U.S. patent application number 10/380201 was filed with the patent office on 2005-01-27 for method for the preparation of dental prosthetic artefacts by means of powder sintering.
Invention is credited to Venturini, Daniele, Venturini, Walther Giuseppe.
Application Number | 20050019200 10/380201 |
Document ID | / |
Family ID | 11437153 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050019200 |
Kind Code |
A1 |
Venturini, Daniele ; et
al. |
January 27, 2005 |
Method for the preparation of dental prosthetic artefacts by means
of powder sintering
Abstract
The present invention relates to a method for obtaining dental
prosthetic artefacts, corrections, additions, welds and the like,
which method uses the sintering of powders of metal alloys in
common dentistry furnaces and comprises the following phases:
adapting a plate of metallic powder with organic compounds added,
modelling said adapted plate, coating the prepared item with
refractory coating material mixed with an organic liquid and
sintering the prepared item. The present invention further presents
the advantage of enabling to work directly on the master model,
avoiding the duplication step with the consequent time saving and
with greater precision.
Inventors: |
Venturini, Daniele;
(Villafranca d'Asti, IT) ; Venturini, Walther
Giuseppe; (Villafranca d'Asti, IT) |
Correspondence
Address: |
BROWDY AND NEIMARK, P.L.L.C.
624 NINTH STREET, NW
SUITE 300
WASHINGTON
DC
20001-5303
US
|
Family ID: |
11437153 |
Appl. No.: |
10/380201 |
Filed: |
March 13, 2003 |
PCT Filed: |
September 13, 2001 |
PCT NO: |
PCT/IT01/00476 |
Current U.S.
Class: |
419/9 |
Current CPC
Class: |
A61K 6/844 20200101;
B22F 3/1283 20130101; A61C 13/0003 20130101 |
Class at
Publication: |
419/009 |
International
Class: |
B22F 007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2000 |
IT |
AL2000A000007 |
Claims
1. A method for obtaining dental prosthetic structures and the
like, characterised in that it comprises the following steps:
adapting a plate made of metal powder with organic compounds added
to a model made of plaster or the like; modelling said plate
adapted on said model made of plaster or the like; coating the
prepared item with refractory coating material and mixed with an
organic liquid; and sintering the prepared item.
2. A method according to claim 1, wherein said metallic powder is a
powder of pure metal.
3. A method according to claim 1, wherein said metallic powder is a
powder of metallic alloys.
4. A method according to claim 1, characterised in that said plate
is obtained by mixing different metallic powders.
5. A method according to claim 1, characterised in that said plate
is obtained by mixing at least two metallic powders of pure
metal.
6. A method according to claim 1, characterised in that said plate
is obtained by mixing at least two metallic powders of pure metal
and metal alloy.
7. A method according to claim 1, characterised in that said plate
is obtained by mixing at least two metallic powders of metal
alloy.
8. A Method according to any of the previous claims from 1 to 7,
wherein said mixing of metallic powders has a volumetric ratio
between the components that ranges between 0.5 and 1.5.
9. A method according to in the previous claim, wherein said
volumetric ratio is equal to 1.
10. A method according to any of the previous claims, characterised
in that said organic liquid contains a substance comprising from 1
to 10 carbon atoms.
11. A method according to the previous claim, characterised in that
the organic liquid is selected from the following compounds: ethyl
alcohol, acetone, methyl alcohol, propyl alcohol,
ethyl-methyl-ketone, diethyl-ketone, acrylic acid, metacrylic acid,
diethanolamine, diethylamine, and the like, and mixtures of two or
more of said substances.
12. A method according to one or more of the previous claims,
characterised in that any excess organic liquid is eliminated by
means of permanence in the furnace at a temperature lower than
sintering temperature.
13. A method according to one or more of the previous claims,
characterised in that said metallic powder is constituted by an
alloy containing at least 50% of Pd.
14. A method according to one or more of the previous claims 1
through 12, characterised in that the metallic powder is
constituted by an alloy containing at least 50% of Au.
15. A method according to one or more of the previous claims 1
through 12, characterised in that the metallic powder is
constituted by an alloy containing at least 50% of Ag.
16. A method according to one or more of the previous claims 1
through 12, characterised in that the metallic powder is
constituted by pure gold.
17. A method according to one or more of the previous claims 1
through 12, characterised in that the metallic powder is
constituted by pure silver.
18. A method according to one or more of the previous claims,
characterised in that said additive for said metallic powder is an
organic compound selected from the following compounds:
Polyethylene glycol, glycerine, butylic rubber, isobutylic rubber,
natural rubber, natural wax, synthetic wax, and the like and
mixtures of two or more of said substances.
19. A method according to one or more of the previous claims,
characterised in that the dimensions of the particles of the
powders used normally range between 0.1 and 1000 .mu.m.
Description
DESCRIPTION
[0001] The present invention relates to a method for obtaining
artefacts or metal structures for odontotechny and dentistry,
providing for the use of powders of the metals and of the alloys
commonly used in the practice of odontotechnical laboratories.
[0002] The processing of metals and alloys is a widely followed
practice in the operations that take place in an odontotechnical
laboratory. Such work processes entail a wide range of different
operations and, for instance, the production--with the so-called
lost wax method--of metallic dental structure for prosthetic uses,
as a consequence of the loss of one or more teeth because of
pathological or traumatic events.
[0003] As it is well known to the persons skilled in the art, the
lost wax technique consists of numerous successive operations
starting with the dentist's taking the impression of the patient's
teeth. From this impression, a cast of the teeth is obtained, with
the aid of which the dentist builds a wax model of the prosthetic
component (crown, bridge or other) to be made of metal. This model
is incorporated in a refractory material known as coating and
which, solidifying, encloses the model in a thermally stable shell.
A subsequent heat treatment allows to eliminate, through
appropriate vents, the wax part and to obtain a case having in its
interior a cavity with the shape of the original wax model. This
cavity is filled with the molten metal casting and, after the
mechanical elimination of the coating, the metallic prosthetic
component is obtained, to be used as it is or coated, for aesthetic
purposes, with ceramic or resin.
[0004] The lost wax technique allows to obtain good results,
but--as the short description provided above shows--it consists of
a long process, not without its difficulties.
[0005] Other dentistry work processes that use metals are, for
instance, welding operations, repairs of broken or damaged
artefacts, correcting or re-heating a component that is not wholly
satisfactory, and the like. Such work processes, mentioned as
examples of a wider range of operations, require additional
metallic weld material. In particular, the addition of further
metal necessarily requires melting said metal. This operation can
cause a deformation of the existing artefact, due to the need to
reach high temperatures. The attempt to avoid this drawback using
different weld alloys, in particular alloys with a lower melting
point than that of the metal of the existing artefact, is also not
free of drawbacks. The presence of different metals in mutual
electrical contact can lead, in the oral environment, to the onset
of corrosion phenomena, with the consequent deterioration of
mechanical properties, aesthetically displeasing discoloration and
the release of ions in the oral cavity of the person wearing the
prosthesis.
[0006] From the above, it is readily apparent that all the
operation that provide for the realisation, modification,
correction and re-adaptation of a prosthetic artefact through the
use or addition of metallic material present quite a few practical
and constructional difficulties. For this reason, different
alternative methods have been proposed; among them, particularly
promising appear the processes that provide for sintering metallic
powders. The consolidation of metallic powders by sintering is a
technique with widespread industrial use and it is described, for
instance, in the book by C. G. Goetzel "Treatise on Powder
Metallurgy" published by Interscience Publishers Ltd., London,
1949.
[0007] The application of powder metallurgy to the practice of
dentistry is described, for instance, in U.S. Pat. No. 4,689,197,
which teaches the realisation of dental prostheses by means of
sintering metallic powders, optionally with the use of glass or
ceramic powders. According to said patent, the metallic powders,
made plastic with water, are adapted and conformed to a prepared
model of the prosthetic component to be obtained, coated with a
thin layer of wax that is eliminated before sintering. Another U.S.
Pat. No., 4,828,95 describes the realisation of metallic prostheses
by sintering a paste obtained from metal powders with an
appropriate organic binder. The paste is modelled on a prepared
component, wherefrom it is isolated by means of another metallic
layer, also obtained by sintering. The powder sintering technique
is also used according to U.S. Pat. No. 4,980,124, which provides
for the metallic powders to be sintered on a thing sheet of
palladium or suitable alloys, adapted to a model of the component
to be realised, in such a way as to obtain a metallic structure
that is difficult to deform, whereon a ceramic crown is
constructed.
[0008] U.S. Pat. No. 5,234,343 discloses a method and a material
that allow to obtain prosthetic components starting from metallic
powders constituted by a metal with high melting point and a metal
with low melting point.
[0009] The technique of sintering metallic powders, as taught in
the aforesaid patents, allows to obtain metallic prostheses in a
faster manner, with fewer scraps and with greater dimensional
accuracy relative to the lost wax technique. However, there are
still some problems that limit the practical and complete
attainment of these advantages. First of all, not all the aforesaid
known techniques allow to complete all of the operations listed
above. Moreover, the need successfully to perform the sintering
process entails come drawbacks, such as the use--often
suggested--of furnaces able to reach high vacuum conditions. This
requirement is imposed by the need to sinter powders suitable for
the metal-ceramic technique. As is well known to those versed in
the art, such alloys contain--in addition to a high percentage of
noble metals--also a certain quantity of non noble and easily
oxidised metals. The latter make the sintering operation more
difficult and not achievable under atmospheric pressure conditions
or with the degree of vacuum reachable in common ceramic
furnaces.
[0010] For example, according to the aforesaid U.S. Pat. No.
5,234,343, sintering is performed at atmospheric pressure, but this
leads to the need to use powders with high noble metal content.
This in turn causes high raw material costs and entails the
impossibility to form chemical bonds between metal and ceramic, so
that adhesion between these two components is left only to
mechanical action.
[0011] Since the establishment of a strong bond between metal and
ceramic is an essential condition for the successful outcome of the
work, the lack of a chemical bond is a non negligible
limitation.
[0012] Moreover, Italian Patent No. 1271360 in the name of the same
Applicant describes a method for obtaining artefacts starting from
alloy powders for metal-ceramic at ambient pressure, providing for
the use of graphite containers, under which the sintering process
takes place. The need to effect the sintering under graphite
containers constitutes a limitation to the application of the
technique, for the following two reasons.
[0013] First of all, the dimension of the work that can be executed
is limited by the dimensions of the graphite container. In the
second place, the introduction of graphite objects into a ceramic
furnace is not viewed favourably by the user, due to the
possibility of contamination from the carbon of the graphite
containers. It is well known that the carbon may combine with the
palladium contained in may alloys used for dentistry, giving rise
to compounds that make the alloy considerably more fragile, to the
point that it is no longer suitable for normal conditions of use.
Moreover, carbon contamination may originate bubbles when the
ceramic is cooked and it may promote the formation of discoloration
and aesthetic flaws in the ceramic.
[0014] Taking the above into account, the aim of the present
invention is to find a method that allows to achieve, in an easy,
precise and economical manner, the production of metallic dental
structures for prosthetic uses and it simultaneously enables also
to achieve the addition of metallic material for modification,
correction, reinforcement or junction purposes, or for any other
requirements, eliminating the drawbacks of the aforesaid known
methods and above all the need to use vacuum conditions or
particular atmospheres as well as graphite containers, and
determining a considerable improvement of the work processes used
thus far, while it allows fully to exploit the advantages of
sintering and to obtain prosthetic structures and to realise
additions and corrections in a more convenient manner relative to
the prior art.
[0015] Moreover, the present invention entails the considerable
advantage and the peculiarity of working directly on the master
model and not on the refractory material, thereby avoiding the
duplication step, with consequent time savings and reduced risk of
imprecision.
[0016] Moreover, the present invention provides for the use of
common dental alloys such as gold or pure silver.
[0017] Hence, the present invention provides a method for obtaining
prosthetic metallic structures, corrections, additions, adaptations
of details, and the like, characterised in that it comprises the
following steps:
[0018] adapting a plate of metallic powder with organic compound
additives to a model made of plaster or the like;
[0019] modelling said plate adapted on said model made of plaster
or the like;
[0020] coating the item thus prepared with refractory coating
material mixed with an organic liquid; and
[0021] sintering the prepared item.
[0022] According to a preferred characteristic of the invention, an
organic liquid is used for the refractory coating material, whose
molecule contains 1 to 10 carbon atoms, preferably from 1 to 5
carbon atoms such as, for instance, methyl alcohol, ethyl alcohol,
propyl alcohol, acetone, ethyl-methyl-ketone, diethyl-ketone,
acrylic acid, metacrylic acid, diethanolamine, diethylamine, and
the like. Mixtures of two or more of said liquids can also be
used.
[0023] Next to carbon, the molecule of the organic liquid used
according to the invention to mix the coating material, can also
contain other elements as well, such as nitrogen, oxygen, sulphur,
chlorine, fluorine and all elements that commonly bind with
carbon.
[0024] The organic liquid and the coating material react to each
other at the time of mixing and/or inside the furnace, to generate
conditions suitable for sintering, strengthening also the normal
protection against contact with the atmosphere, which protection is
determined by the protective shell constituted by the coating
material.
[0025] In a particularly favourable embodiment of the present
invention, a prosthetic artefact is obtained in the following
way.
[0026] The material for obtaining the prosthesis is constituted by
a metallic powder which has the same composition as the alloys and
the pure metals commonly used in dentistry. This powder is employed
as such or it is preferably incorporated in an additive that
facilitates its deposition and/or modelling. Moreover, a diluting
agent can be used to make the paste even more malleable and
workable. Typical, but not limiting, examples of additives are
constituted by polyethylene, glycol, glycerine, butylic, isobutylic
or natural rubber, natural or synthetic wax, as well as mixtures of
one or more of said substances. Typical, but not limiting, examples
of diluting agents are constituted by water, hydrocarbons,
alcohols, poly-oils and mixtures thereof.
[0027] The size of the particles of the powders used normally
ranges from 0.1 and 1000 .mu.m. Powder composition is not critical
and may correspond to the compositions used in common practice with
traditional methods.
[0028] According to an embodiment of the present invention, a
component of a prosthesis for the metal-ceramic technique can be
obtained starting from powders with identical composition to that
of the alloy used normally for the same purposes.
[0029] The metallic powder mixture is worked in such a way as to
obtain plates of defined thickness. Indicative, but not limiting,
values of the thickness of such plates range between 0.15 and 0.40
millimetres. In a single plate, the metallic powder may be
constituted by pure metal, alloy, or a mixture of pure metal/pure
metal or pure metal/alloy or alloy/alloy with a volumetric ratio
ranging between 0.5 and 1.5 and preferably equal to 1.
[0030] The plate (or a part thereof) is adapted directly to the
plaster model of the component to be obtained. After adapting and
modelling this plate, it is coated with a refractory coating
material according to the invention, i.e. mixed with an organic
liquid, as described above.
[0031] After some minutes, the modelled part is extracted from the
plaster model and completely coated with metallic coating as per
the present invention. The whole set is then moved to a common
dentistry furnace, where sintering is performed. It is preferable,
but not binding, to keep the prepared item, before sintering, for a
certain time interval to a temperature lower than sintering
temperature, to obtain the elimination of the excess organic
liquid.
[0032] Sintering is performed in a ceramic or pre-heating furnace,
at ambient pressure and in normal atmosphere, at a temperature
equal to about 80% of the melting temperature of the alloy. The
metallic artefact thus produced can be ceramic coated and worked as
usual.
[0033] The numerous advantages of the invention are readily
apparent to those skilled in the art. The manufacture of metallic
prosthetic structures such as crowns, bridges and the like, as well
as their correction, welding and re-modelling, are considerably
facilitated by the method according to the invention which allows
fully to exploit the advantages of the powder sintering technique
and does not entail any additional equipment complexity or
contamination risks for the materials.
[0034] In addition to the manufacture of prostheses, the method
according to the present invention is particularly advantageous for
effecting modifications, corrections of the biting surface,
corrections of the general shape of said prostheses, as well as
welding different components in order to obtain a single body. In
such cases, the welding material (which preferably has the same
composition of the alloy constituting the prosthetic artefact) is
deposited with extreme precision and ease, thanks to the ease of
manipulation of the metal-additive mix. The component to be
sintered is enclosed in the coating material mixed, according to
the invention, with the organic liquid. The method according to the
present invention, moreover, allows the supermelting technique
using suitable alloys.
[0035] Moreover, the elements produced by sintering the metal
according to the method of the present invention, can thereafter be
united and/or modified with:
[0036] the addition of more material suitable for sintering,
[0037] traditional welding materials
[0038] supermelting (lost wax method).
[0039] Hereafter, some embodiment examples of the method according
to the invention are provided purely by way of illustrative and not
limiting example.
EXAMPLE 1
[0040] A metal crown was manufactured using a quantity of New
Ceramit USA 88 alloy (Nobil Metal, Villafranca, AT) with wax added
(Industria Zingardi, Novi Ligure, Ala.). The composition of the
alloy, as declared by the manufacturer, is as follows:
1 Au Pd Cu Ga Ru 2.0% 79.0% 9.9% 9.0% 0.1%
[0041] The mixture was subjected to pressure to increase the
consistency of the material, obtaining a plate with a thickness of
0.30 mm. A portion cut off from said plate was wound about a
plaster model and then pressed, to adapt it to the shape of the
model.
[0042] At the end of the adapting process, the metal paste was
coated with coating material (Sintercast RDM, Nobil Metal). The
coating material used is characterised by the following
composition:
2 Crystalline silica (quartz) 10-30% Crystalline silica
(cristobalite) 40-70% Phosphate-based powders 10-30% Metal oxides
3-15%
[0043] Four samples (a), (b), (c) and (d) were prepared, each
obtained with the same coating material but mixed each time with
one of the following liquids:
[0044] a) The liquid normally used for mixing the coating
(Sintercast RDM liquid, with aqueous base and 15-40% amorphous
colloidal silica).
[0045] b) Aqua
[0046] c) Denatured ethyl alcohol
[0047] d) Acetone
[0048] The items were sintered in a ceramic furnace (of the kind
commercially known as LECTRA, Nobil Metal, Villafranca, AT) at
1050.degree. C. for 10 minutes.
[0049] The results of the sintering process were assessed through
the visual observation of the products and by means of mechanical
stressing. In particular, the items were blocked by means of clamps
and subjected to bending with pincers. The products were classified
according to a scale from 1 to 5, where "1" means the product
underwent no compacting, whereas "5" means the product has the
suitable consistency for its intended use. The test was repeated
three times for each series of four samples ("a" through "d") and
the results, expressed as the mean of the observations, are set out
in the following table:
3 Sample Result a 1 b 1 c 5 d 5
EXAMPLE 2
[0050] The experiment of Example 1 was repeated with powders of the
Pal Keramit (Nobil Metal, Villafranca, AT) alloy. The composition
of the alloy, as declared by the manufacturer, is as follows:
4 Ag Pd Sn Ga In Ru 32.0% 57.5% 8.0% 1.5% 1.0% 0.1%
[0051] The sintering process was conducted for 10 minutes at
1010.degree. C. Then, the assessment system described in the
previous example was used for the same number of samples and the
following results were obtained:
5 Sample Result a 1 b 1 c 5 d 5
EXAMPLE 3
[0052] The experiment of Examples 1 and 2 was repeated using
powders of a yellow alloy having the following composition:
6 Au Pt Sn In Ir Ru 80.6% 15.4% 1.6% 1.4% 0.4% 0.6%
[0053] The sintering process was conducted for 15 minutes at
990.degree. C., then the same assessment system described in
Example 1 was used and the following results were obtained:
7 Sample Result a 1 b 1 c 5 d 5
EXAMPLE 4
[0054] Using the alloy of sample 1, three separate units were
obtained, destined to a three-element bridge, constituted by two
crowns and by an intermediate element. On the junction points, a
paste obtained from the alloy of Example 1 with wax added was
delicately modelled. The elements were then brought in mutual
contact. Four samples a), b), c) and d) were prepared with
refractory coating material mixed each time with one of the liquids
of Example 1. The sintering process was conducted in the conditions
of Example 1. The finished products do not reveal any trace of
added material at the junction points and perfectly adapt to the
model of the stumps and are suitable to prosthetic use in the case
of samples c) and d), whereas sintering is not satisfactory in the
case of samples a) and b).
EXAMPLE 5
[0055] A metal crown was obtained with the lost wax technique,
using the Pal Keramit alloy as a model. The thickness of the part
destined to cover the stump was measured with a micrometer and a
maximum value of 0.8 mm was recorded. To assess the effectiveness
of the method according to the invention to obtain thickness
increases, the item was uniformly coated with a plate of Pal
Keramit alloy powder, with wax added. The sintering process was
conducted with the times and in the ways of cases b) and d) of
Example 2. Thickness was measured again and a uniform increase of
0.5 mm was recorded in case d), whilst the added powder was not
found to have been sintered in case b).
EXAMPLE 6
[0056] A mixture of pure gold powder was obtained by combining gold
powder and wax in the proportions of 3.5 g of wax per 100 g of
gold. The mixture thus obtained was pressed to obtain a platelet
with a thickness of 0.30 mm. A cut-off portion of said plate was
wound about a plaster model and then pressed, to adapt it to the
shape of the model.
[0057] At the end of the adaptation process, the metal paste was
coated with coating material (Sintercast RDM, Nobil Metal) mixed
with acetone. The items were sintered in a ceramic furnace (LECTRA,
Nobil Metal, Villafranca, AT) a 1030.degree. C. for 4 minutes.
[0058] The results of the sintering process were assessed through
the visual observation of the product and by means of mechanical
stressing, as described in Example 1. The result obtained,
according to the scale described in Example 1, was assigned a value
of 5.
EXAMPLE 7
[0059] A mixture of pure silver powder was obtained by combining
silver powder and wax in the proportions of 6.5 g of wax per 100 g
of silver. The mixture thus obtained was worked to obtain a
platelet with a thickness of 0.30 mm. A cut-off portion of this
platelet is wound about a plaster model and then pressed, to adapt
it to the shape of the model.
[0060] At the end of the adaptation process, the metallic paste was
coated with coating material (Sintercast RDM, Nobil Metal) mixed
with acetone. The items were sintered in a ceramic furnace (LECTRA,
Nobil Metal, Villafranca, AT) at 920.degree. C. for 4 minutes.
[0061] The results of the sintering process were assessed through
the visual observation of the product and by means of mechanical
stressing, as described in Example 1. The result obtain, according
to the scale described in Example 1, was assigned a value of 5.
EXAMPLE 8
[0062] A plate with a thickness of 0.35 mm was obtained by
homogeneously mixing pure gold powder and pure silver powder. The
final plate had a volumetric ratio of 1 to 1. A portion of said
plate was wound about a plaster model and the pressed, to adapt it
to the shape of the model. At the end of the adaptation process,
the metal paste was coated with coating material (Sintercast RDM,
Nobil Metal) mixed with acetone. The items were sintered in a
ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT) at
990.degree. C. for 4 minutes.
[0063] The results of the sintering process were assessed through
the visual observation of the product and by means of mechanical
stressing, as described in Example 1. The result obtained,
according to the scale described in Example 1, was assigned a value
of 5.
EXAMPLE 9
[0064] A plate with a thickness of 0.34 mm was obtained mm by
homogeneously mixing pure gold powder and powder of an alloy with
high gold content (Au+PGM=100%). A portion of the plate was wound
about a plaster model and then pressed, to adapt it to the shape of
the model. At the end of the adapting process, the metal plate was
coated with coating material (Sintercast RDM, Nobil Metal) mixed
with acetone. The items were sintered in a ceramic furnace (LECTRA,
Nobil Metal, Villafranca, AT) at 1086.degree. C. for 8 minutes.
[0065] The results of the sintering process were assessed through
the visual observation of the product and by means of mechanical
stressing, as described in Example 1. The result obtained,
according to the scale described in Example 1, was assigned a value
of 5.
EXAMPLE 10
[0066] A plate with a thickness of 0.36 mm was obtained by
homogeneously mixing pure gold powder and powder of an alloy with
high gold content (Au+PGM=97.8%). A portion of the plate was wound
about a plaster model and then pressed, to adapt it to the shape of
the model. At the end of the adapting process, the metal plate was
coated with coating material (SINTERCAST RDM, Nobil Metal) mixed
with acetone. The items were sintered in a ceramic furnace (LECTRA,
Nobil Metal, Villafranca, AT) at 1075.degree. C. for 8 minutes.
[0067] The results of the sintering process were assessed through
the visual observation of the product and by means of mechanical
stressing, as described in Example 1. The result obtained,
according to the scale described in Example 1, was assigned a value
of 5.
EXAMPLE 11
[0068] A plate with a thickness of 0.33 mm was obtained by
homogeneously mixing pure gold powder and powder of an alloy
characterised by a content of Au+PGM of 84.0%. A portion of the
plate was wound about a plaster model and then pressed, to adapt it
to the shape of the model. At the end of the adapting process, the
metal plate was coated with coating material (SINTERCAST RDM, Nobil
Metal) mixed with acetone. The items were sintered in a ceramic
furnace (LECTRA, Nobil Metal, Villafranca, AT) at 1080.degree. C.
for 8 minutes.
[0069] The results of the sintering process were assessed through
the visual observation of the product and by means of mechanical
stressing, as described in Example 1. The result obtained,
according to the scale described in Example 1, was assigned a value
of 5.
EXAMPLE 12
[0070] A plate with a thickness of 0.35 mm was obtained by
homogeneously mixing pure silver powder and powder of an alloy with
high gold content (Au+PGM=97.8%). A portion of the plate was wound
about a plaster model and then pressed, to adapt it to the shape of
the model. At the end of the adapting process, the metal plate was
coated with coating material (SINTERCAST RDM, Nobil Metal) mixed
with acetone. The items were sintered in a ceramic furnace (LECTRA,
Nobil Metal, Villafranca, AT) at 1000.degree. C. for 8 minutes.
[0071] The results of the sintering process were assessed through
the visual observation of the product and by means of mechanical
stressing, as described in Example 1. The result obtained,
according to the scale described in Example 1, was assigned a value
of 5.
EXAMPLE 13
[0072] A plate with a thickness of 0.35 mm was obtained by
homogeneously mixing powder of an alloy with high gold content
(Au+PGM=100%) and powder of an alloy characterised by Au+PGM=97.8%.
A portion of the plate was wound about a plaster model and then
pressed, to adapt it to the shape of the model. At the end of the
adapting process, the metal plate was coated with coating material
(Sintercast RDM, Nobil Metal) mixed with acetone. The items were
sintered in a ceramic furnace (LECTRA, Nobil Metal, Villafranca,
AT) at 1095.degree. C. for 8 minutes.
[0073] The results of the sintering process were assessed through
the visual observation of the product and by means of mechanical
stressing, as described in Example 1. The result obtained,
according to the scale described in Example 1, was assigned a value
of 5.
EXAMPLE 14
[0074] A series of prosthetic elements obtained as described in the
previous examples (1.fwdarw.13) was welded using portions of a
plate having the same chemical composition as the prosthetic
element. The metallic paste was adapted in the point of interest
joining two single crowns, then proceeding with the sintering
process in a ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT)
with the same parameters used for sintering the initial artefact,
except for the sintering temperature, lower by 5-10.degree. C. than
the initial one. The results of the sintering process were assessed
through the visual observation of the product and by means of
mechanical stressing, as described in Example 1. The result
obtained, according to the scale described in Example 1, was
assigned a value of 5.
EXAMPLE 15
[0075] A series of prosthetic elements obtained as described in
Examples 1.fwdarw.13 was modified adding and modelling portions of
a plate having the same chemical composition as the prosthetic
element. The metallic paste was added in the area of interest,
modifying the anatomic profile of the prosthesis and then
proceeding with the sintering process in a ceramic furnace (LECTRA,
Nobil Metal, Villafranca, AT) with the same parameters used for
sintering the initial artefact, with the exception of the sintering
temperature, 5-10.degree. C. lower than the usual one. The results
of the sintering process were assessed through the visual
observation of the product and by means of is mechanical stressing,
as described in Example 1. The result obtained, according to the
scale described in Example 1, was assigned a value of 5.
EXAMPLE 16
[0076] A series of prosthetic elements obtained as described in
Examples 1.fwdarw.13 was welded using the classic blowpipe welding
method. Two single crowns, after incorporation in the refractory
material and subsequent pre-heating in the furnace were welded with
the aid of the blowpipe, according to the technique widely known as
blowpipe welding, with appropriate welding material. The success of
the welding process was assessed through the visual observation of
the product and by means of mechanical stressing, as described in
Example 1. The result obtained, according to the scale described in
Example 1, was assigned a value of 5.
EXAMPLE 17
[0077] A series of prosthetic elements obtained as described in
Examples 1.fwdarw.13 was modified adding metal (welding material)
with the traditional blowpipe welding technique. The welding
material used, characterised by a working temperature that is
50.degree. C. lower than the sintering temperature, flowed
perfectly on the surface to be modified, thereby demonstrating an
excellent ability to wet said surface. The results of the sintering
process were assessed through the visual observation of the product
and by means of mechanical stressing, as described in Example 1.
The result obtained, according to the scale described in Example 1,
was assigned a value of 5.
EXAMPLE 18
[0078] A series of prosthetic elements obtained as described in
Examples 1.fwdarw.13 was joined using the supermelting technique
(lost wax method). Two crowns were joined modelling an intermediate
element with wax. The bridge structure thereby obtained (crowns
plus wax structure) was then placed in a smelting coating (Proper
Vest Fast Nobil Metal, AT) and incorporated in a smelting cylinder.
The pre-heating and smelting operations were then carried out,
using an alloy having a suitable casting temperature (Keramit Bio
Uno Nobil Metal), close to the sintering temperature. The success
of the supermelting process was assessed through the visual
observation of the product and by means of mechanical stressing, as
described in Example 1. The result obtained, according to the scale
described in Example 1, was assigned a value of 5.
EXAMPLE 19
[0079] A series of prosthetic elements obtained as described in
Examples 1.fwdarw.13 was modified adding metal with the traditional
lost wax technique. Some crowns were modelled adding wax and
thereby modifying the anatomical profile. The structure thus
obtained (crown plus wax addition) was then placed in a smelting
coating (Proper Vest Fast Nobil Metal) and incorporated in a
smelting cylinder. The pre-heating and smelting processes were then
performed, using an alloy with a suitable casting temperature
(Keramit Bio Uno Nobil Metal), close to the sintering temperature.
The success of the supermelting process was assessed through the
visual observation of the product and by means of mechanical
stressing, as described in Example 1. The result obtained,
according to the scale described in Example 1, was assigned a value
of 5.
* * * * *