Intra-oral cavity light measurement device

Abstract

To provide a measurement device capable of monitoring a sanitary state in an oral cavity in real time.SOLUTION: An intra-oral cavity optical measurement device comprises: an inner layer mouth guard that covers tooth crowns of at least part of a tooth row and gingiva supporting the tooth crowns; an outer layer mouth guard that covers the inner layer mouth guard and has light transmissivity; a pair of measurement pieces projected from the outer layer mouth guard with a gap capable of holding liquid; a light emitter that is built in the first projection piece of the measurement pieces and radiates measurement light; a light receiver that is built in the second projection piece of the measurement pieces and receives the measurement light before converting the same into an electric signal; and a power supply for driving the light emitter and a transmitter for transmitting the electric signal obtained by the conversion of the light receiver to the outside, the power supply and the transmitter being interposed between the inner layer mouth guard and the outer layer mouth guard.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an apparatus for optically measuring the turbidity of saliva in the oral cavity. [Background technology]

[0002] The turbidity of saliva, i.e., the decrease in the transmittance of light of a specific wavelength through saliva, reflects the total number of bacteria in dental plaque, tongue plaque, and exfoliated epithelial cells. Therefore, it is expected that the measurement of saliva turbidity will enable the quantitative evaluation of oral hygiene.

[0003] The following Patent Document 1 discloses a biological component detection device that can continuously measure glucose in saliva non-invasively and unconstrainedly, and can be safely housed in a limited space. The following Patent Document 2 discloses an intraoral biological monitoring device that includes a sensor, a communication unit that executes communication in response to a signal input to the sensor, and a mouthpiece that holds the sensor and the communication unit, is attached to the crown of a subject's tooth, and covers at least a part of the subject's gums. The following Non-Patent Document 1 discloses a technology for optically analyzing saliva in the oral cavity using a fiber-type sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-154755 A [Patent Document 2] JP 2020-141789 A [Non-patent literature]

[0005] [Non-Patent Document 1] Farago, P., Galatus, R., Hintea, S., Bosca, AB, Feurdean, CN & Ilea, A. "An Intra-Oral Optical Sensor for the Real-Time Identification and Assessment of Wine Intake" Sensors (2019), 19(21), 4719; https: / / doi.org / 10.3390 / s19214719 Summary of the Invention [Problem to be solved by the invention]

[0006] Oral hygiene status changes from moment to moment throughout the day. However, there is currently no device capable of monitoring this change in real time. The technology described in Non-Patent Document 1 above is merely a proof of principle outside the oral cavity, and has not yet achieved continuous measurement within the oral cavity. An object of the embodiment of the present disclosure is to provide a measuring device capable of monitoring the oral hygiene status in real time. [Means for solving the problem]

[0007] The intraoral optical measurement device of the present disclosure comprises an inner layer mouth guard covering at least some of the tooth crowns of the dentition and the gums supporting the tooth crowns, an outer layer mouth guard covering the inner layer mouth guard and being translucent, a pair of measurement pieces protruding from the outer layer mouth guard with a gap capable of holding liquid, a light emitter incorporated in a first protruding piece of the measurement pieces and irradiating measurement light, a light receiver incorporated in a second protruding piece of the measurement pieces and receiving the measurement light and converting it into an electrical signal, and a transmitter interposed between the inner layer mouth guard and the outer layer mouth guard and transmitting to the outside a power source for driving the light emitter and an electrical signal converted by the light receiver.

[0008] The intraoral optical measurement device of the present disclosure includes a two-layer mouthguard, an inner layer mouthguard and an outer layer mouthguard. A pair of measuring pieces protrude from the outer layer mouthguard. The pair of measuring pieces is composed of a first protruding piece and a second protruding piece. The first protruding piece and the second protruding piece maintain a gap capable of holding liquid in the oral cavity, specifically liquid such as saliva or liquid such as a drink contained in the oral cavity. The first protruding piece and the second protruding piece are each hollow. A light emitter is built into the cavity of the first protruding piece, and a light receiver is built into the cavity of the second protruding piece. A power source and a transmitter are interposed between the inner layer mouthguard and the outer layer mouthguard. The light emitter is composed of an element that emits light by current from a power source, such as a light-emitting diode (LED). The light receiver is composed of an element that receives the measurement light, which is light irradiated by the light emitter, to generate an electric signal, and amplifies this electric signal, such as a phototransistor (PT). The electric signal generated by the light receiver is transmitted to the outside by the transmitter. This transmission may be performed via a wired connection, but is preferably performed wirelessly in consideration of reducing the burden on the subject. The destination of the transmission is preferably an analysis device such as a computer that is equipped with a program for receiving and analyzing the transmitted signal.

[0009] When the intraoral optical measurement device of the present disclosure is attached to the dentition of a subject with the inner layer mouth guard covering the dentition, saliva secreted in the subject's oral cavity or liquid contained in the subject's oral cavity is held in the gap between the pair of measurement pieces. In this state, when the light emitter driven by a power source irradiates measurement light, the measurement light passes through the saliva held in the gap and is received by the light receiver. Note that the outer layer mouth guard is formed of a light-transmitting material, and the measurement light can pass through the measurement piece with almost no attenuation. At this time, the measurement light is attenuated according to the turbidity of the saliva, and the attenuated measurement light is received by the light receiver. Here, if the emission intensity of the measurement light irradiated by the light emitter is I0 and the emission intensity of the measurement light received by the light receiver is I, the optical density (OD) representing the turbidity of the saliva is, for example, OD = -log(I / I0) For example, this value can be used to judge the hygiene state of the oral cavity.

[0010] If the measuring strip is provided so as to protrude inwardly in the oral cavity, i.e., toward the tongue side, the discomfort in the oral cavity caused by the measuring strip can be reduced. If the dentition is the dentition of the mandible, saliva is more likely to remain in the gaps between the measuring strips. Furthermore, if the dentition is the entire dentition of the mandible, the intraoral optical measurement device can be stably attached in the oral cavity. In addition, if the measuring strip is provided at a position corresponding to the back side of the incisors, saliva, mainly from the sublingual line, can be constantly retained in the gaps between the measuring strips, which is convenient for measurement. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a measuring device capable of monitoring the hygiene state of the oral cavity in real time. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view showing an external appearance of an intraoral optical measurement device according to an embodiment. [Diagram 2] The electrical wiring of the light-emitting device attached to the intraoral optical measurement device of Figure 1 is shown typically. [Diagram 3] 2 shows a schematic diagram of electrical wiring of the optical receiver attached to the intraoral optical measurement device of FIG. 1. [Figure 4] 1A to 1C are schematic diagrams illustrating an outline of a manufacturing process for an intraoral optical measurement device according to an embodiment. [Diagram 5] The external shape of the block-shaped measuring piece is shown diagrammatically. [Figure 6] 5A and 5B are schematic diagrams showing an intraoral optical measurement device formed by the manufacturing process of FIG. 4. [Figure 7] 1 is a schematic diagram showing an outline of a system configuration of an intraoral optical measurement device according to an embodiment. [Figure 8] The structure of the test piece is shown diagrammatically. [Figure 9] 1 is a graph showing optical density spectra of formazin solutions with different turbidities. [Figure 10]1 is a graph showing the relationship between turbidity and optical density of a formazin solution, in which the solid line shows the measurement results at a wavelength of 405 nm and the dashed line shows the measurement results at a wavelength of 660 nm. [Figure 11] 1 is a graph showing the optical density spectra of saliva (solid line) and formazin solution (dashed line). [Figure 12] 1 is a graph comparing the optical density of saliva (solid line) and formazin solution (dashed line) at wavelengths of 405 nm and 660 nm. [Figure 13] 1 is a graph showing the effect of the spacing between test strips on the amount of liquid retained in the gaps between the test strips (left vertical axis) and on the liquid retention rate (right vertical axis). [Figure 14] 1 is a graph showing turbidity measurement performance when the measurement strips are spaced 2 mm apart (solid line) and 1 mm apart. [Figure 15] 13 is a graph showing quantitative characteristics with respect to turbidity of the intraoral optical measurement device of the embodiment. [Figure 16] This is a graph showing the results of fitting the optical density (indicated by ■) of the collected saliva using formazin solution to a calibration curve previously obtained with a spectrophotometer (solid line) and an embodiment of the intraoral optical measurement device (dashed line). [Figure 17] 13 is a graph showing the output response when tap water (●) and saliva (◯) are held in the oral cavity using the intraoral optical measurement device of the embodiment. [Figure 18] 1 is a graph showing the optical density spectrum of each beverage that can be applied to the oral cavity of a subject. [Figure 19] 1 is a graph showing the optical density at 405 nm of each beverage that can be applied to the oral cavity of a subject. [Figure 20] 1 is a graph showing the measurement performance of intraoral turbidity using the intraoral optical measurement device of the embodiment. [Figure 21] 21 is a graph showing the relationship between turbidity and optical density in the graph of FIG. 20. [Figure 22] 13 is a graph showing the results of repeatedly measuring turbidity in real time using the intraoral optical measurement device of the embodiment. [Figure 23] 23 is a graph plotting the current difference for each measurement from the graph in FIG. 22. [Figure 24] 13 is a graph showing the results of observing the change over time in output current value due to oral intake of milk using the intraoral optical measurement device of the embodiment. [Diagram 25] FIG. 24 is a graph showing the output current value as an exponential function. [Figure 26] 13 is a graph showing the results of observing changes in turbidity of saliva due to mouth breathing (dashed line) and nasal breathing (solid line) using the intraoral optical measurement device of the embodiment. [Figure 27] 27 is a graph showing the results of FIG. 26 in comparison with the results measured by a spectrophotometer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an intraoral optical measurement device according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the drawings referred to below show the configuration of each part in a schematic manner and do not necessarily reflect the actual size. Furthermore, the reference numerals commonly used in each drawing indicate common configurations or members even if not mentioned in the description of each drawing.

[0014] 1 is a perspective view showing the appearance of an intraoral optical measurement device 10 according to an embodiment. The intraoral optical measurement device 10 includes an inner layer mouth guard 20 that covers all the tooth crowns of the mandibular dentition and the gums that support the tooth crowns, and an outer layer mouth guard 30 that covers the inner layer mouth guard 20. Both the inner layer mouth guard 20 and the outer layer mouth guard 30 are made of a translucent resin material.

[0015] A pair of measuring pieces 40 are provided protruding from the outer layer mouth guard 30 at a position corresponding to the back side of the incisors toward the inside of the oral cavity. A light emitter 50 is built into the first protruding piece 41 of the pair of measuring pieces 40. A light receiver 60 is built into the second protruding piece 42. A power source 51 and a transmitter 61 are interposed between the inner layer mouth guard 20 and the outer layer mouth guard 30. The power source 51 is housed inside the power source housing 31 protruding toward the lip side on the left side of the lower jaw. The transmitter 61 is housed inside the board housing 32 protruding toward the lip side on the right side of the lower jaw. Since the outer layer mouth guard 30 is made of a light-transmitting material, the light emitter 50, the light receiver 60, the power source 51, and the transmitter 61 can be seen through the outer layer mouth guard 30. Furthermore, through the outer mouth guard 30, the enameled wire 55 that connects the power source 51 and the light emitter 50 via the resistor 52, and the enameled wire 65 that connects the transmitter 61 and the light receiver 60 can also be seen.

[0016] As shown in Fig. 2, a light emitter 50 made of an LED is connected to a power source 51 made of two button batteries by an enamel wire 55 via a resistor 52. Also, as shown in Fig. 3, a light receiver 60 made of a PT is connected to a transmitter 61 by an enamel wire 65.

[0017] FIG. 4 is a schematic diagram showing an outline of the manufacturing process of the intraoral optical measurement device 10 of the embodiment. First, an impression of the mandibular dentition of a subject is taken, the impression is shaped to a tooth shape, and gypsum is poured into the impression to form a gypsum model 70 of the mandibular dentition. The gypsum model 70 is placed on a suction-type molding machine, and a mouthguard sheet material softened by heating is placed over it, and then sucked, so that a mouthguard that matches the gypsum model 70 is three-dimensionally shaped. This becomes the inner layer mouthguard 20. Furthermore, a U-shaped block mold 71 as shown in FIG. 5 is attached to the back side of the incisors of the gypsum model 70, and the mouthguard is three-dimensionally shaped in the same manner. As a result, an outer layer mouthguard 30 with a pair of measuring pieces 40 protruding from the back side of the incisors is three-dimensionally shaped.

[0018] Next, the transmitter 61 is placed on the right lip side of the inner-layer mouth guard 20 placed on the plaster model 70, and the power source 51 is placed on the left lip side. Furthermore, the pair of measuring pieces 40 are arranged so that the light emitter 50 is located on the first projecting piece 41 located on the left side, and the light receiver 60 is located on the second projecting piece 42 located on the right side, and then covered with the outer-layer mouth guard 30. Then, the entire assembly is thermally fused with a heat gun at 400°C to form the intraoral optical measurement device 10 shown in Fig. 6.

[0019] Here, the material of the inner layer mouth guard 20 that comes into direct contact with the inside of the subject's mouth is preferably softer than the material of the outer layer mouth guard 30. In addition, since the outer layer mouth guard 30 has a shape in which the measuring piece 40 protrudes, it is preferable that the material has high bending rigidity. From the above, it is preferable that the material of the inner layer mouth guard 20 is a transparent ethylene vinyl acetate resin (product name: Erkoflex, Erkodent, 1.0 mm thick). In addition, it is preferable that the material of the outer layer mouth guard 30 is a transparent polyethylene terephthalate glycol resin (product name: Erkodur, Erkodent, 0.5 mm thick).

[0020] FIG. 7 is a schematic diagram of the system configuration of the intraoral optical measurement device 10 of the embodiment. In a state where a measurement is performed, a liquid L such as saliva is held in the gap 43 between the first protruding piece 41 and the second protruding piece 42. That is, the pair of measuring pieces 40 has a gap 43 capable of holding a liquid. The light emitter 50 built into the first protruding piece 41 is driven by a current supplied from the power source 51 through a resistor 52, and a measuring light of a wavelength described later is irradiated from the LED. The irradiated measuring light passes through the liquid L and is received by the light receiver 60. In the light receiver 60 that receives the measuring light, a current is generated by the PT. The generated current is converted into a digital signal as an electric signal by the A / D converter 62 housed in the substrate housing part 32, and is transmitted to the outside by the transmitter 61 (for example, a BLE wireless module) via the potentiostat 63, specifically to an external device 80 such as a personal computer, a tablet terminal, or a smartphone, and an output response value and an optical density are analyzed from the received signal.

[0021] 8 is a schematic diagram showing the structure of the measuring piece 40. The size of the measuring piece 40 is appropriately set according to the size of the built-in light emitter 50 and light receiver 60. For example, the size of the first protruding piece 41 can be 4 mm in height, 2.2 mm in width, and 5 mm in depth. The size of the second protruding piece 42 can be 4 mm in height, 1.8 mm in width, and 5 mm in depth. The width of the gap 43 between the first protruding piece 41 and the second protruding piece 42 will be mentioned in the examples.

[0022] The intraoral optical measurement device 10 of the present disclosure does not necessarily have to cover the entire dentition, but may be formed to cover at least a part of the dentition. The dentition to which the intraoral optical measurement device 10 is attached does not necessarily have to be the dentition of the mandible, but may be the dentition of the maxilla. Furthermore, the position at which the measuring piece 40 is provided does not necessarily have to be a position corresponding to the back side of the incisor, as long as the flow and retention of saliva can be performed without any hindrance. EXAMPLES

[0023] Below, when measuring intraoral turbidity using the intraoral optical measurement device 10 of the present disclosure, suitable measurement conditions were considered, and then the applicability to the evaluation of the oral hygiene state of actual subjects was also considered.

[0024] (1) Measurement wavelength In previous studies on measuring the turbidity of saliva, the absorbance of the measurement light with a wavelength of 660 nm was used. However, since the intraoral optical measurement device 10 of the present disclosure aims to perform real-time measurement by attaching it to the oral cavity, a more appropriate wavelength of the measurement light was considered.

[0025] Specifically, formazin solutions, which are an index of turbidity, were adjusted to various concentrations, and 2 μL of each concentration of formazin solution was dropped onto the measuring section of a microdroplet absorptiometer (Nanodrop2000, Thermofisher), and the OD spectrum was measured by sweeping the light source spectrum. Here, the turbidity of a solution of 1 mg / L of formazin is considered to be 1 FTU (formazine turbidity unit). Figure 9 is a graph showing the OD spectra of formazin solutions of various FTUs. The graphs in the figure are, from the top, the OD spectra of formazin solutions of 1000, 800, 600, 400, 300, 100, 60, and 20 FTU, respectively. As shown in this figure, the higher the FTU of the formazin solution, the higher the OD obtained.

[0026] FIG. 10 is a graph plotting the relationship between FTU value and OD for measurement light of wavelength 660 nm (dashed line) and wavelength 405 nm (solid line). Here, the wavelength of 405 nm corresponds to the wavelength of violet light used in recent years for tooth whitening in cosmetic dentistry, so a certain degree of safety is guaranteed. It was shown that there is high linearity between the FTU value and OD for both wavelengths. It was also shown that the output is higher at the wavelength of 405 nm than at the wavelength of 660 nm, which is commonly used in turbidity measurement using formazin solution.

[0027] (2) Substitution of saliva with formazin solution FIG. 11 is a graph showing the OD spectrum of saliva (solid line) and formazin solution (dashed line). In the measurement of this figure, a formazin solution adjusted to an FTU value of 553 was used so that the OD was the same as that of saliva at a wavelength of 660 nm. As a result, as shown in the bar graph of FIG. 12, the OD of the formazin solution was almost the same as that of saliva at a wavelength of 405 nm. This shows that a formazin solution with an FTU value of 553 can be a substitute for saliva in an in vitro experiment conducted in developing the intraoral optical measurement device 10 of the present disclosure.

[0028] (3) Configuration of intraoral optical measurement device For the above reasons, in the following examples, turbidity measurement was performed with measurement light having a wavelength of 405 nm. For the intraoral optical measurement device 10 used in the following examples, SM1206UV-405-IL (Bivar) was used for the LED constituting the light emitter 50. In addition, APS3227SP1C-P22 (Kingbright) was used for the PT constituting the light receiver 60. Furthermore, a "BLE data logger transmitter" (custom-made product, Discretek) was used for the transmitter 61. Furthermore, two 1.55V button batteries were used for the power source 51, and a 10kΩ resistor 52 was used.

[0029] (4) Optical path distance Next, in the intraoral optical measurement device 10 of the present disclosure, an appropriate value of the optical path length (OPL), which is the distance from the measurement light irradiated from the light emitter 50 to the light receiver 60, was investigated. The optical path length here is specifically the distance between the pair of measurement pieces 40. Fig. 13 is a graph showing the results of investigating the appropriate OPL when the size of the first protruding piece 41 is 4 mm in height, 2.2 mm in width, and 5 mm in depth, and the size of the second protruding piece 42 is 4 mm in height, 1.8 mm in width, and 5 mm in depth.

[0030] Specifically, the OPL was adjusted to 1 mm, 2 mm, 3 mm, and 4 mm, and the amount of water held between the test pieces 40 (left vertical axis) and the filling rate (right vertical axis) relative to the volume between the test pieces 40 were measured. The measurement was performed by immersing a part of the outer layer mouth guard 30 on which the test piece 40 was formed in water and then pulling it out, recovering the water held between the test pieces 40 with a micropipette, and measuring the volume. The filling rate was calculated as the ratio of the amount of water to the volume calculated by multiplying the height and depth of the test piece 40 and the OPL. The graph shows the average value of five measurements. As a result, it was found that the longer the OPL, the greater the amount of liquid held, and that 2 mm was the best in terms of the balance with the filling rate due to surface tension, followed by 1 mm.

[0031] Fig. 14 shows the results of measuring the turbidity of a formazin solution using the measuring pieces 40 with OPLs of 1 mm and 2 mm, which gave good results in Fig. 13. Specifically, the OD was measured by a wired connection to a spectrophotometer while the position of the outer layer mouth guard 30 equipped with the light emitter 50 and the light receiver 60 was immersed in a beaker filled with a formazin solution with an FTU value adjusted to 20 to 2000. As a result, high linearity between the FTU value and OD was observed in both cases of OPLs of 1 mm and 2 mm, but since the output was higher at , it was shown that a 2 mm OPL provides better measurement performance.

[0032] (5) Verifying wireless connection Based on the above results, it was verified whether the intraoral optical measurement device 10 shown in FIG. 1 can measure turbidity by wireless connection. Specifically, the intraoral optical measurement device 10 shown in FIG. 1 was immersed in a beaker filled with formazin solutions of various FTU values, and the signal transmitted from the transmitter 61 was analyzed by the external device 80 (see FIG. 7). The FTU value of the formazin solution was set to 1 to 4000. The results are shown in the graph of FIG. 15. Here, if the OD shown on the vertical axis is Y and the FTU value shown on the horizontal axis is X, this graph is approximated by the exponential function of the following formula (1). The correlation coefficient was 0.990.

[0033] Y=4.0×10 -4 X 0.78 ...Equation (1)

[0034] From the above results, it was found that the intraoral optical measurement device 10 of the present disclosure can quantify turbidity in the range of 1 to 400 FTU.

[0035] (6) Saliva measurement Next, the measurement of the turbidity of saliva was attempted using the intraoral optical measurement device 10 shown in FIG. 1. Specifically, the saliva collected from the subject was dropped between the measuring pieces 40 of the intraoral optical measurement device 10, and the turbidity was measured. At the same time, the turbidity of the same saliva was measured by a spectrophotometer. The turbidity measured by each was fitted to a calibration curve obtained in advance by measuring a formazin solution having a known FTU value by the intraoral optical measurement device 10 and the spectrophotometer, respectively, to calculate the FTU value. FIG. 16 shows a calibration curve (solid line) obtained by a prior measurement by the spectrophotometer and a calibration curve (broken line) obtained by a prior measurement by the intraoral optical measurement device 10, and the measured turbidity is displayed with a symbol "■". As a result, the FTU value of the saliva measured by the spectrophotometer was 576, while the FTU value of the saliva measured by the intraoral optical measurement device 10 was 553, which is almost the same FTU value. As a result, it was suggested that the measurement of turbidity using the intraoral optical measurement device 10 of the present disclosure is as reliable as the measurement of turbidity using a spectrophotometer.

[0036] (7) Intraoral measurements Based on the above results, next, the measurement of turbidity was attempted in a state where the intraoral optical measurement device 10 of the present disclosure was actually worn in the oral cavity of a subject. Specifically, the subject who wore the intraoral optical measurement device 10 of the present disclosure in the oral cavity was made to hold tap water in the oral cavity and to hold saliva in the oral cavity for about 80 seconds, respectively, and the output response during that time (i.e., the current value transmitted from the transmitter 61) was observed. The results are shown in FIG. 17.

[0037] In FIG. 17, the state in which tap water was held is indicated by a black circle (●), and the state in which saliva was held is indicated by a white circle (○). As a result, the average value of the output response in the state in which tap water was held was 11.9 μA, and the FTU value calculated based on this value was 0. On the other hand, the average value of the output response when saliva was held was 10.8 μA, and the FTU value calculated based on this value was 374. From the above, it was suggested that the intraoral optical measurement device 10 of the present disclosure can measure turbidity that reflects the state of the oral cavity.

[0038] (8) Consideration of alternatives to formazin solution When observing the behavior of a highly turbid solution in the oral cavity while the subject is wearing the intraoral optical measurement device 10 of the present disclosure, since formazin solution cannot be used in living bodies, beverages that can be used as substitutes were examined. Specifically, milk, 100% orange juice, 100% tomato juice, and yogurt were each diluted so that their OD at a wavelength of 600 nm coincided with that of a 1000 FTU formazin solution. Specifically, milk was diluted 80 times, and orange juice, tomato juice, and yogurt were each diluted to 1000 FTU. As a result, the measured OD spectrum of each beverage is shown in FIG. 18. Note that graph a shows a 1000 FTU formazin solution, graph b shows diluted milk, graph c shows diluted orange juice, graph d shows diluted tomato juice, and graph e shows diluted yogurt. It was found that the behavior of the graphs was almost the same as that of the formazin solution.

[0039] The OD at a wavelength of 405 nm in Figure 18 is shown in Figure 19. The symbols a to e in this figure have the same meanings as in Figure 18. As shown in this figure, it was found that the OD of milk is close to the OD of the formazin solution. As a result of the above, it was shown that 80-fold diluted milk can be used as a substitute for formazin solution when conducting experiments on subjects.

[0040] (9) Continuous measurement of turbidity in the oral cavity Next, it was verified whether the turbidity in the oral cavity can be quantitatively measured while the subject is wearing the intraoral optical measurement device 10 of the present disclosure. Specifically, as shown in the graph of FIG. 20, the output response was measured when the oral cavity was soaked in water for 1 minute, then diluted milk was soaked in the oral cavity for 1 minute, and then water was soaked again for 1 minute. The graph of FIG. 20 shows the measurement results of milk diluted so that the FTU values ​​are 100, 200, 400, 600, 800, and 1000, respectively, from the top. As a result, it was shown that the higher the FTU value, the larger the potential change and the higher the turbidity. In addition, based on the results of FIG. 20, it was found that the FTU value of milk and the optical density show linearity, as shown in FIG. 21, which plots the relationship between the FTU value and OD.

[0041] As shown in Fig. 22, even when water and diluted milk were repeatedly absorbed at intervals of one minute, the output current value of each was found to be constant. Also, as can be seen from Fig. 23, which plots the difference (ΔS) in the output current value between water and diluted milk, the intraoral optical measurement device 10 of the present disclosure ensures reproducibility when measurements are repeated.

[0042] (10) Applicability to evaluation of oral hygiene Based on the above results, the applicability of the intraoral optical measurement device 10 of the present disclosure to the evaluation of intraoral hygiene environment was examined. Specifically, the saliva secretion ability was observed by continuously measuring the turbidity in the oral cavity after ingesting milk. Specifically, as shown in FIG. 24, the turbidity of saliva was first measured in the oral cavity for about 1 minute, and then 300 mL of milk was ingested and the turbidity in the oral cavity was continuously measured. As a result, it was shown that the output current value immediately after ingesting milk was significantly reduced and the turbidity increased. After that, the output current value recovered to the original value over about 3 minutes. This indicates that the remaining milk in the oral cavity is replaced by saliva.

[0043] FIG. 25 is a graph in which the output current values ​​during the recovery of turbidity in the oral cavity in FIG. 24 (i.e., the portion surrounded by the dashed line in FIG. 24) are converted into logarithms and plotted. This graph shows that the logarithm of the output current values ​​in the oral cavity shows linearity with respect to the passage of time. Furthermore, the regression line for each plot in FIG. 25 is given by the following formula (2), where I is the output current value on the vertical axis and t is the time on the horizontal axis. The correlation coefficient of this regression line was 0.953.

[0044] I = 0.85 × (0.304 -1 ) t (2)

[0045] From this graph, the turnover rate, which is the rate at which saliva is replaced per unit time, can be calculated. The turnover rate per minute (TO: % / min) can be calculated using the following formula (3).

[0046] TO=(1-I t / I (t+Δt) ) × 100 (3)

[0047] That is, TO = (1-0.304) x 100 = 0.696 Thus, the saliva turnover rate in the example of FIG. 24 was 69.6% / min.

[0048] In addition, when the saliva turnover rate was similarly measured for 15 subjects using the intraoral optical measurement device 10 of the present disclosure, the result was 54.8±19.2% / min. This result is considered to be reasonable compared with the reported value of 46.8±0.3% / min as a measurement result of the saliva turnover rate for 33 healthy subjects (Dawes C. & MacPherson LM: "The distribution of saliva and sucrose around the mouth during the use of chewing gum and the implications for the site-specificity of caries and calculus deposition" J. Dent. Res., 72, 852-857, 1993) and the reported value of 23.3±13.3% / min as a measurement result of the saliva turnover rate for 18 dry mouth patients (Hase JC & Birkhed D.: "Salivary glucose clearance, dry mouth and pH changes in dental plaque in man" Arch. Oral Biol., 33, 875-880, 1988). Therefore, it was suggested that the intraoral optical measurement device disclosed herein can be used to evaluate saliva secretion ability.

[0049] 26 shows the results of measuring the turbidity of saliva in the oral cavity when a subject wearing the intraoral optical measurement device 10 of the present disclosure breathes through the mouth (dashed line) or nose (solid line). As is clear from this figure, it was shown that the turbidity of saliva increases with mouth breathing. It was presumed that this is because the amount of saliva decreases due to intraoral dryness caused by mouth breathing, and the number of bacteria increases.

[0050] In addition, as can be seen from Fig. 27, which shows the results shown in Fig. 26 (bar graphs on the right side) in comparison with the results of measuring the saliva of the same subjects using a spectrophotometer (bar graphs on the left side), the measurement results using the intraoral optical measurement device 10 of the present disclosure were shown to have the same tendency as the measurement results using the spectrophotometer. Therefore, it was suggested that the intraoral hygienic environment can be evaluated using the intraoral optical measurement device 10 of the present disclosure. [Industrial Applicability]

[0051] The present disclosure can be used as a measuring device that can be worn in a subject's oral cavity to monitor the oral hygiene condition in real time. [Explanation of symbols]

[0052] 10. Intraoral optical measurement device 20 Inner layer mouthguard 30 outer layer mouth guard 31 power supply housing 32 circuit board housing 40 Measurement piece 41 First protruding piece 42 Second protruding piece 43 Gap 50 Light emitter 51 Power supply 52 Resistor 55 Enamelled wire 60 Receiver 61 Transmitter 62 A / D converter 63 Potentiostat 65 Enamelled wire 70 Plaster model 71 Block mold 80 External equipment L liquid

Claims

1. an inner layer mouth guard covering at least a portion of the crowns of the dentition and the gums supporting the crowns; an outer layer mouth guard which covers the inner layer mouth guard and is translucent; A pair of test strips protruding from the outer layer mouth guard with a gap large enough to hold a liquid; a light emitter that is incorporated in a first protruding piece of the measuring piece and emits a measuring light; a light receiver that is built into the second protruding piece of the measuring piece and receives the measuring light and converts it into an electrical signal; a transmitter that is interposed between the inner layer mouth guard and the outer layer mouth guard and transmits to the outside an electric signal converted by the light receiver and a power source that drives the light emitter; An intraoral optical measurement device comprising:

2. The intraoral optical measurement device according to claim 1 , wherein the measuring piece is provided so as to protrude inward into the oral cavity.

3. The intraoral optical measurement device according to claim 2 , wherein the dentition is a lower jaw dentition.

4. The intraoral optical measurement device according to claim 3 , wherein the dentition is an entire dentition of a mandible.

5. The intraoral optical measurement device according to claim 4 , wherein the measuring piece is provided at a position corresponding to a back side of an incisor.

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