Out with the Old Fillings, In with the New

Dentists are routinely asked by patients whether or not they need their metal fillings replaced and also make recommendations to patients to remove these fillings for different reasons. Dental amalgams, or “silver” metal fillings have been used to restore cavities for hundreds of years. Amalgams are alloys composed of mercury, silver, tin and copper. It is the roughly 50 percent mercury content that is of concern for many. In recent years, the use of these fillings have come under intense scrutiny, both internationally and domestically, due to environmental and health concerns to the point of being banned in several countries.

Amalgam fillings were an excellent material choice before modern alternatives had been developed. They are simple to place, relatively inexpensive and can last decades. The newer option of composite fillings, or white fillings, had limited success initially because they shrank significantly during curing, which led to sensitivity and failure. They also couldn’t withstand the heavy forces of chewing and would leak after just a few years. With research and development, however, they have become the dominant choice for most dentists and now have excellent longevity when placed with sufficient technical skill. Dentists can be more conservative with tooth structure removal, and most patients find them more appealing. White fillings do not typically last as long as the metal fillings do, but the factors of concern over metal fillings have led to their sharp decline.

These days, trying to filter fact from opinion is a challenge, but what is not disputed is that the mercury in dental fillings has had a significant environmental effect. Studies cited by the U.S. Environmental Agency have shown that as much as 40 percent to 50 percent of waste water mercury contamination may come from dental sources. Environmentally conscious offices install separators that remove most of the mercury from wastewater, but this is a more recent development and not all offices adhere to new guidelines.

What is far more controversial is whether the mercury contained in these fillings poses health risks to individuals. Sources of information range from anecdotal experience to rigorous studies. Perspectives vary widely, and discussing these factors with a dentist is the best advice. They can present their perspective and patients can then exercise their own judgment about the proper next steps.

In addition to the mercury factor, there are other properties of metal fillings which may impact a decision to remove them. Many people that have had metal fillings for decades may experience a cracked tooth, leading to a dentist placing a crown. There are many factors that lead to a cracked tooth, and the properties of metal fillings can indeed be contributors. Metal fillings are designed to undercut tooth structure to lock the filling in place. They are also very rigid, while teeth have some flexibility. Metal fillings also expand and contract differently than tooth structure, so cycles of temperature change over decades can put internal stresses on the tooth. It is possible for these factors, then, to induce microscopic cracks that  grow over time, much like a crack on a windshield. If the cracks grow large enough, or connect with other cracks, that can lead to biting pain or even tooth fracture.

In regard to removing the amalgam, mercury in the fillings can be vaporized during removal, and the resulting exposure is a concern. Protocols have been developed to limit this exposure, but it is a factor to consider when debating removal. The other remaining question is what to replace the filling with. When a metal filling is small or medium and cracking is limited, the composite resins are excellent replacements. However, when fillings are large or extensive cracking is present, resin fillings aren’t strong enough to be long-term fillings.

Crowns are often recommended by dentists, but require removing significant tooth structure to make—usually most, if not all of the tooth enamel is removed. Technological advancements have given us a new option with considerable advantages—a porcelain onlay. In layman’s terms, it is like a partial crown, saving significantly more enamel than traditional crowns. If a dental office has their own in-office CAD/CAM technology such as CEREC, this can even be accomplished in just one visit. As an additional benefit with CAD/CAM technology, patients don’t have to deal with the goopy impression material and two weeks in a temporary restoration.

Not every patient should have all of their metal fillings out as soon as possible; some metal fillings can last for 30 to 40 years with little to no concern. But many patients have questions about these fillings and need some basic information on the dilemmas pursuant with their usage and removal. Individual needs and treatment decisions should be discussed with a personal dentist.

This article was originally featured in Natural Awakenings 2015.