Note: Descriptions are shown in the official language in which they were submitted.
CA 02369677 2002-O1-30
Light Beam Hardening Apparatus
Background of the Invention
The present invention relates to a light beam hardening apparatus.
Light beam hardening apparatus for dental material hardening
applications are today configured either as hand-held devices for the
direct fight polymerization of the dental material in the mouth of the dental
patient or as stationary devices.
In particular with regard to hand-held devices, it is important that
the polymerization be effected relatively rapidly and, at the least, at a rate
which ensures a complete polymerization as well of larger teeth fillings
comprised of light beam hardenable plastic.
The conventional light beam hardening apparatus is by far typically
configured as a halogen bulb lamp having integrated reflectors whose
light emissions are guided by a light guide rod, with the outlet end of the
light guide rod being disposed immediately adjacent the Ailing to be
hardened. The typical light beam hardenable dental plastic exhibits a
spectral sensitivity whose maximum sensitivity lies in the region of visible
light.
On the other hand, typical commercially available halogen 'bulb
lamps emit visible light with substantially reduced ultraviolet (UV) portions
of about 2%, for example. To improve the efficiency of the emitted light
impact, it has been attempted to extend the spectral sensitivity of the
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plastic material which is to be polymerized into the long wavelength
region. These attempts, however, have only succeeded in limited
measure.
It has been further proposed to extend the emitted spectral region
into the higher frequencies by means of filters, which only permit the
passage therethrough of high wavelength light. This approach, however,
requires that a substantial amount of light emitting energy be initially
produced whereby, as a consequence thereof, the efficiency of this
approach is correspondingly poor. At the same time, a cooling air flow
must be regularly introduced which acts to limit the temperature of the
light beam hardening apparatus and this air flow is not altogether
pleasant for the dentist or the dental patient.
Moreover, it has long been known to deploy as light beam
hardening apparatus semi-conductor light emitting sources which operate
as light emitting diodes {LED). For example, German patent publication
DE-GM 295 11 927 discloses a light beam hardening apparatus having
a light emitting diode which emits light in the blue spectral region and
which is powered by a battery or an accumulator.
It has been additionally proposed to deploy a plurality of LEDs for
the power supply of a light guide rod. In this manner, the light output of
the light beam hardening apparatus is improved. However, independent
of whether the LEDs are configured and emit light as modules - that is,
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deployed in a common plastic housing - or as individual LEDs - that is,
each deployed in its own respective plastic housing, the light output of
LEDs is limited. The plastic housings are not only electrically insulating
but they also suppress the shedding of heat so that a certain performance
thickness of each of the fight emitting chips cannot be exceeded due to
the need to provide cooling of the plastic housings from the exterior.
It has, moreover, been proposed in other applications to
adhesively secure light emitting chips on a metallic body. The heat
resistance between the chip and the cooling body in such a configuration
is, in fact, less than that of a configuration in which a chip is integrated
into a plastic module. However, the adhesive Layer acts as a heat blocker
so that the danger exists here as well of an overheating of the chip or
chips.
It has also long been a practice in the mounting ofsemi-conductors
on cooling bodies to use a heat conducting paste. The heat conducting
paste should displace a continuously insulating air layerwhich, due to the
surface roughness of the outer surface, acts as a barrier to heat
shedding. In spite of all efforts, however, the known light beam hardening
apparatus with semi-conductor light emitting sources produce only a
limited light output and are in this respect not especially suitable for
dental applications.
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r
Summary of the Invention
The present invention offers a solution to the challenge of
providing a light beam hardening apparatus which shortens the light
hardening time so that a particularly strong heating up inside the mouth
of the patient does not also occur due to the dental material hardening
procedure.
In accordance with the present invention, it is particularly
advantageous that, for the most part, cold light is used. A relatively
reduced light strength is generated such that the long wavelength
emission component is suppressed, whereby the intensity of the light
beam radiation is higher in comparison to that of conventional devices.
The light beam hardening apparatus of the present invention
unexpectedly generates a reduced temperature level in the mouth of the
dental patient. As a first explanation for this, the intensive emissions
shorten the handling time so that only a reduced heating up occurs in the
area of the filling. However, a further explanation for this phenomenon
lies in the fact that the temperature range of the fight beam hardening
apparatus is itself surprisingly markedly lower so that there is no
particularly intensive heating from this source.
The heat from the light emissions from the chip are, in accordance
with the present invention, immediately conducted away via heat
conducting connections to a base receptacle of substantial size. This
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base receptacle is itself then heated up. However, the base receptacle
can be very effectively cooled in that it can be configured with a
substantially large outer surface. The base receptacle has, however, due
to its mass, a particularly large heat capacity so that its temperature is
raised by only a relatively modest amount in the event of a premature
disposition of heat energy in the course of just a few seconds.
In an advantageous embodiment of the light beam hardening
apparatus of the present invention, a so-called heat pipe is provided for
conducting heat rearwardly away from the base receptacle. The thus
rearwardly conducted heat can be in effect given off to the environment
so that this embodiment can even be operated in a manner which does
not require the blowing of cooling air onto the light beam hardening
apparatus.
In another advantageous embodiment of the light beam hardening
apparatus of the present invention, it is provided that each chip in the
cradle is recessed relative to the outer surface of the cradle. This
configuration results in a still further improved light emission efficiency.
The cradle is preferably provided with an interior mirrored or refilective
surface and operates as a micro reflector whereby the outer surfaces of
the light emitting chips can be disposed in the focal burning point of the
micro reflector. By virtue of this configuration, the light emitted toward the
side is focused so that the loss of light caused by misdirected light
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emissions is markedly reduced.
In accordance with a further advantageous embodiment of the light
beam hardening apparatus of the present invention, micro reflectors
having integrated chips of the configuration just described are uniformly
distributed over the outer surtace of the base receptacle. The light
emissions produced from this arrangement are bundled together in the
front direction - that is, are emitted toward the location to be hardened by
the light emissions - whereby the individual light emission bundles
overlap and mix together.
In connection with such light emission bundling, it is also possible
to provide various colors of the emission spectra of the individual chips
and to undertake an individual control of each chip's emissions. For
example, a focused red tight can be emitted if, in a modified embodiment
of the light beam hardening apparatus of the present invention, a heat
handling procedure is to be performed.
It is particularly favorable, in one embodiment of the light beam
hardening apparatus of the present invention, to use double connector
wires. The especially light intensive chips of the light beam hardening
apparatus ofthe present invention have high requirements for power, and
the use of two gold or aluminum wires, each 30 ~cm, between the power
supply conduit and the chip has shown itself as adequate for handling the
power supply needs of the chips.
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In another advantageous embodiment of the light beam hardening
apparatus of the present invention, which is particularly suited for high
performance chips, the so-called flip-chip technology can be
implemented. In this connection, the contact is made to the underside of
the chip and light emission is from the topside of the chip. The use of a
bonded wire connection can be dispensed with in this embodiment as the
contact can be accomplished, for example, by soldering.
In accordance with the present invention, the metallic heat
conducting connection can be manufactured in any desired, suitable
manner. For example, the base receptacle can also be manufactured
with two coats and, in fact, with a metallic over coat and a ceramic base
coat. Also, in accordance with the present invention, a substantially large
heat capacity can be built in, especially if the metallic over coat
completely covers the ceramic base coat and/orthe silicon body, whereby
the heat distribution is in this respect improved. Alternatively, an
aluminum body can be used.
In a furtheradvantageous embodiment ofthe light beam hardening
apparatus of the present invention, it is provided that the base receptacle
is generally configured in cup form and, in fact, is configured in a form
which corresponds precisely to thatof the receptacle or socket which has
previously been used to support a halogen bulb lamp with reflectors. The
receptacle or socket has cooling ribs along its outer surface and the base
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receptacle is preferably connected to the receptacle via heat conducting
paste. An exchange during the life of the fight beam hardening apparatus
is as a rule generally not required as the LED chips have a very long
operational life so that cost savings relative to light beam hardening
S apparatus with halogen bulb lamps are achieved due to reduced
maintenance costs. It is particularly advantageous that the light beam
hardening apparatus of the present invention eliminates the risk which is
present in connection with halogen bulb lamps, that the breaking off of
the polymerization procedure is caused by a burning through of the bulb
lamp, thus resulting in a half hardened filling which must then be
removed.
In a particularly advantageous embodiment of the light beam
hardening apparatus of the present invention, it is provided that the
emitted light beams are intensified onto a surface of limited cross
1 S sectional area by a prism body. The prism body is configured such that
it shifts the individual light beam emissions in the outer region of the base
receptacle emissions into the middle so that they can be guided
practically without loss of light into the light guide rod. The prism body
can additionally be enclosed within a cooling body having longitudinal
cooling ribs on its exterior which facilitate the shedding of heat.
It is particularly advantageous, in one embodiment of the light
beam hardening apparatus of the present invention, if the base
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receptacle including individual LED chips is substituted for a halogen bulb
lamp having reflectors in a hand-held light hardening device. In this
configuration, the exterior of the base receptacle is dimensioned so as to
correspond with the dimensions of the inner surface of the receptacle,
which receives the halogen bulb lamp. It is preferable if the exterior of
the base receptacle is configured as a truncated cup and that connection
pins are provided at those same locations as such connection pins are
provided on halogen bulb lamps. The substitution of an appropriately
dimensioned base receptacle of the light beam hardening apparatus of
the present invention for a 50 W halogen bulb lamp offers a significantly
improved emitted light performance for the same electrical power input.
If the light beam hardening apparatus is controlled by a programmable
controller, then, in the event that the base receptacle of the light beam
hardening apparatus of the present invention has been substituted for a
halogen bulb lamp with reflectors, the material hardening time will be
correspondingly shortened to, for example, one-half the customary
hardening time or even one-third the customary hardening time, which is
a time saving benefit for the dentist.
Brief Description Of The Drawings
Figure 1 is a perspective view of a base receptacle of an
embodiment of the light beam hardening apparatus
of the present invention;
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Figure 2 is a side elevational view of the base receptacle
shown in Figure 1;
Figure 3 is a plan view of the base receptacle shown in
Figure 1 in its seated disposition in a receptacle of
the light beam hardening apparatus;
Figure 4 is a sectional view of a cradle in the base receptacle
shown in Figure 1 and showing an individual semi-
conductor light emitting source;
Figure 5 is a sectional view of a prism body for handling light
emissions of an embodiment of the light beam
hardening apparatus of the present invention; and
Figure 6 is a perspective view of an embodiment of the light
beam hardening apparatus of the present invention
in its operationally assembled condition with its base
I S receptacle, prism body, and a light beam guide.
Detailed Description of the Preferred Embodiment
In one embodiment of the light beam hardening apparatus of the
present invention, the light beam hardening apparatus includes a base
receptacle 10 having an outer surface 14 on which a plurality of semi-
conductor light emitting sources 12 are disposed. The semi-conductor
light emitting sources 12 are each individually mounted to the floor of a
cradle 16 and are recessed with respect to the outer surface 18 of the
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cradle. As seen in the figures of the drawings showing the embodiment
of the light beam hardening apparatus, a total of 12 semi-conductor light
emitting sources 12 are provided which are uniformly distributed over the
outer surface 14 of the base receptacle 10. Each of the semi-conductor
light emitting sources 12 is soldered by silver solder to the cradle as can
be best seen in Figure 3.
In accordance with the present invention, it is particularly
advantageous if the light strength has a value of at least 200 mWlcm2,
and, especially, has a value of 300 mWlcm2. It is especially beneficial if
a blue or white semi-conductor light emitting source with a light strength
of 1.000 or even 3.000 mcd is used. In accordance with the present
invention, such light emitting diode (LEU) chips produce a lightwave
maximum whose wavelength corresponds to the maximum sensitivity of
the typical dental material which is hardenable by light beam treatment.
In this manner, an intensive light beam hardening is made available with
only a decidedly small energy requirement.
The base receptacle 10 of the light beam hardening apparatus is
comprised of an aluminumlmagnesium alloy or composition such as
AIMg3, which is applied to the outer surface by a galvanic silvering
process. The depth of the silver coating is between 10 to 15
micrometers.
The depth of the solder coating for the manufacture of a metallic
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heat conducting connection is, in contrast to the depth of the silver
coating, significantly greater comprising, far example, 100 micrometers.
The surface 14 of the base receptacle 10 - as can be seen in Figure 2
from the point of view of the cradle 16 - is planar. The base receptacle
10 is in the form of a truncated cone cup whereby a projecting edge 20
is provided for improved side support.
Figure 3 shows one manner in which the base receptacle 10 can
be received in a socket 22. The socket is provided with cooling fins or
ridges along its outer surface and the inner surface of the socket
preferably precisely corresponds with the outer surface 24 of the
truncated cone cup of the base receptacle 10. The heat transfer between
the base receptacle 10 and the cooled socket 22 can, as required, be
improved by the use of a heat conducting paste.
Figure 4 shows the manner in which a chip or an individual semi-
conductor light emitting source 12 can be received in a cradle 1fi. The
cradle 16 is in the form of a reflector and the chip is arranged generally
in the focal burning point of the reflector. The cradle includes a fiat
ground surface 26, which is dirnensioned in correspondence with the
dimension of the chip 12. The chip in its mounted location on the cradle
is soldered to the cradle with a silver solder so that a metallic heat
conducting connection exists between the chip and the base receptacle
90.
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A conducting plate 28 is disposed on the outer surface of the base
receptacle 10 adjacent each cradle 16 and each conducting plate 28
includes conducting leads 30, which serve as the current supply. Each
chip is connected via a conventional coupling wire 32 with the conducting
leads 30. in the illustrated embodiment of the light beam hardening
apparatus, two coupling wires 32 are provided for each side in order to
reduce a drop off in current and the ensuing drop off in power of the chip.
A prism body 34 can be seen in Figure 5, which operates to collect
the emitted lightwaves. The Iightwaves, which are emitted by the chips
that are disposed along the outer periphery of the base receptacle, are
reflected several times in step wise manner by the prism body, whereby
the thus multiple reflected light beams pass through a central area 3fi and
outlet members 38 of the prism body. The prism body acts to intensify
the light beam emissions and to increase the lighting depth, and the prism
body is connected to a light guide 40; as seen in Figure 6.
As can be further seen in Figure 6, the unit comprised of the base
receptacle 10 and the prism body 34 is enclosed in a casing which is
comprised of the socket 22 and an opposed socket 42. The two sockets
22 and 42 are each provided on their outer surfaces with longitudinally
extending cooling fins or ribs, which facilitate the heat shedding capability
of the socket. The heat shedding surface is enlarged through the metallic
connection between the socket 22 and the opposed socket 42 and a
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continuous forced air stream can offer a particularly intensive cooling.
In a further advantageous configuration of the light bear'n
hardening apparatus of the present invention, it is provided that the LEas
are deployed with differing intensity maxima. Thus, for example, LEas
with a peak of 440 nm and 470 nrn are deployed. In this manner, it is
possible to provide a capability for effecting the hardening of a wide range
of dental materials since not every supplier of light hardenable dental
material adjusts the dental material for treatment at a peak of 470 nm.
Measurements have shown that the light beam hardening
apparatus of the present invention produces a light strength of about 600
mWlcm2 as compared with a light strength of 1200 mW/cm2 for a
conventional light beam hardening apparatus; however, the use of the
light beam hardening apparatus of the present invention achieves a
higher relative intensity at lower light strengths.
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