The term “silver fillings” refers to dental amalgam, a restorative material used in dentistry for over 150 years. This material is not made solely of silver but is a compound mixture of liquid mercury and a powdered alloy containing silver, tin, and copper. The presence of mercury, a recognized toxic substance, is the source of ongoing discussion regarding the safety of these fillings. Evaluating the potential health impact requires understanding its composition and the scientific consensus surrounding its use.
What Are Silver Fillings and How Safe Are They
Dental amalgam is composed of approximately 50% elemental mercury by weight, with the remaining portion being the powdered metal alloy. Mercury’s unique chemical property allows it to bind the alloy particles together, creating a strong, moldable, and durable filling material. Once placed and hardened, the filling releases low levels of mercury vapor into the mouth over time. This release is increased by actions such as chewing, brushing, and consuming hot liquids, which cause friction and temperature changes on the filling’s surface.
The elemental mercury vapor released from the filling can be inhaled, absorbed by the lungs, and subsequently enter the bloodstream, accumulating in organs like the kidneys and brain. Regulatory bodies, including the U.S. Food and Drug Administration (FDA), have reviewed the scientific evidence regarding this low-level exposure. The majority of this evidence suggests that the amount of mercury vapor released does not cause harmful health effects in the general population. Therefore, the FDA considers dental amalgam a safe and effective restorative material for most adults and children aged six and older.
Despite the general safety assessment, the FDA updated its recommendations to identify certain groups more susceptible to the adverse effects of mercury exposure. These vulnerable populations are advised to avoid new amalgam fillings and choose non-mercury alternatives. This group includes pregnant women, women planning pregnancy, nursing women, and their developing fetuses. Children under the age of six are also included due to their developing neurological systems.
Individuals with pre-existing neurological diseases, such as Parkinson’s or multiple sclerosis, or those with impaired kidney function, are also considered at higher risk. People with a known sensitivity or allergy to mercury or other components of dental amalgam should likewise opt for alternative materials. This regulatory caution acknowledges the uncertainties regarding acceptable exposure levels and the potential for mercury accumulation in susceptible patients.
Alternative Materials for Dental Restorations
A variety of materials are available today to restore teeth, offering alternatives to dental amalgam that prioritize aesthetics and biocompatibility. The most common alternative is composite resin, often called a tooth-colored filling, made from a plastic and glass mixture. Composite resins offer the advantage of matching the natural tooth color, making them the preferred choice for restorations in visible areas. They bond directly to the tooth structure, often requiring less removal of healthy tooth material during placement.
Composite resin fillings may not be as durable as amalgam, and they are more susceptible to wear and staining over time, particularly with exposure to pigmented foods and drinks. The placement procedure is also sensitive to moisture and technically demanding, requiring a longer chair time than amalgam. Another option is glass ionomer cement, primarily used in non-load-bearing areas or pediatric dentistry. A benefit of glass ionomer is its ability to release fluoride, which helps protect the surrounding tooth structure from further decay.
Glass ionomer is less durable than composite or amalgam, making it unsuitable for areas experiencing heavy chewing forces. For restorations requiring maximum strength and longevity, gold alloys or ceramic materials like porcelain and zirconia are often used. Gold is highly biocompatible and corrosion-resistant, often lasting for decades, but its metallic color is an aesthetic drawback.
Ceramic and zirconia restorations offer exceptional strength and aesthetics, as they can be precisely color-matched to natural teeth. These materials are typically used for inlays, onlays, and crowns, rather than direct fillings, and represent a higher initial investment compared to composite resin or amalgam. The decision between these alternatives involves balancing cost, cavity location and size, and the patient’s aesthetic preferences.
Considerations for Removing Existing Amalgam Fillings
Many patients with existing amalgam fillings wonder if they should have them removed as a precautionary measure. Regulatory agencies do not recommend the removal of intact amalgam fillings solely to prevent health issues. Removing a functioning filling is an invasive procedure that results in the unnecessary loss of healthy tooth structure. Furthermore, the drilling process generates a higher, albeit temporary, release of mercury vapor and fine particles.
This temporary spike in exposure during removal is a primary concern for the patient and the dental team. Removal is only recommended if the filling is failing, cracked, or if the patient has a documented hypersensitivity or allergy to the material. Patients belonging to a vulnerable population group who wish to minimize long-term exposure may also choose to have their fillings replaced.
For those who elect to have their fillings removed, specific safety protocols are employed to minimize mercury exposure. One method is the Safe Mercury Amalgam Removal Technique (SMART), which utilizes specialized equipment and procedures. This technique includes isolating the tooth with a rubber dam to prevent particle ingestion and using a high-volume suction system to capture mercury vapor and debris.
The patient is provided with an external air source through a nasal mask to ensure clean air, and the dental team wears protective gear. These precautions mitigate the risks associated with the removal process. Dentists also use water spray during drilling to cool the filling and reduce the mercury vapor released.