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Joined: May 2006
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This is a tough one to pick, I think the dentists are brainwashed in college, but are they not governed by Dental Associations like the ADA and such? In Canada the College of Dental Surgeons has threatened to take away a dentist's license to practice if they tell patients that mercury is harmful. They are only allowed to say that it can adversely affect about 3 percent of the population. A mercury free dentist actually admitted that to me but I had to swear not to repeat where I heard it. Mercury-free dentists here in Canada remove mercury under the guise of cosmetic dentistry to avoid harassment fromt the college...which would be the equivalent to the ADA, I guess. Terrible huh? <img src="/ubbthreads/images/graemlins/mad.gif" alt="" />
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Joined: Dec 1999
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I completely agree. In fact: In Canada the College of Dental Surgeons has threatened to take away a dentist's license to practice if they tell patients that mercury is harmful. The same is true in the U.S. The ADA code of ethics prohibits dentists from recommending the removal of mercury fillings for health reasons. Dentists have lost their licenses to practice for doing just that.
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Anonymous
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Hi all, Personally I think the issue stems right back to the way we are (or were) taught in school. I think we are not taught to fully understand, challenge and take responsibility for information that is fed to us. For example, I think a lot of the information out there (on anything) has a strong economic foundation (eg almagams are cheap and easy to install) And we tend to automatically trust what ‘professionals’ (doctors/dentists) and the media either directly or indirectly feed to us without fully understanding the biases at play. Personally I will be fully investigating (well giving it a darn good go at least) everything that goes into, or is done to, my body and my families from now on. Just my 2c worth ! Cheers, Karen <img src="/ubbthreads/images/graemlins/cool.gif" alt="" />
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Joined: Dec 1999
Posts: 30,867
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Good point Karen. I would also add that pharmaceutical companies make billions selling drugs to people who have symptoms that are caused by mercury toxicity. Considering...That the FDA is controlled by the pharmaceutical companies, and Considering...Pharmaceutical companies are primarily concerned with increasing shareholder profits, It Bears Consideration That...Pharmaceutical companies love mercury and enjoy the fact that we: - Inject ourselves with it,
- Install it in our mouths, and,
- Spray it on our food and clothing (cotton).
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Anonymous
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The U.S. govt. is to blame for allowing dentistry to be a self policing profession. Most people will do whatever they can get away with. Contrary to popular belief, the FDA never approved " silver" hg fillings. When you have enough $,you get away with anything. Ask O.J.
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Joined: Oct 2006
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"Other"
Us... we patients and citizens are to blame for the continued use of mercury. We have known since the ADA was formed that mercury poisoned people, and we didn't do enough to stop it. We have enabled the use of mercury for over a century. We have enabled ouselves to be poisoned because we don't do enough to force change. We have enabled dentists, the ADA, pharmaceutical companies, and our government to practice such abominations on we, the citizenry.
More than a century of knowing the dangers of mercury and we still allow it and accept it for ourselves and our children. Kill a child and it makes the news, but poison a million children and you get blank stares. A poisoned child is a tragedy - a million poisoned children is a statistic.
We have lost the art of dissent to continually build this country. We forgot how to throw tea into harbors. We talk instead of yell, we walk instead of march. We do what feels good instead of doing what is right. We tell each other to calm down and "not rock the boat". We tell eachother to agree instead of dissent. We call each other crazy for thinking silver fillings make us crazy. We worship those who tell us what to do - Oprah, the president, dentists. We believe that others have our best interest at heart.
We have enabled the abuses. We give people power over our common sense and then cry and wonder why they step all over us. Over a century of exposure to mercury because we haven't done enough to stop such a blatant and obvious abomination to humanity. Such a widespread insult to ourselves and we allow it. Mercury injections of thimerosol and mercury lozenge fillings for our children, still in the year 2006. What Eureka! moments about mercury we do have aren't enough because we don't protect the next generation from the same insult.
We are dumbed down and passive. Ironically, mercury makes people dumb, real dumb. And passive. And crazy. And easy to control. And sources of profit from mercury caused health ailments.
Government is blamed next, but government is only as strong as it's citizenry. By the people for the people. We have enabled the government to become bought and sold because we haven't done enough. Government is not doing it's job of preventing unchecked capitalism and abuses of our rights under the Constitution.
The ADA and pharmaceutical companies are criminal, but they are supposed to be controlled by the government to prevent such abuses and unchecked capitalism. And we, the citizenry, are ultimately responsible for how our government functions. Sometimes voting is enough to force change, but often it takes dissent and sacrifice - things people are less willing to do for the benefit of change and the next generation.
Last edited by RickJRT; 10/25/06 12:30 AM.
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Joined: Dec 1999
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Very well said. Wish you were running for president.
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Anonymous
Unregistered
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I voted " other " because, I simply have come to believe that all the above, are in one another's pockets, anymore. I believe they all silently, work with one another in their unholy alliance.
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Joined: Dec 1999
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Anonymous
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I'm amazed that (so far) 50% of people blame the dental organizations. Most people probably don't know that the ADA, BDA are trade organizations with no (direct) responsibility towards public health. Obviously they are still liable under public health laws, but their main body of concern is towards their own membership.
Dentists can rightly blame their trade organisations for not protecting them from the dangers of mercury, but we the public should not expect the fox to look after the hen-house so to speak.
The real problem lies with our health authorities - the FDA in the US and the NHS in the UK. We the public have every right to demand that the very people appointed to look after our health do not poison us.
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Joined: Dec 1999
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You make a good point...Following is a legal statement from the American Dental Association (ADA). The (red) emphasis I've provided will help you read between the lines. If you're a dentist, you should be outraged and withdraw your membership immediately. "The American Dental Association (ADA) owes no legal duty of care to protect the public from allegedly dangerous products used by dentists. The ADA did not manufacture, design, supply or install the mercury-containing amalgams. The ADA does not control those who do. The ADA's only alleged involvement in the product was to provide information regarding its use. Dissemination of information relating to the practice of dentistry does not create a duty of care to protect the public from potential injury."The Superior Court of the State of California Case No. 718228, Demurrer (October 22, 1992) from: http://amalgamillness.com
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Anonymous
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On a similar note here are some quotes from the British Dental Association (BDA) on mercury:
- “Mercury is a toxic substance”
- “… dental amalgam is not inert. Amalgam fillings release mercury vapour, especially when teeth are chewed on or brushed.”
- “[Mercury] accumulates in certain organs - especially the kidneys but also in the brain, lungs, liver and gastrointestinal tract.”
- “Whether amalgam can be called ‘safe’ is a matter for manufacturers of amalgam and for the Department of Health, and for the toxicologists and other scientists who advise them.”
- “It is never possible to say categorically that anything is safe in all circumstances.”
- "Research in the field is on-going and it is, of course, not ruled out in theory that evidence could one day come to light showing that amalgam is hazardous"
Essentially they are saying mercury is toxic and that amalgam may or may not be dangerous, but its not really their concern.
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Joined: Feb 2007
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The BDA guidelines include that pregnant woman are not to be given amalgams or have amalgams removed. This is because they know that mercury from the amalgams passes through the placenta to the unborn baby. They worry about unborn babies...but don't worry about us.
The NHS will allow its dentists to remove and replace amalgams free of charge if a test proves positive, which it did in my case. I had an appointment with a Consultant Toxicologist/Dental Surgeon at the Royal London Dental Hospital in Whitechapel, London, BUT, she told me the only protection they would use would be a rubber dam and NO OTHER form of protection of any kind..no protective clothing, no high powered suction or drilling, no alternative air supply, etc., etc. Nothing! She said none of it was needed!!!! Also, definitely NO chelation afterwards.
When I told her that I was not prepared to have them removed in that way I was told that I would not get another chance, there was no changing my mind and that I would be struck off their books and would never be welcome back if I refused the treatment there and then. Good! Coz there is no way I'd want to go back there.
As for the tests, I had a metals patch test, urine test and blood test. The one which they were relying on was the metal patch test as they said the amount of mercury, if found in blood or urine, was usually a normal amount, which showed up with me. But, NORMAL AMOUNT??? Surely, as mercury is so toxic there cannot be normal amounts????? No amount of mercury, no matter how small should be in our urine or our blood. That's madness!
A BDA Factfile which I had downloaded from the BDA's website a few years ago stated that high powered instruments were to be used if they did go ahead with removals, so why don't they use them? With reference to this factfile, I noticed about 9 months ago that it is no longer there on their website for public view/download and only members of the BDA who have a password to enter other parts of the site have access to it! Hmmmmmm! I wonder why?
I fought for 3 1/2 years to get the NHS to do the treatment for me and it was a complete waste of time.
Lyn (London)
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"A potential source of exposure to metallic mercury for the general population is mercury released from dental amalgam fillings."
"Estimates of the amount of mercury released from dental amalgams range from 3 to 17 micrograms per day (ug/day). The mercury from dental amalgam may contribute from 0 to more than 75% of your total daily mercury exposure,..."
"Metallic mercury is still used in some herbal or religious remedies in Latin America and Asia, and in rituals or spiritual practices in some Latin American and Caribbean religions such as Voodoo, Santeria, and Espiritismo. These uses may pose a health risk from exposure to mercury both for the user and for others who may be exposed to mercury vapors in contaminated air."
"Up until 1991, phenylmercuric compounds were used as antifungal agents in both interior and exterior paints, but this use was also banned because mercury vapors were released from these paints."
"Because metallic mercury evaporates into the air, these practices may put anyone breathing the air in the room at risk of exposure to mercury. The longer people breathe the contaminated air, the greater their risk will be."
"The use of metallic mercury in a home or an apartment not only threatens the health of the people who live there now, but also threatens the health of future residents who may unknowingly be exposed to further release of mercury vapors from contaminated floors or walls."
"Very small amounts of metallic mercury (for example, a few drops) can raise air concentrations of mercury to levels that may be harmful to health. The longer people breathe the contaminated air, the greater the risk to their health. Metallic mercury and its vapors are extremely difficult to remove from clothes, furniture, carpet, floors, walls, and other such items. If these items are not properly cleaned, the mercury can remain for months or years, and continue to be a source of exposure."
"Dentists and their assistants may be exposed to metallic mercury from breathing in mercury vapor released from amalgam fillings and to a much lesser extent from skin contact with amalgam restorations. Family members of workers who have been exposed to mercury may also be exposed to mercury if the worker’s clothes are contaminated with mercury particles or liquid."
"When you breathe in mercury vapors, however, most (about 80%) of the mercury enters your bloodstream directly from your lungs, and then rapidly goes to other parts of your body, including the brain and kidneys. Once in your body, metallic mercury can stay for weeks or months. When metallic mercury enters the brain, it is readily converted to an inorganic form and is “trapped” in the brain for a long time. Metallic mercury in the blood of a pregnant woman can enter her developing child. Most of the metallic mercury will accumulate in your kidneys, but some metallic mercury can also accumulate in the brain."
"Metallic mercury vapors or organic mercury may affect many different areas of the brain and their associated functions, resulting in a variety of symptoms. These include personality changes (irritability, shyness, nervousness), tremors, changes in vision (constriction (or narrowing) of the visual field), deafness, muscle incoordination, loss of sensation, and difficulties with memory."
"Children who breathe metallic/elemental mercury vapors, eat foods or other substances containing phenylmercury or inorganic mercury salts, or use mercury-containing skin ointments for an extended period may develop a disorder known as acrodynia, or pink disease. Acrodynia can result in severe leg cramps; irritability; and abnormal redness of the skin, followed by peeling of the hands, nose, and soles of the feet. Itching, swelling, fever, fast heart rate, elevated blood pressure, excessive salivation or sweating, rashes, fretfulness, sleeplessness, and/or weakness may also be present. It was once believed that this syndrome occurred only in children, but recent reported cases in teenagers and adults have shown that they can also develop acrodynia."
"Metallic mercury vapors are very toxic and have no odor. Do not remain unnecessarily in that room, and try not to let metallic mercury contact your eyes, skin, or clothing."
"OSHA regulates levels of mercury in the workplace. It has set limits of 0.1 milligrams of mercury per cubic meter of air (mg/m3)for organic mercury and 0.05 mg/m3 for metallic mercury vapor in workplace air to protect workers during an 8-hour shift and a 40-hour work week. NIOSH recommends that the amount of metallic mercury vapor in workplace air be limited to an average level of 0.05 mg/m3 during a 10-hour work shift."
Centers for Disease Control,
Toxicological Profile for Mercury
CAS# 7439-97-6, March 1999
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all of the above, because they are all the same people.
I read somewhere once that the ADA owns 3 patents in regard to amalgam fillings. Kind of a vested interest there.
the ADA may also own the dentists. Do they write textbooks for dental school also?
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At least two patents on dental amalgam exists. They are: - U.S. Patent 4,018,600 April 1977
- U.S. Patent 4,078,921 March 1978
They are both assigned to American Dental Association Health Foundation (Chicago, IL) Below are graphics containing the full text of the patents. [color:"brown"] Patent 4,018,600[/color] <img src="http://herballure.com/Images/Misc/AmalgamRelated/Patent,4018600,Page01.jpg"> <img src="http://herballure.com/Images/Misc/AmalgamRelated/Patent,4018600,Page02.jpg"> <img src="http://herballure.com/Images/Misc/AmalgamRelated/Patent,4018600,Page03.jpg"> [color:"brown"] Patent 4,078,921[/color] <img src="http://herballure.com/Images/Misc/AmalgamRelated/Patent,4078921,Page01.jpg"> <img src="http://herballure.com/Images/Misc/AmalgamRelated/Patent,4078921,Page02.jpg"> <img src="http://herballure.com/Images/Misc/AmalgamRelated/Patent,4078921,Page03.jpg"> <img src="http://herballure.com/Images/Misc/AmalgamRelated/Patent,4078921,Page04.jpg"> <img src="http://herballure.com/Images/Misc/AmalgamRelated/Patent,4078921,Page05.jpg"> [color:"brown"] Full Text for Patent 4,018,600[/color]
United States Patent 4,018,600
Waterstrat April 19, 1977
Method for eliminating gamma.sub.2 phase from dental amalgam and improved dental amalgam composition
Abstract
An improved alloy for a dental amalgam includes silver and tin and the additional element, manganese. The alloy is comprised of a minimum of about 60% by weight silver, a maximum of about 15% by weight manganese and the balance tin. Various amounts of other constituents known to those in the art such as gold, copper, zinc and mercury may be included.
Inventors: Waterstrat; Richard M. (Gaithersburg, MD)
Assignee: American Dental Association Health Foundation (Chicago, IL)
Appl. No.: 05/617,594
Filed: September 29, 1975
Current U.S. Class: 420/501 ; 420/527
Current International Class: C22C 5/06 (20060101); C22C 7/00 (20060101); A61K 6/05 (20060101); A61K 6/02 (20060101); C22C 005/06 (); C22C 007/00 ()
Field of Search: 75/173R,169
References Cited [Referenced By]
U.S. Patent Documents
3762917 October 1973 Johnson
Foreign Patent Documents
45-8552 Mar., 1970 JA
Primary Examiner: Rutledge; L. Dewayne
Assistant Examiner: Weise; E. L.
Attorney, Agent or Firm: Allegretti, Newitt, Witcoff & McAndrews
Government Interests
The invention described herein was made in the course of work under a grant or award from the Department of Health, Education and Welfare.
Claims
What is claimed is:
1. An improved alloy for dental amalgam consisting essentially of about 62% by weight silver, about 12% by weight manganese and the balance tin.
2. An improved alloy for dental amalgam consisting essentially of about 66% by weight silver, about 8% by weight manganese and the balance tin.
3. A dental amalgam consisting essentially of an alloy including a minimum of 60% by weight silver and about 2% to a maximum of 15% by weight manganese and the balance tin; in combination with mercury.
4. An improved method for making a dental amalgam comprising the steps of mixing mercury with an alloy, said alloy consisting essentially of a minimum of 60% by weight silver, about 2% to a maximum of 15% by weight manganese and the balance tin.
5. The improved method of claim 4 wherein the weight ratio of said mercury to said alloy is about 1:1 or greater than 1:1.
Description
BACKGROUND OF THE INVENTION
This invention relates to an alloy for a dental amalgam and, more particularly, to a new class of such alloys which include silver, tin and manganese.
Amalgams are presently the principal material used by dentists for restoration of decayed teeth. About 75% of dental restorations are by amalgams. Amalgams are plastic at normal room and body temperature for a few minutes before they harden. Little or no change in volume occurs as a result of becoming hard. Amalgams combine the characteristics of high compressive and moderate tensile strength with the ability to withstand the corrosive environment defined by the mouth. Additionally, they are substantially non-toxic.
Generally, the alloy from which amalgams are made includes a mixture of silver and tin. The American Dental Association has established various standards for such alloys. Following is the American Dental Association specification for compositions of alloys used in making amalgams:
______________________________________ Silver Tin Copper Zinc Mercury ______________________________________ Min wt Max wt Max wt Max wt Max wt % % % % % 65 29 6 2 3 ______________________________________
The above composition standard was adopted by the American Dental Association effective June 1, 1970 and is also identified as American National Standard No. Z156.1-1970. Incorporated herewith by reference is the publication entitled "Guide to Dental Materials and Devices," Seventh Edition 1974-1975, copyright 1974, American Dental Association. Particular attention is directed to chapter 3 of this reference entitled "Amalgam and Mercury" as well as Specification No. 1 of the A.D.A. specifications for dental materials.
Amalgam alloys complying with present specifications and standards are generally silver-tin alloys containing approximately three parts of silver and one part of tin. This alloy is often referred to as the gamma phase (.gamma.) or Ag.sub.3 Sn. In practice, the powdered alloy and mercury are subjected to trituration, thereby facilitating a reaction between mercury and the alloy. The mercury combines with the alloy to form new solid phases from the pulverized or triturated amalgam.
The chemical reaction during amalgamation may be described as follows:
Thus, in addition to a gamma.sub.1 phase (.gamma.) (Ag.sub.2 Hg.sub.3), a tin-mercury phase, often referred to as the gamma.sub.2 phase (.gamma..sub.2), is formed. The gamma.sub.2 phase has a simple hexagonal crystal structure and may contain 5 to 12% atomic percent mercury. The designation for this phase is uncertain; though, the phase is often designated as Sn.sub.7 Hg or Sn.sub.8 Hg.
The tin-mercury phase in a dental amalgam is known as a weak constituent relative to the silver-tin and silver-mercury phases. Nonetheless, the gamma.sub.2 phase may comprise up to 10% of the amalgam. The gamma.sub.2 phase has been associated with poor corrosion resistance and excessive flow or creep under an applied stress. To overcome the deficiencies noted in the gamma.sub.2 phase, the subject matter of the present invention has been developed.
SUMMARY OF THE INVENTION
Briefly, the invention comprises an improved alloy for amalgams wherein manganese is used in silver-tin based dental alloys to react with the tin during amalgamation and thus reduce or eliminate the tendency of these alloys to form the undesirable gamma.sub.2 phase.
Thus, it is an object of the present invention to provide an improved alloy for dental amalgams.
It is a further object of the present invention to provide an improved alloy for dental amalgams utilizing manganese in order to improve corrosion resistance and reduce excessive flow or creep.
Still another object of the present invention is to provide an improved alloy for dental amalgams which is inexpensive and effective with an ability to perform acceptably and meet standard specifications.
These and other objects, advantages and features will be set forth in the detailed description which follows.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The alloy of the present invention utilizes manganese in combination with a silver-tin dental alloy. The manganese reacts with the tin during the amalgamation process, thus reducing or eliminating the tendency of such alloys to form the undesirable gamma.sub.2 phase during amalgamation.
As an example of the particular class of compounds which result during the amalgamation of the alloy, the following formulation is set forth:
The relative amounts of Ag.sub.2 Hg.sub.3 and MnSn.sub.2 which are formed depend upon the amount of manganese. If no manganese is present, then the reaction which occurs is the standard amalgam reaction recited above in the Background of the Invention. Increased amounts of manganese will decrease progressively the amount of tin which is available to form the gamma.sub.2 phase.
Typically, in such alloys, an amount of the original alloy particles (Ag.sub.3 Sn) remains unreacted. Thus, one normally obtains a solid mixture of the products of the reaction together with residual, unreacted alloy particles. A certain amount of manganese remains in the unreacted portion and thus available for reaction with tin. It is therefore difficult to predict exactly how much manganese is needed to prevent the formation of the gamma.sub.2 phase. A lower limit of the amount, however, can be calculated by assuming that all the manganese is available for reaction. On this base, it is estimated that about 8% manganese should suffice to eliminate all the gamma.sub.2 phase; however, experience indicates that manganese in an amount of 2% by weight to a maximum of 15% by weight is efficacious in the practice of the invention.
Additions of manganese in excess of the amount required to eliminate the gamma.sub.2 phase may provide beneficial effects. Alloys have been tested containing 12% manganese. Such alloys possessed excellent resistance to creep or flow as compared with an 8% manganese alloy of the present invention or with other commercial amalgam alloys. Tests also indicate that amalgams prepared from the above-described alloys are equally as corrosion resistant as other commercial alloys. Following are examples of alloys and specific tests performed:
EXAMPLE No. 1
Homogeneous mixture comprising 62% silver, 12% manganese and 26% tin was prepared by atomization of the molten metal alloy. This resulted in the formation of approximately spherical particles having a particle size between 325 and 400 mesh. An amalgam was prepared from the alloy using a 6.2:6 ratio of mercury to alloy. The amalgam was prepared in a commercial amalgamator in accordance with conventional procedures. All tests were conducted using methods described in the American Dental Association specification No. 1 referenced above. Corrosion resistance was determined to be as good as any of the prior art amalgams. Resistance to creep or flow was improved relative to prior art amalgams. Typical comparative data is set forth below with the amalgam of the 12% alloy of the present invention listed first:
__________________________________________________________________________ Dimensional 24 hr. Diam..sup.3 Alloy ADA Flow Test.sup.1 Change Tensile Strength __________________________________________________________________________ 12% Mn alloy 0.16 to 0.03% 0 to +4 5700 to 7500 psi Dispersalloy.sup.4 0.6% +13 7300 psi 10% Au alloy +20 7750 to 8900 psi Optalloy.sup.5 1.09% -7 10,700 to 11,100 psi Velvalloy.sup.6 0.81% -12 Spheralloy.sup.7 0.86% -17 __________________________________________________________________________
______________________________________ 15 min. Diam..sup.2 Alloy Tensile Strength ______________________________________ 12% Mn alloy 1760-1970 psi Dispersalloy 300 psi Optalloy 800 psi Velvalloy 550 psi Spheralloy 650 psi ______________________________________
This amalgam was sectioned, polished and submitted to examination by X-ray area scanning in an electron microprobe. The characteristic X-ray emission from tin, manganese and silver was mapped separately on the same area of the sample at a magnification of about 1000X. This technique revealed that each residual spherical particle of the gamma.sub.1 phase was surrounded by a layer of manganese-tin compound. There was no evidence of any tin-mercury compound. X-ray diffraction patterns of this amalgam were difficult to interpret due to line overlaps but the strong-intensity line of the gamma phase, usually present in patterns from conventional amalgams, was in this case replaced by a weak-intensity line.
1. American Dental Association Specification No. 1 flow test.
2. American Dental Association Specification No. 1 tensile strength.
3. The same test as defined by No. 2, except after 24 hours.
4. Trade name for amalgam alloy sold by American Silver & Mercury Producers.
5. Trade name for amalgam alloy sold by L. D. Caulk Co., Division of Dentsply International, Inc.
6. Trade name for amalgam alloy sold by S. S. White Division, Pennwalt Corp.
7. Trade name for amalgam alloy sold by Ken Mfg. Co.
EXAMPLE NO. 2
The same experiment was performed using an alloy including 66% silver, 8% manganese and 26% tin. Substantially identical results were observed.
It is clear that changes to the composition may be effected and still remain within the scope of the invention. Thus, the amalgamation procedure may call for additional mercury. Other alloying agents such as copper, zinc or mercury may be included in the alloy. The invention therefore is to be limited only by the following claims and their equivalents.
[color:"brown"] Full Text for Patent 4,078,921[/color]
United States Patent 4,078,921
Waterstrat March 14, 1978
Method for eliminating gamma.sub.2 phase from dental amalgam and improved dental amalgam composition
Abstract
An improved alloy for a dental amalgam includes silver and tin and the additional element, manganese. The alloy is comprised of a minimum of about 60% by weight silver, a maximum of about 20% by weight manganese and the balance tin. Various amounts of other constituents known to those in the art such as gold, copper, zinc and mercury may be included.
Inventors: Waterstrat; Richard M. (Gaithersburg, MD)
Assignee: American Dental Association Health Foundation (Washington, DC)
Appl. No.: 05/713,849
Filed: August 12, 1976
Related U.S. Patent Documents
Application Number Filing Date Patent Number Issue Date
617594 Sep., 1975 4018600
Current U.S. Class: 420/501 ; 420/527
Current International Class: C22C 5/06 (20060101); C22C 7/00 (20060101); A61K 6/05 (20060101); A61K 6/02 (20060101); C22C 005/06 (); C22C 007/00 ()
Field of Search: 75/173R,173C,169
References Cited [Referenced By]
U.S. Patent Documents
1970319 August 1934 Kern
3954457 May 1976 Weikel
3997328 December 1976 Greener
3997329 December 1976 Aliotta et al.
4018600 April 1977 Waterstrat
Foreign Patent Documents
949,063 Aug., 1949 FR
8,552 Mar., 1970 JA
112,902 Jan., 1945 SW
Primary Examiner: Lovell; C.
Attorney, Agent or Firm: Allegretti, Newitt, Witcoff & McAndrews
Government Interests
The invention described herein was made in the course of work under a grant or award from the Department of Health, Education and Welfare.
Parent Case Text
This is a continuation-in-part of copending application Ser. No. 617,594, filed Sept. 19, 1975, now U.S. Pat. No. 4,018,600.
Claims
What is claimed is:
1. An improved alloy for a dental amalgam consisting essentially of at least 2% up to 20% by weight manganese and the balance 60-83% by weight silver and 16-29% by weight tin.
2. An alloy as set forth in claim 1 including 1-5% mercury as a preamalgam.
3. An alloy as set forth in claim 1 including one or more from the group of gold and copper in place of part of the manganese.
4. An alloy as set forth in claim 1 in combination with mercury to form an amalgam.
Description
BACKGROUND OF THE INVENTION
This invention relates to an alloy for a dental amalgam and, more particularly, to a new class of such alloys which include silver, tin and manganese.
Amalgams are presently the principal material used by dentists for restoration of decayed teeth. About 75% of dental restorations are by amalgams. Amalgams are plastic at normal room and body temperature for a few minutes before they harden. Little or no change in volume occurs as a result of becoming hard. Amalgams combine the characteristics of high compressive and moderate tensile strength with the ability to withstand the corrosive environment defined by the mouth. Additionally, they are substantially non-toxic.
Generally, the alloy from which amalgams are made includes a mixture of silver and tin. The American Dental Association has established various standards for such alloys. Following is the American Dental Association specification for compositions of alloys used in making amalgams:
______________________________________ Silver Tin Copper Zinc Mercury Min wt Max wt Max wt Max wt Max wt % % % % % 65 29 6 2 3 ______________________________________
The above composition standard was adopted by the American Dental Association effective June 1, 1970 and is also identified as American National Standard No. Z156.1-1970. Incorporated herewith by reference is the publication entitled "Guide to Dental Materials and Devices", Seventh Edition 1974- 1975, copyright 1974, American Dental Association. Particular attention is directed to chapter 3 of this reference entitled "Amalgam and Mercury" as well as Specification No. 1 of the A.D.A. specifications for dental materials.
Amalgam alloys complying with present specifications and standards are generally silver-tin alloys containing approximately three parts of silver and one part of tin. This alloy is often referred to as the gamma phase (.gamma.) or Ag.sub.3 Sn. In practice, the powdered alloy and mercury are subjected to trituration, thereby facilitating a reaction between mercury and the alloy. The mercury combines with the alloy to form new solid phases from the pulverized and triturated amalgam.
The chemical reaction during amalgamation may be described as follows:
Thus, in addition to a gamma.sub.1 phase (.gamma..sub.1) (Ag.sub.2 Hg.sub.3), a tin-mercury phase, often referred to as the gamma.sub.2 phase (.gamma..sub.2), is formed. The gamma.sub.2 phase has a simple hexagonal crystal structure and may contain 5 to 12% atomic percent mercury. The composition for this phase is uncertain; though, the phase is often designated as Sn.sub.7 Hg or Sn.sub.8 Hg.
The tin-mercury phase in a dental amalgam is known as a weak constituent relative to the silver-tin and silver-mercury phases. Nonetheless, the gamma.sub.2 phase may comprise up to 10% of the amalgam. The gamma.sub.2 phase has been associated with poor corrosion resistance and excessive flow or creep under an applid stress. To overcome the deficiencies noted in the gamma.sub.2 phase, the subject matter of the present invention has been developed.
SUMMARY OF THE INVENTION
Briefly, the invention comprises an improved alloy for amalgams wherein manganese is used in silver-tin based dental alloys to react with the tin during amalgamation and thus reduce or eliminate the tendency of these alloys to form the undesirable gamma.sub.2 phase.
Thus, it is an object of the present invention to provide an improved alloy for dental amalgams.
It is a further object of the present invention to provide an improved alloy for dental amalgams utilizing manganese in order to improve corrosion resistance and reduce excessive flow or creep.
Still another object of the present invention is to provide an improved alloy for dental amalgams which is inexpensive and effective with an ability to perform acceptably and meet standard specifications.
These and other objects, advantages and features will be set forth in the detailed description which follows.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The alloy of the present invention utilizes manganese in combination with a silver-tin dental alloy. The manganese reacts with the tin during the amalgamation process, thus reducing or eliminating the tendency of such alloys to form the undesirable gamma.sub.2 phase during amalgamation.
As an example of the particular class of compounds which result during the amalgamation of the alloy, the following formulation is set forth:
The relative amounts of Ag.sub.2 Hg.sub.3 and MnSn.sub.2 (MnSn, Mn.sub.2 Sn) which are formed depend upon the amount of manganese. If no manganese is present, then the reaction which occurs is the standard amalgam reaction recited above in the Background of the Invention. Increased amounts of manganese will decease progressively the amount of tin which is available to form the gamma.sub.2 phase.
Typically, in such alloys, an amount of the original alloy particles (Ag.sub.3 Sn) remains unreacted. Thus, one normally obtains a solid mixture of the products of the reaction together with residual, unreacted alloy particles. A certain amount of manganese remains in the unreacted portion and thus unavailable for reaction with tin. It is therefore difficult to predict exactly how much manganese is needed to prevent the formation of the gamma.sub.2 phase. A lower limit of the amount, however, can be calculated by assuming that all of the manganese is available for reaction. On this basis, it is estimated that about 8% manganese should suffice to eliminate the gamma.sub.2 phase.
Additions of manganese in excess of the amount required to eliminate the gamma.sub.2 phase may provide beneficial effects. Alloys have been tested containing 12% manganese. Such alloys possessed excellent resistance to creep or flow as compared with an 8% manganese alloy of the present invention or with other commercial amalgam alloys. Preliminary tests also indicate that amalgams prepared from the above-described alloys are equally as corrosion resistant as other commercial alloys. Following are examples of alloys and specific tests performed:
EXAMPLE No. 1
Homogeneous mixture comprising 62% silver, 12% manganese and 26% tin was prepared by atomization of the molten metal alloy. This resulted in the formation of approximately spherical particles having a particle size between 325 and 400 mesh. An amalgam was prepared from the alloy using a 6.2:6 ratio of mercury to alloy. The amalgam was prepared in a commercial amalgamator in accordance with conventional procedures. All tests were conducted using methods described in the American Dental Association specification No. 1 referenced above. Corrosion resistance was determined to be as good as many of the prior art amalgams. Resistance to creep or flow was improved relative to prior art amalgams. Typical comparative data is set forth below with the amalgam of the 12% alloy of the present invention listed first:
__________________________________________________________________________ Dimensional 24 hr. Diam..sup.3 Alloy ADA Flow Test.sup.1 Change Tensile Strength __________________________________________________________________________ 12% Mn alloy 0.16 to 0.03% 0 to +4 5700 to 7500 psi Dispersalloy.sup.4 0.6% +13 7300 psi 10% Au alloy +20 7750 to 8900 psi Optalloy.sup.5 1.09% -7 10,700 to 11,100 psi Velvalloy.sup.6 0.81% -12 Spheralloy.sup.7 0.86% -17 __________________________________________________________________________ 15 min. Diam..sup.2 Alloy Tensile Strength __________________________________________________________________________ 12% Mn alloy 1760-1970 psi Dispersalloy 300 psi Optalloy 800 psi Velvalloy 550 psi Spheralloy 650 psi __________________________________________________________________________
This amalgam was sectioned, polished and submitted to examination by X-ray area scanning in an electron microprobe. The characteristic X-ray emission from tin, manganese and silver was mapped separately on the same area of the sample at a magnification of about 1000X. This technique revealed that each residual spherical particle of the gamma.sub.1 phase was surrounded by a layer of manganese-tin compound. There was no evidence of any tin-mercury compound. X-ray diffraction patterns of this amalgam were difficult to interpret dut to line overlaps but the strong-intensity line of the gamma.sub.2 phase, usually present in patterns from conventional amalgams, was in this case replaced by a weak-intensity line.
1. American Dental Association Specification No. 1 flow test.
2. American Dental Association Specification No. 1 tensile strength.
3. The same test as defined by No. 2, except after 24 hours.
4. Trade name for amalgam alloy sold by America Silver & Mercury Producers.
5. Trade name for amalgam alloy sold by L. D. Caulk Co., Division of Dentsply International, Inc.
6. Trade name for amalgam alloy sold by S. S. White Division, Pennwalt Corp.
7. Trade name for amalgam alloy sold by Kerr Mfg. Co.
EXAMPLE No. 2
The same experiment was performed using an alloy including 66% silver, 8% manganese and 26% tin. Substantially identical results were observed.
Additional experiments have shown that the amount of manganese may be increased to 20% by weight without adversely affecting the efficacy of the invention. Moreover, it is also possible to mix the improved manganese alloy with previously existing amalgam alloys to achieve the improvement of the invention. For example, a prior art alloy including a minimum of 65% by weight silver, a maximum of 29% by weight tin, a maximum of 6% by weight copper, a maximum of 2% by weight zinc and a maximum of 3% by weight mercury may be combined with the alloy of the present invention.
This mixture of alloys may then be formed as an amalgam by proper trituration of mercury and the two alloys. The permitted ratio of the two alloys extends over the full range of possible mixtures. A preferred ratio provides an effective amount of manganese equal to about 10 to 12% of the total weight of the mixed alloys.
The improved manganese alloy of the present invention may also be mixed with more than one additional dental alloy. Thus, two or more dental amalgam alloys may be mixed with the improved alloy of the present invention to provide a composite alloy formable as an amalgam by proper trituration.
Additionally, the manganese component of the alloy of the present invention may be replaced, in part, by copper or gold. For example, about one to thirty parts by weight copper may be substituted for part of the manganese and/or silver.
The alloy may also be preamalgamated. That is, the alloy may contain a small percentage (1-5% by weight) of mercury. This mercury is included as part of the alloy before amalgamation. The preamalgamated alloy may then be formed as an amalgam by proper trituration of additional mercury and the alloy.
In summary, the contemplated range of alloy constituents is set forth below.
______________________________________ Range (by weight) Preferred (by weight) ______________________________________ Tin (Sn) - 16-29% 26 .+-. 0.1% Silver (Ag) - 60-83% about 65 .+-. 3% Manganese (Mn) - 2%-20% about 10 .+-. 3% Copper (Cu) - 1-30% as a substitute for part of the manganese and/or silver Mercury (Hg) - 1-5% as a preamalgam Gold (Au) - 1-10% as a substitute for part of the manganese and/or silver ______________________________________
It is clear that changes to the composition may be effected and stil remain within the scope of the invention. Thus, the amalgamation procedure may call for additional mercury. Other alloying agents such as copper, zinc or mercury may be included in the alloy. The invention, therefore, is to be limited only by the following claims and their equivalents.
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Anonymous
Unregistered
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That is very unfair. If I did not know that mercury was in fillings how should I be the blame? Most people I speak wirth do not know that mercury is in fillings. I called a dentist office to see if they were mercury free. The person answering the phone did not know (I had my answer already). When she came back she told me that there was very little mercury in the fillings, I told her it was almost 50% and she got angry and hung up on me. She doesn't know, I didn't know, many people don't know. Now when you do know that is when you have a responsibility to do something. I think you were being very hard on us.
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Joined: Dec 1999
Posts: 30,867
Master Elite Member
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Hi Margretto, I see that you keep saying "hard on us". I'm not sure what you mean by that. What I mean to ask is: Who is "us"? If "us" is the consumer, then is there a post above that blames the consumer? Sorry. I just have to ask these questions because I don't understand the context of what you're saying. Thanks. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> Russ
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Joined: Jan 2008
Posts: 73
Senior Member
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just to make a point. In '97 I insisted on a metal free estimate for the dental work i needed to be done as I knew by then that I couldn't tolerate metal/mercury amalgams. I paid the money, had the work done and got sicker and sicker. By the time I figured it out, went to another dds who found all the upper back teeth (where I couldn't easily see) were loaded with mercury.
Friends are God's way of appologizing for family.
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Joined: May 2008
Posts: 4,707
Master Elite Member
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Yes... ((( Smiles )))
This is very unfair I agree with that.
Totally...
But,
I don't see Russ blaming the consumer either
but instead warning the consumer instead.
I did not know about the mercury in the fillings long ago.
My parents didn't either should I blame them because they
paid to have my teeth done it was paid for out of care and concern for me back then.
They could have just let my teeth rot though looking back on it..
I don't believe I really had any cavities in my back teeth at such a young age it was a pediatric dentist..
The word pediatric just brings up all kinds of warning flags for
me now.
And when I went back when older to have them redone/fixed/ upgraded..
I had no idea what was in the filling's back then too but
maybe silver..
The choice was silver and gold for backteeth.
Silver was cheaper.
I had no idea what was in thoses vaccines either except a weaken virus to stimulate an immune reaction.
We all were deceived believeing we were doing the right thing
in self care.
Is that our fault we were deceived as we didn't know??
I don't believe so.
Of course looking back on it anger can take hold.
And even Russ had merc fillngs in his teeth he didn't know
the truth about either.
Is that his fault??
I've had to live with guilt myself and if I could take it back??
I can't, so the most a person can do is warn others and get the message out.
Of what we do know now.
About the merc fillings and the merc vaccinations.
Hope your feeling somewhat better Margretto..
I have to deal with two children with autism.
A like cured case of hyperacusis and low grade tinnitus.
And 8 backteeth fillings and then the thought of a loud drill.
I don't think you know how a case of hyperacusis feels.
Talk about unfair blame them.
They did this to us..
Russ is just getting the word out he must be angry as well.
He had to live it too..
Take Care..
I hope your feeling somewhat better..
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Joined: Apr 2007
Posts: 2,153
Master Elite Member
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I found an honest dentist in a low income neighborhood and simply had them extracted a while back.. those rear amalgam loaded since I was a kid molars.
It cost me a grand total of $160.00 for 5 teeth. He did a good job.
Extraction was the only method of repair on those teeth I felt could trust a dentist with.
I do not miss them they were really old, almost as old as me ;), and were causing me a lot of suffering off and on.
This dentist was great he said 2 sentences to me...
- How many are we taking out?
- Which ones?
I laughed all the way home. What a relief. The idea of heading into the new economy, or lack thereoff, with those sick teeth frightened me to death almost. I took a friend last week to get 6 out. I am taking another next month.
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Joined: Jan 2008
Posts: 73
Senior Member
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What if....
you adamantly informed dentist of your extreme sensitivity to mercury
...insisted on and recieved a written estimate for white composits
paid that estimated price and recieved what you thought was the agreed on work
found thru visiting another dentist years later ((that he in fact had installed merc fillings where you could not see them(upper back teeth) even if you had thought to doubt him...
Friends are God's way of appologizing for family.
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Joined: Dec 1999
Posts: 30,867
Master Elite Member
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If the agreement was written, it would make a good lawsuit.
This kind of thing happens because people have not been made accountable in the past. It's time they become responsible for their actions.
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