What Are the Effects of Dental Amalgam on Humans?

Dental amalgam has been used for more than 150 years, and for much of that time it was considered a durable, practical material. However, over the past two decades, a more detailed understanding of mercury exposure, environmental behaviour, and systemic effects has emerged. Importantly, many governments and scientific bodies now take a precautionary approach—not necessarily because amalgam is conclusively harmful for everyone, but because safer alternatives exist, and the environmental burden of mercury is significant.

Below is a balanced, evidence-based summary of what is currently known.

1. Mercury Release: Low But Constant Exposure

Amalgam is approximately 50% elemental mercury.

All scientific reviews acknowledge that amalgam releases small amounts of mercury vapour continuously through:

• Chewing

• Grinding

• Thermal stimulation (hot drinks, etc.)

• Corrosion and ageing of the filling

• Polishing or removal procedures

The key issue is this: mercury vapour is readily absorbed through the lungs, and long-term exposure—especially from multiple or large restorations—adds to total body burden.

The debate is not whether mercury is released (it is), but whether chronic low-level exposure has clinical significance in different types of individuals.

2. Known Effects in Sensitive or High-Exposure Groups

Clinical research has consistently shown that certain groups may be at higher risk from mercury exposure:

Pregnant women and developing foetuses

Mercury crosses the placenta and concentrates in foetal tissue. This is why many countries banned amalgam use in pregnant women years before the full phase-out.

Breastfeeding mothers

Small amounts of mercury can pass into breast milk; again, most regulations advise caution.

Patients with documented mercury allergies

Although rare, some individuals develop true hypersensitivity reactions, including:

• Oral lichenoid reactions

• Dermatitis

• Mucosal inflammation

These cases respond well to replacing amalgam with biocompatible materials.

Individuals with kidney impairment

The kidneys are the main excretory pathway for mercury; impaired renal function can reduce the body’s ability to clear it.

Patients with large numbers of amalgam restorations

Higher cumulative exposure increases the total absorbed mercury load.

Important note: The evidence does not prove systemic disease for all patients, but it does show that certain groups have measurable biological changes or higher vulnerability.

3. Potential Systemic Effects (Still Being Studied)

This is where regulators apply the precautionary principle.

Studies have explored associations—not proven causation—with:

• Cognitive changes or neurobehavioural symptoms

• Memory changes or “brain fog” in high-exposure groups

• Tremors and fine motor changes (classically documented in occupations exposed to mercury vapour)

• Subtle immune system changes

• Changes in renal biomarkers

• Chronic fatigue–type symptoms in sensitive subpopulations

Large population studies have been mixed, which is why regulators do not claim amalgam is universally harmful, but they acknowledge:

Even small daily exposures accumulate over decades, and safer, non-mercury materials exist.

This is the real driver 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. Effects During Unsafe Removal

This is the most under-appreciated risk.

Improper removal can generate sharp spikes in mercury vapour exposure—up to dozens of times higher than normal background levels. This is why countries emphasise:

• Suction protocols

• Rubber dam isolation

• Air filtration

• Fragmented removal (not grinding the whole filling in one go)

At Nuffield Dental, these principles form the basis of our specific, structured protocols for safe amalgam removal.

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In Summary

Dental amalgam:

• Constantly releases small amounts of mercury vapour

• Poses higher risk to certain patient groups

• Has well-documented local tissue effects

• Contributes significantly to environmental mercury pollution

• Can cause clinically relevant exposure during unsafe removal

• Is now considered unnecessary due to newer, safer, biocompatible materials

This combination—not a single dramatic study—is why many regulators have shifted from “phase down” to complete phase out.