Dental amalgam has been used in restorative dentistry for more than 150 years. It has long been regarded as a durable and practical material. However, in recent decades, increased understanding of mercury exposure, environmental behaviour, and possible systemic effects has prompted a more cautious approach.
Many regulatory bodies now recommend reducing or discontinuing amalgam use, not because it is proven harmful for all patients, but because of its mercury content and the availability of effective alternatives.
Below is an evidence-based overview of current scientific understanding.
1. Mercury Release: Continuous Low-Level Exposure
Amalgam is approximately 50% elemental mercury.
Scientific studies confirm that small amounts of mercury vapour may be released through:
• Chewing and grinding
• Exposure to heat (e.g., hot food or drinks)
• Corrosion and ageing of the material
• Polishing or removal procedures
The key issue is this: Mercury vapour can be absorbed through inhalation. Long-term exposure, especially from multiple or large restorations, may contribute to the body’s overall mercury burden.
While mercury release is established, the focus remains on the clinical significance of chronic low-level exposure in individuals with differing sensitivities.
2. Sensitive or Higher-Risk Groups
Evidence indicates that certain populations may have increased susceptibility to mercury exposure:
✅ Pregnant women and developing foetuses
Mercury can cross the placenta and accumulate in foetal tissue, which is why many authorities advise against amalgam placement during pregnancy.
✅ Breastfeeding mothers
Small amounts of mercury may be excreted in breast milk; therefore, a precautionary approach is often taken.
✅ Patients with documented mercury allergies
Some individuals develop hypersensitive reactions like oral lichenoid lesions, mucosal inflammation, and dermatitis. These cases respond well to replacing amalgam with biocompatible materials.
✅ Individuals with kidney impairment
Kidneys are the main excretory pathway for mercury. Impaired renal function can impede the body’s ability to cleanse its system of it.
✅ Patients with numerous amalgam restorations
Greater cumulative exposure may occur in those with multiple fillings. Higher cumulative exposure increases the total load of mercury absorbed.
An important thing to remember is that while these findings do not conclusively prove systemic disease for all patients, they posit that certain groups have measurable biological changes or higher vulnerability.
3. Potential Systemic Effects
Studies have explored possible associations—though not proven causation—with:
Population-level studies remain inconclusive, which is why regulatory agencies apply the precautionary principle. However, regulators acknowledge that even small, daily exposures accumulate over decades and that safer, non-mercury materials exist. These are the real drivers behind global phase-out decisions.
4. Oral and Localised Effects
While systemic effects are debated, local effects are better established:
✅ Oral lichenoid reactions
These are white, inflamed patches in the mucosa adjacent to an amalgam filling. Removal of the amalgam usually resolves the condition.
✅ Galvanic reactions
Metallic taste or electric sensations can occur when different metals (e.g., gold and amalgam) contact each other in the mouth.
✅ Corrosion and marginal breakdown
Older amalgam oxidises and weakens over time, leading to microleakage, staining, and potential crack propagation.
✅ Structural weakening of teeth
Due to the cavity preparation design of amalgam, significant tooth structure is often removed, increasing the risk of cracks and future fracture.
5. Mercury Exposure During Removal
This is the most under-appreciated risk.
An improper removal of amalgam can generate sharp spikes in mercury vapour exposure of up to dozens of times higher than normal background levels. Safe removal practices help minimise this risk, including:
• Use of high-volume suction and rubber dam isolation
• Adequate air filtration and ventilation
• Sectioning amalgam into fragments rather than grinding continuously
At Nuffield Dental, these principles form the basis of our specific, structured protocols for safe amalgam removal.
In Summary
Current evidence indicates that dental amalgam:
• Releases small amounts of mercury vapour over time
• May pose a higher risk for certain populations
• Can contribute to minor local tissue reactions
• Has environmental implications due to mercury content
• Requires specific safety measures during removal
Many authorities have adopted a phased reduction in dental amalgam use, guided by the precautionary principle and the global move toward mercury-free dentistry.