the wavelength of the light emitted from the light source 10 is 500 nm or less, and the angle of incidence θ at which the light is incident on the tip 21 of the indenter 20 is 100 nm or less. i By making the angle be 70° or less, it is possible to detect the contrast between the part where the tip 21 of the indenter 20 is in contact with the surface of the reference piece and the reflected light intensity is low, and the part where the tip 21 of the indenter 20 is not in contact with anything and the total reflection, making it easy to obtain the first captured image.

[0062] The optical caries diagnosis method according to the embodiment of the present invention preferably further comprises a step of acquiring a third captured image by receiving light emitted from the light source 10 and reflected from the tip 21 of the indenter 20 with the light receiving element 30 while the tip 21 of the indenter 20 is not in contact with anything (non-contact). This makes it possible to obtain differential intensity images by subtracting the first captured image and the second captured image from the third captured image, and makes it possible to eliminate variations in reflection due to individual differences in the indenter 20 and contributions other than the reflected light to be observed.

[0063] 3. Caries diagnosis system The caries diagnostic system according to the embodiment of the present invention is a system including an optical caries diagnostic device according to the embodiment of the present invention, and has an information terminal device connected by wire or wirelessly, and optical caries diagnostic information (measured by the optical caries diagnostic device of the present invention) stored in the information terminal device. By storing the optical caries diagnostic information in the information terminal device, the information can be compiled into a database, and the hardness of the diagnosed tooth can be measured more accurately.

[0064] It is preferable that the caries diagnosis system according to the embodiment of the present invention further includes caries diagnosis information measured by a device other than the optical caries diagnostic device of the present invention, for example, information diagnosed by a conventional caries diagnosis method such as a probe, a cariotester, a panoramic X-ray, etc. By accumulating information diagnosed by these conventional diagnostic methods, the caries diagnosis results diagnosed by the conventional diagnostic methods can be associated with the hardness information obtained by the optical caries diagnostic device of the present invention. EXAMPLES

[0065] Example 1 An optical caries diagnostic device was created, and a glass (Edmund Optics, #49-397 N-BK7) indenter was placed against a gold reference piece (Yamamoto Scientific Tool Research, HMV30). The light emitted from the light source and reflected from the tip of the indenter was received by a light-receiving element, and an image was obtained using a microscope. The glass indenter had an aluminum-coated surface, so the surface aluminum layer was removed by immersing it in hydrochloric acid before use in the measurement. The image obtained is shown in Figure 19. The configuration of the optical caries diagnostic device and the imaging conditions are as follows: Light source: Blue LED (wavelength: 455 nm, Thorlabs Japan M455L3) Photodetector: Monochrome CMOS camera (Edmund Optics #89-737) Beam splitter: Thorlabs Japan CCM5-BS016 / M (50% transmission, 50% reflection) Incident angle: 45° Objective lens: Infinity corrected objective lens (Mitutoyo Corporation, M-PLAN NIR 10X) Imaging lens: Mitutoyo Corporation, MT-L

[0066] Comparative Example 1 Except for changing the light source to a red LED (wavelength: 625 nm, M625L3 manufactured by Thorlabs Japan), a received light image was obtained in the same manner as in Example 1. The obtained image is shown in FIG.

[0067] Example 2 Except for replacing the reference block with a copper reference block (HMV40, manufactured by Yamamoto Scientific Tool Research Co., Ltd.), a received light image was obtained in the same manner as in Example 1. The obtained image is shown in FIG.

[0068] Comparative Example 2 A light-receiving image was obtained in the same manner as in Example 2, except that the light source was changed to a red LED (wavelength: 625 nm, M625L3 manufactured by Thorlabs Japan Co., Ltd.) The obtained image is shown in FIG.

[0069] Example 3 A light receiving image was obtained in the same manner as in Example 1, except that the reference block was replaced with a brass (copper: 70%, zinc: 30%) reference block (manufactured by Yamamoto Scientific Tool Research Co., Ltd., HMV100). The obtained image is shown in FIG.

[0070] Comparative Example 3 A light-receiving image was obtained in the same manner as in Example 3, except that the light source was changed to a red LED (wavelength: 625 nm, M625L3 manufactured by Thorlabs Japan Co., Ltd.) The obtained image is shown in FIG.

[0071] Regardless of which reference block was used, when a blue LED was used, a strong contrast was detected between the area where the tip of the indenter was in contact with the surface of the reference block, resulting in low reflected light intensity, and the area where the tip of the indenter was not in contact with anything, resulting in total reflection. [Explanation of symbols]

[0072] 1: Optical caries diagnostic device 10:Light source 11: Incident light 20: Indenter 21: Tip of the indenter 22: Top of the indenter 30: Light receiving element 40: Lens 50: Beam splitter 60: Filter 71: Pressure sensor 72: Rotation axis 80: Cabinet 90: Handle 100: Object c: central axis of the indenter L m :Long axis L s :Short axis O: Centroid of the bottom surface of the indenter p: Perpendicular R:R part r: Radius of curvature of R part S1: The part in contact with the surface of the object S2: Part that is not in contact with anything θ: Angle of the tip of the indenter θ i :Incidence angle

Claims

1. an indenter having optical transparency and a tapered shape, the indenter being adapted to come into contact with the object; A light source that emits light to the indenter; a light receiving element that receives light reflected from the tip of the indenter; a lens disposed at a position where the tip of the indenter and the light receiving surface of the light receiving element are in an image-forming relationship with each other, The wavelength of the light emitted from the light source is 500 nm or less, An optical caries diagnostic device, wherein the angle of incidence of the light emitted from the light source on the tip of the indenter is 70° or less.

2. 2. The optical caries diagnostic device according to claim 1, wherein the light receiving element includes unit cells arranged two-dimensionally.

3. 3. The optical caries diagnostic device according to claim 1, further comprising a beam splitter disposed on an optical path between the indenter and the light source and on an optical path between the indenter and the light receiving element.

4. 4. The optical caries diagnostic device according to claim 1, further comprising a pressure sensor, wherein the light receiving element captures an image when the pressure at which the indenter contacts the object reaches a predetermined value.

5. An optical caries diagnostic device according to any one of claims 1 to 4, which obtains a differential intensity image by subtracting the light receiving intensity of the light receiving element when the tip of the indenter is in contact with an object from the light receiving intensity of the light receiving element when the tip of the indenter is not in contact with anything (non-contact).

6. 6. The optical caries diagnostic device according to claim 5, wherein the differential intensity image is binarized using a predetermined value as a threshold value.

7. 7. The optical caries diagnostic device according to claim 6, which issues an error signal when the ratio of the length of the major axis to the length of the minor axis of the outline of the differential intensity image obtained by the binarization ((length of major axis) / (length of minor axis)) is equal to or greater than a predetermined value.

8. The optical caries diagnostic device according to claim 6 or 7, wherein the area of ​​the region exceeding the threshold value is obtained.

9. 9. The optical caries diagnostic device according to claim 1, further comprising a housing, the indenter being detachable from the housing.

10. A method for operating the optical caries diagnostic device according to any one of claims 1 to 9, comprising: a step of acquiring a first captured image by receiving light emitted from the light source and reflected from the tip of the indenter with the light receiving element while the tip of the indenter is in contact with an object having a known hardness; a step of receiving light emitted from the light source and reflected from the tip of the indenter with the light receiving element while the tip of the indenter is in contact with the tooth, thereby obtaining a second image.

11. The method for operating an optical caries diagnostic device as described in claim 10, further comprising a step of obtaining a third image by having the light receiving element receive light emitted from the light source and reflected from the tip of the indenter while the tip of the indenter is not in contact with anything.

12. A caries diagnosis system including an optical caries diagnostic meter described in any one of claims 1 to 9, the caries diagnosis system having an information terminal device connected by wire or wirelessly, and optical caries diagnosis information (measured by the optical caries diagnostic meter described in any one of claims 1 to 9) stored in the information terminal device.

13. The caries diagnosis system according to claim 12, wherein the information terminal device further has caries diagnosis information measured by a device other than the optical caries diagnostic device according to any one of claims 1 to 9.

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