Whats the difference between these two? Is one silver colored and the other is whitish? I’ve noticed Amalgam fillings are about 20% cheaper than Resin but i don’t know why or what the real difference is.
Alright, i know an Amalgam is a silver/mercury filling while a resin is a tooth colored but what benefits does Resin offer over Amalgam other than aesthetics?
My dentist explained to me that silver fillings do not bond to the teeth: they remain in place by virtue of mechanical dovetailing alone. In contrast, resin fillings actually bond to the tooth. A silver filling offers no strength to the tooth and can act as a wedge and split the tooth; a resin filling can actually strengthen the tooth by bonding to the inside of the hole.
When I asked why not get all future fillings in resin, the technician told me that she only gets resin fillings from now on. If it’s good enough for her, it’s good enough for me.
That said, he put a beautiful resin filling in my very first root canal last year, and he is already wanting me to get a crown on that tooth. He says that root-canal teeth are more fragile.
Oh well.
Amalgam:
Silver amalgams are a concrete made of metal and mercury.
Many people are afraid of the mercury in the amalgam, but the mercury is locked into the amalgam. Body levels of mercury from fillings are miniscule compared to eating fish (even one tuna salad sandwich) and other environmental factors. In one hundred and fifty years of intense scrutiny, there is no credible indication of mercury in amalgam fillings causing health problems.
We are familiar with metal through alloys, but amalgam fillings are a metal with the properties of concrete. Concrete tends to break down at the edges (think concrete road after a hard winter). Eventual marginal breakdown in an amalgam may allow leakage and recurring decay.
Concrete requires a certain bulk of material so it will not fracture, so amalgams fillings must be a certain size, even if the actual cavity is much smaller.
Very few amalgams are bonded to the tooth (it raises the price… might as well use a resin), so undercuts and dovetails must be cut into the healthy tooth structure. Pins into the tooth may be needed to anchor the amalgam in large fillings. Also, because it is not bonded, but just packed into the hole, leakage can quickly reach deeply into the tooth.
The difference in thermal expansion and contraction between the metal and the tooth encourages this leakage. Amalgams are packed tightly into the tooth. This creates an outward wedging pressure from inside the tooth. Eating also tends to wedge the tooth apart. Years of hot and cold and eating may cause a constant flexing that eventually fractures the remaining weakened tooth.
Dental amalgams block x-rays. Most recurring decay is not found until it is way too late and too much damage has already been done. Undiscovered decay greatly increases the possibility of eventually needing a root canal or crown or extraction in a tooth with an old amalgam filling. If the tooth around a filling is dark, replace the filling.
The typical amalgam filling will be replaced in twenty years due to recurring decay.
Resins:
Resins are a composite. A Resin and a filler. They start out as a liquid (no filler) or putty and then solidify. Resin properties vary greatly by the fillers. The properties are constantly improving as our technology improves. In the Fifties, plastics were weak, now industrial composites are stronger than steel.
Liquid resins can flow into the smallest hole so only the decay and softened tooth must be removed. No bulk for strength, no undercuts and dovetails. Minimal tooth reduction.
Resins are bonded to the tooth. There is a layer of resin/tooth between the resin and the tooth…no gaps…less likely to leak, less likely for marginal fracture. A new resin filling or a resin patch can be bonded to an old resin and it becomes one resin.
The thermal expansion properties of resins become that much closer to the properties of tooth with each generation of resin. When resins harden they tend to shrink slightly. If handled properly, the bond is maintained and this inward pressure resists the wedging apart tendancy of eating.
The radiographic (x-ray) properties of resin are also becoming more tooth-like. It is somewhat easier to detect a cavity behind a resin filling.
Resins tend to wear slightly faster that tooth. This is also improving with each generation.
The typical resin will be patched in 15 years due to wear.
Resins are more technique and operator sensitive. There is a longer learning curve to reach optimal results. Resins require more patience and practice than amalgams. Choose a reputable dentist.
Do not let your pocketbook determine your choice. Wait a paycheck if you feel a resin is the way to go.
You don’t always get what you pay for, but if you don’t pay for it you aren’t going to get it.
The answer is not in the calculus of logic, but in the calculus of love.
Ronbo, what do you mean by “leakage?”
Leakage refers to saliva and dissolved sugar and bacteria getting inside the tooth. Bacteria can decay a tooth underneath a filling.
As sharp and pointy as those dental explorers are, they are absolutely humongeous compared to the gaps required for bacteria to get inside a tooth.
There are many experts on amalgam vs resin out there but be careful what you believe. Please consider this as my opinion. In many issues the almighty dollar prevails. I have personally heard many dentists say “I can’t afford to place amalgam fillings.” There is very little incentive for a dentist to place a filling of any kind that will outlast most anything else in dentistry. Every day dentists see many many 50 year old fillings. They hands down outlast resin and pay much less to place thereby reducing the income potential for the dentist. The increased costs of using resin is small per filling vs amalgam. I have wondered: where is some good data regarding durability of amalgam? Why doesn’t anyone do a study to see how long they really last? Well, who would do a study on an issue that has no income potential.
According to insurance companies the typical resin fills last 8 years, to support this they pay to replace fillings after only 3 years.
Resin is plastic, the ceramic part is tiny glass particles added to make it more wear resistant. Those particles never have been fibers as are imbedded in composites (filament wound) that are truly stronger than steel. Therefore composites (resin, plastics) in teeth will probably never approach the strength of steel, even after the 10 years difference between these posts. This remains true!
ALL fillings block x-rays therefore do not show decay through the x-ray. Even resin–if they did not dentists could not tell when they are failing on the bottom (near the center of the tooth). It is true they look more like tooth structure in the x-ray so barium (a metal) is added to block x-rays so they look a little more like amalgams. Because of this they too block recurrent (recurring) decay from view. However, since they still look more like tooth in an x-ray, add to that the fact that the bond layer itself has no barium so that bond layer appears as decay on the x-ray. therefore, decay is much harder to detect on an x-ray below a plastic fill. This is why it is easier to avoid further tooth structure loss with amalgam than resin. Resin fillings without barium look like decay on an x-ray. All modern resin fillings have barium in them.
Who bonds to a plastic (composite or resin) fill to patch it? No one! You would have to micro-etch it (miniture sand blast) then add a silane to adhere to the impregnated glass particles. Then you would only have mechanical adhesion not bonding. There is a layer on a plastic filling called the air inhibited layer, it is a “liquidy” layer that when polished, or chewed on is removed. Without this layer of material it is IMPOSSIBLE to bond to that fill. To claim to do so would be unethical! Very small repairs could be attempted with glass ionomer, which is NOT bonding. When composite fills need fixing they too should be replaced.
The major cause of resin failure is recurrent decay not wear. It is great to see resins last long enough to show wear.
Dovetail retention is indeed the retention of a silver amalgam fill there is no bond, no added strength to the tooth. Then why do they see all these 50 year old fillings? Why have they passes the test of time that the resins have miserably failed?
They seal themselves when the edges leak! They started to fail the day they were placed! That is the how they work. They seal by the corrosion by-products. They leak-seal, leak-seal, leak-seal, for decades until finally they fail just like the resins only they last longer. that is if there is enough tooth left to hold them. Temperature fluctuations do indeed stress teeth with amalgams so sufficient tooth must remain to do one. If not this leads to early failing amalgams. These should have been crowns but elected to cheat and try a fill. Amazingly even many of these last well beyond resins! Resins have an even greater need for tooth structure as the larger they are the sooner they fail.
Resin’s bond also leaks, and when they do they must be replaced quickly, they have no self repair mechanism.
Silver has antibiotic properties, mercury kills everything, together there must be some kind of bacteria resistance. It has been appears that the plastics do not. Perhaps the opposite. Plastics release formaldehyde and some suspect estrogen, mercury is metallically bonded to silver used in amalgams. So both are best avoided. Floss?
Don’t rely on the bond! Even with bonding to tooth structure a dentist should never rely completely on that to support a fill! It is far too weak to withstand the tremendous forces of chewing on the back teeth. Therefore, dovetails are indeed necessary for most plastic resins as well as amalgam. Though not as aggressively. Resins are indeed able to be kept smaller.
Silver looks bad and plastic looks beautiful!
Don’t confuse resin with porcelain. Porcelain restorations must be made outside the mouth then bonded with resin which bond is its weakness.
Resin or amalgam? You choose both are acceptable in this case you get what you pay for only counts in esthetics.
Resin has its place do not fear either use them as you prefer, but don’t avoid amalgam as being old fashioned. There still is not much to compete with it.
Remember if someone tells you something too good to be true be suspicious. Nothing exists that is better than the original tooth NOTHING lasts longer, look what happened to the original, it is only a matter of time before ALL fillings fail.
Moderator Note
Freedee, welcome to the Straight Dope Message Board. Please note that the thread you are replying to is over ten years old. We tend to refer to old threads that have been revived like this as zombies, so don’t be too surprised if you receive a lot of zombie jokes in response to your post.
We do allow zombies here, but we ask that you only revive threads when you have new information or something relevant to contribute. Your post certainly contains a lot of information, so it’s fine. However, be aware that due to this thread’s age, many of the original participants in this thread may no longer be around to view or comment on your reply.
Cite? I got my first filling 19 years ago when I was 19 and have had a handful more since. I’ve never had to replace one and I’d think I’d have heard more of my friends complain if they were replacing their fillings all (on average every 8 years) the time.
I don’t understand these posts that say amalgams last only 20 years. I have over half a dozen of those fillings for over 60 years.
Since we appear to be solidly into anecdata status here…
At my last appointment, I actually asked my dentist about my amalgam fillings. He said that the insurance company tracks the incidence of fillings failing in EVERYONE that they cover, and that they start covering the replacements when a statistically significant percentage (which he didn’t tell me) begin failing.
What this means, he said, is that all those people who don’t brush their teeth, and eat candy apples and popcorn and grind their teeth and chew tobacco and gargle with black tar coffee (you get the idea) are influencing the rates, just like other influences like genetic factors (bad genes mean bad teeth for some people) or geographic factors (hardness of your water supply, grit from sand).
So just because the insurance company says they’ll cover a replacement after a particular point in time, doesn’t mean you specifically as an individual will NEED a replacement by that point, if ever.
Besides, he said that unless it was a significant cosmetic detraction, he as a dentist will not remove amalgam fillings to replace them with resin because the removal is where the problems set in with mercury.
When mine fall out naturally (hoping for a long time for that, but I’ve got a long time to live still) then I’ll probably get resin just because it’s a better cosmetic match, and I’m vain, but then my fillings are not anywhere that people other than me and my husband will ever see them.
On the other hand, despite the expense, if I get a cavity on the front side of my front tooth, I’m getting resin even though it is more expensive, and even IF it fails more quickly. There’s no way I’m having a silver grille if I can avoid it, that’s for damn sure.
Although, hell, by the time the amalgam falls out for me/I get another cavity, they may be at the point they can just nick some of my stem-cells, grow more **tooth **and stick that in there. One can hope, right?
Get gold fillings.
Gold is the standard
Sorry, when I said failure I meant the good ol’ statistics of a bell shaped curve. Many last shorter and many last longer. I was speaking in averages. None last forever! No not one, but you may die before they fail. Unless of course your dentist is deity incognito. Some do have high opinions of themselves…
Amalgam is certainly not a perfect fit for all, but niether is composite. It would be a shame to see either eliminated from the options pool. There are some that want to see amalgam banned. This would be a loss to all. Remember it’s not mercury it’s amalgam. The two are different.
That’s not a cite, neither does it resolve the conflict with the observations I mentioned earlier. You made the claim that the “typical” resin fill lasts 8 years. Besides the question of the validity of that claim overall it raises several questions.
What’s a typical resin fill?
What’s the actual statistical distribution of failures? It can’t be a bell curve, since that’d be symmetrical around the average and 100% of fillings would fail within 16 years.
Wikipedia has similar numbers, but that article cites a single study on patients of a single dentist having “extensive” rather than “typical” fills.
Naita you’re brutal! And right… it must be a SKEWED bell shaped curve. You know what, i am sorry but I don’t know the standard deviation nor the variance, neither do I know the population size. I think they make a difference on the 100% failure don’t they? What I do know is that amalgam lasts longer… a lot longer… On the average. Plus they’re cheaper! Ok they are uglier.
Now my cite: heresay-- from a dental consultant scolding dentists for the short lived composites at a dental convention. The actuarial data is not really public–I can’t find it anyway. I do know that insurance companies do pay every 3 years for a new filling. If they weren’t paying for many they wouldn’t do it. I think that is disgraceful. Doesn’t that bother you? Now in all honesty they’ll pay for amalgams too. Just not as many (I suppose, hope, believe). I guess I can’t even cite that.
Again who really wants to know how long they last? Who will fund a study against amalgams? Where’s the return on investment? I haven’t seen it, neither do I expect to. There’s just no money in it. Now the ADA and the FDA both agree with me that amalgams last longer. My experience adds the “a lot longer” part.
Your questioning did make me think, “Did I bad mouth composites?”
Yes I guess so, not because I am against them but to try to illistrate the benefits of amalgam. I apologize for that, they are good and improving each year.
Please consider, no other medical device in US history has seen the use and the scrutiny that the amalgam has over the past 150 years. Niether, I think, has any been so slandered.
I have never heard anyone bragging about how long their composites last, but I have heard many say “These silver fillings are over 50 years old.” I ask you: What else can you buy and use 3 times a day and have last for 50 years? All right Naita, even 19 years! Is there really anything to compare?
I had better cite:
http://jada.ada.org/content/138/6/775.abstract
States that composites are 3.5 times more likely to develope secondary decay than amalgams.
Here is the conclusion of the American Dental Association:
"Conclusion. Amalgam restorations performed better than did composite restorations. The difference in performance was accentuated in large restorations and in those with more than three surfaces involved.
Clinical Implications. Use of amalgam appears to be preferable to use of composites in multisurface restorations of large posterior teeth if longevity is the primary criterion in material selection."
FDA website:
http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DentalProducts/DentalAmalgam/ucm171108.htm
Their conclusion:
"Disadvantages of composite resin fillings include:
May be less durable than dental amalgam and may need to be replaced more frequently
• Cost more than some other types of dental filling materials"
I’m not brutal, I’m just committed to fighting ignorance properly. 
Your JADA-cite is a great one for showing that amalgams are less prone to develop secondary decay, but looks poor for showing that the typical filling last only 8 years, since even with the higher rate of failure since only 15% of composite fillings had failed during the 7 years the study lasts.
It also got me thinking that people with poor dental hygiene will be over-represented in the basis for actuarial models. They’ll have more fillings, and with secondary caries being the most common reason for failure, they’ll have a higher rate of failure for those fillings. So looking at the average filling they might fail at the rate you mention, but if you clean your teeth properly you’ll not only need fewer fillings, but the ones you do need will last longer.
might the anti-bacteriological action of silver (and due to its lethality mercury) be useful on teeth?
I asked my young lass of a dentist about toxicity of filings and she said she would rather have a well proven silver filing than the less long lived epoxy anyday.