Mercury in Dental Amalgams: An In-depth Look

Dental amalgam, often referred to as "silver fillings," is a commonly used material for filling dental cavities. It is a mixture of metals, consisting of approximately 50% elemental mercury by weight, combined with other metals such as silver, tin, and copper to form an alloy.

Why Mercury Is Used in Amalgams

  • Binding Agent: Mercury is unique in its ability to bind the other alloy particles together, creating a strong, durable, and solid filling material when it sets.
  • Cost-Effectiveness: Amalgam fillings are generally less expensive than other restorative materials.
  • Ease of Use & Durability: It is relatively easy for dentists to work with and place quickly, and it has a long history of clinical use demonstrating good wear resistance, especially in the posterior teeth.

Risks Associated with Mercury Amalgam

A primary concern with dental amalgam is the continuous release of mercury vapor from the fillings. This release can be exacerbated by activities such as chewing, brushing, teeth grinding (bruxism), and the consumption of hot liquids. The inhaled mercury vapor is absorbed into the bloodstream and can accumulate in various body tissues over time.

Potential health risks include:

  • Neurotoxic Effects: Mercury is a known neurotoxin. Chronic low-level exposure has been linked to symptoms such as mood changes, anxiety, irritability, memory loss, and tremors in sensitive individuals.
  • Immunological Effects: Some individuals may experience allergic reactions or autoimmune responses to mercury or other metals in the amalgam.
  • Renal (Kidney) Burden: The kidneys are a primary route for mercury excretion. Chronic exposure can place an ongoing burden on renal function.
  • Developmental Concerns: Exposure in utero or during early childhood is of particular concern for neurological development.

Clinical Handling and Precautions

When dentists prepare dental amalgam for placement, the alloy powder is mixed with liquid elemental mercury using a mechanical device called a triturator or amalgamator. This process creates a pliable mixture that is then packed into the prepared tooth cavity. During this phase, specific precautions are necessary to reduce mercury vapor exposure for both the patient and dental staff:

  • Pre-measured Sealed Capsules: Modern dental practices use pre-measured, sealed capsules of alloy powder and mercury to minimize spills, ensure accurate ratios, and reduce direct handling of liquid mercury.
  • Enclosed Mixing: Trituration is typically performed in a closed chamber within the device to minimize the aerosolization of mercury particles.
  • Prompt Insertion: Amalgam is inserted into the cavity promptly after mixing, and any excess material is removed quickly to limit vapor release.
  • High-Volume Evacuation: Dental offices often use high-volume suction systems close to the operational field during both placement and removal of amalgam fillings to capture mercury vapor and particulate matter.
  • Amalgam Separators: Most dental clinics are equipped with amalgam separators in their wastewater systems. These devices are designed to capture amalgam waste and prevent mercury from entering the public water supply and environment.

Regulatory Stance and Public Health Guidance

  • FDA (U.S. Food and Drug Administration) (2020): While considering amalgam safe for most adults, the FDA issued updated recommendations advising against the use of dental amalgam in certain high-risk groups. These include pregnant women and their developing fetuses, women planning to become pregnant, nursing women and their newborns/infants, children (especially those under six years of age), people with pre-existing neurological diseases (like Alzheimer's, Parkinson's, or Multiple Sclerosis), individuals with impaired kidney function, and people with known allergies to mercury or other components of amalgam. [FDA Guidance]
  • European Union Regulation: As of July 1, 2018, the EU banned the use of dental amalgam for the treatment of deciduous teeth (baby teeth), children under 15 years, and pregnant or breastfeeding women, as part of the Minamata Convention on Mercury.
  • IAOMT (International Academy of Oral Medicine and Toxicology): This organization advocates for mercury-free dentistry and has developed specific protocols for the safe removal of existing amalgam fillings to minimize mercury exposure to patients and dental staff. [IAOMT Website] [SMART Protocol Overview]

Alternatives to Amalgam Fillings

Several mercury-free alternatives are available for dental restorations:

  • Composite Resins: Tooth-colored plastic and glass particle mixtures; aesthetically pleasing and bond directly to the tooth.
  • Glass Ionomer Cement (GIC): Tooth-colored material that releases fluoride, which can help prevent further decay. Generally less durable than composite or amalgam, often used for temporary fillings or non-load-bearing areas.
  • Porcelain/Ceramic Inlays and Onlays: Highly aesthetic, durable, and biocompatible. Custom-made in a lab and then bonded to the tooth. Typically more expensive.
  • Gold Inlays and Onlays: Very durable and biocompatible, but also more expensive and not tooth-colored.

Safe Removal Protocols (e.g., SMART)

Due to the risk of increased mercury exposure during removal, it is crucial that amalgam fillings are removed cautiously. The International Academy of Oral Medicine and Toxicology (IAOMT) has developed the SMART (Safe Mercury Amalgam Removal Technique) protocol, which outlines comprehensive measures to minimize exposure for patients, dental staff, and the environment. Key components include:

  • Use of a rubber dam or similar isolation device to prevent amalgam particles from being swallowed or inhaled.
  • Operation of a high-volume evacuation (HVE) system with a specialized tip to capture mercury vapor and particles at the source.
  • Providing the patient with an alternative source of air (e.g., oxygen delivered via a nasal mask) to avoid breathing contaminated air from the oral cavity.
  • Techniques to cut the amalgam into chunks for removal, rather than grinding it all away, to reduce the generation of fine particulate and vapor.
  • Use of copious amounts of water spray to cool the amalgam during drilling and reduce vapor release.
  • Protective gowns and covers for the patient, dentist, and dental assistant.
  • Use of activated charcoal, chlorella, or other adsorbent rinses for the patient before and after the procedure can be recommended by some practitioners to help bind any ingested mercury particles.
  • Adequate room ventilation and air filtration systems (e.g., mercury vapor ionizers/filters) in the dental operatory.
  • Proper disposal of mercury-contaminated items as hazardous waste.

IAOMT's full SMART protocol details specific equipment and procedures. More information can be found at iaomt.org.