Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR DETECTING DENTAL CARIES
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present relates to the detection of dental
caries and, more particularly, to a system and method
for detecting dental caries.
2. Description of the Prior Art
There are various known methods that are used
to detect the presence of dental caries, including
visual and tactile investigations using the usual dental
explorer. These methods and instruments have their
limits and cannot detect dental caries reliably,
especially when the dental caries is proximal and when
the decay is at an initial stage. X-ray investigation
of teeth structure is also not reliable for detecting
dental caries at the beginning of their formation in
regions where a too great superimposition of enamel is
present on the X-ray film. These obstructing
superimpositions of teeth structures are more typical
for the occlusal aspect of the teeth, and when the angle
between the teeth alignment and the X-ray irradiation
axis induces superimposition. The X-ray evaluation
technique also exposes the patient to potentially
harmful radiations.
Transillumination is another technique used to
detect dental caries. By irradiating visible light
toward a tooth from an aspect (e.g. lingual) and by
observing via another aspect (e.g. buccal) the
transmitted light, the operator can sometimes confirm
the diagnosis of dental caries by observing a luminosity
contrast induced by a dental caries. This technique is
not suitable for all dental caries, especially for
dental caries at their beginning phase. Recently, a
viewing device has been developed to ease the viewing of
transillumination of the teeth structure with the use of
a camera.
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Other devices have been devised for the
detection of dental caries using luminescence or
fluorescence spectroscopy with variable efficiencies
depending, amongst others, on the cleanliness of the
tooth surface. When irradiated with one or more initial
radiations at a specific wavelength, some tooth
structures generate a second radiation with a wavelength
that is different from the initial radiations. The
intensity and wavelength of such a second radiation is
different for sound tooth structures from those for
decayed tooth structures. See U.S. Patents No.
RE31,815, No. 4,479,499, No. 6,186,780, No. 6,102,704,
No. 6,053,731, No. 6,135,774 and No. 5,306,144, and
German Patent Publications No. DE-30 31 249-C2, No. DE-
42 00 741-A1, No. DE-U1-93 17 984, No. DE-303 1249-C2
and No. DE-19541686-A1. In most cases, these devices
include a laser to generate the initial exciting
radiation, which can be potentially harmful to the
patient.
For instance, German Patent Publication No.
DE-93 17 984-U discloses a device for the detection of
dental caries using a light emission unit emitting
pulsed light beams and a detection unit being sensitive
during a time interval delayed with respect to the
emitted light pulse.
German Patent Publication No. DE-42 00 741-A1
and European Patent Publication No. EP-0 555 645-B1
describe a device for the detection of dental caries via
a radiation source, working in a wavelength range from
360 - 500 nanometers and detecting filtered reflected
radiation of wavelengths between 620 and 720 nanometers
with respect to the presence or absence of dental
caries.
German Patent Publication No. DE-297 04 185-U
is directed to a device for the detection of caries,
plaque or bacterial infections of teeth comprising an
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emission/detection unit which has a plurality of
individual emission fibers.
German Patent Publication No. DE-197 09 500-C1
teaches a method for the detection of dental caries,
plaque or bacterial infections of teeth by comparing
fluorescent light levels of different portions of a
tooth in order to find those parts of the tooth which
are most seriously affected by the caries.
German Patent Publication No. DE-297 05 934-U
discloses a device for diagnosing tooth composition
using a first light source as a detection light source
and a second light source as a therapeutic light source.
Electrical probes have also been developed for
the detection of dental caries (U.S. Patent No.
6,230,050) as well as ultrasonic-based detection
systems.
SUMMARY OF THE INVENTION
It is therefore an aim of the present
invention to provide a novel system for the detection of
dental caries.
It is also an aim of the present invention to
provide a novel system for the detection of dental
caries, which automatically detects the caries based on
the intensity of the reflected wavelengths and/or on
spectral reflectance characteristics of the caries.
It is a further aim of the present invention
to provide a system in which a visual, sound-based, or
other, signal is given following detection of dental
caries, wherein this detection results from measurements
made on the tooth and taken iri one or more predetermined
ranges of wavelengths that are appropriate for
discriminating the spectral reflectance characteristics
that constitute a signature of. the presence of caries,
and/or on the intensity of the reflected wavelengths.
Therefore, in accordance with the present
invention, there is provided a system for detecting
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dental caries on a tooth structure, comprising a
conductor for directing at least one initial radiation
onto a tooth structure to be evaluated, a collector for
collecting at least one resulting radiation that has
been reflected by and/or transmitted through the tooth
as a result of said initial radiation, said collector
being adapted to deliver said resulting radiation to a
detection device, said detection device being adapted to
compare at least one intensity of said at least one
resulting radiation with at least one predetermined
value that corresponds to the presence or to the absence
of dental caries, thereby enabling the diagnosis of the
presence or absence of dental caries on the tooth
structure.
Also in accordance with the present invention,
there is provided a system for detecting dental caries
on tooth surfaces, comprising a conductor for directing
at least one initial radiation onto a tooth structure to
be evaluated, a collector for collecting at least one
resulting radiation that has been reflected by and/or
transmitted through the tooth as a result of said
initial radiation, said collector being adapted to
deliver said resulting radiation to a detection device,
said detection device being adapted to compare at least
one wavelength of said at least one resulting radiation
with at least one predetermined value that corresponds
to the presence or to the absence of dental caries,
thereby enabling the diagnosis of the presence or
absence of dental caries on the tooth structure.
Further in accordance with the present
invention, there is provided a method for detecting
dental caries on a tooth structure, comprising the steps
of irradiating the tooth structure with an initial
radiation, collecting a reflected and/or transmitted
resulting radiation, comparing the wavelengths) and/or
the intensity(ies) of radiation(s) with a predetermined
value ( s ) that corresponds to the presence or absence of
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dental caries, enabling to then diagnose the presence or
absence of dental caries.
Still further in accordance with the present
invention, there is provided a dental caries detection
system, comprising a probe adapted to be displaced along
a tooth, illumination means for illuminating with an
incident light a region on the tooth, detection means
for collecting the resulting light reflected by and/or
transmitted through the tooth, and an analyzing system
for providing a signal when measurements on the
resulting light in one or more predetermined ranges of
wavelengths fall within any first predetermined range of
values that are characteristic of dental caries, or when
said measurements do not fall within any second
predetermined range of values that are characteristic of
artifacts other than caries.
Still further in accordance with the present
invention, there is provided adental caries detection
system, comprising a probe adapted to be displaced along
a tooth, illumination means for illuminating with an
incident light a region on the tooth, detection means
for collecting the resulting light reflected by and/or
transmitted through the tooth, and an analyzing system
for providing a signal when intensity measurements on
the resulting light indicate one of the presence and
absence of caries.
Still further in accordance with the present
invention, there is provided a method for detecting
dental caries in teeth, comprising the steps of: (a)
providing an incident light on a region of a tooth; (b)
collecting and measuring the resulting light reflected
by and/or transmitted through said region of the tooth;
(c) analyzing said resulting light to determine if said
resulting light is representative of the presence of
dental caries; and (d) providing a signal to an operator
that indicates that one of presence and absence of
dental caries has been detected in step (c).
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BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of
the invention, reference will now be made to the
accompanying drawings, showing by way of illustration a
preferred embodiment thereof, and in which:
Figs. 1 and 4 are schematic diagrams of a
system for the detection of dental caries in accordance
with a first embodiment of the present invention;
Figs. 2 and 5 are a schematic diagrams of a
system for the detection of dental caries in accordance
with a second embodiment of the present invention; and
Figs. 3 and 6 are schematic diagrams of a
system for the detection of dental caries in accordance
with a third embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention,
Figs. 1 to 6 illustrate three systems for the automated
detection of the presence of caries (tooth decay) in a
patient's teeth.
Each system basically comprises three main
mechanisms, that is (1) an optical hand-held tool (a
buccal, probe) for directing an incident light onto a
tooth T and for capting light reflected by and/or light
transmitted through the tooth T, (2) a device (e.g. a
casing containing optical components, light sources, and
acquisition and signal processing electronics) for
providing a light source to the tool and for analyzing
the reflected/transmitted light and providing a signal
to an operator indicative of the presence of caries, and
(3) a transmission device (e. g. a cable strand that
includes optical fibres) that connects the hand-held
tool to the analyzing device (casing). The hand-held
tool mentioned hereinabove could also take the form of
two distinct tools, which can be manipulated
independently of one another, that is one tool for
directing an incident light onto the tooth T, and
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another tool for capting light reflected by and/or light
transmitted through the tooth T. Some further details
of these components can be found in PCT Publication
No. WO01/23767 (based on PCT Application
No. PCT/CA01/00063).
The systems of the present invention detect
the presence of caries by analyzing the intensity of the
reflected/transmitted light and/or by analyzing
wavelengths of the reflected/transmitted light such as
to discriminate the caries present on the teeth from the
healthy areas thereof, from the gums, from blood, and in
fact from any artefact other than caries that the tool
may encounter when it is directed towards 'the tooth.
The system described herein is suitable for
detection of dental caries anywhere on the tooth T, and
on any teeth.
The device described is for the recognition of
the reflectance and/or transmittance properties of non-
decayed tooth T structures and decayed tooth T
structures when irradiated with visible or invisible
ultra-violet (UV) or invisible infra-red (IR)
wavelengths) radiation(s).
The present invention is a dental caries
detector principally based on a spectroscopic evaluation
system of the reflectance and/or transmittance
properties of dental structures. When a tooth structure
is irradiated with an initial radiation(s) Ir, the
radiation can in part be reflected on the structure
surface and in part penetrate and travel inside this
structure where some or all of such penetrating
radiations can be deviated and/or reflected. Depending
of the composition of the tooth and/or shape thereof
and/or on the surrounding structures that are present, a
specific structure can reflect and transmit a specific
radiation differently than another structure. Depending
on the origin of the irradiation and on the geographical
position of the observation point of the resulting
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radiation(s) Rr (also called hereinafter "collected
radiation"), the transmission and reflection will be
different for a same structure.
In the present invention, initial
electromagnetic radiation is brought to the tooth T
structure, via the tool, using an electromagnetic
conductor coupled with a source S. For example, an
electromagnetic radiation of around 600 nm can be used
alone or with an electromagnetic radiation of around 860
nm. Any other suitable radiation or group of two or
more radiations in the UV, visible or IR spectrum can be
used.
The source S is an electromagnetic radiation
generator (for all or parts of W - Visible - IR).
Multiple sources S can be used to obtain the desired
radiation(s). Filters) F or other optical means can be
used to obtain the desired radiation(s). For example, a
visible radiation (i.e. visible light) of around 600nm
wavelength can be combined with an infrared radiation of
around 860nm wavelength.
An example of sources S that can be used are
LEDs, laser-diodes, lasers, halogens light, neon light,
or any other suitable type of radiation emitting source.
The wavelength of the initial electromagnetic
radiation Ir, which is generated by the source S, is
selected based upon the difference between the
intensities of the collected radiation Rr at the same
wavelength on sound tooth surfaces and on decayed tooth
surfaces. The spectral bands) and the intensity(ies)
of the radiation(s) to be generated by the sources) S
is (are) selected based on the characteristic that
(those) radiation(s), when it (they) encounters directly
or indirectly a dental caries, has a different behaviour
than when it (they) encounters a sound tooth structure
or a non-dental caries structure found around or in the
teeth. The wavelengths) and the intensity(ies). is
(are) selected when the more unambiguous distinction,
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with a determined configuration of the invention
(collector, conductor, detection means, etc.), can be
made between dental caries and non-dental caries tooth
structures.
Three regions of the spectral band have been
identified to have unambiguous discriminative potential
between decay and natural tooth structures, that is two
areas between 550nm et 650nm: around 600nm and around
640nm, and one area under 550nm: around 480nm. To
discriminate between caries and other dental substances
(e. g. plaque and tartar), the same technique as below
can be used, but with other wavelengths (typically in
the red and/or IR).
It has also been determined that, when the
tooth is irradiated with light from the overall
electromagnetic spectrum, a greater amount of
electromagnetic radiations is reflected by dental caries
than by healthy tooth structures . A system can be made
using this discriminative aspect by using any
electromagnetic wavelengths.
A reference wavelength over 650nm can be used
where the reflectance is similar in dental caries and in
healthy tooth structures, e.g. 860nm.
The intensity of the initial radiation(s) Ir
is equal to the source S intensity less the lost in the
conductor. The conductor brings the radiation from the
source S to the tooth structure to be evaluated.
A feedback system can be implemented to
measure the initial radiation.
The conductor can be an optical fibre or a
bundle of optical fibres or any other material suitable
for radiation transmission. For example, the conductor
CN can be made with lenses) and/or mirror(s).
Lenses L, mirrors or other suitable optical
means, can be inserted between the source S and the
conductor to enhance the coupling of the radiation into
the conductor.
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The initial radiation(s) Ir can be modulated
and synchronized with the detector to ease the
recognition of the reflected/transmitted resulting
radiation(s) Rr from this initial radiation(s) Ir from
other radiation(s) resulting from another initial
radiation(s) Ir or from noises. This method is
sometimes called "Lock-in system". One advantage of the
lock-in system is its sensitivity even with very weak
levels of radiation.
The resulting radiation(s) Rr is collected via
a collector that brings the resulting radiation(s) Rr to
a detection device D. The collector can be an optical
fibre or a bundle of optical fibres or any other means
suitable to bring the resulting radiation(s) Rr from the
tooth T to the detection device D. For example, the
collector can be made with mirrors and/or lenses.
The detection device D is used to compare the
resulting radiation(s) Rr to at least one or part of one
of the following measurements: other resulting
radiation(s) Rr (i.e. resulting from irradiation
effected at other times), noises) included in the
resulting radiation(s) Rr or the initial radiation(s) Ir
directly or indirectly, punctually or with variable of
time or by using a function of the (those)
measurements) with a predetermined range of values)
corresponding to dental caries. For example, comparing
the resulting radiation(s) Rr less the noise in that
resulting radiation(s) Rr to a predetermined range of
values that are in relation with the initial radiation
Ir, is a typical way of determining if the measurements
correspond, or not, to the presence of dental caries:
when using a specific Ir intensity, if Rr less noise in
Rr is over a certain value that is in function of Ir,
then the detection of dental caries is positive.
Another example is when an initial
radiation(s) Ir with a wavelength of around 600 nm is
used. The resulting radiation(s) Rr then has a lower
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intensity if the tooth T structure is sound. When the
resulting radiation(s) Rr is higher than a certain
value, which is in relation with the initial
radiation(s) Ir intensity, the diagnosis of dental
caries is positive.
The detection device D can be made with a
semi-conductor detector (e. g. photo-diode or LCD) that
converts the resulting radiation(s) Rr into a signal or
a plurality of signals. This detector sends this
(those) signals) to an electronic or electro-mechanic
system EAM that analyses the signals) so as to
determine if there is presence of dental caries, or not.
A stimulus(i) Stim (e. g. sound, light, vibration, etc.),
is then generated through this electronic system EAM to
inform the operator of the presence of caries. A LED
can be used instead of the above photo-diode. An analog
converter C/A is provided upstream of the stimulus Stim
in the second and third embodiments of Figs. 3 to 6.
The detection device D can also include a semi
conductor radiation detector (e. g. photo-diode)
connected to a system that converts at least one or a
part of one of the following measurements . other
resulting radiation(s) Rr (i.e. resulting from
irradiation effected at other times), noises) included
in the resulting radiation(s) Rr or the initial
radiation(s) Ir directly or indirectly, punctually or
with variable of time or by using a function of the
(those) measurement(s), into the corresponding
stimulus (i) Stim to the operator O (e.g. variable sound
intensity, variable light signal,). The operator O then
makes the distinction between stimuli associated with
dental caries and stimuli associated with a sound tooth
T structure. For example, the detection device can be a
sound generator that emits a sound intensity equivalent
to the intensity of the resulting radiation. Another
example can be a graphical screen display of different
radiation measurements and where the operator 0 uses his
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judgment to identify when dental caries is present, or
not.
The detection device OE of Figs.l and 4 can be
made with physical means that convert at least one or a
part of one of the following measurements on: the
resulting radiation(s) Rr, noise(s) included in the
resulting radiation(s) Rr or the initial radiation(s) Ir
directly or indirectly, punctually or with variable of
time or by using a function of the (those)
measurement(s), into a corresponding stimuli to the
operator O, who again then makes the distinction between
stimuli associated with dental caries and stimuli
associated with a sound tooth T structure. For example,
this detection device OE can be a mirror that reflects-
the resulting radiation(s) Rr to the operator 0.
For example, the electronic analysis system
EAM could be made of an electronic processor and an
algorithm based on independent functions of the two
demodulated signals received, if the initial radiations
Ir of 860 nm and 625nm are used in conjunction with a
lock-in system.
It is noted that the source S can be modulated
in intensity and/or in wavelength. By modulating the
current and/or the voltage of a source, the intensity
and the range of wavelengths can change and the constant
variation in the radiation can be used instead of
multiple sources.
To enhance the detection, it may be desirable
to characterize the typical response radiation on
different structures in the mouth of some patients prior
to beginning detection of dental caries.
The detection system, and more specifically
the hand-held tool, can be partially or totally included
in a device for cavities preparation (e. g. rotative
handpieces, ultrasonic/sonic devices designed for
preparation of teeth prior to filling, air abrasion
system, etc . ) .
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Also, The detection system can be designed to
work in conjunction with an instrument to prepare the
tooth and tooth region before the restoration.
The components of the present systems that
will be put in contact with intra-oral tissues of the
patient can be made sterilizable.
The systems of the present invention can
comprise multiple conductors that can bring the initial
radiation(s) from different angles or regions so as to
possibly enable focalizing radiation on three
dimensional regions or enable obtaining multiple
readings on the same region.
A drying device can be incorporated in the
systems of the invention for reducing the ,number of
contaminants between the viewing tip of the instrument
and the tooth T surface.
An intermediate substance can be inserted
between the viewing end of the conductor, or the
collector, and the tooth T surface to minimize undesired
reflections and/or to act as a filter. For example, a
transparent gel-like substance could be used.
The present systems may comprise a special
marker having an affinity with dental caries and special
reflectance/transmittance radiation property(ies) that
can enhance or enable the detection of dental caries.
For instance, a blue marker that has an affinity with
dental caries will reflect radiation(s) wavelengths)
corresponding to blue.
A combined sonic or ultrasonic generator or
stress generator can be implemented to induce stress or
oscillation or movement in the tooth T surface enabling
interferences and revealing weaker structure.
Teeth have a large morphologic variability
that induces a high variability in optical response.
For that reason, a comparative method can be implemented
to enable the optical response to be standardized. By
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changing the position of the emitting point and the
angle of emission, recorded values can be compared.
A liquid (e.g. water) delivery system can be
incorporated to the invention to enable cleaning and/or
obtaining an optical medium between the viewing end of
the conductor or the collector CL and the tooth T
structure.
The invention can comprise, before the
collector, a perforated component that enables only
radiation that is parallel to the axis of this
perforated component to enter the collector. This
perforated component can enable the determination of the
origin of the radiation ray. For example, this
perforated component can enable to determine if the
radiation comes from the occlusal area or from the
gingival area.
Because an occlusal dental caries is almost
always found in the middle of the tooth surface, it can
be interesting to compare radiation coming from that
middle area to the surrounding areas. This can be done
by having the collector composed of a bundle of optical
fibres. This coherent bundle enables the analysis
region-by-region of the coming radiation. This region-
by-region analysis can be obtained by using a plurality
of semi-conductor detectors or by using an opaque
pattern.
The invention can comprise a mean to archive
data. For example the invention can be connected to a
computer that can save the data for later use, for
instance to follow the evolution of caries of a given
patient.
The probe end (i.e. the distal end of the tool
that faces the tooth T that contains the collector
and/or the conductor) may comprise graduation marks to
facilitate positioning.
The systems of the present invention can also
include some recalibration and/or self-testing
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functions. For example, if optical fibres are used, it
is possible to verify if the fibres are too worn out to
be efficiently used and should thus be replaced by
testing the intensity of a reference light that passed
through the fibres.
Also, as the spectral responses of various
artifacts other than caries are known, such as those of
enamel, of the tooth~s root surface, of the gum, of
blood, of tartar, of tooth fillings, etc., caries can be
either directly detected or indirectly detected as the
detection can be made to either detect caries or the
absence thereof (i.e. the other presence of an artifact
different than caries).
The system may be designed to focus on the
tooth surface to establish if it is opaque or
translucent. In the case of interproximal caries, the
aim is the quantification of mineralization loss,
whereas in the case of occlusal caries, the aim is the
determination of the presence of caries of a size such
that it requires an intervention. A bundle of optical
f fibres could be used to quant i fy the opaque surf ace vs .
the translucent surface.
A probe end having asymmetrical fibres or
emitting rays having different exit axes may constitute
a way to determine a difference between translucent and
opaque surfaces. There could be distinct emitting and
collecting probes, where one probe is mobile and the
other is fixed.
It is also contemplated to use, instead of a
probe, a dental floss that contains an optical fibre as
a way to bring the optical fibre to the interproximal
surface. A band or strip containing a number of optical
fibres could also be used when surveying the
interproximal tooth surfaces, i.e. by passing the strip
between the teeth.
A problem associated with the occlusal caries
resides in attempts to locate the caries by trying to
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look through the tooth's enamel which is at an angle.
To overcome this difficulty, the probe could have a gel-
like tip that penetrates the grooves or wrinkles defined
on the teeth thereby reducing optical effects of these
wrinkles. On the interproximal level, this same tip
could be used as the contacting adjacent teeth form a
type of groove.
The systems of the present invention can be
used during tooth repair surgical procedures, for
instance to ensure that all the decay has been
successfully removed.
The probe end could have a number of fibres
pointing towards the same point where decay is believed
to be present. At the occlusal surface, this could be
useful to determine if the reflection emanates from the
tooth's pulpar chamber or from a more occlusal portion.
References could be taken on a given patient's
sound tooth structures to effect a calibration of the
detection systems of the present invention, which is
~~customized" to this patient, such that measurements
taken thereafter are more representative of the state of
the patient's tooth structures, thereby enhancing the
detection efficiency and facilitating the diagnostic.
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