Note: Descriptions are shown in the official language in which they were submitted.
I r.
I 1
CA 02375889 2002-03-11
'1
METHOD FOR PRODUCING A SYNTHETIC MATERIAL PART
Background of the Invention
The present invention relates to a method for producing a
synthetic material part.
DE 196 42 2~~t discloses a method for producing a tooth
replacement including an initial step of capturing three dimensional
reproduction data and handling the data in preparation for the
w production of the tooth replacement. 1n this method, an electronically .
controlled machine toot is deployed to ensure the quick generation of a
prototype. This method permits the precise production of a tooth
replacement, However, the production method is decidedly expensive
and requires art Atectronically controlled machine tool which performs
the desired workpiece machining in a milling process.
The above-noted conventional method brings with it
disadvantages due to the accompanying discarded materiel and
unclean conditions, as these conditions cannot be tolerated in dental
practice, even when dental labor is available for the task.
~t ~s further conventionally known t~ use a three dimensional
printing technology for the rapid production or prototypes. In this
2t) regard, two methods find usage: in a tirst method, which was
developed by Massachusetts Institute Of Technology, a powder
material, along with a binder medium, is applied by a spray device in
layers built up to correspond to the object to be produced and the
binder medium is hardened layer-by-layer and thereby Uinds to the
-1-
a to? i ~ 704 3 . Ivo~~R rJonh America
i
CA 02375889 2002-03-11
powder material In connection with the completion of the object by
this first method, the excess, unbound powder material is removed.
While the powder material enables this approach to offer flexibility in
the configuration of the object to be produced, there typically remains a
granular or gritty surface.
In another conventional method, the three dimensional printing
technology is used in connection with the application of a material
which is hardenable by contact with air and which is applied by
electrostatic ink vapor spray jets. The spray device having the spray
f 0 jets is similar to an ink vapor spray printing device anri comprises
comparatively more spray jets. In view of the fact that each applied
material particle must be hardened completely, the production of an
object by this method correspondingly requiros a relatively long kime.
Other conventional methods for the rapid production of objects
have been elaborated and are commonly known as "Rapid Prototyping"
methods. In this regard, such methods include the stereo lithography
method, already developed during the 1980's by, in particular, 3U
Systems Inc., by .which a laser beam sculpts material in plate form
based upon CAU data. Such devices require a considerable capital
investment of, for example, a half million Deutschmarks or even a
million Deutschmarks.
It has also been proposed to use laser sintering processes for
the production of tooth replacement parts. These processes require in
_ 2 _.
P 101 71 704,3 . IVOCU~R NoAh America
CA 02375889 2002-03-11
their own right the use of a high energy laser, which thus engenders
various disadvantages.
Summary of the Invention
The present invention provides a method for producing a
synthetic material part including, in particular, a dental restorativA part,
which solves the challenge of reducing the capital investment cost
while nonetOeless providing a rapid production of the synthetic material
part.
' 1'he method of the present invention, as compared to the
conventi4nal meltiods, permits the use of relatively larger Spray drops
for the reason that the complete hardening by means of light
polymerization permits a rapid hardening of a just applied layer. This
permits, as well, a cost favorable execution of the printing process so
that the nur"her of jets, which contribute substantially to the production
cost burden, can be reduced. The relatively larger spray drops
nonetheless permit a more rapid build up of the synthetic material part
or object to 'be produced, whereby, in accordance with a particularly
advantageous embodiment of the present invention, the hardening of
the just applied layer is initially only partially completed and the further
hardening of the layer to its complete hardened condition is only
performed after the layer has been overlaid by the next Layer. This
provides, moreover, the particular advantage that there is a better
interconnection or bonding of the layers to one another. In accordance
with the present invention, it is particularly beneficial to prepare a
-3-
P 1~1 11 70~ 3 ~ IvOCLnR North Amorica
i i
CA 02375889 2002-03-11
dental restorative part comprised of an incomplete polymerizable
monomer or oligomer. A dental restorative part of this type can be
used in a particularly advantageous manner to produce a Cult
prosthesis although it is also suitable for use in producing a partial
prosthesis. Such prostheses exhibit considerable material str~nglh
which is provided by thp uniform, complete hardening of the material.
fn comparison to the conventional methods, the one requirement
in performing the method of the present invention is to definitively '
optically shield the spray jet device during the light hardernng step in
order to prevent an obstruction of the spray jets due to intensive Light
radiation thereon,
Conventional (fight sources are suitable for use with the method
of the present invention, whereby it is preferred to provide, in addition,
ultraviolet compomnts m the light hardening spectrum.
Ire accordance with a further, particularly advantageous aspect
of the present invention, the method of the present invention can be
directly employed in a dental practice. The method of the present
invention does not produce any discard milling material or other debris;
to this extent, the method is similar to those light hardening processes
ZO invoniny the disposition of a light hardening device in the mouth of a
dental patient which dentists, in any event, frequently perform.
As regarded from a further, particularly advantageous viewpoint,
the monomer used in the method of the present invention can comprise
a wax like substance. This substance permits setting of the viscosity to
-4-
P 10t 11 TOa;3 . IVp~~p~ North America
t a; t
CA 02375889 2002-03-11
a correct value al which a run off of the just applied spray drops used
for the layer building is prevented while, on the other hand, the
viscosity value is so small that it is possible to perform a penetration of
the spray jet thereinto in a favorable manner. It is particularly
advantageous if this wax-like substance comprises reactive groups
which can be co-polymerized with the monomer.
The printing technology, which can be adaptively applied in the
method of the present invention, principally correspbnds to the proven
ink spray prinliny method whereby it is to be understood that the spray
devices can be adapted in a desired manner to the method of the
present invention.
According to an advantageous embodiment of the present
invention, it is provided that the layer build up of the synthetic material
part being produced is configured such that the color impression
imparted by color imparting material built into the denial restorative part
is accommodated to the natural color in the patient's mouth.
In accordance with a further advantageous ,embodiment of the
method of the present invention, the transparency of the respectively
later applied layers is greater than that of the previously applied layers
so that the .dental restorative part has a color representatively
corresponding to the natural colors in the patient's mouth. This
embodiment of tt~e method of the present invention is particularly
advantageous for the production of tooth colored crowns, bridges,
inlays, and onlays.
_b_
P t01 11 704.3 . IvOCI~,R NoAh Arne~~ca
CA 02375889 2002-03-11
Detailed Oescriptivn of the Preferred Embodiment
A commercially available printer operable for three dimensional
printing pr~cPSSes can be used to produce a tooth replacement part in
S accordance with the method of the present invention, the printer being
configured for performing the pror:ess developed by Massachusetts
Institute o! Technology involving the spray application and hardening of
a powder material raving a binder added thereto; with the method
including the steps of applying layers of a polymerization initiator and a
i0 wax-like polyrnerizable substance to a potymerirable dental material
comprising a potymerizable monomor or oligorrter. The wax-like
substance is an ester of an alcohol with a polymerization capable
carbon acid derivative.
After the application of each layer. or after the application of
15 several layers, the printing head having the spray device is blocked off
by a black light protection cover which is moved via a linkage on the
printing head and is operable to optically separate the printing head
from the synthetic material. As soon as the stop position of the printing
head is reached, a signitcantly strong halogen lamp having a high
20 ultraviolet component is actuated for several seconds to effect a light
hardening of the appfied materials. Thereafter, the lamp is turned off
and the next layer is applied. This cycle is repeated until the tooth
replacernent part has been fully completed. A heat hardening is then
pertormed to ensure that the polymerization has been completed.
-6-
P 10~ 11 Tp.~,3 _ wOCLAR North America
CA 02375889 2002-03-11
In one mod ification of the method of the present invention,
during the time that the printing head is applying the next layer,
the light source is blocked off instead of being turned vff,
whereby the operating liFe of the light source is lengthened.
BR,TEF DESCRIPTION OF TtIE bRAW.INGS
Fig. 1 is a view of. an appliance for ttw realisation of the
procedure according to the invention in schematic form.
Fig. 2 is another view of the appliance in accordance with
Fiq. 1, during another step in the procedure.
Fig. 3a and b show two different possible layouts of the
nozzles according to the invention.
Fig. 4 is a modified design of an appliance .for the
realization- of- the procedure according to the invention.
From Fig. 1, an appliance for the realization of the procedure
according tc3 the invention a.s to be seen in schematic form. A
nozzle layout lU is provided, that is arranged with its nozzles on
a base 12. The nozzle layout;, which can for example be arranged in
accordance with the two forms in fig. 3, lets plastic: material l4
emerge. The plastic material 14 is applied onto the base 12 in
layers, where in the reprp~entation according to Fig. 1 four layers
16 are applied completely, while one layer 18 is only applied
partially. For the application a relative motion takes place
between the nozzle layout 10 and the base 12. For the manufacture
of a dental. restorative part, a stationarily installed nozzle
layout 10 is preferred, while the base is movable horizontally.
The layers are applied preferentially in a low layer thickness
that allows a pt:ecice Formation of the restorative part, for
example in a layer thickness of 100 microns. Zn accordance with a
modified design, the l.a~yer. thickness is even reduced to 20 microns.
The shaping of the restorative part can now take place so that
material is applied in thicker layers at the positions at which'
raised forms should be realized, during which these surrounding
areas are left free. For the realization oL a complex three-
dimensional restorative part, it i,s also possible to use the base
12 as a dividing-level and to form two separate part-restor~rtion
CA 02375889 2002-03-11
parts, which are secured together ba~,k to back. Fox precise fixing
adjustment markings can be sprayed on, that carr be removed after
the parts have been secured together. The sPCUx.ing can for example
be achieved through gluing, hot pressing or similar.
The applied restorative part i.s still soft at first and not
capable of bearing a load. Through hardening by means of a
polymerization device 20 i» accordance with Fig.2 the desarad
hardening can be achieved. In this regard a light: source 22 is
preferably provided, that like the nozzle layout 10 allows a
relative movement against the base 12 as well. Spontaneous
hardening takes precedence over light hardening every time if a
layer 18 is applied.
It is understood that instead oL pure light hardening, heat
polymerizat3o.n or a combination of these i.s also pUSSible.
The base 12 is moreover vertically movable in order to account
the layer co#rstruction of the layers 16 and 18 little by little..
From Fig. 3, two different possible noazle layouts Z4 are
apparent. According to fig. 3a, the nozzles are arranged in a row.
t3y contrast, they are arranged in three rows according to Fig. 3b,
where the rows are somewhat offset against each other. With the
layout according to 3b, the resolution Can still be somewhat
improved.
A modified desi.qn .is evident :from Fig. 9. With this solut~.on, ~ ,
the light source 22 and the nozzle layout to are secured to a
common support 26'. This so,l.utivn allows the application of the
plastic material 14 and hardening of the material in one step. In
this regard a relative movement 12 takes place between the base
and the support 26 in accordance with the example of an
implementation in accordance with Fig. 1 and 2. roc example the
base 12 is moved from the right to the left in accordance with the
arrow 27. By this means it i.s guarani:eed that an observed area o.f
tire .Layer 16 is at First beneath the nozx.le layout to and then
below the light source 22.
In order to securely prevent premature hardening and also
blockage of the nozzles of the no~2le layout 1U, a shield 22 is
provided between the noZZI~? layout 10 and the light source that
8
CA 02375889 2002-03-11
extends to the layer 18. The shield 28 is preferably soft at least
in its lower area so that it doesn't impair the layer construction
of the uppermost layer 18. For. examplQ, a thin curtain of black
plastic foil can also be inserted.
The present invention is, of course, no way restricted to the
specific disclosure of the specification and drawings, but also
encompasses any modifications within the scope of the appended
claims.
.~c~
