Title: Mixture for the production of a high-expansion stone die
Abstract: The present invention refers to a mixture comprising alpha CaSO.sub.4.times.1/2 H.sub.2 O, CaSO.sub.4.times.2 H.sub.2 O, a combination of a hardening accelerator, a hardening retarder and a setting expansion inhibitor, and optionally a surfactant.The mixture can be used to prepare a die having an extremely high setting expansion.
Patent Number: 6,881,258 Issued on 04/19/2005 to Delee, et al.
| Inventors:
|
Delee; Paul (Leuven, BE);
Horiuchi; Haruhiko (Leuven, BE)
|
| Assignee:
|
GC Europe N.V. (Leuven, BE)
|
| Appl. No.:
|
419664 |
| Filed:
|
April 21, 2003 |
Foreign Application Priority Data
| Current U.S. Class: |
106/788; 106/35; 106/38.35; 106/772; 106/781; 264/333 |
| Intern'l Class: |
C04B 028//14; C04B 011//00; A61K 006//02; A61K 006//00 |
| Field of Search: |
106/35,38.35,772,781,788,778
264/333
|
References Cited [Referenced By]
U.S. Patent Documents
| 2639478 | May., 1953 | Duffy et al.
| |
| 4526619 | Jul., 1985 | Ohi et al.
| |
| 4604142 | Aug., 1986 | Kamohara et al.
| |
| 4647311 | Mar., 1987 | Ohi et al.
| |
| 4909847 | Mar., 1990 | Ohi et al.
| |
| 4911759 | Mar., 1990 | Ohi et al.
| |
| Foreign Patent Documents |
| 27 40 018 | Mar., 1979 | DE.
| |
| 195 48 655 | Jun., 1997 | DE.
| |
| 1 186 577 | Mar., 2002 | EP.
| |
Primary Examiner: Green; Anthony J.
Attorney, Agent or Firm: Frommer Lawrence & Haug LLP, Santucci; Ronald R.
Claims
What is claimed is:
1. A mixture, comprising:
a) 100 parts by weight alpha CaSO.sub.4.times.1/2 H.sub.2 O,
b) 1-20 parts by weight CaSO.sub.4.times.2 H.sub.2 O,
c) 0.005-0.8 parts by weight of at least one additive, which is selected
from the group consisting of a hardening accelerator, a hardening retarder
or a setting expansion inhibitor,
d) up to 2 parts by weight of one or two different surfactants, and
e) 15-65 parts by weight of a colloidal silica suspension.
2. A mixture according to claim 1, wherein the CaSO.sub.4.times.2 H.sub.2 O
is present in amount of 2-15 parts by weight.
3. A mixture according to claim 1, wherein the hardening accelerator is
selected from the group consisting of inorganic acid salts, sodium
chloride, and potassium sulfate,
and the hardening retarder is selected from the group consisting of
carboxylates, citrates, succinates, acetates, phosphates, borates, borax,
water soluble polymers, cane sugar, hexameta phosphate, etylenediamine
tetra acetate, starch, gum arabic, carboxymethyl cellulose and sugar
alcohol,
and the setting expansion inhibitor is selected from the group consisting
of potassium chloride, potassium tartrate, potassium sodium tartrate, and
sodium tartrate.
4. A mixture according to claim 1, wherein the surfactants d) are selected
from the group consisting of anionic surfactants, alkylbenzene sulfonates,
alkylnaphthalene sulfonates, a mixture of naphthalene sulfonates and
formaldehyde polycondensation products, a mixture of melamin sulfonates
and formaldehyde polycondensation products, dialkylsulfosuccinates,
alkylsulfoacetates, alpha-olefin sulfonates, sodium N-acyl methyl
taurates, nonionic surfactants, polyethylene alkylethers, polyoxyethylene
sec-alcoholethers, polyethylene polyoxypropylene alkylethers, and
polyglyceryl fatty acid esters.
5. A mixture according to claim 1, wherein the colloidal silica suspension
(e) has a concentration of 20-50 wt.-%.
6. A die produced by molding the mixture of claim 1.
7. A kit containing the following components:
a) 100 part by weight alpha CaSO.sub.4.times.1/2 H.sub.2 O,
b) 1-20 parts by weight CaSO.sub.4.times.2 H.sub.2 O,
c) 0.005-0.8 part weight of at least one additive, which is selected from
the group consisting of hardening accelerator, a hardening retarder or
setting expansion inhibitor,
d) up to 2 part by weight of one or two different sufactants, and
e) 15-65 part by weight of a colloidal silica suspension, wherein each
component is provided in separate containers.
8. A die produced by mixing and molding the components of the kit of claim
7.
Description
The present invention relates to a mixture for the production of a die.
In recent times dental implants, bridges and crowns were prepared using
gold since gold has superior properties and can be processed quite easily.
Today, people require ceramic materials for aesthetic reasons. However,
processing of ceramic material is quite complex and requires a lot of time
and work so that new improved techniques are needed to process ceramic
materials more effectively.
When producing ceramic implants, crowns or bridges, a model (master model)
of the tooth to be covered with the ceramic material is prepared. Then the
master model is duplicated with a die material like gypsum or plaster as
disclosed in the book "Gips . . . und was man daruber wissen sollte"
(Martin Kuske & Ralf Suckert--teamwork media--2000) especially chapter 1,
page 18 ff. Known dental plasters are divided according to the norm DIN/EN
26873 IS 6873 into five types:
Setting Compression strength in Mpa
Type Expansion % min max
I 0 to 0.15 4 4
II 0 to 0.30 9 --
III 0 to 0.20 20 --
IV 0 to 0.15 35 --
V 0.16 to 0.30 35 --
Such plasters have a setting expansion of at most 0, 3%. The die, produced
with this kind of plaster, is covered with a ceramic suspension to build a
ceramic cap (also called green body before the sintering process) and then
the covered die is dried at temperatures of about 900.degree. C. In a
second step, die and cap are separated and the ceramic cap is heated
(sintered) to about 1400 to 1500.degree. C. At such temperatures the
ceramic material of the cap shrinks to an extent of from about 4% up to
12%. Accordingly, the cap is too small and does not fit on the patient's
tooth so that the ceramic cap has to be adapted to the tooth by removing
ceramic material. Repeatedly, the fit of the cap on the tooth is tested
and excess material removed until a good fit has been achieved. This
procedure is time-consuming, expensive and inconvenient for the patient.
In order to overcome this disadvantage it has been proposed to provide a
die material which expands during setting. If such material is used, the
die material and accordingly the ceramic material covering the die would
have a too big/loose fit in a pre-sintered stage so that a good fit of the
final sintered ceramic cap to the tooth would be achieved. However, no
such material is available: As mentioned above, currently available
plaster has a setting expansion of up to 0.3% which is far from
satisfactory.
It was accordingly an object of the present invention to provide a material
which overcomes this disadvantage of the prior art.
It was especially an object of the present invention to provide a die
material which expands to an extent that the shrinkage of a ceramic cap
can be neutralized. Thus, a die which consists of such material can be
used for the production of a ceramic cap which needs no further
modification and fits exactly onto a patient's tooth.
This object has been achieved according to the present invention by
providing a mixture, comprising:
a) 100 parts by weight .alpha. CaSO.sub.4.times.1/2 H.sub.2 O,
b) 1-20 parts by weight CaSO.sub.4.times.2 H.sub.2 O,
c) 0.005-0.80 parts by weight of at least one additive and
d) up to 2 parts by weight of one or more surfactants.
This mixture can further comprise:
e) 15-65, preferably 23-45 parts by weight of a liquid such as water or a
colloidal silica suspension.
The mixtures according to the present invention can be used to prepare a
die which has a setting expansion of about 4 to about 14%. When such a die
is covered with a ceramic material and heated to, e.g., about 900.degree.
C., the die and accordingly the ceramic material expand to a corresponding
degree. When the ceramic cap is then removed from the die and fired at a
temperature of, e.g. 1400.degree. C. to 1500.degree. C. the ceramic
material shrinks to its original size so that the cap fits exactly to the
patients tooth.
Some or all components a), b), c) and optionally d) and/or e) will usually
be provided in separate containers as a kit of parts so that the dentist
or the dental laboratory can combine them in any appropriate ratio. It is
also possible to provide a mixture of components a)-c) and optionally d)
with a defined expansion ratio. This mixture can be mixed with water in a
recommended ratio. Alternatively component e) can be provided in a
predetermined amount, again resulting in a specific expansion of the die
when all components are mixed.
According to one embodiment of the present invention, a die can be produced
by mixing components a) to c) and e) and optionally one or more of
components d), preferably while stirring the mixture. According to this
embodiment, the material is then poured into a mold which is an exact
negative of the patient's tooth to be treated. Care should be taken at
this stage to avoid voids in the die; if voids are formed at a surface of
the die, protrusions will be formed on the cap which will have to be
removed during further work-up. If voids are formed within the die, the
die will not be homogenous thereby preventing a linear expansion of the
die. This also results in a cap which must be worked-up with considerable
difficulty. Methods to prevent formations of voids in a die are known in
the art and should accordingly be applied in the present case.
When the die has hardened to a degree that it can be handled without being
damaged, it is covered with a ceramic cap e.g. by dipping the die into
ceramic material, drying the ceramic material and repeating these steps
until the required strength and size of the ceramic cap has been achieved.
The materials are then heated to a temperature of e.g. about 900.degree.
C. During this heating step, the die expands to the required degree,
thereby co-expanding the ceramic cap. The cap is then removed from the die
and heated to a temperature of about 1400 to about 1500.degree. C. During
this sintering step, the cap shrinks depending upon the ceramic material
used, e.g. by about 13%, thereby regaining the required size.
A further advantage of the present invention is that the properties,
especially the expansion of the die can be varied to a large extent: If
the ceramic material used for the production of a cap has a specific
shrinkage, the mixture according to the present invention can be adapted
so that the die expands to exactly meet this shrinkage.
There are a number of factors which influence the properties such as
setting and thermal expansion and compressive strength of the die. All
solid materials used in the present invention are preferably employed as
powders or fine grains. They can e.g. have an average particle size of
about 3 .mu.m to about 70 .mu.m.
1. The Type of the .alpha. CaSO.sub.4.times.1/2 H.sub.2 O a)
An important factor is the quality and type of the .alpha.
CaSO.sub.4.times.1/2 H.sub.2 O to be used. Basically any a gypsum
hemi-hydrate or any mixture thereof can be used. Examples are synthetic
gypsum T, natural gypsum K and natural gypsum PL, all of which are
commercially available. If synthetic gypsum T is used, the expansion of
the resulting die is larger than when natural gypsum K or natural gypsum
PL are used, please compare with Table 1.
2. The Amount and the Type of the CaSO.sub.4.times.2 H.sub.2 O b)
A further important factor is the quality and type of the dihydrate to be
used. Basically any dihydrate and any commercially available dihydrate can
be used.
Moreover, the amount of the dihydrate to be added to the mixture has a
large influence on the properties of the resulting die. As can be taken
from table 2 an increase from 2 parts by weight to 10 parts by weight
increases the expansion from 3-4% to 11-12%. The dihydrate can be used in
amounts of about 1-20 parts by weight, while 2-15 parts by weight are
preferred. As mentioned above, the amount will be determined depending on
the requested properties of the die.
3. The Amount and the Type of Additives c)
The mixture according to the present invention can comprise one, two or
more additives. Examples of such additives are hardening accelerators,
hardening retarders, and setting expansion inhibitors. Such components are
described in e.g. Skinner's Science of Dental Materials, Ralph W.
Phillips, 1982, 8.sup.th edition.
For example, as the hardening retarder(s), carboxylates (citrate,
succinate, . . . etc) and water soluble high polymers (cane sugar,
hexameta phosphate, . . . etc) can be used in the present invention.
Preferably tri sodium citrate is used.
For example, as the hardening accelerator(s) inorganic acid salts (sodium
chloride, potassium sulfate, . . . etc) may be used in the present
invention. Preferably potassium sulfate is used.
For example, as the setting expansion inhibitor potassium salts and sodium
salts etc. (potassium chloride, potassium tartrate, potassium sodium,
sodium tartrate, . . . etc) can be used in the present invention.
Preferably potassium tartrate is used.
Depending on the amount and combination of the additives, the physical
properties such as setting time, setting expansion and compressive
strength of the die can be varied, please refer to table 2. The amount of
these additives can vary from 0.005 to 0.8 parts by weight, whereas a
range of 0.01 to 0.4 parts by weight is preferred. One or a mixture of two
or more additives can be used.
4. The Amount and the Type of Surfactant d)
Especially a water reducing agent and/or dispersing agent can be used as a
surfactant. Such agents are, for example,
anionic surfactants like alkylbenzene sulfonate, alkylnaphthalene
sulfonate,
a mixture of naphtalene sulfonates and formaldehyde polycondensation
products,
a mixture of melamin sulfonates and formaldehyde polycondensation products,
dialkyl sulfosuccinates, alkylsulfonates,
alpha-olefin sulfonates, sodium N-acyl methyl taurate,
nonionic surfactants like polyethylene alkylether, polyoxyethylene
sec-alcohol ether,
polyethylene polyoxypropylene alkylether,
polyglyceryl fatty acid ester.
An especially preferred surfactant is a mixture of melamin sulfonates and
formaldehyd polycondensation products.
One function of the surfactant is to reduce the amount of liquid required
for mixing and to increase the setting expansion. Commercially available
surfactants are e.g. Pozzolith NR. 70, NR. 81 MP, NR. NL-1440 or NR.
NL-4000.
The surfactants can be used in amounts of up to 2 parts by weight, while
amounts of 0.2 to 1 parts by weight are preferred. It is, however,
possible to omit the surfactants altogether. Moreover, one or a mixture of
two or more surfactants can be used.
5. The Amount and the Type of the Liquid e) to be Used
The liquid(s) which can be used also can have an important influence on the
properties and especially the setting expansion of the die. Preferably, a
colloidal silica suspension is used. Commercially available examples are
e.g. Levasil (Bayer) 100/45%, 200/40%, LUDOX (Dupont) H540, W30, W50. The
colloidal silica suspension is usually diluted to a concentration of about
20 to 50 weight-% using distilled or tap water. Alternatively, distilled
or tap water can be used as the liquid. Preferred amounts of the liquid to
be added to the mixture of components a)-c) and optionally component(s) d)
are 23 to 45 g liquid per 100 g of the mixture.
Thus, by varying the quality and/or the quantity of the above components,
the properties and especially the expansion of the die can be adapted. For
example, the shrinkage of a desired ceramic material can be determined and
then a specific die can be selected based on the teaching of the present
invention which has the appropriate shrinkage.
The present invention furthermore discloses a kit of parts especially for
dental purposes, containing at least components a), b) and c) preferably
each in separate containers. Additionally it can contain component(s) d),
also in (a) separate container(s).
The components can be provided in pre-determined quantities and qualities
so that a die material with specific properties such as expansion etc. can
be prepared in a dental laboratory by the dentist or technician.
EXAMPLES
Examples of compositions of the present invention are described in the
following tables.
(Instruction for Use)
Powder (components a), b), c) and optionally d))/Liquid ratio:
about 100 g/23 g-45 g
Hand mix powder into liquid for 15 seconds.
Blend to a homogenous mixture.
Pour into mold, especially a duplicate impression.
Bench setting for 10 minutes.
After 10 minutes remove from impression and put into water for total
setting time (EX 2 hours) to get available setting expansion.
TABLE 1
The difference of .alpha. CaSO.sub.4 1/2H.sub.2 O
EX 1 EX 2 EX 3
(Weight (Weight (Weight
(Composition) ratio) ratio) ratio)
.alpha. CaSO.sub.4 1/2H.sub.2 O Synthetic Natural Natural
gypsum gypsum gypsum
T K PL
100 100 100
CaSO.sub.4 2H.sub.2 O 10 10 10
Surfactant: a mixture of 0.2 0.2 0.2
melaminsulfonate and a
formaldehyde
polycondensation product
Hardening retarder: 0.1 0.1 0.1
tri sodium citrate
Hardening accelerator: 0 0 0
potassium sulfate
Setting expansion inhibitor: 0 0 0
potassium tartrate
(Physical properties)
Liquid concentration 40% 40% 40%
Liquid / Powder ratio 28 g/100 g 31 g/100 g 32 g/100 g
Setting time (ISO) 8'00" 10'00" 11'00"
Setting Iso/2 hrs More More More
expansion than 4% than 3% than 3%
In water/2 hrs 11.0.about.11.5% 7.0.about.7.5% 7.0.about.7.5%
Compressive ISO/1 hr 50 Mpa 50 Mpa 50 Mpa
strength In water/2 hrs 30 Mpa 30 Mpa 30 Mpa
TABLE 2
The difference of additives(1)
EX 1 EX 2 EX 3 EX 4
EX 5 EX 6
(Composition) (Weight ratio) (Weight ratio) (Weight ratio) (Weight
ratio) (Weight ratio) (Weight ratio)
.alpha. CaSO.sub.4 1/2H.sub.2 O 100 100 100
100 100 100
CaSO.sub.4 2H.sub.2 O 2 10 15 10
10 10
Surfactant: a mixture of 0.2 0.2 0.2 0
1.0 2.0
melaminsulfonate and a
formaldehyde
polycondensation product
Hardening retarder: 0.005.about.0.05 0.06.about.0.10 0.10.about.0.20
0.06.about.0.10 0.06.about.0.10 0.06.about.0.10
tri sodium citrate
Hardening accelerator: 0 0 0 0
0 0
potassium sulfate
Setting expansion 0 0 0 0
0 0
inhibitor:
potassium tartrate
(Physical properties) 0 0 0 0
0 0
Liquid concentration 40% 40% 40% 40%
40% 40%
Liquid/Powder ratio 28 g/100 g 28 g/100 g 28 g/100 g 28 g/100
g 28 g/100 g 28 g/100 g
Setting time (ISO) 3'00".about.10'00" 5'00".about.10'00"
5'00".about.10'00" 6'00".about.11'00" 5'00".about.10'00" 2'30".about.5'00"
Setting Iso/2 hrs -- -- -- --
-- --
expansion In water/2 hrs 3%.about.4% 11%.about.12% 10%.about.11%
10%.about.11% 11%.about.12% 12%.about.13%
Com- ISO/1 hr 50 Mpa 50 Mpa 50 Mpa 50 Mpa
50 Mpa 50 Mpa
pressive In water/2 hrs 30 Mpa 30 Mpa 30 Mpa 30
Mpa 30 Mpa 30 Mpa
strength
TABLE 3
The difference of additives(2)
EX 1 EX 2 EX 3 EX 4
EX 5 EX 6
(Composition) (Weight ratio) (Weight ratio) (Weight ratio)
(Weight ratio) (Weight ratio) (Weight ratio)
.alpha. CaSO.sub.4 1/2H.sub.2 O 100 100 100
100 100 100
CaSO.sub.4 2H.sub.2 O 10 10 10 10
10 10
Surfactant: a mixture of 0.2 0.2 0.2
0.2 0.2 0.2
melaminsulfonate and a
formaldehyde
polycondensation product
Hardening retarder: 0.06.about.0.10 0.06.about.0.10 0.06.about.0.10
0.06.about.0.10 0.06.about.0.10 0.10.about.0.40
tri sodium citrate
Hardening accelerator: 0 0.1 0.2 0
0 0.2
potassium sulfate
Setting expansion 0 0 0
0.1 0.2 0.2
inhibitor:
potassium tartrate
(Physical properties)
Liquid concentration 40% 40% 40% 40%
40% 40%
Liquid/Powder ratio 28 g/100 g 28 g/100 g 28 g/100 g 28
g/100 g 28 g/100 g 28 g/100 g
Setting time (ISO) 5'00".about.10'00" 4'00".about.8'00"
2'30".about.6'00" 4'00".about.8'00" 2'00".about.6'00" 3'00".about.9'00"
Setting Iso/2 hrs -- -- -- --
-- --
expansion In water/2 hrs 11%.about.12% 10%.about.11% 8%.about.9%
8%.about.9% 6%.about.7% 3%.about.4%
Compressive ISO/1 hr 50 Mpa 50 Mpa 50 Mpa 50
Mpa 50 Mpa 50 Mpa
strength In water/2 hrs 30 Mpa 30 Mpa 30 Mpa 30
Mpa 30 Mpa 30 Mpa
TABLE 4
The difference of liquid and Liquid/Powder ratio
EX 1 EX 2 EX 3 EX 4
EX 5
(Composition) (Weight ratio) (Weight ratio) (Weight ratio)
(Weight ratio) (Weight ratio)
.alpha. CaSO.sub.4 1/2H.sub.2 O 100 100 100
100 100
CaSO.sub.4 2H.sub.2 O 10 10 10 10
10
Surfactant: a mixture of 0.2 0.2 0.2
0.2 0.2
melaminsulfonate and a
formaldehyde
polycondensation product
Hardening retarder: 0.1 0.1 0.1
0.1 0.1
tri sodium citrate
Hardening accelerator: 0 0 0 0
0
potassium sulfate
Setting expansion inhibitor: 0 0 0
0 0
potassium tartrate
(Physical properties) 0 0 0 0
0
Liquid concentration 20% 40% 50% 40%
40%
Liquid/Powder ratio 28 g/100 g 28 g/100 g 28 g/100 g 23
g/100 g 45 g/1.00 g
Setting time (ISO) 10'00" 8'00" 6'30"
4'00" 13'00"
Flow (ISO) 38 33 29 25
60
Setting Iso/2 hrs -- -- -- --
--
expansion In water/2 hrs 6% 11% 12%
13% 7%
Compressive ISO/1 hr 50 Mpa 50 Mpa 50 Mpa 50
Mpa 50 Mpa
strength In water/2 hrs 30 Mpa 30 Mpa 30 Mpa 30
Mpa 30 Mpa
*
