what is the material that cavity fillings are made of and how does it remain so solid after setting?

Chief’s Domain -

Stupidium. (Also known as Duh.) Densest material in the known galaxy.

Years of hammering at it with the sharpest wits have not worn it away.

And there’s a never-ending supply of it too!

your humble TubaDiva
Sorry, attack of the sillies.

I assume that you’re not talking about gold fillings, but rather the silvery metal. It’s called amalgum. It’s an alloy (mixture) of several things, including mercury. This is of some concern to me, but my dentist has assured me that the mercury will stay in the fillings and not cause any problems.

As for why it stays in there… I have mostly repressed my memories of the dentist’s office, but IIRC, the amalgum was packed in with one of those bent-ice-pick-like tools. Apparently it has enough self-cohesion that it stays together inside the excavated cavity hole. Does anyone know if amalgum hardens or cures in any way?

“I had a feeling that in Hell there would be mushrooms.” -The Secret of Monkey Island

It’s amalgam, and they haven’t used mercury in it for about 20 years.

Uh, Nickrz, are you sure about that? For one thing, the main definition of “amalgam” is “an alloy of mercury with another metal or other metals” (and then it uses fillings as the example given).

Also, from the Quackwatch page on amalgam: "In January 1998, American Dental Association Council on Scientific Affairs issued a report on dental amalgam safety, with emphasis on studies that had been published since the 1993 review. The report concluded:

Millions of people have amalgam restorations in their mouths, and millions more will receive amalgam for restoring their carious [decayed] teeth. Over the years, amalgam has been used for dental restorations without evidence of major health problems. Newly developed techniques have demonstrated that minute levels of mercury are released from amalgam restorations, but no health consequences from exposure to such low levels of mercury released from amalgam restorations have been demonstrated. Given the available scientific information and considering the demonstrated benefits of dental amalgams, unless new scientific research dictates otherwise, there currently appears to be no justification for discontinuing the use of dental amalgam."

In other words, the ADA says they’re still being used…

(For the full article, go to – it deals with dubious claims related to mercury amalgams.)

Well, I had a roommate who was a dentist, and yes, the common amalgam used to fill teeth does contain mercury, though the dentist is in greater danger than the patient in problems this may cause. 1) Liquid Mercury metal is a chronic and not acute toxin. That means that it takes long term exposure to cause damage. 2) It is Mercury Vapors that is the problem. Mercury in its pure liquid form has a rather high vapor pressure, hense the danger. Mercury in an amalgum is “solid” and has no appreciable vapor pressure. 3) While the dentist in preparing the amalgam may be exposed to mercury in liquid form day-in and day-out for years of their life, your exposure (as a patient) is on the order of minutes. Once it is in the amalgam, it is perfectly harmless. Most dentists, for their own safety and to allay any (unnecessary) concerns of their patients, have switched increasingly cheaper methods of ceramics. Ceramics last longer, are safer, and are easier to “cure”. They are still marginally more expensive, but when the cost of less likelhood of needing a replacement are factored in, are cheaper and better in the long run.

Jason R Remy

“No amount of legislation can solve America’s problems.”
– Jimmy Carter (1980)