Silver amalgam and composite resin are the two most common materials used to restore teeth damaged by decay. There are situations where one material is preferable over the other, and similarly, there are disadvantages to both of these filling materials. Additionally, there are some health experts who question the safety of amalgam fillings and say they should not be used under any circumstances.

Silver amalgam—a health hazard?

The American Dental Association’s official position regarding silver amalgam is that it is a “safe, durable and cost-effective material that dentists have used in tooth restorations for more than 150 years.” But there are some practitioners who have expressed serious concern over the safety of amalgams, and the controversy over its use continues.

What is causing such concern?

It’s the fact that amalgam is composed of 35 percent silver, 15 percent tin or tin mixed with copper, a trace of zinc, and 50 percent mercury—a highly toxic heavy metal.

Anti-amalgam dentists point out that the amalgam releases mercury vapor when there is friction on the surface of the filling, such as when you chew. Mercury vapor is cyto-toxic, which means that it kills cells, even when the exposure is minute.

Mercury is absorbed through the lungs and into the arterial blood and is stored by your body, primarily in your kidneys, liver and brain. And no level of this mercury vapor is considered safe. However, the ADA counters that, once bound to the other metals, the mercury in dental amalgam is completely harmless.

While “it is highly unlikely that such small concentrations of mercury can or do harm the typical human, there is a remote chance that persons who have immunocompromised systems could have some negative influence from this mercury presence, or the presence of other metals,” said Gordon J. Christiansen, D.D.S., M.S.D., Ph.D. Also, those allergic to mercury should not have amalgam fillings placed in their mouths.

It’s important to note that no controlled scientific studies have been conducted that demonstrate ill effects to human health resulting from amalgam fillings. The evidence, to date, is all anecdotal. The World Health Organization has stated that it recognizes the importance of continued monitoring of the safety and effectiveness of all dental restorative materials, including dental amalgam.

Amalgam’s advantages

Silver amalgam is a more durable tooth filling material than composite resin in teeth that are subjected to a lot of biting pressure.

An amalgam filling costs considerably less than a comparable composite filling.

The disadvantages of amalgam

Silver fillings are less attractive than tooth-colored composite resin fillings; for this reason, they’re typically not placed in teeth located near the front of your mouth.
The mercury in amalgam fillings expands and contracts with heat and cold (think of the mercury in a thermometer). This can eventually cause the filling to fracture your tooth, so a crown will be required to restore its functionality.
Silver fillings will eventually corrode and leak, which can cause new decay to develop underneath the filling. The leakage can also give a gray appearance to the entire tooth.

Tooth-colored composite resins—the pros and cons

Resin fillings result in a natural-looking smile. The color can be closely matched to your natural teeth, so the restorations are nearly undetectable. And because the resin compound actually bonds to your tooth, the seal is tighter and the restored tooth can be even stronger than it was before.

Composite resin fillings can also be made much smaller than an amalgam filling used to restore the same amount of decayed tooth, so less natural tooth structure is lost. The durability of resin tooth-filling material has not been time-tested, but continual improvements in the product have made resins nearly as durable as amalgam fillings.

So where’s the catch?

In the cost. A resin filling costs about 150 to 200 percent more than a comparable silver filling. Most insurance benefits don’t cover the additional cost of composite fillings, so you must pay the difference.

Which to choose?

Overall, resin fillings are a more conservative treatment, because less of your natural tooth structure needs to be removed in preparation for their placement. They also do a better job of protecting your tooth in the long run, as there’s less chance that your tooth will fracture and require a crown in the future.

Ultimately, the choice is a personal one for both dentists and patients. Do amalgam’s benefits outweigh the possible risks? Are tooth-colored fillings worth the significant extra cost? Which filling material will prove to be most cost-effective in the long run? We recommend that you research your options, discuss them with your dental healthcare providers, and choose the filling material that’s right for you, based on what you’ve learned.