U.S. patent application number 10/038786 was filed with the patent office on 2003-08-28 for dental material.
Invention is credited to Primus, Carolyn M..
Application Number | 20030159618 10/038786 |
Document ID | / |
Family ID | 27752587 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030159618 |
Kind Code |
A1 |
Primus, Carolyn M. |
August 28, 2003 |
Dental material
Abstract
A white, substantially non-iron containing dental material
formed from Portland cement. The material may be a dental cement,
dental restorative or the like.
Inventors: |
Primus, Carolyn M.;
(Sarasota, FL) |
Correspondence
Address: |
DENTSPLY INTERNATIONAL INC
570 WEST COLLEGE AVENUE
YORK
PA
17404
|
Family ID: |
27752587 |
Appl. No.: |
10/038786 |
Filed: |
January 3, 2002 |
Current U.S.
Class: |
106/35 ;
106/737 |
Current CPC
Class: |
C04B 7/527 20130101;
C04B 7/527 20130101; A61K 6/77 20200101; C04B 7/32 20130101; C04B
7/02 20130101; C04B 2111/10 20130101; C04B 2111/00836 20130101;
C04B 2111/802 20130101; C04B 7/02 20130101; C04B 7/32 20130101;
C04B 2111/00215 20130101; A61K 6/851 20200101 |
Class at
Publication: |
106/35 ;
106/737 |
International
Class: |
C04B 007/00; C04B
014/00 |
Claims
What is claimed is:
1. A dental material comprising Portland cement and which contains
less than about 0.5 percent by weight of iron oxide based upon 100
percent by weight of the material.
2. A dental material as in claim 1 which is white in color.
3. A dental material as in claim 1, comprising from about 61 to
about 70 weight percent calcia, from about 19 to about 29 weight
percent silica, from about 5 to about 15 weight percent alumina and
from 0 to about 0.5 weight iron, based upon 100 weight percent of
the material.
Description
TECHNICAL FIELD
[0001] The present invention is directed toward a dental material,
such as a cement or a restorative material. More particularly, the
invention relates to a dental material that is prepared with a
Portland cement. Specifically, the invention is such a material
that is substantially free from iron oxide, and which has a CaO
content of from about 50 to about 75 percent by weight and an
SiO.sub.2 content of from about 15 to about 25 percent by
weight.
BACKGROUND OF THE INVENTION
[0002] U.S. Pat. No. 5,415,547 describes a composition of cement
for dental applications. However, the composition of that Portland
cement is gray in color. This color is deleterious in dental
applications. The grayness of the cement produces a very
unaesthetic result when the cement is visible through thin tissue,
such as in the smaller teeth in pedodontics, or at the gum line.
According to the present invention, two types of white cement can
be substituted for such a gray Portland cement: white Portland
cement or calcium aluminate cement. A white cement has an advantage
of being more similar in tooth color to teeth than the '547 patent.
Therefore, the dark color from a conventional, gray Portland cement
will not be present.
SUMMARY OF THE INVENTION
[0003] It is an object of the invention to provide a dental
material.
[0004] It is another object of the invention to provide a white
dental material, such as a cement, a restorative or the like.
[0005] It is an additional object of the invention to provide such
a dental material that contains Portland cement.
[0006] It is a still further object of the invention to provide
such a material that is substantially free of iron oxide.
[0007] A white Portland cement according to the invention contains
virtually no iron, unlike the '547 patent composition which
contains about 5% iron oxide. Without iron oxide, the cement will
have a white color, and fall within the compositional range of
Portland cements, given as follows, all percents being by
weight:
[0008] 61 to 70% calcia
[0009] 19 to 29% silica,
[0010] 5 to 15% alumina and
[0011] 0 to 0.5% iron.
[0012] Preferably the material contains less than about 0.5 percent
by weight of iron, based upon 100 percent by weight of the
material.
PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0013] A dental material such as a cement, restorative or the like,
according to the invention, preferably has the following
percentages by weight of components:
[0014] 61 to 70% calcia
[0015] 19 to 29% silica,
[0016] 5 to 15% alumina and
[0017] 0 to 0.5% iron.
[0018] Preferably the material contains less than about 0.5 percent
by weight of iron, based upon 100 percent by weight of the
material. More preferably, the material according to the invention
is substantially free of iron oxide, meaning that it contains less
than about 0.5 percent by weight of iron. Most preferably, the
inventive material contains no iron. The material is visually
observed to be white in color, and is therefore, more desirable in
dental applications than gray-colored materials previously
employed. A comparison of one embodiment of the present inventive
material to known gray-colored materials is provided in TABLE
I.
1TABLE I Normalized Composition of Cement Samples US '547 Colton
Exemplary Inventive Component Patent Fast Set White Material Calcia
65.00 64.2 68.9 Silica 21.00 20.8 25.2 Iron oxide 5.00 4.3 0.3
Alumina 4.00 3.9 2.0 Magnesia 2.00 3.2 0.6 Sulfates 2.50 2.6 2.2
Soda, potassia <0.5 0.6 0.4 Titania -- 0.2 0.07 Phosphorous
pentoxide -- 0.09 0.12 Manganese oxide -- 0.05 0.02 Strontia --
0.07 0.13 LOI -- 1.3 1.0 As (ppm) -- 16** ND Pb (ppm) -- 4.2** ND
In TABLE I, Colton Fast Set cement is commercially available from
the California Portland Cement Company. Analysis was conducted by
x-ray fluorescence technique, normalized excluding LOI (loss on
ignition at 95.degree. C.), and "ND" means "not detected."
[0019] Without iron oxide, the Portland cement has less of the
calcium-alumino ferrite phase, as noted in Table II.
2TABLE II Composition by Phase of Cement Samples.paragraph.
Exemplary Prior Exemplary Inventive Comnonent Material White
Material 3CaO.SiO.sub.2 62 68 2CaO.SiO.sub.2 11 20
3CaO.Al.sub.2O.sub.3 3 5 4CaO.Al.sub.2O.sub.3.Fe.sub.2O.sub.3 13 1
TOTAL Crystalline Phases 89 94 Calculated from composition
[0020] White Portland cements are primarily used in decorative
architectural applications, although their properties are similar
to that of gray cements. See Table III, where the "Exemplary Prior
Cement" is manufactured according to the '547 patent, and is
commercially available. The expense to exclude iron oxide from
their formula makes them more expensive and more difficult to
manufacture.
3TABLE III Physical Properties of Cement Samples Exemplary
Exemplary Prior Inventive White Property Cement Material Surface
area (m.sup.2/kg) 451 409 Particle Size distribution 90% finer than
(.mu.m) 27 25 50% finer than (.mu.m) 9.4 9 10% finer than (.mu.m)
1.85 3 Setting time, initial (min.) 47 74 Setting time, final
(min.) 332 210 Compressive strength (psi) after 1 day 1,550 2,370
after 3 days 3,900 4,120 after 7 days 5,300 5,360 Sulfate, weight %
of cement: as gypsum, CaSO.sub.4.2H.sub.2O 0.2 not detected
(K.sub.2SO.sub.4.CaSO.sub.4.H.sub.2O) % plaster (hemi-hydrate) 86
50 (calculated as % SO3)
[0021] Calcium aluminate cements can be used instead of a white
Portland cement. The calcium aluminate cements contain from about
32 to about 57 weight percent alumina, and are clearly outside the
'547 patented composition. The silica content is usually less than
6 weight percent, the iron content is less than 20 weight percent
(especially low when white cement is needed), and the titania
content is also less than 2 percent. Titania makes the cement
whiter.
[0022] The calcium aluminate cements generally set in one-half the
time of Portland cements. However, a very fast set may be achieved
by combining calcium aluminate and Portland cements. A "flash" set
phenomena can occur where the setting time is reduced to less than
1 hour when a 50/50 mixture of calcium aluminate and Portland
cements is made. TABLE IV shows that calcium aluminate cements set
more quickly than do Portland cements. In this graph, the final set
time is about 4.25 hours for a calcium aluminate cement, and about
7 hours for a Portland cement.
[0023] FIG. 1: Setting time of Portland and calcium aluminate
mixtures.
[0024] Calcium aluminate cements can be stronger than Portland
cements, in some cases twice as strong when fully set. Furthermore,
calcium aluminate cement develops its strength sooner. Calcium
aluminate cements an achieve 50% of their total strength in less
than 1 day whereas a portland cement may require between 1 and 6
days to achieve 50% of their final strength.
[0025] Calcium aluminate cements are not usually used in
applications that hover around ambient temperature; they are
usually used for refractory applications. Below 27.degree. C., an
unstable hydrate is formed: CaO.Al.sub.2O.sub.3.10H.sub.2O. Above
27.degree. C. these hydrates release their water in a process
called conversion and form the stable hydrates of
2CaO.Al.sub.2O.sub.3.8H.sub.2O, 3CaO.Al.sub.2O.sub.3.6H.sub.2- O
and Al.sub.2O.sub.3.3H.sub.2O. Unfortunately this process creates
pores that reduce the strength. We have a unique situation in
dentistry with using calcium aluminate cements in the body where
the temperature is constant and above 27.degree. C. Therefore, a
stable hydrate can be formed that does not convert. High strengths
and quick setting scan be achieved without risk of conversion.
[0026] Sample compositions of two inventive calcium aluminate
cements are given in Table V, compared to a gray and two inventive
white Portland cements.
4TABLE V Comparison of Cement Compositions Portland Type Cement
Colton Portland Portland Calcium Calcium Oxide Fast Set White White
Aluminate Aluminate Calcia 64.2 66.3 68.2 29.8 33.9 Alumina 3.9 4.3
1.9 56.5 53.0 Silica 20.8 21.9 24.8 2.9 2.2 Iron oxide 4.3 0.3 0.4
1.3 1.1 Magnesia 3.2 2.0 0.5 0.4 0.7 Sulfate 2.5 3.3 2.2 0.2 0.0
Potassia 0.3 0.3 0.1 0.1 0.2 Soda 0.3 0.1 0.1 4.8 4.7 Strontia 0.1
0.1 0.1 0.0 0.0 Manganese oxide 0.1 0.0 0.0 0.0 0.0 Phos. Pentoxide
0.1 0.1 0.1 0.1 0.0 Chlorine 0.0 0.0 0.1 0.0 Scandia 0.0 0.0 0.1
0.1 Titania 0.2 0.2 0.1 2.1 2.2 Bromine 0.0 0.0 0.1 0.2 Chromia 0.0
0.0 0.0 0.1 Zirconia 0.0 0.0 0.1 0.0 Silver oxide 0.0 0.0 1.0 1.1
Platinum oxide 0.0 0.0 0.1 0.0 TOTAL 100.0 100.0 100.0 100.0
100.0
[0027] According to the invention, fluoride can also be added to a
Portland cement in the form of calcium fluoride. Additions of 1.7
wt % fluorine in the cement before firing, increase the strength
(at 28 days of setting) about 10%. The fluoride may or may not be
released from such a cement.
[0028] Some dental applications do not require high radiopacity,
such as pulp capping. The sealing and capacity for dentinal bridge
formation are more important than radiopacity for use of the
material in a thin layer required for pulp capping. For added
effectiveness in some dental applications, a cement can be made
radiopaque. For instance, with the addition of 20 wt % bismuth
oxide, the mixture will have a radiopacity equal to 3 mm of
aluminum at a cement thickness of 1 mm. The gray and white portland
cements have equal radiopacity, 3 mm of Al equivalent, at 1 mm of
cement thickness, when blended with 20% bismuth oxide. As much as
40% bismuth oxide can be added to the mixture, however, the bismuth
oxide slows the setting and strength development. The bismuth oxide
imparts a pale yellow color to the mixture because the bismuth
oxide is yellow-colored.
[0029] Another radiopacifier can be blended with the cement. For
instance, a radiopaque glass used for dental composites can be
mixed with portland cement, as an alternative to bismuth oxide. The
color of the mixture is white. A glass such as Corning 7724 or 7726
can be used. Such glasses are covered under U.S. Pat. Nos.
4,920,082 or 4,775.646, respectively. If a fluoride-releasing glass
is used, this mixture would be radiopaque and release fluoride
ions. The fluoride release would help prevent internal resorption
or cervical decay.
[0030] A third radiopaque addition would be barium sulfate instead
of bismuth oxide. The barium sulfate is not soluble in water;
therefore it would not be a toxic heavy metal compound. This
material is white and would also avoid gray coloration of the
mixture.
[0031] Another addition to cement is Bioglass. Bioglass, a patented
formula of glass, is known to be biologically active, and encourage
bone growth (see U.S. Pat. No. 4,232,972). Its formula is within
this compositional range (all percentages being by weight (wt
%)):
5 Silica 40-62% Soda 10-32% Calcia 10-32% Phosphorous pentoxide
0-12% Calcium fluoride 0-18% and Boron oxide 0-20%.
[0032] The Bioglass can be added as coarse powder, about 170 to
140-mesh size. The large, coarse form of the glass has been found
to be more conducive to bone growth than a finer size. Bioglass
particles could be used as an "aggregate" in a portland cement and
create a concrete. Bioglass (see U.S. Pat. No. 4,775,646) is a
white powder, and would not color a mixture with white cement. This
would be of most interest for filling bony defects or root-end
filling where bone re-growth is important. Hench has patented the
mixture of Bioglass and cement. See U.S. Pat. No. 4,775,646 to L.
Hench et. al for a fluoride-containing Bioglass. U.S. Pat. No.
4,171,544 to L. Hench et. al for bonding to bone with a high
surface area porous, silica-rich surface. This teaches about
portland cement for BONDING (not as the restorative for) dental
implants, and cement mixed with a biologically active glass.
[0033] Other compositions of cement can be considered to create a
white cement, as long as they do not include iron oxide. For
instance, barium oxide can be partially or wholly substituted for
calcium oxide. This is a new ingredient, not specified in the first
Torabinejad patent (U.S. Pat. No. 5,415,547). This would create a
cement that is inherently radiopaque and needs no further
additions.
[0034] The fineness of the cement also affects its usefulness in
dentistry. For instance the Torabinejad patent refers to cements of
Type 3, a relatively fine cement having a surface area of 450 to
550 m.sup.2/kg. However, such cements are perceived as grainy or
sandy by dentists, having lesser quality, and less packable into
fine orifices. The surface area measurement gives a general
indication of the fineness of the powder, but does not adequately
characterize the distribution of the powder particles sizes.
[0035] Two approaches can be followed to improve the performance of
such dental materials: removal of coarse particles, or reduction in
the average particle size. The removal of coarse particles can be
achieved by sieving or air elutriation. The particle size reduction
can be achieved by milling processes such as ball milling, air
attrition, or attrition milling.
[0036] Finer cements are more suitable for either a root canal
sealing material or a root canal obturation material. The use of a
cement with a surface areas of about 1,000 m.sup.2/kg allows it to
be easily filled in a root canal, including lateral canals. We
tested such a cement for a root canal sealer and found it
preferable to a cement have a lower surface area. Furthermore, the
removal of particles coarser than 400 mesh (44 .mu.m) improved the
handling of the gray cement used in the commercially available
ProRoot MTA material. This process increased the measured surface
area from 454 to 509 m.sup.2/kg.
[0037] Therefore, it is apparent that a dental material according
to the invention as described above, is useful in meeting the
stated objectives of the invention. It will be understood that
amount of various components, can be varied and still fall within
the scope of the invention. Similarly, specific formulation
components as provided above are merely exemplary and other
components similar or otherwise are also within the scope of the
invention. The scope of the invention will be determined only by
the claims.
* * * * *