JP4471709B2 - Caries detection device - Google Patents

Description

  The present invention relates to a technique for detecting tooth decay, and more particularly to a technique for non-destructively detecting an initial stage tooth decay based on fluorescence information from the tooth.

  As a conventional technique for detecting caries using light, there is an apparatus described in Patent Document 1. Such an apparatus irradiates teeth with red light (600 to 670 nm) as excitation light, and measures only the intensity of light received by a photodiode from the teeth. In addition, since the device detects cavities by fluorescence derived from bacteria in the oral cavity, detection of cavities occurs when the cavities progress and holes are formed in the teeth, and the bacteria are proliferating in them. Is possible.

  However, the progress of early caries does not necessarily correlate with the presence and amount of bacteria. In particular, in the case of early caries, it is difficult to detect such initial caries with the device described in Patent Document 1 because bacteria in the composition for oral cavity are often not detected at the corresponding locations. That is, since the result analyzed by such fluorescence information depends on the presence or absence of bacteria in the oral cavity, it is difficult to accurately determine the presence or absence of initial caries.

  In order to solve the problem of Patent Document 1, a QLF (quantitative light-induced fluorescence) method described in Non-Patent Documents 1 and 2 and an apparatus that realizes the method have been developed. This apparatus irradiates with ultraviolet rays of 380 ± 70 nm and detects only the intensity of fluorescence obtained above 520 nm, and the fluorescence intensity from the caries site is weaker than the fluorescence intensity from the healthy tooth site. Using this phenomenon, tooth decay is detected. Since the caries detection in this case is not affected by the presence of bacteria, the presence / absence of caries can be detected more accurately as compared with the apparatus disclosed in Patent Document 1. However, as shown in Comparative Example 2 which will be described later, since the actual change in the mineral decrease rate does not match the change in the fluorescence intensity of 520 nm or more, it is difficult to measure the progress of the initial caries.

  Furthermore, as a device for detecting caries, there is a device that irradiates 360-580 nm ultraviolet rays on a tooth and measures fluorescence of 620 nm or more from the tooth (Patent Document 2). This apparatus is intended to measure only red fluorescence specific to the caries site, and does not detect oral bacteria as in Patent Document 1. However, since the apparatus described in Patent Document 2 only measures red fluorescence with low fluorescence intensity, the fluorescence intensity is insufficient to detect the presence or absence of caries and is easily affected by the measurement environment such as external light. There is a problem of low detection sensitivity.

  On the other hand, there is a technique described in Non-Patent Document 3 as a technique that can accurately detect and quantify the degree of progress of caries. This technology slices the extracted dental caries, shoots the cross-section with a micro X-ray, calculates the mineral reduction rate while comparing with healthy teeth based on the information in the photo, and quantifies the progress of dental caries To do. Such a method can surely check the progress of caries, but has a problem that it cannot be measured unless the tooth is removed and sliced.

Japanese Patent Laid-Open No. 2001-299699 European Patent Application No. 0555645 Stookey, G.K., et al. Dental caries diagnosis, Dent Clin North Am., 43; 665-77, 1999. Shi X.Q, et al. Comparison of QLF and DIAGNOdent for quantification of smooth surface caries, Caries Res., 35 (1): 21-6, 2001. Masayoshi Yoshikawa et al., “Effects of pH and duration of 0.1M lactic acid on enamel demineralization”, Journal of Oral Hygiene, 1990, Vol. 40, p. 671-677

  An object of the present invention is to provide a caries detection device, a caries detection method, and a program for realizing the caries detection method capable of detecting initial caries with high sensitivity and accuracy and detecting the progress of caries.

  When the present inventors irradiate ultraviolet rays (i-line 365 nm of mercury lamp) on teeth, strong fluorescence is generated in the vicinity of 400 to 500 nm (equivalent to blue) for healthy teeth, while 400 for dental caries. It was found that the fluorescence in the vicinity of ˜500 nm was weakened, while the fluorescence was generated in the vicinity of 600 to 800 nm (corresponding to red).

  In addition, when the intensity of irradiation light of ultraviolet light is decreased, the present inventors have weakened the fluorescence corresponding to blue and red for caries, whereas the fluorescence corresponding to blue is weak for healthy teeth. However, it was found that the fluorescence corresponding to red was intensified.

  The present invention has been made on the basis of the above findings, and includes an ultraviolet light source, a fluorescence light receiving unit that receives fluorescence from teeth by the ultraviolet light emitted from the ultraviolet light source, and fluorescence data transmitted from the fluorescence light receiving unit. A dental caries detecting device comprising: a fluorescence data analysis unit for analyzing the analysis data; and an analysis data display unit for displaying the analysis data analyzed by the fluorescence data analysis unit, wherein the fluorescence data analysis unit It is a caries detection device which analyzes based on the fluorescence intensity in two or more wavelength bands of an optical region.

  By using the detection apparatus according to the present invention, it is possible to detect the initial caries with high sensitivity, so that treatment by non-surgical treatment without removing the initial caries becomes easier. Furthermore, the caries detection apparatus according to the present invention can also measure the progress of caries. Since it is possible to observe the treatment progress of the initial caries and the degree of recovery can be confirmed, the progress and recovery status of the caries can be specifically shown to the patient. Furthermore, it is possible to obtain an understanding of the importance of the dental caries prevention treatment and the effect of the treatment, thereby contributing to the maintenance and improvement of oral health.

  By measuring the surface of the tooth with the caries detection device according to the present invention, it is possible not only to detect caries with high accuracy, but also to parts that are difficult to measure, such as tooth gaps (measured at one place), It is also possible to perform contrast measurement (measured at two locations) between a healthy site and a carious site. Further, by analyzing these fluorescence data based on the fluorescence intensity in two or more wavelength bands in the visible light region, it is possible to detect caries (especially the initial caries) and the degree of progression thereof with high sensitivity and accuracy.

  In addition, by using the dental caries detecting device according to the present invention, a wavelength band showing a change different between a caries and a healthy tooth is selected from fluorescence data from a tooth that changes with a change in the intensity of irradiation light of ultraviolet rays, and the wavelength Analysis can be performed based on a plurality of fluorescence intensities in the band, whereby the caries (especially the initial caries) and the degree of progression thereof can be detected with high sensitivity and accuracy.

  In the present application, the “first wavelength band” means a wavelength band having an arbitrary wavelength width selected from a wavelength band of 550 to 810 nm including not only a wavelength corresponding to red but also a wavelength corresponding to green. The “second wavelength band” means a wavelength band having an arbitrary wavelength width selected from a wavelength band of 380 to 550 nm including not only a wavelength corresponding to blue but also a wavelength corresponding to green. The “third wavelength band” means a wavelength band having an arbitrary wavelength width selected from a wavelength band of 450 to 650 nm including not only a wavelength corresponding to green but also a wavelength corresponding to red and a wavelength corresponding to blue. .

  The wavelength width of the first wavelength band is from 0.1 nm to 260 nm, preferably from 10 nm to 260 nm, and more preferably from 50 nm to 260 nm. The wavelength width of the second wavelength band is 0.1 nm to 170 nm, preferably 10 nm to 170 nm, and more preferably 50 nm to 170 nm. The wavelength width of the third wavelength band is from 0.1 nm to 200 nm, preferably from 10 nm to 200 nm, and more preferably from 50 nm to 200 nm.

  In addition, when the fluorescence data is divided into a plurality of wavelength bands using a bandpass filter, the numerical range of wavelengths included in the wavelength band may change depending on the performance of the filter. For example, when a primary color CCD in which a bandpass filter is already incorporated in the element is used, the first wavelength band (corresponding to red) has a center wavelength of 650 ± 50, and the second wavelength band (corresponding to blue) is The center wavelength is 450 ± 50, and the third wavelength band (corresponding to green) is typically center wavelength 550 ± 50, but is not limited to these wavelengths. This includes the case where the wavelength ranges overlap each other.

The center wavelength of the first wavelength band and the center wavelength of the third wavelength band are preferably separated by 10 nm or more, more preferably 20 nm or more. Further, the center wavelength of the second wavelength band and the center wavelength of the third wavelength band are also preferably separated by 10 nm or more, more preferably 20 nm or more. The center wavelength means an intermediate wavelength between the points where the relative transmittance at two points of the band pass filter is 50%.
In the case of the filter shown in FIG. 1 (filter characteristics), the red wavelength bands are 350 to 450 and 550 to 750, which are also included in the first wavelength band of the present application.

  According to the present invention, it is possible to obtain a caries detection apparatus and a caries detection method that can detect initial caries with high sensitivity and accurately detect the progress of the caries.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a most preferred embodiment of a caries detection device, caries detection method and caries detection program of the present invention will be described in detail.
As shown in FIG. 2, the caries detection system (caries detection apparatus) 1 of the present embodiment includes an ultraviolet irradiation device (ultraviolet light source) 2 and fluorescence that receives fluorescence from teeth by ultraviolet rays emitted from the ultraviolet irradiation device 2. A light receiving device (fluorescence light receiving unit) 3, a data analysis unit 4 that analyzes data transmitted from the fluorescence light receiving device 3, and a display device (analysis data display unit) 5 that displays analysis data analyzed by the data analysis unit 4. And.

The data analysis unit 4 is configured to divide the fluorescence data into two or more wavelength bands in the visible light region and perform analysis based on the fluorescence intensity in each wavelength band.
First, the caries detection system 1 will be described in detail.

  The caries detection system 1 has a main control unit 10 (details will be described later) for comprehensively controlling the entire system. The main control unit 10 is connected to the ultraviolet irradiation device 2 and the fluorescence light receiving device 3 through the input / output control unit 11, and is also connected to the storage device 12, the display device 5, and the output device 13. Yes.

  The ultraviolet irradiation device 2 irradiates ultraviolet rays having a wavelength of about 300 to 400 nm, and it is sufficient that the irradiation light intensity is adjustable. Examples of such an ultraviolet irradiation device 2 include an ultraviolet LED, a mercury lamp, and a metal halide lamp. The ultraviolet LED is configured so that the irradiation light intensity of the ultraviolet light is adjusted. For example, the input / output control unit 11 controls the energization amount, or the light intensity adjustment is performed by changing the number of lighting of a plurality of LEDs.

In the mercury lamp or the metal halide lamp, the irradiation light passes through the visible light cut filter and becomes ultraviolet light, and the intensity of the ultraviolet light can be adjusted. The intensity adjustment is performed, for example, by controlling the current value or using an ND filter.
There is no particular limitation on the light guiding device from the ultraviolet irradiation device 2 as long as it has a low ultraviolet absorptivity. For example, the teeth can be passed through an optical fiber having a core made of quartz glass or a polymer material. It is designed to be irradiated directly.

The fluorescence light receiving device 3 absorbs the light in the ultraviolet region when the fluorescence from the teeth passes through the ultraviolet cut filter 14 when irradiated with ultraviolet rays, and only the light in the visible region is received by the optical device through the optical fiber. It is configured as follows.
The optical device only needs to be capable of capturing information including color information as fluorescence data from fluorescence in the visible light region and transmitting the information to the input / output control unit 11. The input / output control unit 11 is configured to AD convert information from the optical device.

Examples of the optical device include a spectral luminance meter, a color CCD, a CMOS, or an optical sensor with two or more color filters.
Specifically, the spectral luminance meter is configured to obtain information for each color by color-separating fluorescence with a prism or the like and capturing each color light (red light, green light, blue light, etc.) with an optical sensor. Yes.

The color CCD is configured to receive light with a two-dimensional array of elements having color filters (primary colors RGB, complementary colors CMYG) and obtain color information based on electrical signals from the respective elements.
Furthermore, an optical sensor with two or more color filters (bandpass filters) can detect only a specific wavelength of fluorescence for each wavelength band based on, for example, an electrical signal from a light receiving element such as a photomultiplier or a silicon photodiode. It is configured to obtain information.

  The storage device only needs to be able to store the analysis data analyzed by the data analysis unit 4, and includes, for example, a hard disk, a flexible disk, and an optical disk.

The display device 5 may be any device that can display the analysis data and information necessary for selection of the analysis data (the number of measurement sites and changes in light intensity). Examples thereof include a CRT display and a liquid crystal display.
The output device 13 may be any device that can output the analysis data, such as a printer.

The main control unit 10 includes a CPU 15, an internal memory 16, a fluorescence data analysis unit 4, and the like. The CPU 15 is configured to decode and execute a command from a control program such as an OS (Operating System) or a caries detection program. The internal memory 16 temporarily stores information from the input / output control unit 11 and analysis data from the storage device 12.
The fluorescence data analysis unit 4 is configured as a means in which the caries detection program and the hardware resources (computer) such as the CPU 15 and main memory cooperate with each other when the caries detection program is executed by the CPU 15.

  The caries detection program has a function to select the number of measurement parts, a light intensity change function, a data capture function, a wavelength band selection function, a caries degree calculation function, a caries presence / absence / progress degree judgment function, etc. With these functions, the caries detection method described below is constructed.

Next, the method for detecting tooth decay of the present embodiment will be described with reference to FIGS. 3 to 9 in association with various functions of the tooth decay detection program.
The caries detection method has a common main process (S1 to S3, S5), and a single part measurement method (S4, S11 to S19), a contrast measurement method (S21 to S30), light, depending on the detection purpose and the detection method. There are roughly three types of intensity change measurement methods (S31 to S35, S41 to S48, S51 to S58, S61 to S68).

The single site measurement method is a method for detecting the presence or absence of caries in an invisible carious part such as a tooth part visible from the outside or a part suspected of caries, especially a tooth gap or meshing, or the progress of the caries. Measure at least one place that appears to be a caries site.
The contrast measurement method is a method for detecting the presence or absence of caries of a carious part or a carious part of a carious tooth (simply referred to as “carious part”) that is visible from the outside, or the degree of progression of the caries. These two points are measured independently.
The light intensity change measurement method is a method for detecting the presence or absence of caries and the progress of the caries, regardless of whether they are visible from the outside. Measure once.

Specifically, as shown in FIG. 3, the CPU 15 displays whether or not to measure on the display device 5 (S1), and when measuring, the measurement is performed based on the measurement site number selection function of the caries detection program. Whether or not the number of parts is “1” is displayed (S2).
If the number of measurement parts is not “1”, the process branches to the “contrast measurement method” process (branch B, details will be described later). If the number of measurement parts is “1”, the CPU 15 detects tooth decay. Whether or not the light intensity of the light source is changed is displayed based on the light intensity change selection function of the program (S3).

  When the light intensity of the light source is changed, the process branches to the “light intensity change measurement method” process (branch C, details will be described later). When the light intensity of the light source is not changed, the CPU 15 performs “single part measurement”. The process of “Method” is executed.

Here, in the single part measurement method, first, the measurer irradiates the target part using the ultraviolet irradiation device 2 and obtains information from the fluorescence from the teeth using the fluorescent light receiving device 3.
Next, the CPU 15 captures information from the optical device into the internal memory 16 as a digital signal AD-converted by the input / output control unit 11 based on the data capture function of the caries detection program, and the digital signal is first to first The luminance (fluorescence intensity) R, B, G for each third wavelength band is stored in the internal memory 16 (S4).

Here, in the first wavelength band (corresponding to red), in the visible light region (380 to 810 nm), the wavelength is preferably 550 to 810 nm, and more preferably 600 to 700 nm.
The second wavelength band (corresponding to blue) preferably has a wavelength of 380 to 550 nm, more preferably 400 to 500 nm in the visible light region.
Furthermore, in the third wavelength band (equivalent to green), the wavelength is preferably 450 to 650 nm, more preferably 500 to 600 nm in the visible light region.

Thereafter, as shown in FIG. 4, the CPU 15 obtains the luminances R, B, and G based on the caries degree calculation function of the caries detection program, and calculates the caries degree CD ₁ according to the following equation (1) ( S11).
CD ₁ = R / B ... formula (1)
This dental caries degree CD ₁ uses the characteristic that the luminance R increases while the dental caries progress while the dental caries progress, while the brightness B and G decrease, and the degree of dental caries progresses as a quantitative increase function. It is a representation.

Here, since the absolute intensity of the luminance B is larger than the luminance G, the noise is less affected by external light and the noise is small, and therefore the dental caries degree CD ₁ can be calculated with higher accuracy.
Alternatively, the tooth decay degree CD ₁₂ may be calculated according to the following formula (1.2) using the brightness G instead of the brightness B.
CD ₁₂ = R / G ... Formula (1.2)

The processes of S12 to S19 are processes executed by the CPU 15 based on the caries presence / absence / progress degree determination function of the caries detection program.
In S12, the dental caries degree CD _1, compared with the lower threshold E _1. Here, the “lower threshold value” is a value for discriminating between healthy teeth and caries (especially initial caries, hereinafter the same), conditions such as irradiation light intensity and irradiation area in the ultraviolet irradiation device 2, fluorescence, and the like. It depends on conditions such as the optical path length in the light receiving device 3 and the sensitivity of the light receiving element, and is determined by calibration in the caries detection system 1.

Dental caries degree CD ₁ is the lower threshold E ₁ less than, or equal to the lower threshold E ₁ is the fact that they are healthy tooth Display (analysis data) Return to S1 of the main processing (S18, 19) If the dental caries degree CD ₁ is larger than the lower threshold E ₁ , the fact that it is a caries (analysis data) is displayed (S 13).

In S14, the dental caries degree CD _1, compared with the upper threshold F _1. Here, the “upper threshold value” is a value for discriminating mild caries from severe caries, and is determined in the same manner as the lower threshold value.

If the dental caries degree CD ₁ is smaller than the upper threshold F ₁ , the fact that it is a mild initial caries (analysis data) is displayed (S15), and the dental caries degree CD ₁ is larger than the upper threshold F ₁ . or equal to the lower threshold F ₁ displays indicating that severe early dental caries (the analysis data) (S16), returns to S1 of the main processing (S17).

If the number of measurement sites is not “1” in S2, the CPU 15 executes the “contrast measurement method” process.
Here, in the contrast measurement method, first, the measurer uses the ultraviolet irradiation device 2 to apply ultraviolet rays to the caries site (site suspected of caries) and the healthy part in the vicinity thereof on the same tooth. The first information is obtained from the fluorescence of the carious site using the fluorescence light receiving device 3 and the second information is obtained from the fluorescence of the healthy site.

Next, as shown in FIG. 5, the CPU 15 converts the first and second information from the optical device as digital signals AD-converted by the input / output control unit 11 based on the data acquisition function of the caries detection program, respectively. Incorporated into the internal memory, each digital signal is decomposed for each of the first to third wavelength bands based on the wavelength band selection function of the caries detection program, the brightness of the caries site (R _c , B _c , G _c ), healthy site of the luminance _{(R n, B n, G} n) a, respectively stored in the internal memory 16 (S21).

Thereafter, the CPU 15 calculates the average of the brightness of the caries part (R _c , B _c , G _c ) and the brightness of the healthy part (R _n , B _n , G _n ) based on the caries degree calculation function of the caries detection program. The value is obtained, and the average value of each is calculated as the dental caries degree CD ₂ according to the following equation (2) (S22).
_{CD 2 = | R n -R c} | × | B n -B c | ... formula (2)

The degree of dental caries CD ₂ is such that, as the caries progress, the luminance R _c of the carious part becomes larger than the luminance R _{n of the} healthy part, and the luminances B _c and G _{c of the} carious part are the luminance B _{n of the} healthy part. Using the property of being smaller than G _n , the degree of progress of caries is expressed as a quantitative increase function.

Here, since the absolute intensity of the luminance B is larger than the luminance G, the luminance G is not used from the viewpoint of increasing the accuracy of the caries degree CD ₁ because the noise is less affected by outside light and the noise is small. From the viewpoint of comparison with R, the tooth degree CD ₂₂ is calculated according to the following equation (2.2) using the luminance G instead of the luminance B, or the following equation (2) using the luminance G together with the luminance B: .3) The dental caries degree CD ₂₃ may be calculated.
CD ₂₂ = | R _n −R _c | × | G _n −G _c |... Formula (2.2)
CD ₂₃ = | R _n −R _c | × {| B _n −B _c | + | G _n −G _c |} Expression (2.3)

  The processes of S23 to S30 are processes executed by the CPU 15 based on the caries presence / absence / progress degree determination function of the caries detection program, and are substantially the same as the processes of S12 to S19.

In S23, the dental caries degree CD _2, compared with the lower threshold E _2.
Dental caries degree CD ₂ is lower threshold E ₂ is less than or equal to the lower threshold E ₂ may display a message indicating a healthy tooth returns to S1 in the main processing (S29, S30), caries If the degree CD ₂ is greater than the lower limit threshold E ₂ , the fact that it is a caries is displayed (S24).

In S25, the dental caries degree CD _2, compared with the upper threshold F _2.
If the caries degree CD ₂ is smaller than the upper threshold F _2, it is displayed that the caries is a mild initial caries (S 26), and the caries degree CD ₂ is greater than the upper threshold F ₂ or the upper threshold. If equal to the value F ₂ displays the effect that the severe early dental caries (S27), returns to S1 of the main processing (S28).

In S3, when the light intensity of the light source is changed, the CPU 15 executes the process of “light intensity change measuring method”.
Here, in the light intensity change measuring method, first, the measurer uses the ultraviolet irradiation device 2 to apply the ultraviolet rays whose light intensities U ₁ and U ₂ (U ₁ > U ₂ ) are changed to the same in the same tooth. Each part is irradiated, and using the fluorescence light receiving device 3, the first information is obtained from the fluorescence with respect to the light intensity U ₁ and the second information is obtained from the fluorescence with respect to the light intensity U ₂ .

Next, as shown in FIG. 6, the CPU 15 converts the first and second information from the optical device as digital signals AD-converted by the input / output control unit 11 based on the data fetching function of the caries detection program, respectively. incorporation in the internal memory 16, the respective digital signal, the first through third luminance of the light intensity U ₁ for each wavelength band _{(R 1, B 1, G} 1), the luminance of the light intensity U ₂ (R _2, B ₂ , G ₂ ) are stored in the internal memory 16 (S31, S32). The light intensity is not limited to two and may be two or more.

Then, CPU 15, based on the dental caries presence and progression degree determining function dental caries detecting program, the magnitude relationship between the luminance R ₁ of the light intensity U _1, the luminance R ₂ of the light intensity U _2, i.e., (R ₁ -R ₂ ) Is determined to be “positive (+)” (S33). If it is “positive (+)”, it indicates that there is a possibility of caries (S34), and “negative ( In the case of “−)”, the fact that it is a healthy tooth is displayed, and the process returns to S1 of the main process (S35). The determination method is not limited to this, and a correlation between a plurality of luminance data and irradiation intensity is obtained. Good.

Processing S33~S35, for the caries sites, brightness R ₂ is smaller than the luminance R ₁ whereas (positive correlation to ultraviolet radiation intensity), for healthy area, brightness R ₂ is greater than the luminance R ₁ Using the characteristic of (negative correlation with ultraviolet irradiation intensity), the presence or absence of caries was determined before determining the progress of caries.

The processing after proceeding to S34, the difference calculation processing of dental caries degree, processing of dental caries degree CD ₃ (branch D _1, S41~S48), the process of dental caries degree CD ₄ (branch D _2, S51 to S58), Branches into _three processes (branch D ₃ , S61 to S68) of the caries degree CD ₅ .

As shown in FIG. 7, in the process of the caries degree CD ₃ , the CPU 15 performs the brightness (R ₁ , B ₁ , G ₁ ) of the light intensity U ₁ and the light intensity based on the caries degree calculation function of the caries detection program. Each value of the luminance (R ₂ , B ₂ , G ₂ ) of U ₂ is obtained, and the dental caries degree CD ₃ is calculated from each value according to the following equation (3) (S41).
CD ₃ = (R ₁ / R ₂ ) × (B ₁ / B ₂ ) (3)

This dental caries degree CD ₃ has a luminance R ₂ , B ₂ , G ₂ smaller than the luminance R ₁ , B ₁ , G ₁ for the carious part, respectively, while the luminance B ₂ , G _2, respectively, although smaller than the luminance B _1, G _1, in which the luminance R ₂ is using the characteristic of becoming larger than the luminance R _1, showing the degree of progress of dental caries as a function.

The processes of S42 to S48 are processes executed by the CPU 15 based on the caries presence / absence / progress degree determination function of the caries detection program, and are substantially the same as the processes of S23 to S30.
In S42, the dental caries degree CD _3, compared with the upper threshold F _3. Dental caries degree CD ₃ is larger than the upper threshold F _3, or equal to the upper threshold F _3, display to the effect that a healthy tooth returns to S1 in the main processing (S47,48), caries If the degree CD ₃ is smaller than the upper limit threshold F ₃ , the process proceeds to S43.

In S43, the dental caries degree CD _3, compared with the lower threshold E _3. If the dental caries degree CD ₃ is larger than the lower threshold E _3, it is displayed that it is a mild initial caries (S 44), and the dental caries degree CD ₃ is smaller than the lower threshold E ₃ or the lower threshold. If it is equal to the value E ₃ , the fact that it is a severe initial caries is displayed (S45), and the process returns to S1 of the main process (S46).

As shown in FIG. 8, in the process of the caries degree CD ₄ , only the process of S51 is different when compared with the process of the caries degree CD ₃ .
In S51, the luminance intensity _{U 1 (R 1, B 1} , G 1), and the light intensity U ₂ luminance _{(R 2, B 2, G} 2) caries a respective values according to the following equation (4) The degree CD ₄ is calculated.
CD ₄ = (R ₁ / R ₂ ) × (G ₁ / G ₂ )... (4)
The other processes are the same as described above, and thus description thereof is omitted.

As shown in FIG. 9, in the process of the caries degree CD ₅ , only the processes of S61, S62, and S63 are different when compared with the process of the caries degree CD ₃ .
In S61, the luminance intensity _{U 1 (R 1, B 1} , G 1), and caries the respective values in accordance with the following equation (5) of the light intensity U ₂ luminance _{(R 2, B 2, G} 2) The degree CD ₅ is calculated.
CD ₅ = (R ₁ / R ₂ ) × {(B ₁ / B ₂ ) + (G ₁ / G ₂ )} Expression (5)
In S62, different method of setting the upper threshold F _5, in S63, the setting of the lower threshold E ₅ how different. The other processes are the same as described above, and thus description thereof is omitted.

In such a light intensity change measuring method, although not shown, in addition to the caries degree CD ₃ , CD ₄ , CD ₅ , the caries degree CD ₆ may be calculated according to the following equation (6).
CD ₆ = (R ₁ / R ₂ ) × (B ₁ / B ₂ ) × (G ₁ / G ₂ ) (6)

  As described above, according to the present embodiment, in the caries detection method, the caries degree CD is expressed by a quantitative function based on the luminances R, B, and G over high and low energy values, and the caries degree CD is expressed as a lower limit. By comparing with the threshold value E and the upper threshold value F, whether the initial stage caries that have not been invaded by bacteria is “normal tooth”, “mild caries” or “severe caries” Can be accurately determined with high sensitivity.

  In addition, according to the present embodiment, the caries detection method is largely divided into three methods: a measurement method using data obtained from one place, a measurement method that compares data obtained from two places, and a measurement method that changes light intensity. By making it possible to separately use and combine these methods depending on the detection purpose and measurement site, it is possible to efficiently and accurately detect the presence or absence of caries and the progress of caries.

That is, in the measuring method using data obtained from one place, it can be used not only for the visible part but also for a part where a comparative part such as a tooth gap or meshing is difficult to obtain. By simply measuring the location, it is possible to detect the presence and progress of caries. This measurement method is advantageous for measurement of any part as a method capable of instantaneously detecting caries based on the obtained caries degree CD ₁ .

In addition, in the measurement method for comparing the data obtained from two places, the presence or progression of caries is measured by measuring two places in the comparison with the healthy part for the part of the caries that is visible or the part that is suspected to be caries. The degree can be detected. This measurement method is advantageous in that the progress degree of the caries can be detected instantaneously based only on the caries degree CD ₂ taking into consideration the comparison between the carious part and the healthy part.

Furthermore, in the light intensity change measuring method, the progress of caries can be detected by measuring at least twice for the same carious site while changing the light intensity of ultraviolet rays. In this measurement method, the presence / absence of caries can be determined instantaneously by simply comparing the brightness R ₁ and R ₂ with different light intensities, and the degree of progress of caries according to the depth of the tooth due to changes in light intensity. It is advantageous in that it is obtained.

  The caries detection method according to the present invention can be realized by using the caries detection system 1 incorporating a caries detection program.

The present invention is not limited to the above embodiment, and various changes can be made.
For example, in the above light intensity measurement method, the light intensity is changed to two types, but not limited to this, the light intensity is changed to three or more types, and any two pieces of information (fluorescence data) are captured. The dental caries degree CD _{3 to} CD ₆ may be calculated.

In calculating the caries degrees CD _{3 to} CD ₆ , the luminance ratio (R ₁ / R ₂ ) or the like having different light intensities is used, but instead, the luminance gradient or correlation can be used.

  Furthermore, in addition to the comparison of the dental caries degree CD with the lower threshold value E and the upper threshold value F, by adding another threshold value, a moderate degree of intermediate between severe and mild is shown. You can also Furthermore, in addition to data indicating that the tooth is a healthy tooth, the degree of dental caries CD itself may be displayed as analysis data on the display device 5, and such analysis data may be output to the output device 13.

  The present inventors are concerned with the present invention by determining the correlation between the method described in Non-Patent Document 3 and Examples 1 to 4 and Comparative Examples 1 and 2 that can measure the degree of progress of caries most accurately at present. The detection accuracy of the caries detection device was evaluated.

  The extracted tooth used in the experiment was selected to be an initial caries that could be recovered by non-surgical treatment without losing the surface layer. These extracted teeth were classified into three types according to the visual observation of an experienced dentist: an extremely early one (mild), an advanced one (moderate), and a hole just before drilling (severe).

  The extracted extracted teeth were first measured with the caries detecting device according to the present invention. Thereafter, based on the method described in Non-Patent Document 3, the extracted tooth was sliced to prepare a sample for micro X-ray photography. In Examples, the accuracy of the caries detection device of the present invention is obtained by obtaining a correlation coefficient between the measurement result of the caries detection device according to the present invention and the mineral reduction rate obtained by the method shown in Non-Patent Document 3. Verified.

  The mineral reduction rate indicates the degree of progress of dental caries, and is a value obtained by computer image analysis for a region from the surface to a depth of 300 microns using a micro X-ray photograph in accordance with Non-Patent Document 3 above. The mineral reduction rate of the healthy part is 0%, and when all the teeth are lost after melting, the mineral reduction rate is 100%.

The caries detection system 1 used in the present embodiment and the caries detection method using the caries detection system 1 will be described. A mercury lamp (manufactured by Nikon Corporation, model: CSHG1) was used as the ultraviolet irradiation device 2. This mercury lamp was able to efficiently irradiate i-line by mounting a band-pass filter (Nikon Corporation, model: E365 / 10) that transmits ultraviolet light having a wavelength of 400 nm or less. In addition, the mercury lamp can be changed in two steps of light intensity U ₁ (= 340 mV / cm ² ) and U ₂ (= 94 mV / cm ² ) by mounting an ND filter (made by Nikon, model: ND4). I made it. The ultraviolet rays from the mercury lamp were directly applied to the teeth by an optical fiber (made of quartz).

A color CCD camera (manufactured by Polaroid, model: PDMCIIi) was used as the fluorescence light receiving device 3. The color CCD was made to be able to image fluorescence in the visible light region by mounting a UV cut filter (Nikon Corporation, model: BA400) that transmits light of 400 nm or more. The data was subjected to A / D conversion to obtain luminance R, B, and G of 16 bits each.

The measurement by changing the tooth measurement site and the light intensities U ₁ and U ₂ will be described.
For the caries site, the measurement was performed on the mild site L, the moderate site M, and the severe site H, and the healthy site (light) L ′ for each healthy site in the vicinity (in the same tooth). Three sites, a healthy site (middle) M ′ and a healthy site (heavy) H ′, were measured.

For each measurement site, subscripts “1” and “2” are attached to the symbols of the measurement site corresponding to the light intensity U ₁ and the light intensity U ₂ . For example, “L ₁ ” indicates a measurement site for a mild caries portion irradiated with ultraviolet light having a light intensity U ₁ , and “H ₂ , 1” is irradiated with ultraviolet light having a light intensity U ₁ or U ₂ , respectively. The measurement site | part about the severe site | part of a caries is shown.
Measured in this embodiment, the light intensity U _1, U ₂ and brightness R for each measurement site, B, shown in FIG. 10 the relationship between the G, the light intensity U _1, U _2, the luminance R, B, G- Data (maximum 2 ¹⁶ = 65536) are shown in Table 1, Table 2, and Table 3.

[Example 1]

In Example 1, according to the “measurement method using data obtained from one place” of the caries detection method shown in the above embodiment, measurement sites L ₁ , M ₁ , H ₁ , L ₁ ′ of light intensity U ₁ For M ₁ ′ and H ₁ ′, the degree of dental caries CD ₁ was calculated, and the correlation coefficient between the degree of dental caries CD ₁ and the mineral reduction rate was determined.
[Comparative Example 1]

In Comparative Example 1, in accordance with the technique described in Patent Document 2, the light intensity of ultraviolet rays was set to U ₁ , and the measurement sites L ₁ , M ₁ , H ₁ , L ₁ ′, M ₁ ′, and H ₁ ′ were measured. A cut filter that transmits light of 620 nm or more is attached to the color CCD so that the color CCD can capture an image of only red fluorescence. This image was converted into a gray image, and red luminance (16 bits) was obtained for each measurement site. Respective correlation coefficients between red brightness and mineral reduction rate were obtained. Table 4 shows the measurement results of Example 1 and Comparative Example 1.

As shown in Table 4, when the mineral reduction rate is high, it means that the decayed tooth is progressing. The correlation coefficient between the caries degree CD ₁ and the mineral reduction rate of Example 1 according to the present invention was high, and it was demonstrated that the caries degree CD ₁ can objectively quantify the progress of caries.
In order to accurately grasp the progress of the decayed tooth, the brightness of red must be increased according to the value of the mineral reduction rate. On the other hand, in the case of Comparative Example 1, the magnitude relationship of red brightness is reversed between the moderate part M ₁ and the severe part H ₁ of the caries, and the degree of progress of the caries is not necessarily the same. Therefore, it is difficult to detect the progress of caries.
[Example 2]

In Example 2, according to the “contrast measurement method” of the caries detection method shown in the above embodiment, the measurement sites (L ₁ , L ₁ ′), (M ₁ , M ₁ ′), (H ₁ ) of the light intensity U ₁ are used. , H ₁ ′), the degree of dental caries CD ₂ was calculated, and the correlation coefficient between the degree of dental caries CD ₂ and the mineral reduction rate was determined.
[Comparative Example 2]

In Comparative Example 2, in accordance with the conventional technique shown in Patent Document 1, the ultraviolet light intensity is set to U ₁ , and the measurement sites (L ₁ , L ₁ ′), (M ₁ , M ₁ ′), (H ₁ , H Measured for ₁ '). A cut filter that transmits light of 520 nm or more is attached to the color CCD so that the color CCD can capture an image of monochromatic light of 520 to 800 nm. This image was converted into a gray image, and for each measurement site, the luminance of the caries site (16 bits) and the brightness of the healthy site (16 bits) were obtained, and the ratio was calculated as relative luminance. Each correlation coefficient between the relative luminance and the mineral reduction rate was obtained. Table 5 shows the measurement results of Example 2 and Comparative Example 2.

Table 5 demonstrates that the correlation coefficient between the dental caries degree CD ₂ and the mineral reduction rate is high, and the dental caries degree CD ₂ can be expressed as an objective quantitative value for the degree of dental caries progression. On the other hand, the magnitude relationship of the relative luminance is reversed between the moderate part (M ₁ , M ₁ ′) of the caries and the severe part (H ₁ , H ₁ ′). Since it does not coincide with the progress of the caries, it is difficult to detect the progress of the caries.
Example 3

In Example 3, according to the “light intensity change measuring method” of the caries detection method shown in the above embodiment, the measurement sites L2, ₁ , M2, ₁ , H2, ₁ , L2, ₁ ′ of the light intensities U ₁ and U ₂ are used. for _{M2, 1 ', H2, 1} ', respectively, the luminance change _{(R 1 -R 2), (} G 1 -G 2), and (B ₁ -B _2), and a dental caries degree CD _3, CD ₄ Calculations were made to obtain respective correlation coefficients between the caries degree CD ₃ and CD ₄ and the mineral reduction rate. Tables 6 and 7 show the measurement results of Example 3.

From Table 6, it became clear that the sign of the luminance change (R ₁ -R ₂ ) is an objective criterion for the presence or absence of caries. Also, from Table 7, the correlation coefficient between the caries degree CD ₃ and CD ₄ and the mineral reduction rate is high, and the caries degree CD ₃ and CD ₄ can be expressed as objective quantitative values for the degree of progress of caries. Proven.
Example 4

In Example 4, as in Example 3 above, the caries degrees CD ₅ and CD ₆ were calculated, and the respective correlation coefficients between the caries degrees CD ₅ and CD ₆ and the mineral reduction rate were obtained.
The above-mentioned caries degree CD ₃ , CD ₄ is the target of calculation of the brightness R and either one of the brightness B, G, whereas the caries degree CD ₅ , CD ₆ is the brightness R, B, The difference is that the three members of G are subject to calculation. The measurement results of Example 4 are shown in Table 8.

Table 8, a high correlation coefficient between dental caries degree CD _5, CD ₆ and mineral reduction rate, dental caries degree CD _5, CD _6, it is demonstrated that can be shown in objective quantitative value for the degree of progress of dental caries It was.
According to the present invention, it is possible to obtain a caries detection apparatus and a caries detection method that can detect initial caries with high sensitivity and can detect the progress of the caries.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a technique for detecting the presence or absence of initial caries and the progress of initial caries in the technical field of non-destructively detecting initial caries.

It is a figure which shows the filter characteristic of a color CCD. It is a figure showing a schematic structure of a caries detection system of this embodiment. It is a flowchart which shows a caries detection process (a main process and a single site | part measurement process) based on the caries detection program of this embodiment. It caries detection process (single-site measurement processing, CD ₁₎ on the basis of a dental caries detecting program of the present embodiment is a flowchart illustrating a. Caries detection processing (comparison measurement process, CD ₂₎ on the basis of a dental caries detecting program of the present embodiment is a flowchart illustrating a. It is a flowchart which shows a caries detection process (light intensity change measurement process) based on the caries detection program of this embodiment. Caries detection processing (light intensity change measuring process, CD ₃₎ on the basis of a dental caries detecting program of the present embodiment is a flowchart illustrating a. Caries detection processing (light intensity change measuring process, CD ₄₎ on the basis of a dental caries detecting program of the present embodiment is a flowchart illustrating a. Caries detection processing (light intensity change measuring process, CD ₅₎ on the basis of a dental caries detecting program of the present embodiment is a flowchart illustrating a. (A)-(f) shows the relationship between the light intensity and the brightness | luminance used for Examples 1-4. (A) is a graph showing a healthy tooth site (light), (b) is a graph showing a healthy tooth site (middle), (c) is a graph showing a healthy tooth site (heavy), (d) is The graph shown about the mild site | part of a caries, (e) is a graph shown about the moderate site | part of a caries, (f): The graph shown about the severe site | part of a caries.

Explanation of symbols

1 Caries detection system (Caries detection device)
2 UV irradiation device (UV light source)
3 Fluorescence receiver (Fluorescence receiver)
4 Fluorescence data analysis part 5 Display device (analysis data display part)
CD ₁ , CD ₂ , CD ₃ , CD ₄ , CD ₅

Claims (7)

An ultraviolet light source, a fluorescence light receiving unit that receives fluorescence from the teeth by ultraviolet light emitted from the ultraviolet light source, a fluorescence data analysis unit that analyzes fluorescence data transmitted from the fluorescence light receiving unit, and the fluorescence data analysis unit A caries detection device comprising a data display unit for displaying the analyzed data,
The fluorescence data analysis unit is a caries detection device that performs analysis based on a plurality of fluorescence intensities in one or more wavelength bands that change in accordance with a change in the intensity of irradiation light of the ultraviolet rays. The fluorescence data analysis unit includes the fluorescence intensity in a first wavelength band having a wavelength width of 0.1 nm or more and 260 nm or less selected from a wavelength band of 550 to 810 nm, and 0.1 nm or more selected from a wavelength band of 380 to 550 nm. The caries detection device according to claim 1, wherein the progress of caries is calculated based on the fluorescence intensity in the second wavelength band having a wavelength width of 170 nm or less. The fluorescence data analysis unit includes the fluorescence intensity in a first wavelength band having a wavelength width of 0.1 nm or more and 260 nm or less selected from a wavelength band of 550 to 810 nm, and 0.1 nm or more selected from a wavelength band of 380 to 550 nm. Based on the fluorescence intensity in the second wavelength band having a wavelength width of 170 nm or less and / or the fluorescence intensity in the third wavelength band having a wavelength width of 0.1 nm or more and 200 nm or less selected from the wavelength band of 450 to 650 nm. The caries detection device according to claim 1 which computes the progress of caries. The fluorescence light receiving unit, the visible light claim fluorescence intensity information regarding extractable optical devices are provided in said first wavelength band and the second and / or third wavelength band from the area 1-3 The carious tooth detection apparatus in any one of. The caries detecting device according to claim 4 , wherein the optical device is any one of a spectral luminance meter, a color CCD, a CMOS, or an optical sensor with two or more color filters. The caries detecting device according to claim 4 or 5 , wherein the ultraviolet light source is configured such that an output intensity can be adjusted. The caries detecting device according to claim 6 , wherein the ultraviolet light source is an ultraviolet LED.

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