U.S. patent application number 09/929664 was filed with the patent office on 2002-03-07 for fluoride-releasing amalgam dental restorative material.
This patent application is currently assigned to Medical College of Georgia. Invention is credited to Mettenburg, Don, Rueggeberg, Fred, Whitford, Gary.
Application Number | 20020028856 09/929664 |
Document ID | / |
Family ID | 24293933 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020028856 |
Kind Code |
A1 |
Rueggeberg, Fred ; et
al. |
March 7, 2002 |
Fluoride-releasing amalgam dental restorative material
Abstract
A fluoride-releasing dental amalgam composition for a tooth
restoration comprising a dental amalgam alloy material and an
fluoride-containing, the glass particulate powder component of a
fluoride-leachable acid-etchable glass ionomer cement. The
invention further provides a method for using the composition to
prevent or reduce secondary caries in an existing tooth
restoration, which is classified as a dental amalgam in nature.
Inventors: |
Rueggeberg, Fred; (Augusta,
GA) ; Whitford, Gary; (Augusta, GA) ;
Mettenburg, Don; (Evans, GA) |
Correspondence
Address: |
LaVonda R. DeWitt
NEEDLE & ROSENBERG, P.C.
The Candler Building, Suite 1200
127 Peachtree Street, N.E.
Atlanta
GA
30303-1811
US
|
Assignee: |
Medical College of Georgia
|
Family ID: |
24293933 |
Appl. No.: |
09/929664 |
Filed: |
August 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09929664 |
Aug 13, 2001 |
|
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|
09573922 |
May 18, 2000 |
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Current U.S.
Class: |
523/115 ;
433/206 |
Current CPC
Class: |
A61K 6/847 20200101 |
Class at
Publication: |
523/115 ;
433/206 |
International
Class: |
A61K 006/05 |
Claims
What is claimed is:
1. A fluoride-releasing dental amalgam composition for a tooth
restoration comprising a dental amalgam alloy material and the
glass particulate powder component of a fluoride-containing,
fluoride-leachable acid-etchable glass ionomer cement.
2. The fluoride-releasing dental amalgam composition of claim 1,
wherein the glass particulate powder component of the
fluoride-containing, fluoride-leachable acid-etchable glass ionomer
cement is sintered with elemental silver.
3. The fluoride-releasing dental amalgam composition of claim 2,
wherein the sintered glass particulate powder component of the
fluoride-containing, fluoride-leachable acid-etchable glass ionomer
cement and the dental amalgam alloy material form a chemical bond
to each other, resulting in the retention of the glass ionomer
cement throughout the bulk of the restoration and on the surface of
the restoration by other than purely mechanical means.
4. The fluoride-releasing dental amalgam composition of claim 1,
wherein the glass particulate powder component of the
fluoride-containing, fluoride-leachable acid-etchable glass ionomer
cement is present on the outer surface and throughout the bulk of
the restoration of the amalgam material.
5. A method of preventing or reducing secondary caries around an
existing tooth restoration comprising the step of placing the
fluoride releasing dental amalgam composition of claim 1 in a
prepared cavity area prone to tooth decalcification and/or overt
decay.
6. A tooth bonded to the fluoride-releasing dental amalgam
composition of claim 1.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a composition of a novel
fluoride-releasing dental amalgam restorative material, which
provides the capability to reduce the possibility of secondary
decay approximate to a restoration as a result of fluoride
release.
BACKGROUND OF THE INVENTION
[0002] Dental amalgam is one of the oldest of restorative material
for direct replacement of missing tooth structure, and is still
widely used today. Since its inception at the turn of the century,
little significant change has been made to its composition, with
the exception of the use of high copper materials during the last
quarter century. It is one of the most technique-forgiving
materials, and has met with long-term clinical success. One of the
problems with this material is that it has no capacity to prevent
formation of secondary decay in tooth structure surrounding the
restoration. There are currently other classifications of dental
restorative materials in use which offer such protection as a
result of the slow release of fluoride from the material surface or
bulk. Glass ionomer materials are one such type material, as well
as various resin based products which have fluoride incorporated
either into the polymer matrix, or in the inorganic filler
particles. Compared to dental amalgam, however, glass ionomers are
much more technique sensitive, and do not provide as good wear
resistance in areas of high occlusal force.
[0003] The prior art of amalgam restoration placement involves
preparing the remaining tooth structure to provide adequate
resistance and retention form for the restorative material to
prevent its loss via physical dislodgment during function. Such
planning is required because dental amalgam is not chemically
adherent to tooth structure. After preparation of the tooth
tissues, it is typical that a lining material be placed over the
cut tooth to provide for an early sealing effect. Such materials as
copal varnish and more recently synthetic polymers have been used.
Attempts at incorporating fluoride into this sealing agent have
been performed to provide for fluoride release and provision of
some degree of cariostatic action. However, some of these lining
materials have been shown to dissolve over time, and are replaced
by corrosion products of the dental amalgam, which then help to
form a seal between prepared tooth tissue and the dental amalgam
restoration. Also, materials used as restorative bases to provide
thermal insulation to the tooth have been manufactured with
fluoride as a potential leachable product. The concept of these
materials is that if fluids and bacteria should migrate to this
area, fluoride would be released and result in bacterial membrane
instability, resulting in cell death.
[0004] If means to prevent recurrent decay from developing in a
tooth fail, the entire restoration requires removal and
replacement, resulting in enlargement of the preparation through
the removal of additional tooth structure. It is not uncommon that
this process would be repeated more than once, if an amalgam is
placed at an early age. Thus, secondary decay around an amalgam
restoration necessitates a possible series of replacements, each
removing more tooth structure, resulting in a greatly weakened
tooth. Indeed, it has been documented that approximately 53%-58% of
the reasons for replacement of existing amalgam restoration in
adult patients has been attributed to secondary caries (recurrent
decay). See Mjor I A, Tandlkartdin, 71, 552-556, (1979) and Dahl J
E., et al., Scand. J. Dent. Res., 86, 404-407, (1978). Replacement
of existing amalgam restorations in deciduous teeth has also been
highly correlated with secondary caries: 51% of the reason for
amalgam replacement. See Mjor, I A., et al., NTF's Tidende, 96,
109-112, (1986).
[0005] Several studies have looked at the effect of fluoride
releasing amalgams on the inhibition of caries. One study used
calcium fluoride as the fluoride source in amalgam alloys and
observed the effects of mercury, lactic acid, and fluoride
concentration on fluoride release in the amalgam alloys. Fazzi, R.,
J. of Prosthetic Dent., 38, no. 5, 526-531 (1977). Another study
compared the fluoride release from a fluoride containing amalgam, a
silicate cement and a glass ionomer cement. This study concluded
that the silicate cement and glass ionomer cement exhibited greater
fluoride release than the fluoride containing amalgam. This study
also indicated that less fluoride could be extracted from the glass
ionomer cement powders. See Tveit, A. B. et al, J. of Oral
rehabilitation, 8, no. 3, 237-241, (1981). A later study by
Skartveit, L., et al., Scandanavian Journal Dent. Research, 93, no.
5, 448452, (1985) reported that the release of fluoride (SnF.sub.2)
from an amalgam for a few weeks was probably sufficient to enhance
remineralization.
[0006] U.S. Pat. No. Re. 32073 discloses a dental filling
composition comprising a polymerizable resin binder and an
inorganic glass filler which imparts opacity to X-rays.
[0007] U.S. Pat. No. 4,738,722 discloses a buffered glass ionomer
cement which can be used as a base or liner under restorative
materials, a luting cement and a core material for a cast
restoration.
[0008] U.S. Pat. No. 5, 252,121 teaches tooth restoration
comprising the application of a wet glass ionomer cement on a tooth
lesion and placing an improved wet amalgam restorative on the wet
glass ionomer cement and hardening.
[0009] U.S. Pat. No. 5,273,574 ('574) teaches a tooth restoration
comprising a layer of glass ionomer cement bonded to the tooth and
a layer of amalgam disposed on the layer of glass ionomer cement.
U.S. '574 states that it is known in the art to add a silver alloy
powder to glass ionomer cements, which are subsequently used as
bases for amalgam restoratives. U.S. '574 also states that the
corrosion that occurs as a result of the silver alloy additive
might be overcome by the addition of a non-corrosive additive.
[0010] Currently, there are no commercial dental amalgam
restorative materials which release fluoride. Development of such a
material could greatly decrease the need for use of
fluoride-releasing liners and bases, which may only provide
temporary protection. If the component which releases fluoride is
chemically bonded to the metallic portion of the amalgam matrix,
the potential for fluoride release will not be lost. Should the
outer surface become abraded or worn away, there will be additional
bonded glass particles at the new surface to provide for fluoride
release. Also, if the glass particle leaches fluoride in increased
amounts upon acidic exposure, the released fluoride is correlated
with environments which are most prone to result in tooth
decalcification and overt decay. An additional benefit of the
system is that the leached fluoride can be replenished in the glass
particle as a result of the use of a fluoride containing dentrifice
or the use of a topical fluoride treatment, as is commonly
performed at periodic dental hygiene appointment.
[0011] None of the above-cited documents disclose compositions or
methods, which achieve the above proposed system to solve the
previously discussed problems in the art, such as those claimed
herein.
SUMMARY OF THE INVENTION
[0012] The above-mentioned disadvantages with respect to the
potential for secondary caries of dental amalgam restorative
material are overcome by the use of the present invention.
Specifically, the present invention consists of combining concepts
of two major families of existing dental restorative materials,
amalgams and glass ionomer.
[0013] In one embodiment the invention provides a fluoride
releasing dental amalgam composition comprising a dental amalgam
alloy material and the glass particulate powder component of a
fluoride-containing acid etchable glass ionomer cement.
[0014] In another embodiment, the invention provides a method of
preventing or reducing secondary caries around an existing tooth
restoration comprising the step of placing the fluoride releasing
dental amalgam composition in a prepared cavity area prone to tooth
decalcification and/or overt decay.
[0015] Additional advantages of the invention will be set forth in
part in the description which follows, and in part will be obvious
from the description, or may be learned by practice of the
invention. The advantages of the invention will be realized and
attained by means of the elements and combinations particularly
pointed out in the appended claims. It is to be understood that
both the foregoing general description and the following detailed
description are exemplary and explanatory only and are not
restrictive of the invention, as claimed.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention may be understood more readily by
reference to the following detailed description of the invention
and the examples included herein.
[0017] The present invention relates to a composition comprised of
a novel dental amalgam restorative material that releases fluoride
through the judicious incorporation of an acid-leachable glass
component which has been preferably sintered with elemental silver.
The silver contained in the glass becomes incorporated into the set
amalgam matrix (gamma 1), thus chemically bonding the particle to
the restoration surface. Upon exposure to an acid environment, the
acid leachable glass particle at the restoration surface will elute
small amounts of fluoride, which provides a cariostatic effect on
surrounding tooth structure. The glass particles may be similar in
concept and formulation to that currently used in a
metal-reinforced ionomer dental restorative material. An additional
advantage to this system is that the fluoride content of the glass
particles can be recharged with the use of a fluoride-containing
dentrifice, or with periodic applications of topical fluoride, such
as performed at periodic dental hygiene visits. See
Hatibovic-Kofman S., et al., J. Dent. Res. 73, (abstract 260), 134
(1994) and Alvarez, A N, et al., J. Dent. Res., 73, (abstract 259)
134 (1994).
[0018] It must be noted that, as used in the specification and the
appended claims, the singular forms "a," "an" and "the" include
plural referents unless the context clearly dictates otherwise.
[0019] Ranges are often expressed herein as from "about" one
particular value, and/or to "about" another particular value. When
such a range is expressed, another embodiment includes from the one
particular value and/or to the other particular value. Similarly,
when values are expressed as approximations, by use of the
antecedent "about," it will be understood that the particular value
forms another embodiment.
[0020] A weight percent of a component, unless specifically stated
to the contrary, is based on the total weight of the formulation or
composition in which the component is included.
[0021] In one embodiment the invention provides a fluoride
releasing dental amalgam composition comprising a dental amalgam
alloy material and the glass particulate powder component of a
fluoride-containing acid etchable glass ionomer cement.
[0022] In another embodiment, the invention provides a method of
preventing or reducing secondary caries around an existing tooth
restoration comprising the step of placing the fluoride releasing
dental amalgam composition in a prepared cavity area prone to tooth
decalcification and/or overt decay.
[0023] As a restorative material, dental amalgam is packaged to
have an alloy portion (termed gamma) and a mercury portion, Craig,
R. G., Restorative Dental Materials, 10.sup.th Edition, 209-243,
Mosby, St. Louis, Mo. (1993). The alloy portion generally consists
of the elements silver, copper, and in some cases small amounts of
tin. The two elemental components are forcefully mixed in a
trituration device, or amalgamator, to cause mercury to wet the
alloy surface. Upon wetting, the alloy particle surface dissolves,
resulting in elements selectively entering solution. Dissolved
silver complexes with mercury forming the compound Ag.sub.2Hg.sub.3
(gamma 1), which hardens and holds the components together in a
rigid mass. In some amalgams, the dissolved tin forms an undesired
complex with mercury (Sn.sub.7-8 Hg, termed gamma 2), which is much
weaker and more prone to corrosion than the gamma 1 phase. Newer
amalgams high in copper prevent the formation of this tin-mercury
compound, favoring formation of a copper-tin compound
(Cu.sub.6Sn.sub.5, the eta phase) and additional gamma 1.
[0024] Amalgam alloy as used herein, refers to an admixture of
various alloyed metals, typically, tin, copper and/or silver with
mercury. This admixture can result from the inclusion of two
dissimilar shaped alloy particles, one which is spherical and the
other which is irregular as a result of being processed by
lathe-cutting. Only a few commercial alloy compositions include the
incorporation of elements such as palladium and indium with the
aforementioned elements.
[0025] A preferred dental amalgam is sold by Caulk Dentsply in
Millford, Del., under the trade name DISPERSALLOY. DISPERSALLOY is
a high-copper admixed material containing both lathe-cut and
spherical alloy particles pre-proportioned in a capsule with
appropriate amounts of elemental mercury. When placed in a
triturator, a thin membrane is torn, allowing a mixture of mercury
with the alloy powder, enhanced by the presence of a small plastic
pestle. Any dental amalgam capable of bonding with elemental silver
will function in this invention. The dental amalgam is present in
the range of from about .1% to about 99.9% of the total
composition, preferably from about 95% to about 99.9% of the total
composition, more preferably from about 97% to about 99.9% of the
total composition.
[0026] Glass ionomer cements, also known as glass ionomers, as used
herein, refers to powders comprised of calcium aluminum silicate
glass or aluminum fluoride type glass and a liquid comprising an
aqueous solution of either polyacrylic acid, polymaleic acid or
tartaric acid.
[0027] Glass ionomer restorative materials are typically
powder-liquid systems consisting of a special acid etchable glass
and a mixture of polyacrylic organic acids respectively. See
Anusavice, K. J., Science of Dental Materials, 10.sup.th Edition,
530-543, W. B. Saunders Co., Philadelphia, Pa. (1996). The glass is
typically an acid-soluble calcium fluoroaluminosilicate. The
generic composition of fluoroaluminosilicate glasses is: SiO.sub.2
(41.9-35.2%), Al.sub.2O.sub.3 (28.6-20.1%), AlF.sub.3 (1.6-2.4%),
CaF.sub.2 (15.1-20.1%), NaF (9.3-3.6%) and AlPO.sub.4 (3.8-12.0%),
Upon mixture of these two substances (acid etchable glass and
polyacrylic organic acid), the organic acid attacks the outer glass
particle, causing the leachable components to enter into solution.
The released calcium ions link together the long polyacrylic acid
chains through chelation bonding causing a setting reaction when
sufficient lengths of cross-linked acids precipitate from solution.
Later in the setting process, aluminum causes increased
cross-linking and enhances restoration properties. In an attempt to
increase some physical properties of the brittle restorative
material, manufactures have added metals to the glass powder. In
one method, the metal and glass are sintered, resulting in the
incorporation of the element silver into the particle glass itself.
In this invention, silver-sintered glass ionomer powder particles
are preferably utilized. Such a combination of metal and glass
ionomer particle has been termed a "CERMET." Non-sintered, i.e.,
non-metal, ionomer cement glass powders may also be utilized;
however, enhanced particle retention is best achieved when the
ionomer cement glass powder is coated with a metal that is capable
of reacting with the amalgam during setting.
[0028] A preferred acid-etchable glass ionomer powder used in this
invention is sold by ESPE Corporation of Seefeld, Germany under the
brand name of KETAC-SILVER. The acid-etchable glass powder used in
this invention is derived from the powder portion of the glass
ionomer product. Preferably, the powder portion contains
acid-etchable glass that has been sintered with elemental silver.
However, any acid-etchable, fluoride-releasing glass component
containing elemental silver, or some other inorganic component
capable of reacting with and bonding to the setting amalgam matrix
will work as well. The acid-etchable glass ionomer cement sintered
with elemental silver is present in the range of from about 99.9 to
about .1% of the total composition, preferably from about 0.5% to
about 5% of the total composition, more preferably from about 1% to
about 4% of the total composition.
[0029] In another embodiment, the invention provides that the
dental composition of sintered fluoride-containing,
fluoride-leachable acid-etchable glass ionomer cement and the
dental amalgam alloy form a chemical bond to one another resulting
in the retention of the particles of glass ionomer cement
throughout the bulk of the restoration and on the surface of the
restoration by other than purely mechanical means. The chemical
bond sets the amalgam material or matrix. The set amalgam material
or matrix retains the sintered, acid-etchable, fluoride-releasing
glass particle for an increased period over dental compositions
containing a similar glass particle that has not been
metal-sintered.
[0030] In another embodiment, the invention provides that the
dental composition is present on the outer surface and within or
throughout the material bulk of the amalgam material. The presence
of the ionomer on the outer surface enhances the release of
fluoride when the glass is in an acidic environment.
[0031] The anticipated setting reaction of the combination of
dental amalgam components with the CERMET powder relies on the fact
that the glass contains elemental silver available at the particle
surface. This metal has the capability of entering into reaction
with mercury introduced through the amalgam reaction and forming a
gamma 1 complex. Such a formation chemically bonds the filler
particle to the amalgam matrix, permitting enhanced particle
retention over that solely by mechanical means, as when a non-metal
containing glass particle is used. The retained glass particle also
reacts to acid environments by leaching fluoride, as it does when
present in the glass ionomer product. Through the combination of
these two technologies, it is possible to combine the capability of
fluoride release with the properties of a dental amalgam, and
create a fluoride-releasing, metal-based dental restorative
material.
[0032] In another embodiment, the invention provides using the
dental composition to prevent secondary caries around an existing
restoration by releasing fluoride to areas which are prone to tooth
decalcification and/or overt decay.
[0033] The fluoride-leachable acid-etchable glass ionomers have the
ability to replenish its fluoride-releasing capacity when the outer
surface of the glass ionomer has been previously depleted of
fluoride following acid attack. The fluoride releasing capacity is
correlated with environments which are most prone to tooth
decalcification and overt decay. The depleted or leached fluoride
is replenished in the glass ionomers either continuously, by the
presence of additional bonded glass particles, or periodically with
a fluoride-containing dentrifice or topical fluoride treatment.
[0034] In another embodiment, the invention provides a tooth bonded
to the fluoride releasing dental amalgam composition.
[0035] The compositions of the present invention may further
comprise one or more additives that are typically utilized in
restorative compositions. These additives include, but are not
limited to, a metal base, a metal salt, a metal oxide, a metal
hydroxide, zinc phosphate, magnesium sulfate, zircon, an inorganic
or organic filler, polymeric materials, a radiopaque agent, an
antioxidant, a stabilizer, a coupling agent, a dye, a pigment, and
other conventional dental amalgam additives.
EXAMPLES
[0036] The following examples are put forth so as to provide those
of ordinary skill in the art with a complete disclosure and
description of how the compositions claimed herein are made and
evaluated, and are intended to be purely exemplary of the invention
and are not intended to limit the scope of what the inventors
regard as their invention.
Example 1
[0037] Compressive Strength
[0038] To establish that the presence of the glass powder did not
have a detrimental effect on the amalgam physical properties, the
1-hour compressive strength of amalgam with various proportions was
determined. To make different mixtures of these components, the
amalgam capsule was removed and opened, and the alloy powder was
weighed. Then one of the five treatments were performed:
[0039] 1. No change in alloy content was made. The metals were
replaced directly into the capsules (Control Treatment).
[0040] 2. 1% of the alloy weight was removed, and replaced with an
equivalent weight of the glass powder (1% Subtractive).
[0041] 3. 5% of the alloy weight was removed, and replaced with an
equivalent weight of the glass powder (5% Subtractive).
[0042] 4. 1% of the alloy weight was determined and was supplanted
with an equivalent weight of the glass powder (1% Additive).
[0043] 5. 5% of the alloy weight was determined and was supplanted
with an equivalent weight of the glass powder (5% Additive).
[0044] Of the above five treatments in example 1, treatments #2 and
#4 fall within the scope of the invention.
[0045] The composition of the amalgam alloy used in example 1 is
known to one of skill in the art and may comprise the following
components in the various ranges set forth below:
[0046] 40-70% Silver
[0047] 26-30% Tin
[0048] 2-3% Copper
[0049] 0-2% Zinc
[0050] The composition of glass ionomer particle used in example 1
is also known to one of skill in the art and may comprise the
following components in the various ranges set forth below:
1 SiO.sub.2 41.9-35.2% Al.sub.2O.sub.3 28.6-20.1% AlF.sub.3
1.6-2.4% CaF.sub.2 15.7-20.1% NaF 9.3-3.6% AlPO.sub.4 3.8-12.0%
[0051] The glass ionomer particle composition ranges recited above
does not include the weight of the elemental silver that is
sintered onto the glass ionomer particle.
[0052] The amalgam was then mixed according to the manufacturer's
instructions in a triturator, and cylindrical specimens (4 mm
diagonal by 7-8 mm in length) were made according to the American
Dental Association's Specification test for 1-hour compressive
strength. See Council on Dental Materials and Devices, J. Am. Dent
Assoc., 95, 614-617, (1977). The order of specimen fabrication and
testing was completely randomized in order to reduce the effect of
operator error on the test results. After 1 hour of setting time,
the specimens were tested at a cross-head speed of 0.25 mm/min
using a Universal testing machine (model TTB, Instron Corporation,
Canton, Mass.). The stress at specimen failure was recorded, and is
presented in Table 1.
2TABLE 1 1-Hour Compressive Strength of Amalgam* Specimens
Composition Mean Strength (MPA) Standard Deviation 5% Additive 64.5
40.3 1% Additive 157.8 7.6 Control 167.1 21.4 1% Subtractive 164.8
14.7 5% Subtractive 85.8 51 *DISPERSALLOY was used as the dental
amalgam.
[0053] Statistical analysis of the results were performed using-a
1-way ANOVA followed by Dunnett's 2-tailed t-test using the
treatment "control" as control. The level of statistical
significance was established at a pre-set alpha of 0.05. The
results indicated the presence of a significant difference among
mean values. The post-hoc analysis indicated that the following
groups were statistically equivalent: control, 1% additive and 1%
subtractive. The strength of the 5% groups were severely
compromised from the amount of glass powder incorporated into the
dental amalgam alloy. Thus, it has been shown, using commercially
available materials, that the glass powder can be successfully
added into the dental amalgam without compromising strength
values.
[0054] Fluoride Release
[0055] In order to show that fluoride would be released into an
aqueous solution from the glass-impregnated dental amalgam,
additional specimens in the "1% additive" and "1% subtractive"
groups were made as described above. There were five specimens in
each group. In addition, five "control" specimens, which did not
have glass powder added, were also prepared.
[0056] Each specimen was placed individually in a test tube
containing 10 mL of deionized water. The tubes were swirled
continuously on a rotary shaker. After 24 hours, the specimens were
removed and placed in tubes containing 10 mL of fresh water. This
procedure was repeated two more times. Thus, fluoride release rates
from each of the 15 specimens were determined for four sequential
24-hour periods.
[0057] The solutions were analyzed for fluoride content using
ion-specific electrode following overnight diffusion using the
hexamethyldisiloxane (HMDS)-facilitated diffusion method described
in Whitford, G. M., Some Characteristics of Fluoride Analysis With
the Electrode, 2.sup.nd Edition, 24-29, S. Karger, New York (1996).
Table 2 contains the fluoride release rates expressed as nanograms
of fluoride over 24 hours and as mean .+-.SD (n=5).
3TABLE 2 Fluoride Release From Test Specimens GROUPS 24-hour Period
Control 1% Additive 1% Subtractive 1.sup.st 24.3 .+-. 5.5 1499 .+-.
157 1508 .+-. 2.7 2nd 13.1 .+-. 1.6 731 .+-. 47 774 .+-. 97 3rd
11.8 .+-. 1.4 459 .+-. 39 497 .+-. 45 4th 10.2 .+-. 0.3 447 .+-. 38
442 .+-. 42
[0058] The release rates from the 1% Additive and 1% Subtractive
groups did not differ with statistical significance, but both were
significantly higher than those from Control group. In fact, the
amounts of fluoride analyzed in the Control solutions were near the
limit of detection, so that it is possible that virtually no
fluoride was released from the Control specimens. Thus, it is
demonstrated, using commercially available materials, that the
glass powder can successfully be added into the dental amalgam in
an amount which has been shown not to compromise restoration
strength, and which will also release measurable amounts of
fluoride.
Example 2
[0059] Preparation of the Fluoride Releasing Acid-Etchable Dental
Amalgam from a Combination of Existing Commercial Product
Components
[0060] Step 1
[0061]
[0062] An amount of 100% by weight of packaged DISPERSALLOY
containing alloy powder particles and 100% of the contained
elemental mercury were placed in a plastic capsule and triturated,
wherein a thin membrane was torn allowing mixture of the elemental
mercury with the alloy powder, which was further mixed with a
pestle to form an alloy/mercury complex. The trituration period for
the mercury component was in accordance with the manufacturer's
packaging instructions.
[0063] Step 2
[0064] To 100% of the amalgam alloy mixture was added 1% by weight
of the powder portion of an acid etchable glass ionomer powder
sintered with elemental silver. The resultant admixture was
excellent for a fluoride-releasing dental amalgam restorative
material, as it did not show amalgam strength degradation while
providing evidence of significant fluoride leaching.
[0065] The recommended use for the fluoride-releasing dental
amalgam materials of the invention are as a dental restoration
material.
[0066] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the scope or spirit of the invention. Other
embodiments of the invention will be apparent to those skilled in
the art from consideration of the specification and practice of the
invention disclosed herein. It is intended that the specification
and examples be considered as exemplary only, with a true scope and
spirit of the invention being indicated by the following
claims.
* * * * *