Note: Descriptions are shown in the official language in which they were submitted.
CA 02383181 2002-04-24
LIGHT HARDENING APPARATUS PARTICULARLY FOR A DENTAL
PRACTICE
Background of the Invention
The present invention relates to a dental light hardening apparatus
which is suitable not only for the complete hardening of photo
polymerizable dental material but is also suitable for whitening of teeth as
well as for deployment as a diagnostic apparatus for cavities. Other
therapy possibilities, which are not herein mentioned, can be realized with
the dental light hardening apparatus of the present invention. In the
1U following description? the dental light hardening apparatus of the present
invention is described including a configuration thereof as a dental
restoration piece hardening apparatus.
Light devices have been deployed, among other applications, in
dental applications in which a light polymerizable plastic is hardened by
1 ~~ irradiation with light. In order to achieve a high light density, energy
rich
light sources are typically deployed such as halogen glow lamps, xenon
photoflash, or even high-tension discharge lamps. The high-tension
discharge lamps have, in fact, an especially high light intensity and,
thereby, a correspondingly high light density. However, the operational
2U tension reaches at least 3.5 kV and a corresponding activation device is
required so that such lamps are not suitable for deployment in the dental
practice-at least, insofar as hand operable devices are concerned.
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CA 02383181 2002-04-24
Numerous attempts have been undertaken to improve the light
density of the known light apparatus in order to achieve a complete
hardening of the deeper lying layers in a rapid manner. A long-time
known, conventional light hardening apparatus with a light intensity of, for
example, 50 mW/cm2 produces, in fact, by a correspondingly longer light
irradiation, a good over surface hardening of the plastic or artificial piece
that is to be polymerized. However, deeper lying layers are not at all
hardened or, at most, only incompletely hardened. There arises a
hardness gradient which leads to the result that the deeper lying, middle
regions remain somewhat soft or that these regions are hardened
completely at a time later than the complete hardening of the over surface
areas.
The known light hardening apparatus lead to restoration results
that are compromised by, or suffer from, in part, edge spalling problems.
The known light hardenable plastics shrink slightly during the hardening
process. With the known light hardening apparatus, a complete
hardening initially occurs first in the over/outer regions of the restoration
piece. The thereafter following complete hardening of the deeper lying,
't
central regions leads to contractions and, thus, to edge spalling
formation.
It is further known to deploy light hardening apparatus that work
with semi-conductor light beam sources such as LEDs. Forexample, DE-
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CA 02383181 2002-04-24
GM 295 11 927 discloses a light-hardening device which uses a light
diode which emits light in the blue spectra( region which is supplied from
a battery or an accumulator.
It has, additionally, already been proposed to deploy a plurality of
LEDs for the energy supply of the light guiding conduit. In this manner,
the light output of the light-hardening device is improved. Independent
of whether the I_EDs are configured as module - that is, in a common
plastic housing - or as individual LEDs - that is, each respectively
disposed in an individual plastic housing - the light output of such
1p arrangements is limited. The plastic surroundings do not effect an
electrical insulation of the LEDs but, instead, block the transfer or giving
off of heat by the LEDs, so that it is necessary, even with a cooling of the
plastic housing from the exterior, that a predetermined density of the light
emitting chips not be exceeded.
1<_; It has further been proposed to use a light emitting diode as a
semi-conductor light source, which emits light in the visible or ultraviolet
range. However, there are disadvantages associated with this approach.
Investigations have shown that color changes occur precisely , in
connection with light or non-dark materials. On the other hand, such
20 conventional systems do not permit the use of white photo initiators.
At the same time, the tendency of the dental restoration piece to
suffer from edge spelling formation remains unabated in connection with
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the conventional systems.
Summary of the Invention
The present invention offers a solution to the challenge of a light
hardening apparatus for dental practice, which reduces the tendency of
light-hardenable masses to incur edge-spalling formation while at the
same time permitting fabrication of such light hardening apparatus in a
cost favorable manner and offering a light hardening apparatus that is
flexible in its deployment.
In accordance with the present invention, une embodiment of the
1e7 light hardening apparatus includes a semi-conductor light source with an
emission spectrum of at least two maximums. In accordance with the
present invention, the two maximums are clearly separate from one
another. For the first time, the possibility is offered to use plastic or
artificial. material which comprises two different catalyst systems which
harden one after the other. In accordance with the present invention, the
tendency towards edge spalling formation is reduced.
In accordance with the present invention, it is particularly
advantageous that the tight emitting source can be comprised of two
different wavelengths for complete hardening of the material
simultaneously, in order to effect the excitation of all dental materials
initiators from 400 to 500 nm.
Through the excitation of a semiconductor light source with an
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emission spectrum, whose maximum corresponds to the spectral
sensitivity of a first catalyzer, a pre-hardening is undertaken. As
necessary, a follow-up working of the material can already have been
accomplished in that the plastic or artifcial material in this condition
exhibits a high viscosity but is nonetheless malleable. By activation ofthe
other lighting source with an emission spectrum having a maximum which
is clearly different than the first maximum and is, preferably, of a short
wavelength, the second catalyzer can be activated whose sensitivity
maximum corresponds to the second maximum. Preferably, this
sensitivity maximum lies around 420 nm. The plastic or artificial material
can be brought to complete hardness by the activation of this catalyst.
Surprisingly, the solution of the present invention allows
adjustment without further working or special measures to nonetheless
yield a reduced tendency towards edge spalling formation. Through the
heretofore conventional light hardening by means of a light source in
connection with the deployment of a catalyzer, the hardening typically
follows a course by which at first the thinner edge layers and the over
surface layers of the dental restoration piece are hardened. Thereafter,
the deeper lying and central layers of the dental materials, which light
emissions, due to their penetration depth, have more difficulty in
reaching, are hardened. By virtue of the contraction of these deeper lying
and central layers, edge spalling is produced in that the over surface
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region and the edge region of the dental restoration piece typically
already have a higher firmness or hardness than the still soft deeper lying
middle region.
In contrast, in accordance with the present invention, the
:> contraction by virtue of the hardening process occurs during a condition
in which neither the material in the edge region nor the material in the
middle region is yet completely hardened. In this manner, the adhesion
forces clearly overcome the forces which resist malleability of the material
so that the contraction or shrinking deformation occurs in such a manner
that the layer strength of the material is somewhat reduced. This is not
a problem and can, as necessary, also be handled by application of
additional layers or can be compensated by a previously applied
increased layer strength.
It is to be understood that as necessary and in connection with the
1_'i operation of the apparatus, the possibility exists to select the
catalyzer
and the emission maximum with respect to one another and to
accommodate these to a wide range of requirements. Thus, as
necessary, a substantially long wavelength emission maximum can be
t
realized for the first light source and the catalyzer for the first light
source
can have an emissions maximum of, for example, more than 500 nm.
The dental material can be follow up treated with light as well as
additional heat to effect the hardening thereof.
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In accordance with the present invention, a dual hardening system
is made possible.
In an advantageous embodiment ofthe light hardening apparatus
of the present invention, the apparatus is deployed with the light sources
:i directly on the teeth. In a particularly advantageous embodiment, a
coupling sleeve (a pullover) is provided which can be disposed against
the tooth in an elastic manner and which serves to deliver the emitted
light completely onto the dental restoration piece. Due to this
configuration, the hardening can be exactly reproduced in that the light
1t) output given off by the light hardening apparatus as well as the light
output which ultimately reaches the dental restoration piece can be fixed
in a predetermined manner.
Additional advantages, details, and features are provided in the
hereinafter-following description of two embodiments of the light
1:> hardening apparatus of the present invention.
Brief Description Of The Drawings
The object and advantages of the present invention will appear
more clearly from the following specification in conjunction with the
accx~mpanying drawings, in which:
2p Fig. 1 is a perspective view of details of one embodiment
of the light hardening device of the present invention
for hardening a dental restoration piece and
CA 02383181 2002-04-24
showing, in particular, a base body having integrated
fighting sources thereon;
Fig. 2 is a perspective view of another embodiment of the
light hardening apparatus of the present invention;
and
Fig. 3 is a graphical representation of a spectrum of the
light sources of an embodiment of the light
hardening apparatus of the present invention.
Detailed Description of the Preferred Embodiment
As seen in Figure 1, a light hardening apparatus of the present
invention suitable for complete hardening of dental restoration pieces
includes a base body 10 having a plurality of LED-chips 12 on its upper
side 14. The LED-chips 12 are each respectively disposed in a hollow or
recess 16 and are in a sunken disposition with respect to the surface 18.
1= In the one embodiment of the light hardening apparatus shown in Figure
1, a total of nine of the LED-chips 12 are provided. By virtue of the
sunken disposition of the LED-chips 12 in the recesses, there is produced
a plurality of micro reflectors which increase the light output of the
',
apparatus.
2p A portion of the LED-chips have an emission maximum of 470 nm.
A further portion of the LED-chips have an emission maximum of 420 nm.
Each of the portions is organized into a group of LED-chips which are
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commonly actuated, whereby the groups each have an output which is
controlled by a dedicated control device operating independently of the
control device for the other respective groups of LED-chips.
The LED-chips 12 of a first group 22 form the semiconductor light
sources 24 having an emission maximum of 470 nm and the LED-chips
12 of a second group 20 form the semiconductor light sources 26 having
an emission maximum of 420 nm.
Conventional bond wires 28 are arranged in an interconnecting
manner over the individual LED-chips 12 of each group partially in a
parallel actuation circuit, partially in a series actuation circuit, and are
connected to collective rails 29.
The collective rails 29 are connected to separate energy supply
connectors (not shown) and are connected with a control device (not
shown).
Another embodiment of the light hardening apparatus of the
present invention is shown in Figure 2. In this embodiment, the LED-
chips 12 are mounted in close relationship with one another and here, as
well, a first group of the LED-chips form the semiconductor light sources
24 and another group 20 of the LED-chips form the semiconductor light
2~) sources 26.
The control device associated with the first group 22 initially
actuates the semiconductor light sources 24, whereby the light hardening
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apparatus, which is in immediate adjacent relationship with the over
surface of the dental restoration piece, irradiates the dental restoration
piece. In this condition, the first catalyzer is activated and this leads to a
pre-hardening of the photo polymerizable mass. Thereafter, as desired,
a follow up working is undertaken, if this is deemed to be necessary.
Also, for example, an additional layer of dental restoration material can
be applied.
Thereafter, the semiconductor light sources of the second group
20 are activated and a complete hardening is performed.
It is to be understood, that the light sources can be partitioned or
distributed in any suitable desired manner within the scope of the present
invention.
Figure 3 graphically shows the emission of the light hardening
apparatus of the present invention in the condition in which ali of the
semiconductor light sources have been activated. A first maximum 30
and a second maximum 32 can be seen, whereby the light intensity of the
second maximum 32, which lies at approximately 420 nm, is clearly
higher.
The present invention is, of course, in no way restricted to the
2~p specific disclosure of the specification and drawings, but also
encompasses any modifications within the scope of the appended claims.
to
