What each material is
Dental amalgam is a metal alloy made of approximately 50% mercury combined with silver, tin, and copper. It has been used in dentistry for over 150 years and was the dominant restorative material for most of the 20th century. It hardens quickly, is extremely durable under chewing pressure, and is relatively inexpensive to place.
Composite resin is a tooth-colored restorative material made from a mixture of plastic (bis-GMA or UDMA) and fine glass or ceramic particles. It bonds chemically and mechanically to the tooth structure — meaning it doesn't just fill a cavity but actually adheres to it. It has been the preferred material for front teeth for decades and has become the dominant choice for back teeth in recent years as formulations have improved.
Head-to-head comparison
| Factor | Composite Resin | Dental Amalgam |
|---|---|---|
| Mercury content | None | ~50% by weight |
| Appearance | Tooth-colored, virtually invisible | Silver/dark, visible in mouth |
| Bond to tooth | Bonds directly (adhesive) | Mechanical retention only |
| Tooth structure removed | Less — only decayed tissue | More — undercuts needed for retention |
| Durability (molars) | Good; may need replacement sooner | Excellent; very long-lasting |
| Typical lifespan | 7–12 years | 10–20+ years |
| Sensitivity to moisture | High — requires dry field | Low — tolerates moisture |
| Placement time | Longer (technique-sensitive) | Shorter |
| Average cost per filling | $150–$400 | $80–$250 |
| Insurance coverage | Often covered up to amalgam rate | Usually fully covered |
| Thermal expansion | Close to natural tooth | Higher — can stress tooth over time |
When composite is generally preferred
- Front teeth and visible areas — aesthetics are a significant consideration
- Small to medium cavities — composite performs very well and the bonding preserves more tooth structure
- Patients avoiding mercury — those who prefer not to introduce new amalgam for any reason
- Teeth with existing cracks — the bonding quality of composite can help stabilize a tooth
- Children and pregnant patients — per FDA 2020 guidance, composite is preferred for these groups
When amalgam may still be considered
While composite has become the dominant choice, there are still clinical situations where some dentists consider amalgam:
- Very large posterior restorations under extreme chewing pressure where composite has historically had higher failure rates
- Difficult moisture control — composite requires a very dry field to bond properly; in some patients or tooth positions this is hard to achieve
- Cost constraints — in some public health settings where cost is the primary factor
Cost differences in practice
Composite consistently costs more than amalgam per filling — typically 1.5–2x more. However, because composite bonds to the tooth and requires less removal of healthy tooth structure, some practitioners argue it preserves long-term tooth health in ways that reduce downstream costs.
Insurance plans typically cover composite restorations up to the cost of an equivalent amalgam filling. You pay the difference out of pocket — usually $50–$150 per tooth depending on your plan. Always verify your specific coverage before scheduling. See our Insurance Coverage Guide for how to check.
MercuryFreeDental.com focuses on mercury amalgam removal. For broader dental education, these partner sites are useful complements: