DE19649689A1 - Method of determining vitality of tooth - Google Patents

Abstract

The method involves irradiating the tooth in the region of the pulp a with non-ionising electromagnetic radiation. The intensity of the radiation transmitted from the tooth is measured according to wavelength in a spectral range where the absorption coefficient of a blood content substance has at least a maximum and a minimum. Two parameters are calculated from the measured intensities. The values of the parameters depend on the position and height of the maxima and minima in the transmission spectrum, on the curve of the spectrum in the region of the maxima and minima or on the envelope of the spectrum in the observed wavelength range. The method then involves determining whether the pair of parameters lies within or outside a predetermined value range.

Description

1 Introduction

The human tooth can be morphologically divided into three regions divide: the external enamel, the dentin or Toothbone and the pulp, also known as dental pulp. Of the Tooth enamel consists of 95% by weight of the very hard and che mixed stable hydroxyapatite, from 4% by weight water and 1% by weight organic material. In terms of volume, it's under the tooth enameled dentin is the largest component of the tooth. It contains only about 70% by weight of hydroxyapatite, while 20% by weight on organic components (mainly collagen and elastin) and 10% by weight are water. The dentin has one Variety, up to 5 mm long, about 3 µm wide and in Channels extending towards the pulp. The pulp forms that Inside of the tooth. It is about the one from the tooth root blood supply to the blood vessels. In addition to dentin-forming Cells, the pulp also contains pain-sensitive cells, which in advanced caries but also by external Stimuli (cold, heat, vibration) are stimulated.

2. State of the art

In practice, the irritability of the pulp is pre-used available nerve cells to ensure the vitality of a tooth check. The frequently used spraying of the relevant number However, using a refrigerant is for the patient extremely uncomfortable, often even associated with pain. To the results of the conventional cold test difficult to interpret.

With the help of imaging techniques of x-ray technology lets also examine the vitality of a tooth. The Evaluation of the x-rays, however, leads to only a few  Cases to a clear result. There are also parts the medical profession and the patients of this examination method increasingly critical of, as damage to the Do not exclude the irradiated area with certainty can.

There are currently a number of clinical trials of methods for optical measurement of pulp vitality. Everyone The procedure together is to examine the fluoroscopy tooth with non-ionizing electromagnetic Radiation and measuring the intensity of the trans from tooth averaged light at wavelengths in the range of 400 nm ≦ λ ≦ 900 nm. The time dependence is evaluated, for example the transmitted intensity I (λ) [1] or the ratio I (λ1) / I (λ2) of the transmitted intensities at suitable Wavelengths λ1 and λ2 [2].

3. Object, aims and advantages of the invention

The invention relates to a method for optical measurement the vitality of a tooth. The procedure should be through ei ne high reliability, no damage to the cause radiated tissue and especially the con conventional cold test with regard to distinctness at least equal to vital / avital.

The application of the completely painless procedure requires no special medical knowledge or skills. Vita Le teeth can be easily removed from vital teeth divide, the tooth geometry being the result of the evaluation not or only slightly influenced.

4. Drawings

The invention is explained below with reference to the drawings tert. Show it:  

. Figure 1 shows the logarithmic measured in vivo TRANSMISSI onsspektren a vital and non-vital tooth in an area of an absorption band of the oxyhemoglobin;

FIGS. 2a and 2b show the graphical representation of a first method for evaluating a logarithmic transmission spectrum;

FIG. 3 shows the parameter pairs {I _BL (λ _c ), m _AB } for avital teeth, upper incisors and premolars (see FIG. 2) determined as points of a diagram using the first evaluation method;

Fig. 4 is a graphical representation of a second method for evaluating a logarithmic transmission spectrum;

Fig. 5-7 the parameter pairs {I _BL (λ _B ) / I _BL (λ _c )} determined with the aid of the second evaluation method and represented as points on a diagram for all tooth types, for molars and premolars and for incisors ( see Fig. 4);

Figure 8 shows the logarithmic transmission spectrum of a vita len tooth and the curvature K (λ) of the transmission spectrum.

FIGS. 9 and 10, the centers of a plurality of transmission Spek different tooth types derived values of the parameter pair {curvature of the second maximum; Curvature in the minimum} or the parameter pair {curvature in the first maximum; Minimum curvature};

Fig. 11 and 12, the transmission of a plurality of different types of teeth Spek centers derived values of the parameter pair {curvature of the second maximum; Position of the second maximum in the transmission spectrum} or of the parameter pair {curvature in the minimum; Location of the minimum in the transmission spectrum} (cf. FIG. 8);

FIG. 13 is the different from a plurality of transmission spectra types of teeth calculated by using the singular value analysis, as a pair of parameters Darge set weighting factors spectra of the most important intrinsic;

Fig. 15 and 16, devices for carrying out the method.

5. Description of the embodiments

As mentioned at the beginning, the vital tooth has a pulp that is well bleeding. The network of fine blood vessels in the pulp supplies the tissue and nerve cells with oxygen, mineral salts and other substances required for metabolism. In the wavelength range between λ ≈ 500 nm and λ ≈ 600 nm, the oxyhemoglobin (HbO) responsible for oxygen transport acts as a strong absorber, with the absorption coefficient of the oxyhemoglobin having a maximum at λ ≈ 540 nm and λ ≈ 578 nm and at λ ≈ 560 nm passes through a minimum. If the pulp of a healthy tooth is irradiated with white light, the behavior of the main absorber oxyhemoglobin determines the structure of the spectrum of the transmitted radiation in the wavelength range mentioned. As shown in Fig. 1 dependency of the logarithmic intensities I (λ) of the transmitted radiation on the wavelength λ, the spectrum at the wavelengths λ ≈ 540 nm and λ ≈ 578 nm has the expected minima, at λ ≈ 560 nm that Minimum of the HbO absorption coefficient corresponding maximum. The comparatively steep increase in the transmitted intensity I (λ) at wavelengths λ <580 nm corresponds to the sharp drop in the HbO absorption coefficient in this spectral range. In the transmission spectrum of an vital tooth, which is also measured in vivo, there are no corresponding structures to be assigned to the HbO, since the blood supply is interrupted and the pulp has died. The analysis of the course, the shape and / or the curvature of the transmission spectrum in the area and in the vicinity of the absorption band of the HbO thus provides information about the amount of oxyhemoglobin present in the irradiated volume and thus the blood flow to the pulp and the vitality of the tooth.

In the following, a number of parameters P _i , P _{j are} given which depend on the structure of the transmission spectrum in the wavelength range of interest or which serve as a measure for the course or the curvature of the transmission spectrum. The combination of the parameters extracted from the spectra into pairs of values {P _i ; P _j } and their representation in a diagram makes it possible to differentiate between vital and vital teeth.

1. Evaluation procedure

Suitable parameters for the assessment of the vitality of a tooth are, for example, the vertical distance of the maximum of the logarithmic intensity ln I (λ _c ) at λ _c ≈ 560 nm from the the minima ln I in FIG. 2a with I _BL (λ _c ) (λ _A ) and ln I (λ _B ) at λ _A ≈ 540 nm and λ _B ≈ 578 nm connecting straight lines AB as well as through

given slope of the straight line AB. The parameter I _BL (λ _c ) is through

I _BL (λ _c ): = ln I (λ _c ) - ln I _AB (λ _c ) (2)

defines, where ln I _AB (λ _c ) the size

ln I _AB (λ _c ): = ln I (λ _A ) + m _AB . (λ _c -λ _A ) (3)

designated.

Since the pulp of a vital tooth contains a comparatively large amount of HbO, the maxima and minima of the transmission spectrum are correspondingly pronounced, i.e. the value of the parameter I _BL (λ _c ) is comparatively large. In contrast, the transmission spectrum of an avital tooth is only slightly curved in the same wavelength range. It deviates consequently from only insignificantly from the points A * and B * connecting lines, so that the parameter assumes I _'BL (λ _c) is only small values I' _BL (λ _{c *)} <I _BL (λ _c) ( see Fig. 2b).

The results of the above-described evaluation of a large number of transmission spectra are shown in FIG. 3. The values of the parameter pair {I _BL (λ _c ) are shown in each case; m _AB }, (λ _c = 560 nm) which were derived from the transmission spectra of the upper anterior teeth (incisors without the canines) and anterior molars (premolars). Measurements on root-treated and thus safely avital incisors, molars and teeth, which could be classified as avital due to the conventional cold test, served as a reference. The measured values of root-treated teeth stand out clearly in the majority from the measured values of vital teeth, the intensities I _BL (λ _c ) and gradients m _AB assigned to root-treated teeth being comparatively strongly scattered due to the noise in the respective transmission spectra. The noise in the transmission spectra of root-treated teeth can be attributed to the filler material, which is often highly absorbent and is placed in the pulp cavity, which prevents the central passage of the injected light. The detector-side glass fiber then mainly detects those photons whose scattering path outside the pulp cavity in the tin is perpendicular to the channels present therein. The photon flux in the area of the end face of the detector-side glass fiber bundle is consequently only very small, often no longer measurable.

The intensities I _BL (λ _c ) derived from the transmission spectra of vital teeth (cold test) are generally outside the range of values covered by vital teeth. Compared to the transmission spectra of root-treated teeth, the transmission spectra of avital teeth are significantly less noisy, which indicates a more translucent filling of the pulp cavity.

As can be seen from FIG. 3, the measured values of the individual tooth types fall into different but overlapping value ranges. For the relatively thin incisors equipped with a small pulse, the values of the slope m _AB and the intensity I _BL (λ _c ) are somewhat smaller than for the thicker premolars. The larger value of the intensity I _BL (λ _c ) in molars and premolars is probably due to the larger volume of the pulp and thus to the larger amount of oxyhemoglobin in the tooth. This results in a stronger expression of the two minima in the corresponding transmission spectrum compared to the maximum in between (see FIG. 2b).

The larger gradient m _{AB of} the straight line AB in the spectra of the molars can be explained by the wavelength-dependent scattering. Since short-wave light is scattered more than long-wave light, the first minimum of the transmitted intensity (point A) in all spectra is lower than the second minimum (point B), with the lowering of the first minimum compared to the second minimum in the spectra of Because of the greater thickness of the hard tooth substance, molars are stronger than in the transmission spectra of the thinner incisors.

In principle, the transmission spectra in the wavelength range between λ ₁ ≈ 500 nm and λ ₂ ≈ 540 nm with the maximum at λ ₃ ≈ 525 nm could also be analyzed in the manner described above. However, only very small intensities are measured in this spectral range, which makes the evaluation considerably more difficult.

In addition to the gradient m _AB , the ratios ln I (λ _B ) / ln I (λ _A ) or ln I (λ _c ) / ln I (λ _A ) serve as parameters for the assessment of the vitality of a tooth ) into consideration.

2. Evaluation procedure

The certainty of the assignment of the vital / avital property can be improved if the course of the transmission spectrum in the long-wave range λ 580 nm is also analyzed and taken into account in the evaluation. In particular, the sizes designated in FIG. 4 with I _BL (λ _{B '} ) and I _BL (λ _c' ) can serve as parameters for assessing the vitality of a tooth. While the size I _BL (λ _{B '} = 578 nm) is the vertical distance of the logarithmic intensity ln I (λ _B' ) from that of the intensities ln I (λ _{A '} = 560 nm) and ln I (λ _c' = 595 nm) connecting straight lines A'C ', I _BL (λ _c' = 595 nm) corresponds to the vertical distance of the intensity ln I (λ _{c '} ) from the intensities ln I (λ _B' = 578 nm) and ln I (λ _{D '} = 615 nm) connecting straight line B'D'. The point C 'defining the straight line A'C' is advantageously set such that the size I _BL (λ _{c '} ) for a given position of the point D' in the range λ _{D '} <600 nm and λ _D' <630 nm in Transmission spectra is as large as possible, in particular maximum.

How gen the results of the evaluation of a variety of transmission spectra shown in FIGS. 5, 6 and 7 zei, the measured values vital teeth lift very well from the measured values of root-treated because of the cold tests than non-vital classified teeth and the measured values teeth. Wear the parameter pair {I _BL (λ _{B '} ); I _BL (λ _{c '} )}.

3. Evaluation procedure

In addition to the intensities of the transmitted light at selected wavelengths, the curvature K (λ) of the transmission spectra in the area of the absorption band of the oxyhemoglobin also provides information about the blood flow to the tooth. A high concentration of oxyhemoglobin in the radiated tooth leads to pronounced maxima and minima in the transmission spectrum and thus to a strong curvature K (λ) of the spectrum in the range of the wavelengths λ ≈ 540 nm, λ ≈ 560 nm and λ ≈ 580 nm (see the curve of the curvature K (λ) of the transmission spectrum of a vital tooth shown in FIG. 8).

In Fig. 9, the value of the second maximum of the curvature at λ ≈ 578 nm is plotted against the value of the curvature in the mini mum at λ ≈ 560 nm for a large number of tooth spectra. The curvature values of the two extremes derived from the transmission spectra of healthy teeth are generally significantly larger than those of avital and root-treated teeth. A similar result is obtained by plotting the value of the curvature in the first maximum at λ ≈ 540 nm against the value of the curvature of the transmission spectrum in the minimum at λ ≈ 560 nm (see FIG. 10).

The exact location of the extrema of the curvature K (λ) of the transmission spectrum also provides information about the vitality of the respective tooth. If, for example, the value of the curvature is plotted in the second maximum or in the minimum against the associated shaft length (see FIGS . 11 and 12), it is shown that the measured values derived from transmission spectra of vital teeth are comparatively large and all in a very narrow, approximately 2 nm wide wavelength range. In contrast, the root values acted and the curvature values K (λ) assigned to the teeth classified as avital in the cold test are generally smaller. In addition, the wavelengths at which the extrema of the curvature occur scatter much more strongly.

4. Evaluation procedure

The tooth spectra can also be evaluated using the so-called singular value analysis (Principle Component Analysis). This mathematical method described in [3] is based on a theorem of linear algebra, according to which each M × N matrix A with M rows and N ≦ M columns is a product of a column-orthogonal M × N matrix U, an N × N Diagonal matrix W with elements w _i ≧ 0 and the transpo ned a column orthogonal N × N matrix V can write (see Equation 4).

The evaluation method based on the singular value analysis is characterized in detail by the following steps:

• - Selection of a number N of typical transmission spectra of vital and avital teeth, each of the, for example, N = 60 smoothed spectra by M = N bases ln I (λ _i ), i = 1. . . N is defined;
• - Structure of an M × N Marix A such that each column vector of the matrix A represents the M = N nodes of one of the N selected transmission spectra
  S _1j , S _2j , S _3j . . . S _Nj : nodes of the transmission spectrum no. J
• - Singular value analysis of matrix A, ie decomposing matrix A into a product
  U _{k = 1. . . N} : column vector of the matrix U _i ; w _{k = 1. . . N} : singular values
• - Selection of a number N ₁ ≦ N of the largest singular values with w _k1 ≧ w _k2 ≧. . . ≧ w _N1 and the assigned column vectors U _k1 , U _k2 . . ., U _N1 (example: the singular value w ₃ is assigned to the column vector U _{3 of} the matrix U);
• - Approximate description of the transmission spectrum S * of a tooth to be examined as a linear combination of the N ₁ column vectors U _ki ("eigenspectrums") represented as an N × 1 matrix and defined by N reference points.
  with the weighting factors α _k1 , α _k2 . . ., α _N1 ;
• - Representation of a pair {α _ki ; α _kj } of weighting factors in a diagram or determine whether the weighting factors lie within the range of values assigned to vital / vital teeth.

In general, N ₁ ≦ 4 intrinsic spectra are sufficient to reconstruct a measured transmission spectrum with sufficient accuracy. If, for example, only the two largest of the weighting factors α _k are plotted against one another (see FIG. 13), the parameter values assigned to vital teeth stand out clearly from the parameter values derived from transmission spectra of avital and root-treated teeth.

It is of course also possible to analyze the curvatures K (λ) of these spectra in a corresponding manner instead of the transmission spectra or to represent the transmission spectra or their curvatures K (λ) by a number N '<N of support points (the matrix A is then no longer square). The advantage of the PCA analysis of the transmission spectra ln I (λ) or their curvature K (λ) is in particular that the entire wavelength range 400 nm ≦ λ ≦ 1000 nm is included in the evaluation and therefore no information is lost. However, the singular values w _i or weighting factors α _ki that contain the information can no longer be interpreted physically.

6. Devices for carrying out the evaluation process

The device shown schematically in FIG. 14 is similar in construction to a pair of pliers. It consists of two rotatable miteinan the connected legs 2/3 , the comparatively short front parts (jaws) grasp the tooth 4 to be examined in each case. The required contact pressure is generated by the leg bracket 1 (spring-loaded screw or groove) which generates a corresponding torque. The end pieces of the two legs 2/3 designed as handles are not shown. The arranged in the baking of the upper leg 2 glass fiber bundle 5 detects the radiation emitted by the white light source 6 (halogen lamp) and couples it into the tooth 4 in the area of the pulp. On the glass fiber bundle 5 gegenüberlie constricting side of the tooth 4, a weakened radiation tion processes by scattering and Absorp enters the detector-side glass fiber bundles. 6 In the lower leg 3 inte grated detector system consists in the embodiment shown game of four units, the detector units each having an interference filter 71/72/73/74 (optical bandpass filter) and an Si photodiode 81-84 as radiation receivers . The transmission properties of the interference filters 71-74 are chosen so that the radiation intensities registered in the downstream photodiodes 81-84 represent a measure of the amount of blood or the degree of oxygenation of the blood which is largely independent of the tooth geometry. As explained above, the transmission maxima of the four interference filters 71-74 can be in particular in the range of the wavelengths λ ₁ ≈ 540 nm, λ ₂ ≈ 560 nm, λ ₃ ≈ 580 nm and λ ₄ ≈ 600 nm or λ _{1 '} ≈ 560 nm, λ _{2 '} ≈ 580 nm, λ _3' ≈ 590-600 nm and λ _{4 '} ≈ 610-630 nm. The calculation of the parameters relevant to the assessment of the vitality of tooth 4 {P _i ; P _j } and their comparison with predetermined limit values defining the vitality range takes place in the evaluation electronics 9 .

A battery 10 supplies both the evaluation electronics 9 and the white light source 6 with the required operating voltages.

The radiation source of the device shown in FIG. 15 consists for example of a total of 4 light emitting diodes 11/12 , the radiation of the wavelength λ ₁ ≈ 540 nm, λ ₂ ≈ 560 nm, λ ₃ ≈ 580 nm and λ ₄ ≈ 600 nm or λ _{1 '} ≈ 560 nm, λ _2' ≈ 580 nm, λ _{3 '} ≈ 590-600 nm and λ _4' ≈ 610-630 nm. The evaluation electronics 13 controls the driver unit 14 assigned to the light emitting diodes 11/12 in such a way that the tooth 4 is successively irradiated with light of the desired wavelength in a predetermined sequence. A glass fiber bundle 5 or a curved glass rod serves as the light guide. Since the light emitting diodes 11/12 emit one after the other in time, a single ge is integrated into the jaw of the lower leg 3 inte grated photodiode 15 as a radiation receiver. Your output signal is amplified and the evaluation electronics 13 leads. A battery 10 supplies the evaluation electronics and the driver unit 14 with the required operating voltages.

If the intensity of the transmitted radiation is to be measured with high resolution not only at the 4 wavelengths classified as particularly relevant, but in the entire spectral range 400 nm ≦ λ ≦ 1000 nm, the following, however, comparatively expensive measurement setup is recommended:
White light source-optical waveguide-tooth-optical waveguide-grid thermonochromator-detector unit (photodiode array or CCD) - evaluation electronics (PC). Corresponding systems are available on the market. With them, a spectral range of more than 300 nm width can be recorded within a few milliseconds, which excludes disturbances of the measured value acquisition due to movements of the clamp (wobble).

7. Refinements and training

The invention is of course not limited to the exemplary embodiments described above. For example, it is also possible

• - instead of the logarithmic intensities ln I (λ) in each case evaluate the intensities I (λ) itself in an analogous manner,
• - More than 4 light emitting diodes or detector units in the be to provide written devices;
• - The tooth simultaneously with radiation of different wavelengths λ _{i = 1. . .} To examine _N3 , the intensity of each radiation having a different frequency f _{i = 1. . . N is} modulated / frequency- and wavelength-selective detection of the transmitted radiation ("heterodyne reception")
• - The evaluation of the measured intensities in a computer to make;
• - to visually display the result of the evaluation to the user gene.

8. Literature

• [1] US-A-5,040,539
• [2] US-A-4,836,206
• [3] Numerical Recipes in FORTRAN, "The Art of Scientific Com puting ", W.H. Press et al .; Cambridge University Press (1992); Pp. 51-63.

Claims (16)

1. Procedure for determining the vitality of a tooth by performing the following steps:

• a) illuminating the tooth in the area of the pulp with non-ionizing electromagnetic radiation;
• b) Wavelength-dependent measurement of the intensity I (λ) of the radiation transmitted by the tooth in a spectral range where the absorption coefficient of a blood substance has at least a minimum and at least a maximum;
• c) Calculation of two parameters P _i and P _j from the measured intensities I (λ), the values of the parameters P _i , P _j on the position and height of the maxima and minima in the transmission spectrum, on the curvature of the transmission spectrum in the range of Maxima and minima or depend on the course of the transmission spectrum in the wavelength range under consideration;
• d) determining whether the parameter pair {P _i ; P _j } lies within or outside a predetermined value range.

2. The method according to claim 1, characterized in that the parameters P _i and P _j belong to the group of the following variables:

• a) Difference I _BL (λ ') of the intensities with I _BL (λ'): = | ln I (λ ') - ln I ₁₂ (λ') |, where ln I ₁₂ (λ ') is the one by the intensities intensity values ln I (λ ₁ ) and ln I (λ ₂ ) connecting first straight line of defined intensity at the wavelength λ 'denoted by λ ₁ <λ'<λ₂;
• b) slope m _{12 of} a straight line connecting the intensity values ln I (λ ₁ ) and ln I (λ ₂ );
• c) ratio V ₁ = In I (λ ₂ ) / In I (λ ₁ ) or ratio V ₂ = In I (λ ') / In I (λ ₁ );
• d) Difference of the intensities I _BL (λ ''): = | ln I (λ '') - ln I ₃₄ (λ '') |, where ln I ₃₄ (λ '') is determined by the intensity values ln I (λ ₃ ) and ln I (λ ₄ ) connecting second straight line defined intensity at the wavelength λ '' with λ ₃ <λ ''<λ₄;
• e) curvature K ⁱ _{max of} the transmission spectrum in the area of the i-th maximum;
• f) curvature K ^j _{min of} the transmission spectrum in the region of a jth maximum;
• g) wavelength λ ^K _max at which the curvature K (λ) of the transmission spectrum passes through a maximum;
• h) wavelength λ ^K _min at which the curvature K (λ) of the logarithmic transmission spectrum passes through a minimum.

3. The method according to claim 2, characterized in that it is determined whether the parameter pair {I _BL (λ '); m ₁₂ }, {I _BL (λ '), V ₁ }, {I _BL (λ'); V ₂ }, {I _BL (λ '); I _BL (λ '')}; {K ⁱ _max ; K ^j _min }, {K ⁱ _max ; λ ^K _max } or { ^K _min ; λ ^K _min ] lies within a predetermined value range. 4. The method according to claim 2 or 3, characterized in that the wavelengths λ ₁ , λ ₂ and λ 'are selected as follows:

• λ ₁ lies in a spectral range where the absorption coefficient of oxyhemoglobin has a first maximum,
• - λ ₂ lies in a spectral range where the absorption coefficient of the oxyhemoglobin has a second maximum;
• - λ 'lies in a spectral range where the absorption coefficient of the oxyhemoglobin passes through a minimum.

5. The method according to claim 4, characterized in that the following applies: λ ₁ ≈ 540 nm, λ ₂ ≈ 578 nm and λ '≈ 560 nm. 6. The method according to claim 2 or 3, characterized in that the incoming wavelengths in the calculation of the parameters I _BL (λ ') and I _BL (λ'') are selected as follows:

• a) λ ₁ lies in a spectral range where the absorption coefficient of oxyhemoglobin passes through a minimum;
• b) λ 'lies in a spectral range where the absorption coefficient of oxyhemoglobin has a second maximum;
• c) λ ₃ = λ 'and λ ₂ = λ'';
• d) λ ₄ <λ ''.

7. The method according to claim 6, characterized in that λ '' is selected so that the parameter I _BL (λ '') has a Ma ximalwert. 8. The method according to claim 6 or 7, characterized in that the wavelengths are selected as follows:
λ ₁ = 560 nm, λ '= 575-585 nm, λ ₂ = λ''= 590-620 nm and λ ₄ = 615-630 nm. 9. The method according to any one of claims 1 to 8, characterized, that instead of the logarithmic intensities ln I (λ) each the measured intensities I (λ) are evaluated. 10. The method according to any one of claims 1 to 9, characterized, that the intensity I (λ) of the transmitted radiation in the world lenlength range 400 nm ≦ λ ≦ 1000 nm is measured. 11. The method according to claim 1, characterized in that

• a) a number N of recorded transmission spectra, each defined by a number M ≧ N support points, are represented as column vectors of an M × N matrix A,
• b) the matrix A is subjected to a singular value analysis and as the product A = UWV ^T an M × N matrix U, an N × N diagonal matrix W with diagonal elements w _k ≧ 0, k = 1, 2,. . . N and the transposed of an N × N matrix V is represented;
• c) a number N ₁ ≦ N of diagonal elements w _k1 ,. . ., w _N1 with w _k1 ≧ w _k2 ≧. . . ≧ w _N1 and the assigned column vectors U _k1 , U _k2,. . ., U _{N1 of} the matrix U are selected;
• d) a transmission spectrum S defined by a number of M support points and represented as a column vector by the linear combination S = α _k1 U _k1 +. . . + α _N1 U _{N1 of} the column vectors U _{ki is} approximated, and that
• e) it is determined whether the parameter _pair {α _k1 ; α _kj } lies within or outside a predetermined range of values.

12. The method according to claim 11, characterized in that in each case the curvature K _i (λ) of a number N of transmission spectra is calculated and each defined by a number M ≧ N support points that the curvatures K _i (λ) as column vectors of an M × N matrix A 'are shown and that the process steps b) to e) are carried out in a corresponding manner. 13. The method according to claim 11 or 12, characterized, that instead of the transmitted intensities, the logarith mated intensities are evaluated. 14. Device for performing the method according to claim 1 with the following features:

• - A first and a second leg ( 2 , 3 ) are rotatably connected to each other in the manner of a pair of pliers;
• - Each of the two legs ( 2 , 3 ) has a front part formed as a jaw and a rear serving part as a handle;
• - In the first leg ( 2 ) there is a photon source ( 6 , 11 , 12 , 14 ), in the second leg ( 3 ) a detector unit ( 71-74 , 81-84 ) connected on the output side to an evaluation unit ( 13 ).

15. The apparatus according to claim 14, characterized in that the photon source ( 6 ) emits white light and that the detector system comprises at least three units, each unit being assigned a light-conducting element and each unit having a photon detector ( 81-84 ) and one of the photons detector ( 81-84 ) upstream optical bandpass filter ( 71-74 ) contains. 16. The apparatus according to claim 14, characterized in that the photon source ( 6 ) has at least three individually controllable, in different spectral ranges emitting light sources ( 11 , 12 ).