In "Amalgam, Politicians and all the Pink Trees" I briefly reviewed the historical and scientific history of dental amalgam, the ever-controversial restorative material that contains silver, copper and mercury in its modern formulations. At the present time the science indicates that, since a person's mercury exposure in the course of a day from silver amalgam fillings is between 1/10 and 1/100 of the total we receive from air, water and certain foods, then there are no serious concerns about mercury toxicity. (And that's if you have a lot of them in your mouth.) Keep in mind the crowded, industrialized society that many of us live in; mercury is given off in various forms from diverse industries, particularly in power generation from coal.
(It's all a trade-off, isn't it? I mean, I'm glad that this computer is running for me whenever I want it...)
Anyway as I sign and have patients sign these ridiculous forms from the City of Philadelphia, forms that explain "choice" in dental restorative materials and are really an anti-amalgam crusaders' Machiavellian tactic, I get to thinking on a daily basis how we need to talk about the other aspects of these metal nettles. You see, we don't place them in our office anymore for other, more enlightened reasons. Meaning: technology has provided us with better alternatives. For one, gold foil preceded dental amalgam, at least in the U.S. I understand that Paul Revere placed gold foil restorations during the time that he dabbled in dentistry. Composite resins had initial challenges but among us Composite Cognoscenti it's well known that these materials were refined into excellence in the late 1980's, and with the latest "self-etching primers" we can treat teeth in ways that remind us of Arthur C. Clarke's line that "Any sufficiently advanced technology is indistinguishable from magic."
Yet so many insist that amalgam lasts longer than composite resin, all things being nearly-equal. Well, I removed an old amalgam today, most recent in a long line of these little beasties, one with decay under it. Statistics are more important than anecdotal observations of course, but photos are so very visceral... So I took a shot of an amalgam in one of my staff (which we will be replacing shortly), then of the piece of material that I removed from my patient.
Amalgam does not bond to a tooth per se, but it seals- and it does this by corrosion. Little by little the corrosion occurs. It reaches the optimal point in about 2 years after placement. After that, it's all downhill. Yes, composite resins have their issues too. There's incomplete hybridization and collapse of the collagen net and transudation... But we can control all of that to an astonishing degree these days and it's only going to get better. Amalgam hasn't gotten significantly better since the manufacturers took the tin out and replaced it with copper in the 1970's. Anyway have a go at the corroded margins, or edges:
But this is my fav- like some kind of CSI-Amalgam officer, I removed a large piece en masse, polished the outer layer for comparison to clean metal, and photographed the inside of the material, the part that was up against the (decayed) inside of our patient's tooth:
The silver turns pretty thoroughly black, doesn't it? Yah, it's time for these things to go by the wayside. Recall- it's technology from 1833, with an eight, and that's being generous. We have better now. Yet- there's no dental or medical reason to remove dental amalgam restorations that are relatively new and functioning well, with no breakdown. It all depends on how they're doing.