CA1039538A - Dental amalgam and method of making same - Google Patents
Dental amalgam and method of making sameInfo
- Publication number
- CA1039538A CA1039538A CA216,699A CA216699A CA1039538A CA 1039538 A CA1039538 A CA 1039538A CA 216699 A CA216699 A CA 216699A CA 1039538 A CA1039538 A CA 1039538A
- Authority
- CA
- Canada
- Prior art keywords
- tin
- silver
- copper
- particle
- weight ratio
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/0466—Alloys based on noble metals
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K6/00—Preparations for dentistry
- A61K6/80—Preparations for artificial teeth, for filling teeth or for capping teeth
- A61K6/84—Preparations for artificial teeth, for filling teeth or for capping teeth comprising metals or alloys
- A61K6/847—Amalgams
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C7/00—Alloys based on mercury
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S75/00—Specialized metallurgical processes, compositions for use therein, consolidated metal powder compositions, and loose metal particulate mixtures
- Y10S75/955—Producing dental product
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Oral & Maxillofacial Surgery (AREA)
- Organic Chemistry (AREA)
- Metallurgy (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Veterinary Medicine (AREA)
- Public Health (AREA)
- General Health & Medical Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- Epidemiology (AREA)
- Plastic & Reconstructive Surgery (AREA)
- Dental Preparations (AREA)
- Powder Metallurgy (AREA)
Abstract
Abstract of the Disclosure An amalgamable silver-base metal powder containing about 8% to about 27% copper, 20% to about 32% tin, and the balance consisting essentially of silver, which upon admixture with about 42% to 54% mercury forms a dental amalgam of improved strength and corrosion resistance.
Description
~03~538 BACKGROUND OI; TilE INVENTION
Conventionally, silver-bas~ alloys adapted for use as dental amalgams contain a minimum of about 65% silver, a maximum of about 6~ copper, a maximum of about 2% zinc and a minimum of about 25~ tin. The aclmixture of such silver-base alloys with from about 45~ to about 55% mercury by the dentist as needed are adapted to harden within a matter of a few minutes, enabling shaping by carving for a period of up to about 15 min-utes and the amalgamation reaction is usually complete after about 24 hours. Typically, silver alloys suitable for forming amalgams in accordance with American Dental Association specif-ications contain from about 26% to about 28~ tin, about 1~ to about 2% zinct about 2~ to about 4% copper, with the balance essentially all silver. Of the foregoing alloying constituents present, it has been generally accepted that the quantity of copper should be restricted to a maximum of about ~% due to the tendency of dental amalgams incorporating greater quantities of copper to corrode and/or discolor in actual use. On the other hand, quantities of copper in excess of about 6% are known to improve the compressive strength of the resultant dental amalgam.
The general requirements of a dental amalgam include a retention of shape, color and appearance; a bioli~ical com-patibility~ a restoration of the tooth to its original function, and a long durable operating life. Extensive investigation and test work of dental restorative materials including dental amalgams has revealed that creep resistance is perhaps the single most important mechanical property followed by compres-sive strength as it relates to failure or racture of dental restorations.`--These tests have convincingly established a `' ' `' " , ' ` ` '~" .
~" ~ , s~
~.93953~
relationship between a hig incidence of marginal fracture of dental restorations with high dynamic creep values. Attempts to improve the marginal fracture characteristics and other mechanical properties of dental amalgams by increasing the quantity of copper in the alloy have been unsuccessful due to the increased corrosivity and tendency of discoloration of the - resultant amalgams.
- The present invention provides for an amalgamable silver alloy containing amounts of copper substantially greater 10than those heretofore considered useable which improves not only the resistance of the dental amalgam toward corrosion and/or discoloration/ but also provides for substantially superior mechanical properties, including increased resistance to dynamic creep.
SUMMARY OF THE INVENTION
-The benefits and advantages of the present invention are achieved by an amalgamable silver alloy powder derived from a microcasting of a molten mass of alloy, such as by fluid atomization techni~ues or the like, and wherein each particle is of substantiàlly the same composition and is further character-ized by having~a gradient composition in which the concentrati~n of the individual alloying constituents changes on moving in a, direction from the surface of the particle toward the center thereof. The amalgamable powder contains tin and copper in com-bination with silver as the essential alloying constituent and wherein the silver-to-ti~ ratio is controlled from about 1.8:1 to about 3.0:1, while the tin-to-copper ratio is controlled from about 1:1 to about 3 1. On a weight percent basis of the individual alloying cons~ituents, the amalgamable silver alloy ~ ~ .
~ - 2 -jrc ,9 . ~
.~.. ..
. . . . . .
3~S38 po~Jder contains from about 8~ to about ~7~ copper, from about 20% to about 32% tin, with the balance consisting essentially of silver but, in any event, a minimum of 47% silver. The alloy powder can also contain up to about 2% zinc without any adverse effects. The powder particles are of an average size less than about 100 microns and pref~rably range from about S microns - to about 44 microns.
The dental amalgam is prepared employin~ the amal-gamable silver alloy powder by admixture with mercury in an amount of from about 42~ up to about 54% and preferably in an amount such that mercury in the final product is present from about 46~ to about 50~ by weight.
Additional benefits and advantages of the present invention will ~ecome apparent upon a reading of the description of the preferred embodiments, the specific examples provided, taken in conjunction with the accompanying drawing.
BRIEF DESGRIPTION OF THE DRAWING
. ~:
The drawing graphically portrays the range o com-position gradients of the amalgamable silver alloy particles between the surface and interior of the particle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS .
- The proportions of the individual alloying constit-uents comprising the amalgamable silver alloy powder and the resultant dental amalgam prepared therefrom are herei~ defined in terms of percentages by weight and on a weight ratio basis unless clearly indicated to the contrary.
The permissible as well as the preferred ratios and corresponding percentages of the three essential alloying con-stituents are set forth in Tabl~ 1.
` -.. irc ~ r',Q
395~8 METZ~L POWDI~:R COMPOSITION
Perr.lissible Range Preferred Range Asg Ratio 1.8 - 3.0 2.2 - 2.6 Cu Ratio l.0 - 3.0 1.5 - 2.5 Cu 8~ - 27~ 10% - 18~
Sn 20~ - 32% 23% - 28%
Ag 47% - 70% 57% - 65%
As shown in Table l, the ratio of silver-to tin is broadly controlled within the range of about 1.8 up to about 3.0, while the permissible ratios of tin-to-copper are from about l to about 3. Expressed in terms of percentages of the three alloying constituents, based on the foregoing weight ~ -ratios, the minimum percentages are specified with the -~ recognition that when any one of the three is at the minimum level, one or both of the remaining alloys-are present in amounts greater than their respective minimums in order that the total percent is lO0. The foregoing is also applicable to the preferred percentages of these three alloying con-stituents as set forth in Table 1. For the purposes of conven~
ience, the relative proportions o~ the three metals are set forth in terms of their weight ratios in which tha silver-to-tin ratio preferably is controlled within a range of about ~.2 to - about 2.6,while the tin-to-copper ratio is preferably controlled within a range o~ about 1.5 to about 2.5. It is also contem-plated that zinc can be included in amounts up to about 2~ by weight o~ th~ total alloy. ~3~53~
It is an important feature of the present invention that the amalgamable silver alloy powder is derived by a micro-casting technique in which molten fine sized droplets of the desired composition are cooled in a manner to effect a progres-sive solidification during the cooling commencing on the sur~
face and moving inwardly thereof. The differential cooling and solidification rate of each droplet contributes toward a stratification or composition gradient in the final solidified particle which is at least in part responsible for the unex-pected improved mechanical and chemical properties of dental amalgams prepared therefrom.
The microcasting of a molten mass of the silver alloy can be achieved by a variety of techniques including gas -- atomization, airless spraying and centrifugal fragmentation for effecting a subdivision of the molten mass into a plurality of fine-size liquid droplets wh ch are all of substantially the same composition. Of the foregoing techniques, the gas atomiz-ation technique has been found particularly satisfactory and a specific embodiment thereof is described in United States Patent No. 3,253,783. In accordance with the apparatus disclosed in ; the aforementioned United States patent, a molten stream of the metal alloy passes downwardly and i5 atomized in response to the impingement of a conically-shaped vortex of gas and wherein the resultant droplets progressively solidify as they fall downwardly through the collection chamber. Metal powder produced in accordance with the arrangement described in -the aforementioned patent under proper operating conditions gen-- erally is of a spherical configuration and where th~-predom-inant portion thereof is of a particle size wi hin the desired range.
.~ .
- ; ir~
: .: . ... ~: .
~L~3~538 The amalg~mable powder can be of any particle configuration, although particles of a substantially spherical configuration are preferred. The powder can be of an average particle size of less than about 100 microns, although powders having average particle sizes ranging from about 45 microns to about 5 microns are usually preferred.
While air can be satisfactoril~ empLoyed as the atom-izing and collection medium, the contact of the molten silver alloy with the oxygen in the atomizing gas occasions the form-ation of undesirab].e oxides on the particle surfaces. While such oxides can subsequently be reduced by heating the powder in a reducing atmosphere, such as hydrogen, for example, it is preferred to employ a substantially inert gas, such as a sub-stantially dry argon, nitrogen or helium gas, for effecting the atomization of the powder and also as the cooling medium within the powder collection chamber.
The amalgamable powder of the desired composition and particle size can be employed for forming a dental ama`lgam at the time required by admixture with from about 42% up to about 54% mercury and, more usually, from about 46% to about 50%
mercury. The wetting of the particle surfaces with mercury initiates the amalgamation reaction, whereby the intermetallic compounds formed by a consumption of the surface strata of the particles serves to bond the residual unreacted particle cores to aach other, forming a matrix characterized as a continuous phase of amalgam, having interspersed therethrough discrete discontin-uous phases of the un~eacted particle cores. Of the several inter-metallic compounds formed, the tin-mercury intermetallic com-pound comprises the weakest alloy with respect to compressive jrc ~
: ,: ~ . , .
, '~:'. " , ~ ' ' . . ' , .
`. ' , ` ' ' . ', ': ' . . ' .' ~ ` ' ': , `
i~3~538 strength and also is the most susceptible to corrosion and/or discoloration.
A possible explanation of the different behavior of the spherical alloy containing high copper to that of the commin-utive alloys having the same composition is the difference in their manufacturing and solidification pattern of the alloy.
In the spherical alloy, the outer surface of each particle con-tains a higher concentration of silver and copper, whereas the tin-rich phase is concentrated in the inner part of the part-icle. Using a hydrochloric acid solution as a washing agent, some tin ions are dissolved from the outer surface, while the silver and copper ions on the surface are left almost unaffected.
This process would actually increase the relative concentration of silver-to-tin on the surface, which should cause amalgam alloys to harden in a very short period of time. ~ However, after acid washing of particles, the surface of particles be-comes spongy in appearance, producing some microscopic channels : to the central part of the sphere where the higher concentration of tin exists. During heat-treating of spherical particles, a considerable amount of tin ions, through the mi¢roscopic channels, migrate toward the surface. Increased amount of tin on the surface would increase the working time of the alloy.
The affinity of mercury to tin is greater than to silver. The affinity-of the cbpper ion to mercury at room temperature is very low and thus the copper will remain unreacted, during tri-. ~
turation, increasing the ratio of Cu/Ag to a higher value than before amalgamation.
While the particular mechanism by which the un-expe~ted res-~lts of the present invention are obtained i~ not '' :
7 _ ? '``~
`:: : . , . . . - :
: : ~ , . .: .
: . . : , . .:: ., ~ q~39538 entirely und~rstood ~t the pr~sent time, a possible explan-ation is that the outer surface of each of the particles con-tains a higher concentration of silv~r and copper with the inner core of the particle comprising a tin-rich phase. This minimiz-es the formation of detrimental tin intermetallic compounds, whereby the properties of the resultant dental amalgam are substantially improved. The forlegoing is substantiated by microprobe analyses of the spherical alloy particles employ-ing x-ray beams which show a variation in the composition be-tween the inner portions of each particle relative to the per-ipheral portions thereof. The range of composition values obtained by microprobe analyses of large amalgam alloy particles are set forth in Table 2.
MICROPROBE ANALYSIS OF LARGE SPHERICAL PARTICLES
Location of Composition, Percent by Weight Analysis Silver Tin Copper -` Center of particle 51-58 27-29 9-19 ~- Edge of particle 64-84 10-20 6 16 The results of incremental microprobe analyses of an individual particle to determine the range of variation in the composition of the three alloying constituents on moving from the particle surface toward the central core of the part-icle is graphically illustrated in the drawing. As shown, the concentration of the silver constituent progressively decreases on moving from the surface toward the particle core. In con-trast, the concentration of tin progressively increases on mov ing from the particle surface toward the particle core, while - the quantity of copper remains substantially constant but with ., . . , ~
~ ~rc:.
.. ~ ,..... . .
. .: : . ,: - .~ , . :
. - . . . . . . . - : .
~ 13~53~3 a reduction in the breath of the range of values on moving toward the core.
In order to further illustrate the amalgamable silver alloy po~der of the present invention and the improved properties of amalgams prepared therefrom, the following specific - ~xample is provided. It will be understood that the example is included solely for illustrative purposes and is not intended to be limiting of the scope of the invention as herein described and as set forth in the subjoined claims.
EXAMPLE
An amalgamable silver alloy powder is prepared by the argon atomization of a molten mass of material containing a silver-to-tin ratio of 2.23:1 and a tin-to-copper ratio of
Conventionally, silver-bas~ alloys adapted for use as dental amalgams contain a minimum of about 65% silver, a maximum of about 6~ copper, a maximum of about 2% zinc and a minimum of about 25~ tin. The aclmixture of such silver-base alloys with from about 45~ to about 55% mercury by the dentist as needed are adapted to harden within a matter of a few minutes, enabling shaping by carving for a period of up to about 15 min-utes and the amalgamation reaction is usually complete after about 24 hours. Typically, silver alloys suitable for forming amalgams in accordance with American Dental Association specif-ications contain from about 26% to about 28~ tin, about 1~ to about 2% zinct about 2~ to about 4% copper, with the balance essentially all silver. Of the foregoing alloying constituents present, it has been generally accepted that the quantity of copper should be restricted to a maximum of about ~% due to the tendency of dental amalgams incorporating greater quantities of copper to corrode and/or discolor in actual use. On the other hand, quantities of copper in excess of about 6% are known to improve the compressive strength of the resultant dental amalgam.
The general requirements of a dental amalgam include a retention of shape, color and appearance; a bioli~ical com-patibility~ a restoration of the tooth to its original function, and a long durable operating life. Extensive investigation and test work of dental restorative materials including dental amalgams has revealed that creep resistance is perhaps the single most important mechanical property followed by compres-sive strength as it relates to failure or racture of dental restorations.`--These tests have convincingly established a `' ' `' " , ' ` ` '~" .
~" ~ , s~
~.93953~
relationship between a hig incidence of marginal fracture of dental restorations with high dynamic creep values. Attempts to improve the marginal fracture characteristics and other mechanical properties of dental amalgams by increasing the quantity of copper in the alloy have been unsuccessful due to the increased corrosivity and tendency of discoloration of the - resultant amalgams.
- The present invention provides for an amalgamable silver alloy containing amounts of copper substantially greater 10than those heretofore considered useable which improves not only the resistance of the dental amalgam toward corrosion and/or discoloration/ but also provides for substantially superior mechanical properties, including increased resistance to dynamic creep.
SUMMARY OF THE INVENTION
-The benefits and advantages of the present invention are achieved by an amalgamable silver alloy powder derived from a microcasting of a molten mass of alloy, such as by fluid atomization techni~ues or the like, and wherein each particle is of substantiàlly the same composition and is further character-ized by having~a gradient composition in which the concentrati~n of the individual alloying constituents changes on moving in a, direction from the surface of the particle toward the center thereof. The amalgamable powder contains tin and copper in com-bination with silver as the essential alloying constituent and wherein the silver-to-ti~ ratio is controlled from about 1.8:1 to about 3.0:1, while the tin-to-copper ratio is controlled from about 1:1 to about 3 1. On a weight percent basis of the individual alloying cons~ituents, the amalgamable silver alloy ~ ~ .
~ - 2 -jrc ,9 . ~
.~.. ..
. . . . . .
3~S38 po~Jder contains from about 8~ to about ~7~ copper, from about 20% to about 32% tin, with the balance consisting essentially of silver but, in any event, a minimum of 47% silver. The alloy powder can also contain up to about 2% zinc without any adverse effects. The powder particles are of an average size less than about 100 microns and pref~rably range from about S microns - to about 44 microns.
The dental amalgam is prepared employin~ the amal-gamable silver alloy powder by admixture with mercury in an amount of from about 42~ up to about 54% and preferably in an amount such that mercury in the final product is present from about 46~ to about 50~ by weight.
Additional benefits and advantages of the present invention will ~ecome apparent upon a reading of the description of the preferred embodiments, the specific examples provided, taken in conjunction with the accompanying drawing.
BRIEF DESGRIPTION OF THE DRAWING
. ~:
The drawing graphically portrays the range o com-position gradients of the amalgamable silver alloy particles between the surface and interior of the particle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS .
- The proportions of the individual alloying constit-uents comprising the amalgamable silver alloy powder and the resultant dental amalgam prepared therefrom are herei~ defined in terms of percentages by weight and on a weight ratio basis unless clearly indicated to the contrary.
The permissible as well as the preferred ratios and corresponding percentages of the three essential alloying con-stituents are set forth in Tabl~ 1.
` -.. irc ~ r',Q
395~8 METZ~L POWDI~:R COMPOSITION
Perr.lissible Range Preferred Range Asg Ratio 1.8 - 3.0 2.2 - 2.6 Cu Ratio l.0 - 3.0 1.5 - 2.5 Cu 8~ - 27~ 10% - 18~
Sn 20~ - 32% 23% - 28%
Ag 47% - 70% 57% - 65%
As shown in Table l, the ratio of silver-to tin is broadly controlled within the range of about 1.8 up to about 3.0, while the permissible ratios of tin-to-copper are from about l to about 3. Expressed in terms of percentages of the three alloying constituents, based on the foregoing weight ~ -ratios, the minimum percentages are specified with the -~ recognition that when any one of the three is at the minimum level, one or both of the remaining alloys-are present in amounts greater than their respective minimums in order that the total percent is lO0. The foregoing is also applicable to the preferred percentages of these three alloying con-stituents as set forth in Table 1. For the purposes of conven~
ience, the relative proportions o~ the three metals are set forth in terms of their weight ratios in which tha silver-to-tin ratio preferably is controlled within a range of about ~.2 to - about 2.6,while the tin-to-copper ratio is preferably controlled within a range o~ about 1.5 to about 2.5. It is also contem-plated that zinc can be included in amounts up to about 2~ by weight o~ th~ total alloy. ~3~53~
It is an important feature of the present invention that the amalgamable silver alloy powder is derived by a micro-casting technique in which molten fine sized droplets of the desired composition are cooled in a manner to effect a progres-sive solidification during the cooling commencing on the sur~
face and moving inwardly thereof. The differential cooling and solidification rate of each droplet contributes toward a stratification or composition gradient in the final solidified particle which is at least in part responsible for the unex-pected improved mechanical and chemical properties of dental amalgams prepared therefrom.
The microcasting of a molten mass of the silver alloy can be achieved by a variety of techniques including gas -- atomization, airless spraying and centrifugal fragmentation for effecting a subdivision of the molten mass into a plurality of fine-size liquid droplets wh ch are all of substantially the same composition. Of the foregoing techniques, the gas atomiz-ation technique has been found particularly satisfactory and a specific embodiment thereof is described in United States Patent No. 3,253,783. In accordance with the apparatus disclosed in ; the aforementioned United States patent, a molten stream of the metal alloy passes downwardly and i5 atomized in response to the impingement of a conically-shaped vortex of gas and wherein the resultant droplets progressively solidify as they fall downwardly through the collection chamber. Metal powder produced in accordance with the arrangement described in -the aforementioned patent under proper operating conditions gen-- erally is of a spherical configuration and where th~-predom-inant portion thereof is of a particle size wi hin the desired range.
.~ .
- ; ir~
: .: . ... ~: .
~L~3~538 The amalg~mable powder can be of any particle configuration, although particles of a substantially spherical configuration are preferred. The powder can be of an average particle size of less than about 100 microns, although powders having average particle sizes ranging from about 45 microns to about 5 microns are usually preferred.
While air can be satisfactoril~ empLoyed as the atom-izing and collection medium, the contact of the molten silver alloy with the oxygen in the atomizing gas occasions the form-ation of undesirab].e oxides on the particle surfaces. While such oxides can subsequently be reduced by heating the powder in a reducing atmosphere, such as hydrogen, for example, it is preferred to employ a substantially inert gas, such as a sub-stantially dry argon, nitrogen or helium gas, for effecting the atomization of the powder and also as the cooling medium within the powder collection chamber.
The amalgamable powder of the desired composition and particle size can be employed for forming a dental ama`lgam at the time required by admixture with from about 42% up to about 54% mercury and, more usually, from about 46% to about 50%
mercury. The wetting of the particle surfaces with mercury initiates the amalgamation reaction, whereby the intermetallic compounds formed by a consumption of the surface strata of the particles serves to bond the residual unreacted particle cores to aach other, forming a matrix characterized as a continuous phase of amalgam, having interspersed therethrough discrete discontin-uous phases of the un~eacted particle cores. Of the several inter-metallic compounds formed, the tin-mercury intermetallic com-pound comprises the weakest alloy with respect to compressive jrc ~
: ,: ~ . , .
, '~:'. " , ~ ' ' . . ' , .
`. ' , ` ' ' . ', ': ' . . ' .' ~ ` ' ': , `
i~3~538 strength and also is the most susceptible to corrosion and/or discoloration.
A possible explanation of the different behavior of the spherical alloy containing high copper to that of the commin-utive alloys having the same composition is the difference in their manufacturing and solidification pattern of the alloy.
In the spherical alloy, the outer surface of each particle con-tains a higher concentration of silver and copper, whereas the tin-rich phase is concentrated in the inner part of the part-icle. Using a hydrochloric acid solution as a washing agent, some tin ions are dissolved from the outer surface, while the silver and copper ions on the surface are left almost unaffected.
This process would actually increase the relative concentration of silver-to-tin on the surface, which should cause amalgam alloys to harden in a very short period of time. ~ However, after acid washing of particles, the surface of particles be-comes spongy in appearance, producing some microscopic channels : to the central part of the sphere where the higher concentration of tin exists. During heat-treating of spherical particles, a considerable amount of tin ions, through the mi¢roscopic channels, migrate toward the surface. Increased amount of tin on the surface would increase the working time of the alloy.
The affinity of mercury to tin is greater than to silver. The affinity-of the cbpper ion to mercury at room temperature is very low and thus the copper will remain unreacted, during tri-. ~
turation, increasing the ratio of Cu/Ag to a higher value than before amalgamation.
While the particular mechanism by which the un-expe~ted res-~lts of the present invention are obtained i~ not '' :
7 _ ? '``~
`:: : . , . . . - :
: : ~ , . .: .
: . . : , . .:: ., ~ q~39538 entirely und~rstood ~t the pr~sent time, a possible explan-ation is that the outer surface of each of the particles con-tains a higher concentration of silv~r and copper with the inner core of the particle comprising a tin-rich phase. This minimiz-es the formation of detrimental tin intermetallic compounds, whereby the properties of the resultant dental amalgam are substantially improved. The forlegoing is substantiated by microprobe analyses of the spherical alloy particles employ-ing x-ray beams which show a variation in the composition be-tween the inner portions of each particle relative to the per-ipheral portions thereof. The range of composition values obtained by microprobe analyses of large amalgam alloy particles are set forth in Table 2.
MICROPROBE ANALYSIS OF LARGE SPHERICAL PARTICLES
Location of Composition, Percent by Weight Analysis Silver Tin Copper -` Center of particle 51-58 27-29 9-19 ~- Edge of particle 64-84 10-20 6 16 The results of incremental microprobe analyses of an individual particle to determine the range of variation in the composition of the three alloying constituents on moving from the particle surface toward the central core of the part-icle is graphically illustrated in the drawing. As shown, the concentration of the silver constituent progressively decreases on moving from the surface toward the particle core. In con-trast, the concentration of tin progressively increases on mov ing from the particle surface toward the particle core, while - the quantity of copper remains substantially constant but with ., . . , ~
~ ~rc:.
.. ~ ,..... . .
. .: : . ,: - .~ , . :
. - . . . . . . . - : .
~ 13~53~3 a reduction in the breath of the range of values on moving toward the core.
In order to further illustrate the amalgamable silver alloy po~der of the present invention and the improved properties of amalgams prepared therefrom, the following specific - ~xample is provided. It will be understood that the example is included solely for illustrative purposes and is not intended to be limiting of the scope of the invention as herein described and as set forth in the subjoined claims.
EXAMPLE
An amalgamable silver alloy powder is prepared by the argon atomization of a molten mass of material containing a silver-to-tin ratio of 2.23:1 and a tin-to-copper ratio of
2.10:1, resulting in an alloy consisting essentially of 13%
copper, 27% tin and 60% silver. The resultant powder particles are generally of a sphexical configuration and the collected powder is screened to separate and recover particles of an aver-age particle size ranging from 44 microns to about 5 microns.
The balance of the powder particles are recycled.
T~ resultant heat~treated and washed amalgamable powder is triturated for ten seconds with approximately 46% mer~
cury, whereafter the mixture is shaped into a test specimen allowed to set for a period of seven days. Test evaluations of the resultan~ dental amalgam tast specimen reveal a compres sive strength of greater than about 75,000 psi, a creep resist~
ance of less than 0.20~ ~in three hours, and an observable re-sistance to tarnish and corrosion.
- While it will be apparent that the invention herein . ' , '.
-- 9 -- .
.
~ jrc~
' ': i ' . ' . ' . i ' ' ' ' ' ' ~ ~3~S38 disclosed is well calculated to achieve the benefits and advantages set forth above, it will be appreciated that the invention is susceptible to modification, variation and change ~ without departing from the spirit thereof.
:`
jrc - ~ v ~.3 . ..
. .
, . . . .
copper, 27% tin and 60% silver. The resultant powder particles are generally of a sphexical configuration and the collected powder is screened to separate and recover particles of an aver-age particle size ranging from 44 microns to about 5 microns.
The balance of the powder particles are recycled.
T~ resultant heat~treated and washed amalgamable powder is triturated for ten seconds with approximately 46% mer~
cury, whereafter the mixture is shaped into a test specimen allowed to set for a period of seven days. Test evaluations of the resultan~ dental amalgam tast specimen reveal a compres sive strength of greater than about 75,000 psi, a creep resist~
ance of less than 0.20~ ~in three hours, and an observable re-sistance to tarnish and corrosion.
- While it will be apparent that the invention herein . ' , '.
-- 9 -- .
.
~ jrc~
' ': i ' . ' . ' . i ' ' ' ' ' ' ~ ~3~S38 disclosed is well calculated to achieve the benefits and advantages set forth above, it will be appreciated that the invention is susceptible to modification, variation and change ~ without departing from the spirit thereof.
:`
jrc - ~ v ~.3 . ..
. .
, . . . .
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An amalgamable silver alloy powder in which all of the particles are of substantially the same composition and consist essentially of silver, tin and copper; said silver and tin being present at a weight ratio of from about 1.8 1 to about 3.0:1 and said tin and copper being present at a weight ratio of about 1:1 up to 3:1, said powder con-taining from 0 to about 2% by weight zinc and being further characterized as having an average particle size less than about 100 microns and wherein each particle is of a gradient composition in which the concentration of silver decreases on moving from the surface of the particle inwardly toward the core thereof, while the concentration of tin increases on moving from the surface of the particle toward the core thereof.
2. The amalgamable silver alloy powder as defined in claim 1 in which said weight ratio of silver-to-tin ranges from about 2.2:1 to about 2.6:1.
3. The amalgamable silver alloy powder as defined in claim 1 in which said weight ratio of tin-to-copper ranges from about 1.5:1 to about 2.5:1.
4. The amalgamable silver alloy powder as defined in claim 1 in which the average particle size thereof ranges from about 45 microns to about 5 microns.
5. A dental amalgam consisting essentially of a continuous matric composed of an amalgam having interspersed therethrough a plurality of discrete phases chemically bonded by said continuous phase into an integral matrix, said discrete phases comprising particles of an alloy consisting essentially of silver, tin and copper and wherein the particles are of a gradient composition in which the concentration of silver decreases on moving from the surface of the particle inwardly toward the core thereof, while the concentration of tin increases on moving from the surface of the particle toward the core thereof, said continuous phase comprising intermetallic compounds of mercury with silver, tin and copper; said dental amalgam containing from about 42%
to about 54% by weight mercury and from 0 to about 2% by weight zinc based on said silver, tin and copper which are present in amounts so as to provide a weight ratio of silver-to-tin of from about 1.8:1 up to about 3.0:1 and tin-to-copper of from about 1:1 up to 3:1.
to about 54% by weight mercury and from 0 to about 2% by weight zinc based on said silver, tin and copper which are present in amounts so as to provide a weight ratio of silver-to-tin of from about 1.8:1 up to about 3.0:1 and tin-to-copper of from about 1:1 up to 3:1.
6. The dental amalgam as defined in claim 5, wherein the concentration of mercury ranges from about 46% to about 50% by weight.
7. The dental amalgam as defined in claim 5 in which said weight ratio of silver-to-tin ranges from about 2.2:1 to about 2.6:1 while the weight ratio of tin-to-copper ranges from about 1.5:1 to about 2.5:1.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US451840A US3871876A (en) | 1974-03-18 | 1974-03-18 | Dental Amalgam |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039538A true CA1039538A (en) | 1978-10-03 |
Family
ID=23793912
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA216,699A Expired CA1039538A (en) | 1974-03-18 | 1974-12-23 | Dental amalgam and method of making same |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US3871876A (en) |
| JP (1) | JPS5435860B2 (en) |
| BR (1) | BR7501521A (en) |
| CA (1) | CA1039538A (en) |
| DE (1) | DE2505934C3 (en) |
| FR (1) | FR2264521B1 (en) |
| GB (1) | GB1476100A (en) |
| IT (1) | IT1028449B (en) |
| NL (1) | NL167318C (en) |
| SE (1) | SE425049B (en) |
Families Citing this family (27)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2511194C3 (en) * | 1975-03-14 | 1979-03-15 | Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler, 6000 Frankfurt | Alloy powder mixture for the production of dental amalgams |
| US3975192A (en) * | 1975-03-28 | 1976-08-17 | Sybron Corporation | Dental alloy and amalgam |
| US3985558A (en) * | 1975-03-28 | 1976-10-12 | Sybron Corporation | Dental alloy and amalgam |
| US3954457A (en) * | 1975-04-28 | 1976-05-04 | Gary Maurice Weikel | Dental amalgam |
| US4164419A (en) * | 1975-12-22 | 1979-08-14 | Shofu Dental Manufacturing Company, Limited | Powdered alloy for dental amalgam |
| US3997329A (en) * | 1975-12-29 | 1976-12-14 | Engelhard Minerals & Chemicals Corporation | Dental composition |
| US3997328A (en) * | 1975-12-29 | 1976-12-14 | Engelhard Minerals & Chemicals Corporation | Dental amalgams |
| US3997327A (en) * | 1975-12-29 | 1976-12-14 | Engelhard Minerals & Chemicals Corporation | Dental composition |
| US3997330A (en) * | 1975-12-29 | 1976-12-14 | Engelhard Minerals & Chemicals Corporation | Dental amalgams |
| US4080199A (en) * | 1976-05-27 | 1978-03-21 | Johnson & Johnson | Lathe cut dental alloy powder |
| US4030918A (en) * | 1976-05-27 | 1977-06-21 | Johnson & Johnson | Indium containing dental alloy powder |
| GB1594643A (en) * | 1977-01-17 | 1981-08-05 | Engelhard Min & Chem | Corrosion-resistant dental alloy having improved handling characteristics |
| US4234339A (en) * | 1978-08-24 | 1980-11-18 | Engelhard Minerals & Chemicals Corporation | Corrosion-resistant dental alloy |
| US4226622A (en) * | 1978-08-24 | 1980-10-07 | Engelhard Minerals & Chemicals Corporation | Corrosion-resistant dental alloy |
| US4235631A (en) * | 1978-08-24 | 1980-11-25 | Engelhard Minerals & Chemicals Corporation | Corrosion-resistant dental alloy having improved handling characteristics |
| AR223024A1 (en) * | 1980-01-31 | 1981-07-15 | Macrodent Sa | A PRODUCT TO BE USED IN COMPRESSED DENTAL AMALGAMAS OR DISINTEGRABLE PILLS OBTAINED BY AGGLOMERATION OF SUCH PRODUCT AND AMALGAMAS OBTAINED FROM THIS LAST |
| JPH0214202Y2 (en) * | 1980-02-20 | 1990-04-18 | ||
| US4374085A (en) * | 1980-05-29 | 1983-02-15 | Special Metals Corporation | Silver-tin-copper-palladium alloy and amalgam thereof |
| DE3240256C1 (en) * | 1982-10-30 | 1983-09-29 | Blendax-Werke R. Schneider Gmbh & Co, 6500 Mainz | Process for the production of silver-tin master alloys for dental amalgams |
| US4664629A (en) * | 1983-06-27 | 1987-05-12 | Dentsply Research & Development Corp. | Dental composition mixture |
| US4664855A (en) * | 1985-11-12 | 1987-05-12 | Special Metals Corporation | Method for producing amalgamable alloy |
| US5091114A (en) * | 1988-08-23 | 1992-02-25 | Asahi Kasei Kogyo Kabushiki Kaisha | Conductive metal powders, process for preparation thereof and use thereof |
| WO1995010379A1 (en) * | 1993-10-08 | 1995-04-20 | The United States Of America, As Represented By The Secretary Of Commerce | Acid assisted cold welding and intermetallic formation and dental applications thereof |
| US5490870A (en) * | 1993-10-28 | 1996-02-13 | Special Metals Corporation | Amalgamable composition and method of production |
| US5354353A (en) * | 1993-10-28 | 1994-10-11 | Special Metals Corporation | Amalgamable composition and method of production |
| FR2772265B1 (en) * | 1997-12-12 | 2001-09-07 | Schiller Henri | REDUCED MERCURY RATE DENTAL AMALGAM AND PROCESS FOR PRODUCING SUCH AN AMALGAM |
| US6458180B1 (en) * | 2001-01-10 | 2002-10-01 | Jiin-Huey Chern Lin | Amalgamatable dental alloy powder having an effect of reducing initial mercury vapor release rate |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1612782A (en) * | 1923-12-19 | 1926-12-28 | Lee S Smith & Son Mfg Company | Dental alloy and process of making the same |
| US1963085A (en) * | 1933-08-05 | 1934-06-19 | Arthur W Gray | Comminuted alloy |
| US2281991A (en) * | 1938-04-27 | 1942-05-05 | Poetschke Paul | Dental amalgam alloy |
| US3305356A (en) * | 1963-08-30 | 1967-02-21 | William V Youdelis | Dental amalgam |
| US3554738A (en) * | 1968-05-21 | 1971-01-12 | Victor E Beldham | Dental amalgam |
| US3676112A (en) * | 1970-05-19 | 1972-07-11 | Indiana University Foundation | Anticariogenic dental amalgam |
-
1974
- 1974-03-18 US US451840A patent/US3871876A/en not_active Expired - Lifetime
- 1974-12-23 CA CA216,699A patent/CA1039538A/en not_active Expired
-
1975
- 1975-01-17 IT IT19378/75A patent/IT1028449B/en active
- 1975-02-13 DE DE2505934A patent/DE2505934C3/en not_active Expired
- 1975-02-20 JP JP2142775A patent/JPS5435860B2/ja not_active Expired
- 1975-03-06 SE SE7502497A patent/SE425049B/en not_active IP Right Cessation
- 1975-03-12 NL NL7502941.A patent/NL167318C/en not_active IP Right Cessation
- 1975-03-14 BR BR1521/75A patent/BR7501521A/en unknown
- 1975-03-18 GB GB1123875A patent/GB1476100A/en not_active Expired
- 1975-03-18 FR FR7508437A patent/FR2264521B1/fr not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| AU7715375A (en) | 1976-07-08 |
| GB1476100A (en) | 1977-06-10 |
| DE2505934C3 (en) | 1979-01-04 |
| DE2505934B2 (en) | 1978-05-11 |
| IT1028449B (en) | 1979-01-30 |
| SE7502497L (en) | 1975-09-19 |
| BR7501521A (en) | 1975-12-23 |
| NL167318B (en) | 1981-07-16 |
| US3871876A (en) | 1975-03-18 |
| DE2505934A1 (en) | 1975-09-25 |
| SE425049B (en) | 1982-08-30 |
| FR2264521A1 (en) | 1975-10-17 |
| NL167318C (en) | 1981-12-16 |
| NL7502941A (en) | 1975-09-22 |
| FR2264521B1 (en) | 1978-12-29 |
| JPS50125922A (en) | 1975-10-03 |
| JPS5435860B2 (en) | 1979-11-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1039538A (en) | Dental amalgam and method of making same | |
| Demaree et al. | Properties of dental amalgams made from spherical alloy particles | |
| EP0397117B1 (en) | Method and material for dental structures | |
| JPH0244443B2 (en) | ||
| US3980472A (en) | Dental amalgam | |
| EP0118717B2 (en) | Sintered material for electrical contacts and its method of manufacture | |
| US4664855A (en) | Method for producing amalgamable alloy | |
| US4235631A (en) | Corrosion-resistant dental alloy having improved handling characteristics | |
| US5914185A (en) | Moldable dental material composition | |
| CA1176083A (en) | Setting compositions for dental purposes | |
| US4129944A (en) | Dental constructions and dental alloys | |
| US4226622A (en) | Corrosion-resistant dental alloy | |
| CA1066924A (en) | Dental alloy and amalgam | |
| KR910001326B1 (en) | Process and composition for improved corrosion resistance | |
| Zappala et al. | Microstructural aspects of the Captek alloy for porcelain-fused-to-metal restorations | |
| CA1067316A (en) | Dental alloy and amalgam | |
| US5354353A (en) | Amalgamable composition and method of production | |
| US4030918A (en) | Indium containing dental alloy powder | |
| CA1069347A (en) | Corrosion-resistant dental alloy having improved handling characteristics | |
| US5490870A (en) | Amalgamable composition and method of production | |
| Reynolds Jr | The redistribution of mercury as observed in the phase transformations in amalgams | |
| US3429696A (en) | Iron powder infiltrant | |
| CA1154616A (en) | Corrosion-resistant dental alloy having improved handling characteristics | |
| US3901693A (en) | Method of preparing dental restorative material | |
| EP0623335A1 (en) | A moldable dental composition |