AT2459U1 - DEVICE FOR COLOR DETECTING TEETH - Google Patents

Abstract

The invention relates to a device for determining the color of a tooth (12) in the oral cavity of a patient with - a light source (10) with a defined spectrum of visible light - a first light guide (20) for guiding the light from the light source (10) towards the examining tooth (12) - a second light guide (24), the end of which is aligned with the end of the first light guide (20), for receiving light reflected from the tooth surface, - a common flexible covering (18) of both light guides (20, 24) and - evaluation means (16, 26, 28) for analyzing the spectrum of the reflected light. Easy handling and error-free measurement is made possible by the fact that an elastic sleeve (22) suitable for shielding the tooth (12) from extraneous light is arranged on the end (19) of the light guide (20, 24) and the flexible sheath (18).

Description

AT 002 459 Ul

The invention relates to a device for determining the color of a tooth »in the oral cavity of a patient τη-it. a light source with a defined spectrum of visible light, a first light guide for guiding the light of the light source onto the tooth to be examined, a second light guide, the end of which is aligned with the end of the first light guide, for receiving light reflected from the tooth surface, a common one flexible covering of both light guides and evaluation means for analyzing the spectrum of the reflected light.

In the manufacture of dental prostheses, such as bridges, crowns, etc., it is desirable for aesthetic reasons that the artificial tooth looks as natural as possible. Above all, this means that the artificial tooth has the same color as the patient's own teeth, so that the artificial tooth, for example when the prosthesis wearer smiles, is not immediately recognizable as artificial. 2 AT 002 459 ul dental prostheses are usually manufactured by dental technicians in independent laboratories, i.e. spatially separated from the dentist's practice. For example, if a dentist wants to crown an incisor tooth damaged by an accident, it is highly desirable that the most accurate information possible about the tooth color of the adjacent incisor teeth is transmitted from the dentist's practice to the dental technician's laboratory, for example the crown technician made from a suitable ceramic material.

So far, dentists and dental technicians have had to determine the tooth colors of patients using a subjective method. This consisted essentially of holding differently colored material patches as scar samples in the patient's oral cavity and the early prosthesis. Compare the natural tooth shades until the examiner has found a shade sample that is as close as possible to the natural tooth shade. It is in the nature of things that the results of such a subjective test method are not always satisfactory. The inadequacy of the human eye, disturbing daylight or artificial light, color reflections from the immediate surroundings of the tooth as well as the psychological and physical constitution of the examiner negatively influence the selection process.

Since a typical range of materials for ceramic materials of different colors includes, for example, 120 different artificial tooth shades, the subjective selection process is also comparatively time-consuming.

Devices of the type mentioned at the outset for the objective measurement of tooth shade are known from ut 193 34 517 Al, DE 90 12 977 Ul and WO 87/03470.

Despite the relatively extensive development of the evaluation methods of the known devices, these still have considerable handling disadvantages and falsifying influences of extraneous light. 3 AT 002 459 Ul

The invention is therefore based on the object of creating a device for determining the color of a tooth in the oral cavity of a patient of the type mentioned at the outset, which is easy to handle and enables error-free measurement.

To solve this problem, a device of the type mentioned in the invention is characterized in that an elastic sleeve (rubber sleeve) suitable for shielding the tooth from extraneous light is arranged at the end of the light guide and the flexible sheath near the tooth.

In the device according to the invention, the light guides preferably consist of glass fiber cables which can be flexibly handled with the common flexible sheath and which can be inserted together as a flexible, thin tube into the oral cavity of the PaLleuLeu. Glass fiber cables for conducting low powers can have a very small cross section, so that a simple and precise device can be used. Shielding against foreign air is provided by the rubber arranged at the distal end of the sheath, the diameter of which is preferably smaller than the width of the average human tooth. The rubber sleeve shields the light guide that receives the reflecting light from extraneous light. In this way it is ensured that only light of a precisely known composition falls on the tooth to be tested and that exact conclusions can be drawn from the reflected light as to the objective color of the tooth to be determined.

The light reflected by the tooth, which enters through the end-side opening of the second light guide, is guided by the latter and, when it emerges from the two lenses, can be fed to a corrugation detector, which can be a grating or a prism. This enables spectral analysis of the reflected light. 4 AT 002 459 Ul

The standard color value proportions or standard valences can be determined from the spectral analysis. It is preferred, however, that depending on. the next coming color is selected from the stored spectral analysis. An alphanumeric characteristic value is assigned to all colors, which in turn represents the color of a certain material.

The dentist or his assistant can thus determine an objective value in a matter of seconds, which can be transmitted as an alphanumeric code to the dental laboratory that produces the corresponding denture. The dental technician performing the order knows exactly which color the ceramic or other material to be used must have based on the code specified.

Further preferred embodiment * forms of the invention are described in the subclaims.

The invention is described below with reference to several exemplary embodiments shown in the drawing. The drawing shows:

Figure 1 is a schematic representation of the essential components of the device according to the invention,

Figure 2 - an illustrative representation of a flexible

Light guide according to a preferred embodiment of the invention,

FIG. 3 - an enlarged detailed representation according to FIG. 2,

Figure 4 - a schematic representation of the basic beginning of an inventive (device under

Use of a light source with a defined spectrum of defined light, 5 AT 002 459 Ul

Figure 5 - a device according to the invention according to Figure 4, wherein instead of a color-sensitive CCD-Aufnelunur three monochromatic Phot .orieteletoren are used, and

Figure 6 - an alternative embodiment, in which three monochromatic light sources are used instead of a light source with a defined spectrum of visible light.

FIG. 1 shows the schematic structure of the most important components of a device according to the invention. A light source 10 throws light onto a 2ahn 12, the tooth color of which is to be determined. Light reflected from the tooth is fed to a wavelength-selective light detector 14 and then to an evaluation means IG. Depending on the distribution of the three basic colors red, green and blue or the determined standard valences, the evaluation means 1ß shows an alphanumeric value which is assigned to one of, for example, 12 days factory camouflages.

Figure 2 shows a structure according to Figure 1 in a specific embodiment. Figure 3 shows a detailed representation. A flexible sheath 18 is so flexible and has such a thin diameter that its end 19 in the oral cavity of the patient can easily be placed on any tooth 12 to be examined. As FIG. 3 shows, the flexible sheath 18 contains a first light guide 20, through which the light from the light source 10 is guided and strikes the tooth 12 to be examined. A rubber sleeve 22, which is grounded at the distal end 19 of the flexible sheath 18, prevents extraneous light, for example from the powerful treatment lamp of the dentist, from falling onto the tooth 12 to be examined and falsifying the measurement result. The light reflected by the tooth 12 is returned through a second fiber optic cable 24 and fed to a wavelength-selective element. This can be a grating or a prism. The light beams, deflected differently depending on the wavelength, are assigned to an arrangement of photosensitive diodes. The intensity of the individual wavelength components can be determined in this way. tin aus-warLittel 30, for example in the form of a laptop computer, generates an alphanumeric characteristic value, which is assigned to one of 120 different material colors, for example.

A Noxmprube 32 can be used to calibrate the device.

Figure 4 shows the schematic structure of a device according to another embodiment. The light thrown by the light source 10 onto the tooth 12 to be examined is reflected and reaches a light-sensitive CCD chip 33. Lenses 34 can be provided to direct the light from the light source 10 onto the tooth 12 to be examined or. to focus the reflected light on the CCD unit 33.

The values generated by the CCD unit 33 - for example voltages - can be evaluated and stored in a buffer 36. The buffer 36 can then be connected to an evaluation means 38, which carries out the assignment to one of 12 C color values.

FIG. 5 shows an alLej.uaLive embodiment in which three monochromatic photodetectors 38 are used instead of the CCD chip 33.

FIG. 6 shows another conceivable alternative embodiment, in which 1 e instead of a T.irhtqnel. three monochromatic light sources 42 are used in a defined spectrum of visible light. These emit, for example, with defined wavelengths in red, green and blue. The intensity of the reflected components can be determined by means of a photodetector 44, which in turn enables an alphanumeric display to be generated in a display means 38. 7

Claims (8)

AT 002 459 Ul claims 1. Device for determining the color of a tooth (12) in the oral cavity of a patient with a light source (10) with a defined spectrum of visible light, a first light guide (20) for guiding the light from the light source (10) onto the To be examined tooth (12), a second light guide (24), the end of which is aligned with the end of the first light guide (20), for receiving light reflected from the tooth surface, a common flexible sheath (18) of both light guides (20, 24) and Evaluation means (16, 26, 28) for analyzing the spectrum of the reflected light, 8 AT 002 459 Ul characterized in that at the end near the tooth (19) the light guide (20, 24) and the flexible sheath (18) one for shielding the tooth (12) of suitable external elastic cuff (22) is arranged. 2. Apparatus according to claim 1, characterized in that the evaluation means comprise a wavelength-selective element (26) for analyzing the spectrum of the reflected light. 3. Apparatus according to claim 2, characterized in that the wavelength-selective element (26) is a grid. 4. Apparatus according to claim 2, characterized in that the wavelength-selective element (26) is a prism. 5. Device according to one of claims 2 to 4, characterized by an arrangement (28) of light-sensitive diodes for evaluating the light beam broken down by the wavelength-selective element. 6. Device according to one of claims 1 to 5, characterized in that the evaluation means comprise a color-sensitive CCD chip (33). 7. Device according to one of the preceding claims, characterized in that the device identifies an intermediate memory (36) for intermediate storage of a value generated in the evaluation unit. 8. Device according to one of claims 1 to 7, characterized in that it has a plurality of monochromatic light sources (42) instead of a light source (10) with a defined spectrum of visible light. 9