DE102013226777B4 - Observation unit for detecting fluorescence and a device for detecting caries - Google Patents

Abstract

Observation unit (3) for detecting fluorescence from teeth, having a mount (20) or a spectacle frame and at least one filter element (5), the filter element (5) being mounted on the spectacle frame (4) or with the mount (20). a dental hand instrument (21) or foldable on glasses, characterized in that the filter element (5) has at least one first and at least one second transmission property (8), the first and second transmission properties (8) differing.

Description

technical field

The invention relates to an observation unit for detecting fluorescence, which has at least one filter element, and a device for detecting caries that includes this observation unit.

State of the art

When preparing carious cavities, it is essential to remove all of the decayed parts of a tooth. In order to enable or simplify the detection of carious areas, the different fluorescence properties of carious and healthy tooth substance are often used. If the tooth substance is excited with light of a suitable wavelength, typically between 360 and 580 nm, for example approx. 400-410 nm, the spontaneously emitted light from the carious areas differs significantly from the light emitted from healthy areas. While the fluorescence of the carious areas is in the red wavelength range, the healthy tooth substance fluoresces in the green wavelength range.

From the DE 42 00 741 A1 a device is known which uses these fluorescence properties in order to detect caries on teeth and, if necessary, also to treat it directly. For this purpose, the device has an illumination device, for example a radiation source with a radiation filter that only lets through the desired excitation wavelength. Furthermore, the device includes an edge or band filter that reflects or absorbs all wavelengths that are smaller than a cut-off wavelength of about 620 nm, and possibly also all wavelengths that are greater than a cut-off wavelength of about 720 nm. This filter is mounted in a goggle frame, leaving the wearer's hands free for other activities and not restricting the viewing angle and/or head movement when observing the fluorescence.

However, it is not possible with the glasses described to recognize the green fluorescence of the healthy tooth substance, since the corresponding frequency ranges are filtered out by the mounted filter.

In order to be able to perceive both the green and the red fluorescence, edge or long-pass filters with a correspondingly lower limit wavelength of, for example, 520 nm are used, for example, as is the case, for example, in U.S. 6,325,623 B1 and the U.S. 2003/022126 A1 is known.

In order to be able to better distinguish between the fluorescence of healthy and carious tooth substance, a combination of bandpass and edge or longpass filters can also be used. Such a filter can, for example, transmit light in the wavelength range of the fluorescence of healthy tooth substance, e.g. 500-570 nm, as well as wavelengths greater than 600 nm as completely or at least partially as possible and filter out all smaller wavelengths or wavelengths in between.

Compared to a pure edge or long-pass filter, such a combined filter achieves a greater contrast with regard to the fluorescence properties, which makes it easier to distinguish between healthy and carious tooth substance. This is particularly desirable for reliable control. The disadvantage, however, is that such a combined filter produces an overall darker image than a pure long-pass filter, which means that physical structures in the image area are harder to recognize. This is particularly disadvantageous when a tooth is being processed, for example during an excavation. A brighter image would be desirable during editing.

From the DE 10 2013 206 466 B4 a fluorescence microscope with an illumination device is known which excites a fluorescent sample to emit fluorescence radiation. An imaging device has an emission filter for selecting wavelengths, which is designed as a color gradient filter. This filter is part of a larger optical setup.

From the U.S. 5,503,559 A1 an endodontic device for examining root tips is known. An optical analysis device is used with a spectrometer or a sensor with a dichroic filter, which is opaque to the light used for illumination from the observation beam path.

The object of the present invention is to provide an observation unit for detecting carious tooth substances, which provides both an image that is as rich in contrast as possible in terms of fluorescence and as bright as possible of one or more teeth stimulated to spontaneously emit.

Presentation of the invention

The invention relates to an observation unit for detecting fluorescence from teeth, having a mount or a spectacle frame and at least one filter element, the filter element being mounted on the spectacle frame or with the mount on a dental hand instrument ment or foldable on a pair of glasses. The filter element has at least a first and a second transmission property, with the first and the second transmission property being different.

When treating teeth, their different fluorescence properties can be used, for example, to differentiate between carious and healthy tooth substance. For this purpose, the teeth are illuminated with light with a wavelength that stimulates fluorescence, with the teeth reflecting this excitation light and also typically green light in healthy areas, e.g. between 480 nm and 560 nm, and typically red light in carious areas, e.g. between 630 nm and 790 nm, emit due to fluorescence.

The detection of these different fluorescences, in particular the areas affected by caries, can be simplified or improved by using a suitable filter element. Filter element refers to a medium with any special optical filter characteristic, i.e. special transmission properties for light. The filter characteristic shows the transmittance as a function of the wavelength. This can range from complete transmission to complete blocking by reflection or absorption.

Since the intensity of the reflected excitation light is usually significantly greater than that of the fluorescence during fluorescence excitation, filtering out the excitation light by means of a filter element with suitable transmission properties in an observation beam path can significantly simplify the detection of the fluorescence.

Furthermore, when teeth are excited by fluorescence, the green fluorescence of the healthy tooth areas is typically more than twice as intense as the red fluorescence of the carious areas, which is why attenuating the green fluorescence using a filter element with suitable transmission properties can significantly simplify the detection of the carious areas.

It is also possible to completely filter out the green fluorescence of healthy tooth areas using a filter element with appropriate transmission properties. However, the contrast between the red and the green fluorescence is particularly high or distinguishing between red and green is particularly easy for the human eye, in particular higher than a contrast of red fluorescence compared to darkness. Therefore, the at least partial remaining of green fluorescence in the observation beam path can simplify the detection of the carious sites.

Overall, filtering out light reduces the light intensity and thus the impression of brightness that an observer can gain. This can make it difficult to see physical structures, such as the external shape of a tooth. It is therefore more advantageous for certain work steps in the treatment of a tooth to filter out or absorb or reflect as little or no light as possible.

For example, it may be desirable to view a tooth through a filter element with a specific filter effect during a diagnostic step and not to have any filter effect in the observation beam path during a processing step, for example an excavation.

The inventive combination of at least two different transmission properties in one filter element makes it possible to provide all desired filter properties in a simple manner, without the observation unit having to be changed or removed. The first as well as the second transmission property can each be one of the aforementioned filter properties or also any other filter property.

The filter element advantageously has at least a first area with the first transmission property and a second area with the second transmission property.

The spatially separate arrangement of the different transmission properties within a filter element enables the observer to look through the at least one first or through the at least one second area, for example simply by moving the head and/or the viewing angle and/or the filter element, and thereby select the most suitable transmission property .

The choice of the number of different transmission properties and the corresponding number of different areas depends essentially on a desired application, a size of the filter element and a necessary minimum size of the individual areas.

The filter element advantageously has a transition area between the first and the second area. The transition area advantageously has a transmission property that has a graded progression from the first transmission property to the second transmission property.

The transition area makes it possible to design the transition from a first to a second transmission property. In particular, a graded progression enables a smooth transition in the image impression and avoids disruptive image effects that can occur as a result of a sharp edge in the transition from at least one first transmission property to at least one second transmission property.

The filter element advantageously has an electrochromic layer.

As a result, it is possible to switch between the at least two different transmission properties of the filter element by means of a current and/or voltage change.

The filter element can be made of plastic or glass, for example, which is coated with an electrochromic layer. Or an electrochromic layer can be sandwiched between two layers of glass or plastic. Electrochromic layer refers to a layer that can also be divided into further layers and has electrochromic properties, i.e. the transmission property of this layer changes with a suitable change in an applied current or an applied voltage.

Furthermore, for example, a battery or a connection to a voltage source can be arranged on the observation unit and connected to the electrochromic layer via a control unit, for example a rotary potentiometer. For example, the transmission property of this layer can be changed by changing the voltage applied to the electrochromic layer.

This makes it possible to equip an observation unit with a filter element, which always has exactly one transmission property, it being possible to switch very easily between at least two different transmission properties, for example by means of an electrical circuit, without having to change the observation unit for this purpose.

The observation unit advantageously has a sensor for detecting light of one wavelength and a control unit for controlling a voltage applied to the electrochromic layer.

This enables automatic control of the transmission property. For example, when excitation light is detected by the sensor, a desired filter property can be automatically activated by automatically controlling the voltage or current at the electrochromic layer by means of the control unit such that the filter element has the desired transmission property. If no excitation light is detected by the sensor, the current or the voltage at the electrochromic layer can be regulated or switched off by means of the regulating unit, for example, such that the filter element has a desired filter effect, for example no filter effect.

The filter element advantageously has a thin dielectric layer.

Constructive and destructive interference occurs as a result of reflection and transmission on a thin dielectric layer due to the path difference between the various reflected and transmitted light components. Such filters are often referred to as interference filters. The thickness of the dielectric layer is typically less than the wavelength of the light to be filtered.

The interferences that occur on thin layers are angle-dependent, so that different transmission properties occur by means of a thin dielectric layer for different angles of incidence of light on the layer. As a result, the thin dielectric layer makes it possible to provide the at least two transmission properties of the filter element, for example over the entire filter element, with a user being able to choose between the different transmission properties by changing the viewing angle, for example by moving the head, the gaze and/or the filter element.

Such a thin dielectric layer can in turn be made up of several different layers in order to have the desired transmission properties.

The at least one filter element advantageously has at least one further transmission property that differs from the first and the second transmission property.

Combining one or more further transmission properties with the first and the second transmission property in one filter element makes it possible to provide several filter properties in a single observation unit.

Advantageously, the first or the second or the further transmission property has an edge wavelength, with light having a wavelength that is smaller than the edge wavelength being absorbed or reflected and with light having a wavelength longer than the first edge wavelength is transmitted.

The edge wavelength thus designates the filter-specific wavelength that separates an absorption and a transmission range from one another. Filters with such transmission properties or such an edge wavelength are often referred to as edge filters or as long-pass filters.

If the first or the second or also a further transmission property of the filter element is a long-pass filter, it is possible to filter out the excitation light in particular, which is more energetic than the fluorescence and therefore has a shorter wavelength, and with a suitable choice of the edge wavelength at the same time ensure that all Fluorescence or at least the desired wavelengths are transmitted as completely as possible.

The edge wavelength is advantageously between 490 nm and 520 nm.

Such an edge wavelength makes it possible to filter out the reflected excitation light, which typically has a wavelength of around 400 nm for teeth, for example, and at the same time ensure that the fluorescence is transmitted as completely as possible and reaches the observer.

Advantageously, the first or the second or the further transmission property has an edge wavelength and a stop band, wherein light with a wavelength that is smaller than the edge wavelength or is in the stop band is absorbed or reflected and wherein light with a wavelength that is greater than the Edge wavelength is and is not in the stop band, is transmitted.

Such a transmission property enables, for example, good recognition of the fluorescence of carious tooth areas. The short-wave excitation light is filtered out by means of the edge wavelength or the filter effect corresponding to a long-pass filter, and the light with wavelengths between the green fluorescence of healthy tooth substance and the red fluorescence of carious tooth substance is filtered out by means of the band stop filter. Essentially only the green and the red fluorescence remain in the observation beam path, these being particularly easy to distinguish from one another by the human eye. The red areas in particular, i.e. the areas affected by caries, are clearly visible.

The edge wavelength is advantageously between 490 nm and 520 nm, as a result of which short-wave excitation light can be removed from an observation beam path.

The blocking range is advantageously between 560 nm and 600 nm, as a result of which light with wavelengths in the range between the fluorescence of healthy and carious tooth substance can be removed.

Advantageously, the first or the second or the further transmission property has an attenuation range, with at least a proportion of light having a wavelength in the attenuation range being absorbed.

This enables, for example, a high-contrast display of carious areas by additionally weakening the green fluorescence of the healthy tooth areas so that it only partially remains in the illumination beam path. The attenuation is necessary because the fluorescence of the healthy tooth area otherwise dominates, since the intensity of this fluorescence is significantly greater than the intensity of the fluorescence of the carious tooth area and because the areas of healthy tooth substance are usually larger in terms of surface area than the areas affected by caries.

The attenuation range is advantageously between 500 nm and 560 nm and the proportion is 50%.

In this way, in particular, the fluorescence of healthy tooth substance is damped to such an extent that the remaining intensity is comparable to the intensity of the fluorescence of carious tooth substance and an image impression optimized for caries detection is generated.

Advantageously, the first, the second or the further transmission property is designed in such a way that light of any desired wavelength is completely transmitted.

This makes it possible to also provide an impression of an observed object without a filter effect without changing the observation unit. For example, when processing the tooth, it can be advantageous to observe the tooth without further filter effects and thereby better recognize the physical structure of the tooth.

The observation unit is a pair of glasses and includes a pair of glasses on which the filter element is mounted.

A pair of glasses with filter elements mounted in them allows an object, such as a tooth, to be observed through the observation unit, in particular by the filter element, without being restricted in the freedom of movement, with the hands in particular being free to carry out other activities.

As an alternative, the observation unit comprises a holder with which the filter element can be foldably mounted on a pair of glasses.

This allows it to be easily folded away, for example upwards, should it not be needed.

Alternatively, the observation unit includes a holder with which the filter element can be attached to a dental handpiece.

As a result, the observation unit can be used without having to hold it with one hand for this purpose.

Furthermore, the invention relates to a device for detecting caries with an illumination unit for exciting fluorescence, the device comprising an observation unit according to the invention for detecting fluorescence.

The lighting unit can be, for example, a light probe to be held by hand or a light source which can be attached to a spectacle frame, for example to the observation unit comprising a spectacle frame, or can be attached to the head with a corresponding holder.

character list

• 1 eine Vorrichtung zur Erkennung von Karies, die
• 2 eine als Brille ausgebildete Beobachtungseinheit mit einem ersten und einem zweiten Bereich mit jeweils unterschiedlicher Transmissionseigenschaft, die
• 3a-d verschiedene Transmissionseigenschaften
• 4 eine Beobachtungseinheit mit einem Übergangsbereich, die
• 5a, b ein Filterelement mit einer elektrochromen Schicht, die
• 6 ein Filterelement mit einer dünnen dielektrischen Schicht, die
• 7 eine an einem zähnärztlichen Instrument angeordnete Beobachtungseinheit und die
• 8 eine klappbar an einem Brillengestell angeordnete Beobachtungseinheit.

The invention is explained with reference to the drawings. It shows that

• 1 a device for detecting caries, the
• 2 an observation unit designed as glasses with a first and a second area, each with different transmission properties, the
• 3a-d different transmission properties
• 4 an observation unit with a transition area, the
• 5a, b a filter element with an electrochromic layer which
• 6 a filter element with a thin dielectric layer, the
• 7 an observation unit arranged on a dental instrument and the
• 8th an observation unit arranged foldable on a spectacle frame.

example

the 1 1 shows a device 1 for detecting caries, which comprises an illumination unit 2 designed as a light probe and an observation unit 3 . The observation unit 3 is designed as a pair of glasses with a frame 4 and filter elements 5 .

The filter elements 5 of the observation unit 3 can be used as in 2 shown having a first and a second region 6, 7, the first region 6 having a first transmission property 8 and the second region 7 having a second transmission property 8.

In 3 different transmission properties 8 are shown as a filter characteristic. In each case, the transmission is plotted as a function of the wavelength A.

3a shows a filter characteristic of an edge filter with an edge wavelength 9. Such a transmission property 8 is particularly suitable for filtering out light used for exciting fluorescence through absorption or reflection and thereby being able to recognize the excited fluorescence better. A filter element 5 with this transmission property typically has a yellow color.

3b shows a filter characteristic of a filter element 5 with a slow transition from complete absorption or reflection to complete transmission.

In 3c a filter characteristic curve is shown, which has an edge wavelength 9, an attenuation range 10 and a blocking range 11. Such a transmission property 8 is tailored in particular to the simple identification of carious tooth areas, with the excitation light for the fluorescence being filtered out and the fluorescence of healthy tooth substance being weakened. A filter element 5 with these transmission properties typically has the color orange.

3d shows a filter characteristic of a completely transparent medium. A filter element 5 with this transmission property is typically clear.

In a filter element 5, in addition to the in 3 Transmission properties shown 8 other transmission properties 8, which are advantageous for a desired application than first, second or further transmission property 8 of a filter element 5 can be implemented.

This in 2 Filter element 5 shown can, for example, have a first region 6 with a transmission property 8 according to 3a and a second region 7 having a transmission property 8 according to FIG 3d exhibit.

It is also possible for a filter element 5 to have three or more regions, each with different transmission properties 8, for example with a first transmission property according to FIG 3d , according to a second transmission property 3a and a further transmission property according to 3c.

The filter elements 5 can also have a transition area 12 between a first area 6 and a second area 7, as is shown in 4 is shown. The transition region 12 can, for example, have a transmission property 8 according to 3b exhibit. This can shape the transition between the first and the second area, for example when the first area has a first transmission property 3a and according to the second transmission property 3c having . However, the transition region 12 can also have a transmission property 8 that changes continuously or in the smallest possible steps from the first transmission property 8 of the first region 7 to the second transmission property 8 of the second region 8 . This avoids edges in the transition from one transmission property 8 to another.

In 5a an observation unit 3 designed as glasses is shown, which has filter elements 5 with an electrochromic layer 13 mounted in a glasses frame 4 , a battery 14 mounted on the glasses frame 4 and a potentiometer 15 mounted on the glasses frame 4 . The electrochromic layer 13 is arranged between a base material 16 , for example plastic or glass, and is connected to the battery 14 via the potentiometer 15 . The voltage applied to the electrochromic layer 13 can be changed by means of the potentiometer 15, as a result of which the transmission property 8 of the electrochromic layer changes. In this way, a first transmission property 8 can be achieved by means of a first position of the potentiometer 15 or a first applied voltage and a second transmission property 8 of the filter element 5 by means of a second position of the potentiometer 15 or a correspondingly applied second voltage.

It would also be possible to provide a connection for a current or voltage supply on the spectacle frame 4 instead of a battery 14 . A battery could then be connected to this via a cable, for example, which is attached to a holder, for example a clip, with which it can be attached to the edge of a trouser pocket, for example.

Switching between different transmission properties 8 of the electrochromic layer 13 and thus of the filter element 5 can take place, for example, by turning the potentiometer 15 or by a switch/button etc. arranged on the spectacle frame 4 .

However, it is also possible to provide automatic regulation of the transmission property 8 via the voltage or the current. For this purpose, for example, a control unit 17 and a sensor 18, for example a photodiode, can be arranged on the spectacle frame 4, which is suitable for detecting the light that is used to excite fluorescence, as is shown in 5b is sketched. If the photodiode 18 does not detect any excitation light, the voltage or current is controlled by the control unit 17 on the electrochromic layer 13 in such a way that it has a first transmission property, for example no filter effect, i.e. the filter element 5 has a transmission property 8, for example 3d having. As soon as the photodiode 18 detects excitation light, the voltage or the current at the electrochromic layer 13 is adjusted by means of the control unit 17 such that the electrochromic layer 13 has a second transmission property, for example the desired transmission property 8 for detecting fluorescence. This can be a transmission property according to 8, for example 3a or 3c being.

In 6 a filter element 5 is shown, which has a base material 16 and a thin dielectric layer 19 . The thin dielectric layer 19 brings about a transmission property 8 that is dependent on the angle of incidence or viewing angle 3a on. In contrast, for light which is incident at a second angle of incidence a2, the filter element 5 has a second transmission property 8, for example according to FIG 3c on.

The thin dielectric layer 19 can, for example, also be designed in such a way that it is suitable for light which is at a third angle of incidence α3, which is between the first and the second angle of incidence a1 and a2, a third transmission property, for example according to 3b having.

Thus, by means of a thin dielectric layer 19 for an angle of incidence a1, a transmission property 8 according to 3a , for an angle of incidence a3 a transmission property 8 according to 3b and for an angle of incidence a2 a transmission property according to 3c will be realized. This enables a user to select or switch between these different transmission properties 8 by changing the viewing angle or the orientation of the observation unit 3 .

As in 7 shown, the observation unit 3 can also include a filter element 5 and a holder 20 and can be connected by means of the holder 20 to a dental hand instrument 21, for example the one shown in 1 illustrated light probe 2 or a file or a drill etc. can be attached or attached.

It is also possible to arrange the observation unit 3 with a foldable holder 22, for example on a pair of glasses, so that the observation unit can be folded away if necessary, as is shown in 8th is shown.

reference list

1

Caries detection device

2

lighting unit

3

observation unit

4

glasses frame

5

filter element

6

first area

7

second area

8th

transmission property

9

edge wavelength

10

damping range

11

restricted area

12

transition area

13

electrochromic layer

14

battery

15

potentiometer

16

base material

17

control unit

18

sensor

19

thin dielectric layer

20

bracket

21

dental hand instrument

22

foldable bracket

a1

angle of incidence

a2

angle of incidence

α3

angle of incidence

λ

wavelength

Claims (17)

Observation unit (3) for detecting fluorescence from teeth, having a mount (20) or a spectacle frame and at least one filter element (5), the filter element (5) being mounted on the spectacle frame (4) or with the mount (20). a dental hand instrument (21) or foldable on a pair of glasses, characterized in that the filter element (5) has at least one first and at least one second transmission property (8), the first and second transmission properties (8) differing. observation unit (3) after claim 1 , characterized in that the filter element (5) has at least one first region (6) with the first transmission property (8) and at least one second region (7) with the second transmission property (8). observation unit (3) after claim 2 , characterized in that the filter element (5) between the first and the second area (6,7) has a transition area (12). observation unit (3) after claim 3 , characterized in that the transition region (12) has a transmission property (8) which has a graduated course from the first transmission property (8) to the second transmission property (8). observation unit (3) after claim 1 , characterized in that the filter element (5) has an electrochromic layer (13). observation unit (3) after claim 5 , characterized in that the observation unit (3) has a sensor (18) for detecting light of a wavelength (λ) and a control unit (17) for controlling a voltage applied to the electrochromic layer (13). observation unit (3) after claim 1 , characterized in that the filter element (5) has a thin dielectric layer (19). Observation unit (3) according to one of Claims 1 until 7 , characterized , that the at least one filter element (5) has at least one further transmission property (8) which differs from the first and the second transmission property (8). Observation unit (3) according to one of Claims 1 until 8th , characterized in that the first or the second or the further transmission property (8) has an edge wavelength (9), wherein light with a wavelength (λ) which is smaller than the edge wavelength (9) is absorbed or reflected and wherein light having a wavelength (λ) greater than the first edge wavelength (λ) is transmitted. observation unit (3) after claim 9 , characterized in that the edge wavelength (9) is between 490 nm and 520 nm. Observation unit (3) according to one of Claims 1 until 10 , characterized in that the first or the second or the further transmission property (8) has a cut-off wavelength (9) and a stop band (11), wherein light with a wavelength (λ) smaller than the cut-off wavelength (9) is absorbed or is reflected and wherein light with a wavelength (λ) which is greater than the edge wavelength (9) is transmitted and wherein light with a wavelength in the stop band (11) is absorbed or reflected. observation unit (3) after claim 11 , characterized in that the edge wavelength (9) is between 490 nm and 520 nm. observation unit (3) after claim 11 or 12 , characterized in that the blocking range (11) is between 560 nm and 600 nm. Observation unit (3) according to one of Claims 1 until 13 , characterized in that the first or the second or the further transmission property (8) has an attenuation area (10), wherein at least a portion of light with a wavelength (λ) is absorbed in the attenuation area (10). observation unit (3) after Claim 14 , characterized in that the attenuation range (10) is between 500 nm and 560 nm and that the proportion is 50%. Observation unit (3) according to one of Claims 1 until 15 , characterized in that the first, the second or the further transmission property (8) is designed such that light of any wavelength (λ) is completely transmitted. Device (1) for detecting caries, having an illumination unit (2) for exciting fluorescence, characterized in that the device has an observation unit (3) for detecting fluorescence according to one of Claims 1 until 16 includes.

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