Silver fillings, formally known as dental amalgam, have been a durable material for restoring decayed teeth for over a century. These restorations are well-known for their longevity and ability to withstand the intense forces of chewing, particularly in the back teeth. However, as these fillings age, and with the rise of new dental technologies, many people question whether their existing silver fillings should be replaced. While amalgam is a tough material, it is not immune to degradation, and the decision to replace it depends on factors like its structural integrity and individual health considerations.
Composition and Safety Concerns
Dental amalgam is a mixture of metals, approximately 50% of which is liquid elemental mercury. This liquid mercury is mixed with a powdered alloy composed primarily of silver, tin, and copper to create a putty that hardens rapidly after placement. The mercury binds the alloy particles together, creating a strong and stable filling material.
The inclusion of mercury has led to ongoing public discussion about the material’s safety, as the filling releases small amounts of mercury vapor over time, particularly when a person chews or grinds their teeth. Major public health bodies, including the American Dental Association (ADA) and the Food and Drug Administration (FDA), maintain that the low levels of mercury vapor released from set amalgam fillings do not cause harmful health effects in the general population. The FDA recommends that certain high-risk groups avoid amalgam when possible. These groups include:
- Pregnant women
- Nursing women
- Children under the age of six
- Individuals with pre-existing neurological diseases or impaired kidney function
When Clinical Failure Requires Replacement
The most common and necessary reason for replacing an amalgam filling is structural failure, not concerns about the material’s composition. Over time, the margins where the filling meets the tooth can break down, creating a tiny gap. This marginal breakdown allows oral bacteria and debris to seep beneath the restoration, leading to a new cavity known as secondary decay.
Another frequent reason for replacement is a fracture of the surrounding tooth structure. Amalgam does not bond directly to the tooth. As it expands and contracts with temperature changes, it can exert wedging pressure on the remaining tooth. This pressure can cause cracks to form, potentially leading to a tooth fracture or severe sensitivity. If an existing filling is compromised, or if a large portion of the tooth has fractured away, replacement is recommended to prevent further damage or infection.
Weighing the Risks of Removal
While a patient may elect to have a sound filling removed for aesthetic or personal reasons, the removal process carries risks that must be considered. Removing an intact filling involves drilling, which can inadvertently remove healthy tooth structure. This loss of natural tooth material can weaken the tooth, potentially requiring a larger restoration, such as a crown, in the future.
The removal process temporarily increases the release of mercury vapor, which poses a brief exposure risk to both the patient and the dental staff. To mitigate this, many dentists employ specific safety protocols: using a rubber dam to isolate the tooth, high-volume suction to capture debris and vapor, and providing the patient with an alternative air source. Health authorities generally advise that a structurally sound amalgam filling should not be removed solely to prevent disease, as the risks of the procedure often outweigh the benefits.
Modern Alternatives to Amalgam
When an amalgam filling must be replaced, several modern materials offer alternatives. Composite resin is the most common choice, offering a tooth-colored option that can be closely matched to the natural tooth, providing a significant aesthetic advantage. Unlike amalgam, composite resin bonds directly to the tooth structure, which helps support the remaining tooth.
For larger restorations, dentists often use porcelain or ceramic materials to create inlays or onlays. These restorations are fabricated in a lab and cemented into place, offering greater durability and resistance to wear than composite fillings. Gold remains an alternative for maximum longevity, as it is highly biocompatible and resistant to corrosion, though it is typically the most expensive option.