The debate between composite and amalgam fillings has been ongoing in dentistry for several decades, and patients in Surrey are right to want a clear answer rather than a vague “it depends”.
Both materials have been used successfully for years. But they differ meaningfully in their composition, their appearance, how they interact with tooth structure, and what the current direction of dental practice looks like. If you’re considering a dental filling at Coniston Dental Practice, here’s what you need to know.
What Amalgam Is and How It Works
Dental amalgam is an alloy containing mercury, silver, tin, and copper. It’s been used in dentistry since the mid-nineteenth century and has an extraordinary track record for longevity — well-placed amalgam fillings can last fifteen years or more under heavy biting loads, which is part of why the material remained dominant for so long.
Amalgam works mechanically rather than adhesively. The filling doesn’t bond chemically to the tooth; instead, it’s packed into a preparation shaped specifically to retain it through geometry. This means more healthy tooth structure must often be removed to create the undercuts and mechanical features that hold the amalgam in place.
The material is sensitive in the mouth to temperature: it expands and contracts with heat and cold, which over decades can place cumulative stress on surrounding enamel — a factor linked to the cracked-tooth presentations we occasionally see in older patients with large amalgam restorations.
The mercury content of amalgam has attracted ongoing public discussion. The NHS guidance on filling materials notes that amalgam fillings are considered safe for most patients, as the mercury is bound within the alloy and not released in clinically meaningful quantities during normal use. However, their use in the UK has been restricted for certain patient groups — specifically pregnant women, children under fifteen, and patients with kidney disease — and a phase-down across the European Union began in 2021 as part of the Minamata Convention. Amalgam is no longer placed at Coniston Dental Practice.
What Composite Is and How It Works
Composite resin is a tooth-coloured material comprising an acrylic base and fine glass or ceramic particles. It’s been available since the 1960s but has improved substantially in the past two decades, with modern formulations significantly more durable and stain-resistant than earlier versions.
Composite bonds adhesively to the tooth. An etching agent and bonding resin are applied to the cavity walls before the composite is placed, creating a chemical and micromechanical link between the filling and the surrounding enamel and dentine. This means the cavity preparation can be more conservative — we remove decay and any compromised tooth structure, but we don’t need to remove additional healthy tooth to create retention features.
The material is placed in layers and hardened with a blue-spectrum curing light. Once set and polished, it’s indistinguishable from natural tooth enamel at conversational distances.
Comparing the Two Materials
| Feature | Composite Resin | Amalgam |
|---|---|---|
| Appearance | Tooth-coloured | Silver-grey, darkens with age |
| Bonding mechanism | Adhesive — bonds to tooth structure | Mechanical retention only |
| Tooth preparation | Conservative | More tooth removal required |
| Mercury content | None | Approximately 50% by weight |
| Typical lifespan | 7–12+ years | 10–15+ years |
| Suitability for front teeth | Excellent | Poor (aesthetics) |
| Thermal expansion | Low | Higher — stress on surrounding enamel |
| Regulatory status (UK) | No restrictions | Phase-down; restricted for vulnerable groups |
Durability: Is Amalgam Really Stronger?
Amalgam’s reputation for durability is well-founded, particularly for large posterior restorations. It handles compressive loading well and doesn’t require as precise an isolation technique as composite does during placement.
But the durability comparison is more nuanced than it first appears. Modern composite materials, placed with proper technique under adequate isolation, produce consistently excellent outcomes in posterior teeth. Numerous long-term clinical studies now show posterior composite restorations performing comparably to amalgam over ten-year follow-up periods. The gap in durability has narrowed considerably.
And the adhesive nature of composite has a significant advantage that matters over the long term: because the filling bonds to the tooth, it actually reinforces remaining tooth structure rather than placing stress on it. That protective effect is genuinely clinically significant.
Aesthetics and Everyday Considerations
For most patients, appearance is a meaningful factor. Amalgam fillings — particularly large ones — are clearly visible when laughing or opening the mouth wide. They darken over time, and the metal can occasionally cause a greyish discolouration of surrounding tooth structure. Composite, by contrast, is matched to the natural tooth shade and effectively invisible in normal use.
In our experience, patients who had amalgam fillings placed some years ago and later have them replaced with composite report that the difference in appearance is considerably more noticeable than they’d expected — in a positive sense. Teeth that had looked dark and filled for years can look clean and natural again.
Getting a Filling at Our West Byfleet Practice
If you need a filling, or you’d like to discuss replacing existing amalgam restorations with white composite fillings, we’d be happy to talk through your options. You’re welcome to get in touch with Coniston Dental Practice on 01932 343 675 to arrange an appointment at our West Byfleet practice.
