Dental amalgam, often called “silver fillings,” is a restorative material composed of liquid mercury and a powdered alloy primarily containing silver, tin, and copper. This material has a long history in dentistry, spanning over 150 years, making it one of the most studied filling materials available. The question of whether these fillings need replacement is a common concern, driven by the material’s composition and physical condition.
Understanding the Mercury Component
Amalgam is approximately 42% to 50% elemental mercury by weight. Once placed, the mercury is chemically bound within the alloy structure, but it can still release small amounts of elemental mercury vapor. This vapor release occurs at low levels and is slightly increased by activities such as chewing or brushing, as these actions create friction and heat.
Major health organizations conclude that mercury vapor released from intact amalgam fillings is not high enough to cause harmful effects in the general population. However, the FDA identifies specific groups more susceptible to mercury exposure. These include pregnant women, nursing women, children, people with neurological diseases, and individuals with impaired kidney function.
For these vulnerable populations, the FDA recommends avoiding new amalgam fillings, favoring non-mercury alternatives. Scientific consensus supports the safety profile of existing, intact fillings for the majority of adults. The primary concern is not the stable material, but the potential for increased exposure during placement or removal.
Criteria for Medically Necessary Replacement
The decision to replace an amalgam filling is often structural, relating to the failure of the restoration. Recurrent decay, or secondary caries, is the most frequent reason for non-elective replacement, requiring removal of the amalgam to treat the underlying tooth structure where bacteria have created a new cavity under the margin.
Another sign of failure is marginal breakdown, where the edges of the filling no longer seal tightly against the tooth, leading to leakage. This compromised seal allows fluids and bacteria to penetrate beneath the restoration. Amalgam can also expand and contract with temperature changes, and over many years, this cyclical fatigue can contribute to cracks in the surrounding tooth structure, necessitating replacement to prevent fracture.
Fractures within the filling material itself, or the loss of a portion of the restoration, also mandate replacement to restore the tooth’s function and contour. These criteria focus strictly on the physical failure of the restoration, making replacement a necessary dental procedure.
The Decision to Electively Replace Intact Fillings
If an amalgam filling is structurally sound, has tight margins, and shows no evidence of decay underneath, professional consensus advises against its removal. Removing a functional filling inevitably results in the loss of some healthy tooth structure.
Removing an intact filling is also associated with an increase in mercury vapor exposure for the patient and staff during the drilling process. The FDA and ADA recommend against removing intact amalgam fillings solely for preventing systemic disease or for general health reasons. Elective replacement is often considered by patients for cosmetic reasons, desiring a tooth-colored restoration.
Patients must understand that replacing a stable restoration can sometimes lead to complications, such as post-operative sensitivity or an inflammatory response in the tooth’s nerve. Therefore, the minimal risk from a sound, intact filling is often considered lower than the risks associated with an invasive removal procedure.
Removal Protocols and Alternative Materials
When an amalgam filling is removed, specific safety precautions are recommended to minimize mercury vapor exposure for the patient and staff. Key measures include:
- Use of a dental dam to isolate the tooth and prevent particle inhalation.
- Continuous high-volume suction near the filling to capture debris and vapor.
- Copious water spray to cool the filling and reduce vapor release.
- Use of a secondary air filtration system.
- Providing the patient with an alternative air source, such as a nasal cannula.
Once the amalgam is removed, the tooth can be restored with various materials. The most common alternative is composite resin, a tooth-colored plastic and glass mixture bonded directly to the tooth. Other options include glass ionomer cement or laboratory-fabricated restorations like porcelain or ceramic inlays and onlays, which offer excellent durability and aesthetics.