A dental filling is a material used by dentists to restore the function and shape of a tooth damaged by decay or trauma. The process involves removing the decayed material and then filling the resulting cavity to prevent further damage. Historically, metallic options dominated restorative dentistry, but modern advancements have introduced a wide variety of non-metallic materials, offering more choices than ever before.
The Amalgam Answer
The material commonly referred to as “metal fillings” is dental amalgam, sometimes called “silver fillings.” Amalgam is a mixture of metals, with liquid elemental mercury making up approximately 50% of its weight. The remaining half is a powdered alloy primarily composed of silver, tin, and copper, sometimes with trace amounts of zinc.
The mercury reacts with the alloy powder, binding the particles together to form a strong, durable, and moldable material. This amalgamation process results in a material that hardens quickly and is highly resistant to the forces of chewing. Amalgam has been used successfully in dentistry for over 150 years.
Its durability is a major historical advantage, often allowing restorations to last well over a decade. This strength and longevity made it suitable for restoring large cavities in posterior teeth, such as molars, which bear the brunt of chewing pressure. Its relative ease of placement and low cost also contributed to its widespread use.
Non-Metallic Alternatives
A broad range of materials containing no metal are now commonly used to restore teeth, offering significant aesthetic and functional benefits. The most frequently used alternative is composite resin, a tooth-colored mixture of plastic and fine glass or quartz particles. This material is cured with a specialized light after being placed into the prepared cavity.
A primary advantage of composite resin is that it can be closely matched to the natural color of the tooth, making the restoration virtually invisible. Unlike amalgam, composite material chemically bonds directly to the tooth structure. This bonding helps support the remaining tooth and often allows the dentist to remove less healthy tooth material during preparation.
Other options include ceramic fillings, typically made from porcelain and known for their stain resistance and superior strength. These restorations are often fabricated as customized inlays or onlays in a laboratory. Glass ionomer cement is another tooth-colored material, primarily used for smaller restorations or in areas with less chewing force. Some glass ionomer materials also release fluoride, which helps protect the surrounding tooth structure from further decay.
Addressing Safety Concerns
The primary concern associated with dental amalgam stems from its mercury content. A small amount of elemental mercury can be released as a vapor from the filling over time, particularly during actions like chewing or brushing. While exposure to high levels of mercury vapor is harmful, the vapor release from amalgam occurs at low levels.
Major public health organizations, including the U.S. Food and Drug Administration (FDA) and the World Health Organization (WHO), have consistently concluded that dental amalgam is a safe and effective restorative material for the general population. The amount of mercury vapor released is considered below the level that causes adverse health effects in most people.
The FDA has advised that certain vulnerable groups may benefit from avoiding amalgam when possible, due to potential increased sensitivity. These groups include:
- Pregnant women.
- Children.
- People with pre-existing neurological conditions.
- Those with known heightened sensitivity to mercury.
Overall, the consensus among regulatory bodies is that for the vast majority of people, scientific evidence does not show a link between amalgam fillings and systemic health problems.