Thanks to technological advances, dentists and patients now have several options when it comes to selecting materials to fill cavities. Options include natural tooth-colored materials, such as resin-based composite fillings, and more traditional dental fillings, such as those made of metal amalgam.

The appearance of new materials for fillings has been beneficial, especially in terms of aesthetics, but it does not eliminate the relevance of traditional dental materials that are stronger, more durable and less expensive. These materials are best in situations where the restored teeth must withstand extreme forces resulting from biting, such as in the back of the mouth.

What is a dental amalgam?

Most people recognize dental amalgam fillings as silver fillings. Dental amalgam is a mixture of mercury, silver, tin, and copper. Mercury, which makes up about 50% of the compound, is necessary to bond the metals together and provide a strong, hard, long-lasting filling. After years of research, mercury remains the only element that can bind these metals together in a way that can be easily manipulated to fill cavities.

Dentists often prefer dental amalgam because it is easier to manipulate than other alternatives. Many dentists find amalgam stronger than resin-based composite fillings and therefore use amalgam for fillings in back teeth. Many patients prefer dental amalgam for the same reasons, plus its cost-effectiveness and ability to fill cavities quickly. It is estimated that more than one billion amalgam fillings are placed each year 

What are resin-based composite fillings?

Resin-based composite fillings are made from composites of ceramic and plastic. Since resins mimic the appearance of natural teeth, these fillings have been used on front teeth for years. However, when they first appeared, resin composites were not strong enough for use in posterior teeth, where high-pressure chewing and crushing require greater durability. 

In the last 10 years, technology has improved enough to allow the use of resin materials in posterior teeth. Still, many dental plans, do not cover resin fillings in teeth that are not visible when smiling, and many dentists choose not to use resins for one or more of these reasons:

Since the most durable resin material has been available for only a decade, resins have not stood the test of time in teeth where chewing and grinding cause extensive wear; by contrast, the durability of amalgam fillings is well documented: the average life of amalgam fillings is 8 to 10 years, but many last 20 years or more.

Amalgam is one of the best filling materials when dentists have to place them in areas of the mouth that are difficult to keep dry, such as molars (back teeth) or cavities below the gum line. Resin fillings must be placed in a specific environment; for example, the prepared tooth must be completely dry when the resin material is applied and hardens. Clinical experience has consistently shown that amalgam is still, for many reasons, the most reliable filling material for long-term, low-maintenance function. 

Resin costs more than amalgam, which can make the cost of the service higher than a comparable amalgam filling service

For these reasons, most dental health insurance companies pay coverage for resin fillings on teeth that are visible when the patient smiles.

ADA and FDA recommendations for fillings

Dental amalgam has a proven 150-year history as one of the safest, most durable, and least expensive materials used to fill cavities. Ongoing scientific studies over the past 100 years continue to show that amalgam is not harmful.

Much of the concern regarding the safety of amalgam stems from the use of mercury as a bonding agent. But when mercury combines with other materials in dental amalgam, its chemical nature changes and it becomes harmless. The amount of mercury that is released in the mouth under the pressure of chewing and crushing is extremely small and is not a cause for concern. In fact, it is less than the amount patients are exposed to through food, air, and water, and less than is released in patients who choose to have an existing amalgam filling removed.

The American Dental Association (ADA) maintains that dental amalgam remains a safe, affordable, and long-lasting option as a cavity filling for dental patients. The US Food and Drug Administration (FDA) does not recommend removal of amalgam fillings in patients who have them because this could cause further damage to tooth structure and pose other health risks to the patient.

It is best for the patient and dentist to decide what type of filling will be used, taking into account the size and location of the cavity, the patient's history, cosmetic concerns, and cost. Ask your dentist to discuss all the options available for dental fillings and to help you decide which alternative is right for you.