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Michael C. Goldman, DDS

BPA and Dental Composites - Are They SAFE ?

Bisphenol-A [BPA]
        and Other Estrogenic chemicals found
                in Dental Composite Fillings

.....there is no dental material known that has no known or suspected toxic potential!  They are ALL potentially toxic to some degree! But some are much worse than others!!!!

 

Sept. 2008

The Problem

Recently, many patients have become concerned and emailed me asking about the possible toxicity of dental composite filling / bonding materials.  There has been  concern that they may have hormone-like behavior. It has been reported that they contain "BPA" - bisphenol-A - which  is thought to act as an estrogenic substance and is said to  have endocrine-disrupting actions. 

There are many questions to be concerned about this. First, if used  in the teeth of very young children,  could it have a hormonal effect on their development? If used  in  women's teeth, could it  promote hormonal changes or even stimulate estrogen-sensitive cancers, like some types of breast cancers?  Could it have a feminizing [estrogenic] effect on men?  These are all fair and reasonable and scary questions!

Why is it important

In my practice, I see many patients that  want to get rid of their  silver-mercury [amalgam] fillings because they are concerned  about the potential toxicity of mercury. [ All amalgam fillings are one-half made up of mercury! ] There are other articles on this site more about  amalgams and mercury.  When amalgams are removed the most common material used to replace them is "composite", which is basically a hard plastic material filled  with tiny, powdered, tightly packed, granules of ground up glass, porcelain, quartz, silica and other materials to  give it the color, hardness, and toughness it needs for a particular type of filling application.

People that are concerned enough about  the toxicity of mercury to have their fillings removed and replaced, certainly don't want to get rid of one toxic material, just to have another different one put in, right? Right!

 

I have been looking at the research literature to try to get a handle on this difficult question.  The ADA and other organizations  tend to say "don't worry, it's fine".... but they have also been saying that about the mercury in amalgam for a hundred and fifty years, so who  do we  believe?  In looking at the literature and hearing information at  continuing education courses,  I have begun to feel more comfortable with some general conclusions, which I will try to share here.

Present Situation

The present situation as I see it is this.  With possibly one exception that I know of, all composite filling / bonding materials are just about the same chemically.  They may differ a little here and there for several reasons but their basic chemistry is very closely related to each other.

Now, having said that, I have to add this.  Composites are basically  "plastics" as far as their chemistry goes, and "plastics" are very complicated.  They are also all around us, used in almost everything we see, touch, and use every day in one form or another.  The cars we drive - that used to  be made of steel - are almost half made of plastics now!  and so it is from our expensive filtered water bottles, to our iPhones and computers, from our baby bottles and toys to the lining inside the  cans of food we buy at the market.  To AVOID plastics in this day and age, is almost impossible ....you'd  have to work very hard at it, indeed!

The problem  with plastics being "complicated" is that the industrial processes that are involved in making them are also very complicated and complex. Many steps are involved and depending on the degree of "quality control" used in the manufacture of them, there may be more or less "impurities" produced and left in them.  Impurities are undesirable chemicals that were never meant to be in there but are accidental by-products of complicated chemical reactions used to make the plastics.  Or they can be undesirable  by-products that are expected and known about,  but not  adequately and completely enough removed.  You  could  almost think of it as the process of planting a lawn.  If  you do it carefully, using  good seed and dirt and fertilizers and good technique,  you  get a  good thick  lush lawn with no weeds.  Do it less carefully and you get weeds, brown, bare spots and so on. Still a lawn, but not nearly as good.

The other problem with it being complicated that I think of is that there are many complicated chemicals produced by the reactions so that the chemistry is much  more than just what is mixed together in the beginning, because those things react with  each other and produce a whole bunch of other things, sometimes only temporarily and sometimes they  stay in there.   So when  we talk about "BPA" we are really talking about a long list of somewhat related but still different chemicals that differ slightly by brand and by quality control.....I hope I haven't just made it more confusing  than ever for you!

How to make Sense out of it All

I came across what I thought was  an interesting and informative research article   http://jdr.iadrjournals.org/cgi/reprint/83/3/222.pdf  that I will try to  highlight what I think are the  important points.

The authors of the paper state clearly that certainly "the release of estrogenic compounds from  composite is ...undesirable" . But they researched 24 popular composite materials to determine the level of BPA's in them and the makeup of that BPA and the estrogenicity of each brand of composite tested.

Compared to a "control" sample which  was not estrogenic and just used for comparison, they found  a significant range among the 24 composites. Six of them were much more estrogenic than the control and the others  were very close to or even less than the control.  Since the control was realistically "zero" the  slight variations must be, I concluded, due to slight inaccuracies in the technique or the instrumentation used to get the measurements.  Keep in mind that we are dealing here with EXTREMELY SMALL AMOUNTS of chemicals being measured.  Like trying to measure the length of a flea with a ruler!

Overall, they seemed to conclude that while more research  should be done, the results they  got, strongly suggest that the amount of estrogenic effect is VERY SLIGHT and probably negligible for humans. 

Other, older, studies had also shown that  the levels of BPA in composite were in the range of  a hundred times LOWER than what was thought to be acceptable exposure [by the Canadian government which  tends to be more strict  on such issues than in  the USA].

I would highly recommend looking at an article written for IAOMT -International Organization of Medical Toxicology - an excellent  organization  for dentists and physicians and researchers dedicated to non-toxic treatment.  They are into scientifically  verified procedures rather than "trendy, holistic-sounding but unproveable ideas.  http://www.iaomt.org/articles/files/files276/BPA%20review.pdf

 

What  Do I do?

First, studies like this one help guide me in the choices of which products I chose to buy and use.  It helps to verify what I have long thought that good name brand manufacturers tend to have  better  quality control.  Usually, but not always, they charge more for their products and it's worth it.  3M is one, but not the only, such good  company in my view.  Off-brand, generic, products, may be  just as good in some cases but there's a level of trust missing with them.  You never know who's actually making the stuff and it could change from month to month and still end up with the same label on it at the end!  We all remember the toys from China with the lead-paint !

Another idea that seems to make sense recently to me is that rinsing  well after getting a composite filling is a good idea because much of  the various BPA chemicals end up in your saliva and can be washed out. And while  spitting them down the sink is not the greatest  thing, it's better than keeping it in your mouth to be swallowed.

Luckily, research  shows that unlike the mercury in amalgam fillings, which is released constantly over years and years for as long as the amalgam is there, the BPA's and related  compounds are  released  mostly when the composite filling is first done and chemically or light cured [hardened] , and then drops off rapidly after that to almost nothing for the duration of the life of the composite filling. 

The Near Future

There is a lot of concern about composites and a lot of money to be made in the  making and selling of them by dental materials manufacturers.  Manufacturers are concerned about the public's anxiety about BPA and other possibly toxic ingredients and they are  aware of regulations limiting or banning it in this country and in other countries.  So I can't imagine it will be long  before they find a way  to make composites without these undesirable  compounds or with levels so low that they will be almost absent.

There is one composite, as I mentioned in the beginning, that is  claimed by many holistic dentists to have no BPA's.  It's chemistry is a bit different than all the others as far as I can tell, so perhaps it's true.  It is called Diamond Crown, Diamond Flow, Diamond Lite etc.   I have recently  gotten some  literature from the manufacturer [or perhaps it's just the distributor], and it looks very interesting.  I asked for  research articles and what I got was pretty old and not  really dealing with the questions discussed here.  I have not, unfortunately, been able to find reliable scientific research to back up the claim of no BPA made by many  of its supporters.  While they claim to be "non-toxic" they don't specifically mention BPA or the sub-chemicals resulting from BPA. 

Many "holistic" dentists claim it to be a fact  that the "Diamond" products are free of BPA and other  undesirable compounds; however, I  have found nothing in the literature to back up that claim.  That bothers me!

 

UPDATE 2009

There is a fairly new Composite material from a German  manufacturer Heraeus-Kulzer, called  Venus Diamond.  It claims to be totally BPA-free.  I wonder if they didn't buy the  "Diamond..." line of  products mentioned above and put a new name on them, but I'm not sure.   I have not used  the Venus Diamond composite.  I imagine it's  pretty good but I had a bad experience with Kulzer several years ago when I used another composite product they promoted heavily and it  seemed to be great, but it turned out to be pretty bad!  So I have  very limited  confidence in Kulzer even though they are a large major manufacturer of dental materials.

2011

As far as I can tell now, the Kulzer Venus Diamond is not at all related to the Diamond Crown, Diamond Flow, Diamond Lite  [mentioned above] materials made by a Canadian  manufacturer, I believe.  I'm not sure if the Kulzer products are bpa free but searching the  MSDS sheets does not  indicate any bpa that I could see.  The Canadian  Diamond Crown, Diamond Flow, Diamond Lite composites are, I believe totally free of bpa because they are based on a very different chemistry.  They are phenolic plastics, whereas the American and European composites seem to be methacrylate plastics.  I hope that's helpful and not more confusing!  Then there's the question of whether phenolic plastics pose a different kind of possible toxicity?  Generally speaking phenolics are not good things but perhaps it  it's ok in this form.

 

If you  know of what looks like a reliable research article that shows the Diamond line of composite materials - or any other composite product for that matter - to be  free of potentially toxic compounds, please  email that info to me so I can share it with others!!!!

UPDATE October 2012

With considerable interest from you, the readers and followers of my website,  I have tried to keep up with changes in the dental composite technology.  I recently came across ESSTECH, a company that manufactures chemicals used in the manufacture of dental composite.  They have a patented BisGMA that, apparently is sold to dental manufacturers.  They claim that their BisGMA is different from others in that it  releases so much  less bpa than other BisGMA's that composites using their BisGMA is "considered to be essentially bpa-free".

I asked them which composites use their BisGMA, and they told me the line of ULTRADENT Composites use it and therefore are considered bpa-free.  ULTRADENT makes several composite materials which you  can look up since each has a different name and a slightly different  suggested use.   www.ultradentdental.com

This makes it confusing because when I look up the ingredients for  a composite material, if I see it contains BisGMA or similar chemistry, I have always assumed it has bpa.  So, maybe this changes things.  I'm not absolutely sure at this point but it seems interesting and worth  keeping an eye on.

 

 
   

In Conclusion

It seems to me, as I have stated  many times in other articles on this website [which I strongly  encourage you to read], that there is no dental material known that has no known or suspected toxic potential!  They are ALL potentially toxic to some degree! But some are much more so than others!!!!  So while there are some legitimate concerns about specific ingredients in composite filling materials, it does seem to me that while there is  some risk, that risk appears to be VERY SMALL when  viewed in its proper context and when compared to other materials  available to use. 

An exception to this statement might be that there may be some people that could have specific - and unusual - allergies to, or hypersensitivity to the specific chemical compounds found in dental composites. That would not apply to most of us.

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March 2013 update

As I have expressed above,  quality control in the manufacture of composite material seems to me to be crucial in limiting the undesirable by-products and contaminants in the end process of what is a very complex set of chemical  reactions and processes.  That is why I believe it is  so important to stick to reliable solid manufacturers that have a good track record of quality control.  There are many "generics" out there  sold by dental suppliers that could be made  one month by a factory in the USA and the next month in a factory in China or Mexico where the quality control might be better or worse.  All of them would likely have the same labels and MSDS sheets.  A recent lengthy article seems to me to support the idea that quality control is perhaps the key factor in keeping the BPA to a minimum or even absent in the final product.  It's a bit much to read but I know some of you want as much information as possible.

July 2013 update  

The Kulzer composites Venus Diamond, Venus Pearl and, I believe, Venus Diamond Flow are all supposedly based on a different chemistry using Urethane instead of the common methyl methacrylate used in just about all other composites as far as I can tell.  As a result of this, Kulzer claims  these composites are completely bpa-free. 

Bisphenol A in Dental Materials
Stephen E. Gruninger, Amer Tiba, Nina Koziol


 

The issue. The controversy about Bisphenol A (BPA) and its potential impact on health and human development received increased media attention in the past year. Headlines have linked BPA to heart disease, coronary artery disease, obesity, diabetes, and immune system and reproductive disorders. 

BPA is a common component used to make polycarbonate plastic and epoxy resins. Polycarbonate plastics are found in countless everyday items such as food and beverage containers, eye glasses, cell phones, bike helmets, children’s toys, plastic tableware, some types of receipts, self-adhesive labels and a host of other consumer products. Epoxy resins are often used as protective coatings inside metal food cans. The primary source of exposure to BPA for most people is assumed to occur through the diet1 although industrial and household wastes released into the environment are other sources. 

BPA, which has been used in consumer products since the 1960s, was used in the manufacture of some dental materials.2-4 Dental sealants were identified in 1996 as a source of very low-level BPA exposure5 and a recent study published in the Journal of the American Dental Association reports that “placement of resin-based composite restorations was associated with detectable increases in saliva of BPA and other study compounds within one hour after restoration placement and increased concentration of BPA in urine nine to 30 hours after restoration placement.”6

Some manufacturers of dental composites and sealants market their products as “BPA-free,” yet some studies have detected BPA in the saliva of patients within minutes following placement. BPA-free usually means that no BPA is added to the product, or that residual BPA is below the detection limit of the analytical method used to make the claim.

So, why would BPA appear in “BPA-free” dental materils?

Composite restorative materials are made from a mixture of ingredients where bisphenol A glycidyl methacrylate (bis-GMA) is the major component. BPA is a critical starting material used to manufacture bis-GMA and many other methacrylates used in sealants and bonding materials.

Looking at the structures of BPA and estradiol (Fig.1) you will find similar features between the two compounds that impart at least some ability for BPA to bind to mammalian estrogen receptors.5

Bis-GMA is an extremely viscous material making inclusion of polymerization initiators very difficult without adding modifiers to change its handling properties. An example of one of these modifiers is bisphenol A dimethacrylate (bis-DMA), which, when mixed with bis-GMA, reduces viscosity sufficiently to allow the addition of stabilizers and polymerization initiators resulting in a homogeneous mixture that is easily handled. BPA also is used to synthesize bis-DMA. 

Materials containing bis-DMA can release very small quantities of BPA after coming in contact with salivary enzymes (esterases) (Fig.2).7

Several alternative aliphatic viscosity modifiers often are used instead of bis-DMA. One of these alternatives is TEGDMA, which is not synthesized from BPA, nor does it decompose to BPA (Fig 3).

Materials made with bis-GMA do not undergo esterase hydrolysis.7 Sealants, bonding agents and composite resins developed with bis-DMA and/or bis-GMA may contain trace amounts of BPA as a byproduct of the manufacturing process. Careful formulation during the manufacturing process for bis-GMA keeps the unreacted levels of BPA to a minimum, but some residual trace levels of BPA can remain. Manufacturers of materials containing dental resins do not manufacture bis-GMA themselves. Bulk bis-GMA is purchased from at least 22 worldwide suppliers of bis-GMA.8 Four suppliers are based in the United States, 11 in mainland China, three in Hong Kong, three in Germany and one in the United Kingdom. It is unknown how well residual levels of BPA are controlled among these manufacturers.

Polymerization of bis-GMA containing materials involves free-radical chemical reactions. Oxygen in the air interferes with this process causing incomplete polymerization at the bis-GMA/air interface. Thus, any newly placed restoration or sealant will have a thin surface layer of incompletely polymerized material, which is rapidly lost within hours post-placement. This could be the reason that the Kingman study6 detected higher levels of composite components (including BPA as well as bis-GMA) in saliva and urine after placement than before placement. However, as in other studies, component release became significantly reduced or undetectable within hours,6 and exposure to these substances seems to be acute, not chronic.

What level of BPA exposure produces harmful effects in humans?

This is a key question and the subject of active research today. A decade or more ago, several studies showed that clinical levels of BPA in various body fluids were transient and rapidly fell below the detection limit of 1.0 to 5.0 ng/mL (1.0 - 5.0 ppb) by the high pressure liquid chromatography (HPLC) methods used at that time. However, a proliferation of subsequent studies using more sensitive liquid chromatography/mass spectrometry (LCMS) analytical methods reduced BPA detection limits to 0.02 ng/mL (50 times lower). The more sensitive methods appeared capable of detecting BPA at significantly lower levels than the earlier methods. Furthermore, other studies implicated dental resins as a potential cause of harmful effects such as neurobehavioral disorders9 or obesity in children.10 In an apparent response to concerns surrounding potential harmful effects of dental resins, many dental resin manufacturers have stated that their product contains no detectable level of BPA. However, manufacturers often do not state the detection limit or the analytical method employed. Any dental material made with bis-GMA potentially can contain trace levels of BPA.

The fact that the presence of a perceived harmful material can be detected does not mean the material is harmful at that detection limit. More than 500 years ago, a German physician, Philippus von Hohenheim, better known as Peracelsus, stated:

“All substances are poisons; there is none which is not poison. The right dose differentiates a poison from a remedy.”11 

In other words, the dose makes the poison. This is an extremely important concept that the dental professional always must be mindful of when evaluating studies or reports claiming that a toxic substance was found in a dental material.

Patients may be alarmed by media reports of environmental exposure to BPA from a multitude of common items, and the media reports usually mention dental materials in the same breath. 

Acceptable BPA exposure limits are:

EPA:12 <0.05 mg/kg body weight/24 hours, which is the same as <50,000 ng/kg/day

Thus for a 70 kg man = 3.5 x 106 ng/day, and for a 10 kg child = 0.5 x 106 ng/day 

The National Toxicology Program (NTP)17 

suggested: 10,000 ng/kg/day

The recent Kingman study6 measured BPA concentrations in the saliva of study subjects before and after placement of a composite resin restoration. Salivary concentrations of BPA should represent the highest measurable indicator of BPA exposure from composite resin, since saliva is in direct contact with the resin. Salivary concentration should thus be a good indicator of exposure. Salivary BPA measured before placement accounts for any BPA exposure from pre-existing sources and serves as a baseline level. Subtracting the BPA concentrations following placement is an indicator of the amount of BPA originating directly from the composite. 

Geometric means were calculated for three sampling periods post-placement: 0-1; 1-8; and 9-30 hours. The geometric mean average of BPA in saliva within the first hour of placement was 0.21 ng/mL. Following composite placement from one to 30 hours, BPA was not detected in saliva at levels above baseline.6 This indicates that BPA exposure from composite placement is very short and does not persist in saliva in detectable amounts after 60 minutes.

Therefore, these data suggest that the estimated oral BPA exposure from one composite resin restoration over 24 hours is 0.00875 ng/mL saliva/hour. A nanogram is one-millionth of a mg. If we assume average saliva production of 0.5 mL/minute or 30 mL/hour, and an average body weight of 70 kg for each study participant, then the BPA exposure following composite placement is about 6.3 ng/70 kg within the first hour. Since salivary BPA levels were not significantly different from pretreatment baseline levels after one hour and up to 30 hours post-treatment, the average adult daily dose of BPA from one composite resin restoration was 6.3 ng. Another study looked at BPA in saliva following sealant (no bis-DMA) placement in adults. Analysis found an average of 0.32 ng/mL of BPA in saliva immediately following treatment, and essentially no BPA was detected in saliva in excess of pretreatment levels one hour after placement of sealant on an average of six teeth.13 

The above two clinical studies show that BPA exposure from current bis-GMA based composites and sealants is more than 500,000 times lower than the EPA acceptable daily exposure limit for adult humans. If the more conservative NTP exposure limit is used, then BPA exposure from one composite is more than 100,000 times lower. The margin of safety is several orders of magnitude lower than either exposure limit. Trace levels of BPA from dental resins do not appear to present a health hazard based on current exposure limits, especially when one considers that the exposure predominantly is acute only during the first hour post-treatment.

Urethane modified methacrylate restorative resins (UDMA) are available and are not manufactured from BPA (Fig. 4). However, their use as a bis-GMA resin alternative is limited because they do not develop equivalent stiffness and hardness characteristics as bis-GMA based restoratives.14 Consequently, use is restricted primarily to low-stress surfaces. 

Some earlier studies in rodents suggested significant harmful reproductive effects from very low levels of BPA exposure, much lower than the EPA acceptable level, and may have raised concerns that similar exposure levels could have the same effect in humans. However, recent studies have challenged that notion by showing that primates metabolize ingested BPA differently from rodents. Newborn monkeys were found to have a high capacity for inactivating BPA in contrast to newborn rodents. Blood levels of equivalent BPA exposures were found to be 10-fold lower in rhesus monkeys than in rats and mice.15 Another study showed that people who ingested high levels of BPA in their diet did not show high levels of BPA in their blood, which supported findings in the primate studies.16

Despite an absence of documented adverse health risks related to these dental materials, some patients may be concerned. Nevertheless, the benefits of composite resin materials for restoring oral health and preventing caries is well established, while any health risks from their use is not. In 2007, the U.S. Department of Health and Human Services stated that, “Dental sealant exposure to bisphenol A occurs primarily with the use of dental sealants [containing] bisphenol A dimethacrylate. This exposure is considered an acute and infrequent event with little relevance to estimating general population exposures.”17 Furthermore, the medical community continues to support the use of resin-based dental materials based on their proven benefits and brevity of BPA exposure.18

(Editor’s note: A future issue of the ADA Professional Product Review will feature “An Evaluation of Bisphenol A found in Dental Materials,” in which we will report ADA Laboratory test results of BPA and bis-DMA levels from a variety of dental composites, sealants and bonding materials. Although these data will not use human subjects, they will give insight to the potential patient exposure levels of BPA from known amounts of product resin.) 

ABBREVIATION KEY Bisphenol A (BPA): A chemical produced in large quantities for use primarily in the production of polycarbonate plastics and epoxy resins. Bis-GMA: Bisphenol A-glycidyl methacrylate. Bis-DMA: Bisphenol A-dimethacrylate. TEGDMA: Triethylene glycol dimethacrylate. UDMA: Urethane dimethacrylate.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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This article was written in the hope that it will increase understanding about a topic that seems important from time to time. Obviously it is only a part of the whole story, so if you have questions after reading this please do not hesitate to ask or email. Also, if there is a topic that you think would be helpful, please suggest it. Does this help you? Let me know.

Michael C. Goldman DDS

General and Cosmetic Dentistry
3815 East-West Highway
Chevy Chase, Maryland 20815

Phone (301) 656-617

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More info about the following is available  if you select  "topics".

Holistic dentistry is an approach to dental treatment, primarily  caring for  patients' health and safety from both a conventional as well as  "alternative healthcare" point of view.   It is sometimes called "biological" dentistry or "biocompatible" dentistry.  In it's fullest sense, I believe it   acknowledges and deals with  the mind, body and spirit of the patient, not just his or her "teeth".  See Topics / Info.....

Cosmetic dentistry is about doing   quality , esthetic dentistry in a way that looks natural to begin with, and furthermore,   can even  improve  one's  attractiveness through techniques such as bonding, bleaching, veneers, caps, implants and more.  It can   be like "instant orthodontics" in correcting  crooked, twisted or misplaced teeth in many instances.  Dark or misshapen teeth can be restored.   Smiles that lack youthful vigor or beauty can be revitalized! See Topics / Info..

In holistic dentistry there is an effort  to find  biocompatible materials to use to reduce toxicity for  everyone, especially the chemically sensitive.  Amalgam use is avoided   in holistic dentistry (" amalgam free" or "mercury free") due to concern about possible toxicity problems.  Amalgam removal  and replacement with natural-looking bonded materials is a common holistic dentistry treatment as well as a common cosmetic dentistry  treatment.   Detoxification, especially of residual mercury deposits in body tissues from amalgams is often done.  Root canals are controversial  in holistic dentistry and are discussed under topics.  And much more....

Bleaching, veneers, bonding, caps, bridges, and implants  are cosmetic dentistry treatments that are also  discussed in  Cosmetic Dentistry, and more...located in the Bethesda, Chevy Chase, Maryland 20815 area near Washington DC.

 

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