Method of estimating color of restoration of teeth

FIELD: stomatology.

SUBSTANCE: method can be used for objective estimation of color of solid tissues of teeth, filling material and fillings. Method of estimation includes application of light along lightguide onto part of tooth and guiding of reflected light along lightguide to introduce reflected light into spectrum analyzer. Reflection spectrum is subject to colorimetric treatment to determine coloration. The coloration is compared with pre-known coloration of samples. Color is judged to be identical in case both colorations coincide. Light is applied to non-damaged part of tooth and reflected light is collected by means of photometric sphere. Coordinates of coloration are determined from reflection spectrum. The coordinates are compared with known ones of samples of filling material. If difference in color doesn't exceed 2-3 thresholds then filling material is chosen. If color difference is bigger then two filling materials are chosen and imposed one on the other and the third material is added to reduce color difference till specified threshold. Control determination of coordinates of coloration of filling is carried out and in case the coordinates coincide with coordinates of coloration of non-damaged part of tooth doesn't exceed 2-3 thresholds, the estimation is judged to be identical one.

EFFECT: improved precision; higher truth of estimation of color.

2 cl, 4 dwg, 1 ex, 1 tbl

 

The invention relates to dentistry and can be used to objectively determine the color of the hard tissues of the tooth filling material and seals.

The purpose of the invention is improving the quality of the aesthetic restoration of teeth.

A known method for the diagnosis of dental hard tissues and sediments. When implementing this method, irradiated area of intact tooth tissue by radiation from a helium-neon laser through a multi-channel optical fiber. Record the spectrum of the reflected signal to determine the rate of fluorescence in the intact tooth (J). Further, similar to determine the rate of fluorescence (J) all abnormal areas. If J/J>1±0,2, diagnosed with active caries process and/or the presence of supra - and subgingival dental plaque. Treatment is carried out to J/J=1±0,2, that is, unless you remove the entire affected area. Similarly act in assessing the effectiveness of the cleaning channel [1].

Also there is a method of assessing the condition of seals and efficient filling of tooth hard tissues. When implementing this method irradiate the center of the seal by the emission of a helium-neon laser, record the spectrum of the reflected signal to determine the rate of fluorescence J in the center of the seal. Similarly, define the indicator fluorescence J on the border of the seal. Then poziruut solution photosense and incubated for 2-3 minutes for better penetration into the gap between the filling and the tooth. Further, similar to define the indicator J1fluorescence in the center of the seal, then remove the photosense alcohol until J1/J=1±0,3. That is, until with the sealing surface does not delete the entire photosense. Then similarly define the indicator fluorescence J1on the border of the seal and if J1/J=1±0,3, i.e. if the gap is not left photosense, consider sealing quality, otherwise the tooth peraluminous [2].

When implementing the above methods use the spectrum of the signal reflected from the surface of the filling material, and the signal reflected from the boundary of the seal and hard tissues of the tooth, the processing of the reflectance spectrum with the aim of obtaining indicator fluorescence, which is judged on the availability of the affected area or as a filling.

Methods [1] and [2] are examples of methods of diagnosis in dentistry, which use complex spectral device and operate spectra of reflection for its implementation.

Closest to the technical essence (prototype) is a method for color matching of dental prostheses and device for its implementation. The method consists in comparing the color of natural teeth with a reference color scale in the lens device by simultaneous illumination of the investigated tooth Etalon color scale luminous flux from the light source through the light guide with two input and two output ends. Reflected from the reference color scale and the investigated tooth luminous flux forms in the lens bi-color mosaic, which is transferred in a uniform color the picture, changing the standards of the color scale. Control color matching is carried out, the lighting pattern of the light scale and tooth light flux with the other, stepwise variable wavelength [3].

The disadvantage of this method is the low precision of the estimate of the object color. It is a subjective way of assessing quality indicators color depends on the physiological characteristics of view of the observer, his experience colorimetric observations, and observation conditions and comparison [2]. Also a drawback of this method is that the results are valid only for a narrow, specific task - the selection of colors dentures.

In the technique known device is a spectrum analyzer that consists of a group of optical fibers, the inputs of which are optical analyzer inputs and outputs optical fiber group through svetoraspredelenie the prism is optically connected to the inputs of photoelectric converters, analog-to-digital Converter whose outputs are connected respectively to the information inputs of personal computers, information inputs, which are outputs and which of Aligator, the presence of switch information the input of which is connected respectively to the outputs of the photoelectric converters. The output switch is connected to the input of analog-to-digital Converter, and the control input of the switch is connected to the control output of personal computers. The outputs of the optical fibers of the group are located in one line relative to each other, forming the source of radiation, equivalent delavau the radiation source, and a plane passing through the centers of linearly arranged optical fibers, perpendicular to the plane of the prism, in which the color separation. The outputs of the optical fiber group is installed with the possibility of changing the angle of incidence of the light flux on svetoraspredelenie the prism and allow for linear movement along the verge svetorasseivateley prism [5].

The disadvantage of this device is that the spectrum analyzer has never been used in dentistry.

The technical result of the invention is to improve the accuracy and reliability of estimation of the color of the dental restoration.

The technical result is achieved in that the flow of light on the unaffected area of the tooth and collecting reflected light is realized by means of photometric world. The reflected light is sent to a spectrum analyzer, where the special is a true reflection specify the coordinates of the color compare them with the known coordinates of the color samples of the filling material and, if the color difference does not exceed 2-3 threshold, then choose the filling material, and if the color difference is greater than specified, then choose two of the filling material, impose them on each other and add a third to reduce the color differences to the specified limit, to control the determination of the chromaticity coordinates of the seal and at their coincidence with chromaticity coordinates of unaffected area of the tooth does not exceed 2-3 threshold consider the assessment of the identical color. The method provides that the coordinates of the color of the seal is determined by submission to it of light and collecting the reflected light by photometric ball and holding the colorimetric processing of its range.

The method of estimating the color of the dental restoration is implemented using a device block diagram of which is presented in figure 1.

The device comprises a photometric ball 2, connected by optical fibers with lighting unit 1 and the spectrum analyzer 3, the output of which in turn is connected to the input of the colorimetric processing unit 4.

The device operates as follows. The light from the lighting unit enters the photometric ball and illuminates the analyzed surface. Reflected from the surface of the light through the light directed into the anal is ATOR spectrum where is measured at specific wavelengths and is converted into an electrical signal, which is passed to the block colorimetric processing. This unit is a computing machine with a specially designed processing algorithm from a spectrum analyzer signals. The algorithm provides that kolorimetrichesky processing is carried out by the method of weighted ordinate [6]. It provides a measure of the spectral Reflectances at regular intervals of wavelengths from the spectrum analyzer and calculate it the following integrals:

where:function - specific color coordinates standard colorimetric observer, CIE 1931, f (λ) is the spectral reflectance of the surface.

The chromaticity coordinates are determined from the relations:

,.

Are the coordinates of the color in the colorimetric system of the International Commission on illumination (CIE) 1931

To assess differences between the two colors at the highest metric color applies the concept of minimal color threshold - the smallest change the color sensation of viewers who Telem. Specifically to determine the differences of colors developed equicontrasting coordinate system Luv ice 1960 [6]. Therefore, in the algorithm in computers embedded operation recalculation of the coordinates x and y coordinates equicontrasting system u and v by the following formulas:

,.

In the system, Luv the distance between the points corresponds to the degree of color difference between colors represented by these points, with two colors practically does not differ if the coordinates are separated from each other by 2-3 threshold vary unsure if off by 3-5 rapids, and confidently vary in the range 7-9 thresholds and above [6].

The choice of color filling material for dental restoration carried out as follows. The coordinates of the color of the tooth is obtained by measuring the spectrum of the reflection directly in the oral cavity of the patient. And the coordinates of the color of restorative materials is obtained by measuring reflectance spectra specially fabricated samples. Available color scale filling materials not provided by chromaticity coordinates. Therefore, to determine the chromaticity coordinates of the filling material are made microarray from the available set of shades restorative material. Filling material (A1, A2, OS2... etc) decl is devout on pretreated bond and depolimerization white plastic substrate, form size microbreccia 2×2 mm, thickness 2 mm, then the sample will photopolymerized - enamel samples 20 seconds, opaque 40 sec, and subjected to finishing. Then get reflection spectrum of microsamples intestinal the same device, and that the reflectance spectrum of the tooth. The data obtained are entered into the database filling materials.

The algorithm for the choice of filling material for personal computer is illustrated in Figure 2, which shows the area of the color plane with chromaticity coordinates of the tooth (the Object) and the chromaticity coordinates of filling materials (PM No. 1, PM No. 2, PM No. 3). Using the least squares method to determine the material closest in color tinge. If the color difference does not exceed 2-3 threshold, the selecting operation is completed. If the color difference is greater than specified, then choose two materials, impose them on each other and add a third to reduce color differences to the permissible limit.

In the dental office to obtain reflectance spectra directly in the mouth is applied to the input device (Figure 3), which is made in the form of photometric ball [7] small diameter with two optical fibers, one for input of the illuminating light 1, the other input of reflected light in the spectrum analyzer 2. It should be noted that the input is twistie of the ball 3 with a diameter of 1.5 mm allows photoretrieval objects area of about 2 mm 2.

Solution the input device in the form of photometric ball allows you to:

to isolate the final reaction area from stray light;

- locally to cover the final reaction area of the measurement object;

to obtain photometric data from the surface of the micro-objects (seals)

- to comply with the conditions of illumination of the object taken to obtain colorimetric information [6].

In addition, the use of flexible fiber optic cable solves the problem of pairing the biological object and the spectrum analyzer.

Example.

Patient M., 25, at approximal-medial surface with capture of the cutting edge has a deep carious cavity.

For each point localization unaffected area of the tooth (Figure 4. I, II, III), carried out measurements of the reflectance spectrum and the measured chromaticity. To do this, at each specified point was consistently put the inlet of the photometric world. The results are shown in the table. On the obtained spectra reflect on the previously described algorithm PC dentist was invited to apply for fillings restoration materials, presented in the table.

Table
LocalizationCutting edge, III The body of the tooth, IIThe cervical region, I
Coordinates colorx=0,442x=0,442x=0,449
y=0,418y=0,423y=0,429
The proposed restoration materialsWith1OA2OA3,5
(Prisma TPH) + tint I(Spectrum TPH)3(Spectrum TPH) is a shade I(Spectrum TPH)3(Spectrum TPH) + tint I
The color contrast color filling and healthy tooth color, (color threshold)323

After the surgery, fillings were performed control measurements color fillings to locate points specified in figure 4. The color difference does not exceed three thresholds, from which we conclude about the right color of the filling material.

The use of the software in computers along with full automation of the measurement process performs all mathematical operations on spectra in real time. With software designed for operation untrained operator. The proposed method estimates the color restoration of teeth of the spectrum allows to provide the absolute error is ity measurements at the level of 0.005 units of chromaticity coordinates when the colorimetric measurements, the accurate colorimetric assessments at the level of 2-3 rapids.

This method allows you to objectively determine the color of the hard tissues of the tooth filling material, seals, which improves the aesthetic quality of the restoration.

Sources of information

1. RF patent №2112426, class. And 61 In 6/00, 1997.

2. RF patent №2112427, class. And 61 In 6/00, 1997.

3. As the USSR №1750676 A1, 30.07.1992.

4. Loizou AV Color and light. - L.: Energoatomizdat. Leningrad. separa-tion, 1989. - 256 S.

5. RF patent №2164668, CL G 01 J 3/36, 2000.

6. D. Judd, G. Wyszecki. Color in science and engineering. TRANS. from English. - M.: Mir, 1978. - 513 S.

7. Gurevich MM Photometry (theory, methods, and devices). - 2nd ed., revised and enlarged extra - L.: Energoatomizdat. 1983. - 272 S.

1. The method of estimating the color of the dental restoration, including the flow of light through the light to enter the illuminating light to the area of the tooth and the direction of the reflected light through the light input of reflected light in the spectrum analyzer, the colorimetric processing of the reflectance spectrum to determine the color, compare color with known svetlosti samples and, if they match the color identical, characterized in that the flow of light on the unaffected area of the tooth and collecting reflected light is realized by means of photometric ball, on reflection spectrum determine the coordinates of the color, compare them with the known coordinates of the color is in the surrounding area samples filling material, and if the color difference does not exceed 2-3 threshold, then choose the filling material, and if the color difference is greater than specified, then choose two of the filling material, impose them on each other and add a third to reduce the color differences to the specified limit, to control the determination of the chromaticity coordinates of the seal and at their coincidence with chromaticity coordinates of unaffected area of the tooth in not more than 2-3 threshold, consider the assessment of the identical color.

2. The method according to claim 1, characterized in that the coordinates of the color of the seal is determined by submission to it of light and collecting the reflected light by photometric ball and holding the colorimetric processing of its range.



 

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