An amalgam filling is a dental restoration composed of a mercury-based alloy — typically containing silver, tin, copper, and mercury — used to repair teeth affected by dental caries or fracture. It remains one of the most extensively studied and widely used restorative materials in clinical dentistry.
Composition and Setting
The alloy powder — a blend of silver, tin, and copper — is mixed with liquid mercury in a process called trituration. This produces a pliable mass that can be condensed directly into a prepared tooth cavity. As the amalgam sets through a crystallization reaction, it hardens into a strong, stable restoration capable of withstanding significant occlusal forces.
Clinical Significance
Amalgam fillings have been a cornerstone of restorative dentistry for over 150 years. Their durability makes them particularly well-suited for restoring posterior teeth — molars and premolars — where chewing loads are greatest. Key clinical attributes include:
- Longevity: Well-placed amalgam restorations can last 10–15 years or longer under normal function.
- Compressive strength: Amalgam withstands high biting forces better than many tooth-colored alternatives.
- Moisture tolerance: The material is relatively forgiving of a moist field during placement, unlike composite resin.
- Cost-effectiveness: Generally less expensive than ceramic or direct composite restorations.
- Self-sealing properties: Corrosion byproducts can help seal restoration margins and reduce microleakage over time.
Considerations and Alternatives
Despite their proven performance, amalgam fillings have faced increasing scrutiny due to mercury content. Regulatory agencies in several countries have restricted or phased out their use in children, pregnant patients, and individuals with renal impairment. Tooth-colored composite resin has become the preferred restorative material for many clinicians, offering clear aesthetic advantages and often requiring less removal of healthy dentin during cavity preparation.
Unlike adhesive composites, amalgam does not bond chemically to tooth structure — making adequate cavity preparation design, including mechanical retention features, essential for long-term stability. The dentist removes decayed tissue, shapes the preparation, and condenses the amalgam in incremental layers before carving the occlusal anatomy prior to final set.
Weighing amalgam’s durability and clinical track record against aesthetic and safety considerations allows both clinicians and patients to make well-informed restorative decisions tailored to each tooth and clinical situation.