South Kensington
- 20 Old Brompton Road, London SW7 3DL
- Open seven days a week
- 020 7183 2362
Treatment comparison · Wimpole Street, Marylebone
White or silver fillings: composite and amalgam compared
For most of the last century a filling meant a grey plug of amalgam, a metal alloy that is packed into a cavity and hardens in place. Tooth-coloured composite resin has steadily taken over, first in front teeth where appearance matters and increasingly in back teeth too, as the materials have grown stronger. The two still have distinct characters. Composite bonds to the tooth and disappears visually; amalgam relies on the shape of the cavity to stay put and is exceptionally tough in large, hard-working back teeth. Understanding how each behaves helps make sense of what your dentist recommends for a particular tooth.
Decision guide
Which is right for you?
Choose White (composite) fillings if…
- The cavity is small or moderate in size.
- The tooth is visible when you smile or speak.
- You prefer a material that bonds to the tooth and preserves more of it.
- You would rather avoid a mercury-containing material, or fall into a group for which amalgam is not advised.
Choose Silver (amalgam) fillings if…
- The cavity is very large and on a molar that takes heavy biting force.
- The tooth is far back and hard to keep dry during placement.
- Cost is the overriding concern and appearance is not.
- An existing amalgam is being repaired rather than replaced wholesale.
At a glance
Side by side
| Feature | White (composite) fillings | Silver (amalgam) fillings |
|---|---|---|
| Material | Resin filled with glass or ceramic particles | Alloy of silver, tin, copper and mercury |
| Appearance | Matched to the tooth; effectively invisible | Grey metal; visible when the mouth is open |
| How it stays in | Bonded chemically to enamel and dentine | Locked in by undercuts in the cavity shape |
| Tooth removed | Only the decay; little healthy tooth | Decay plus extra tooth to create retention |
| Placement | Layered and light-cured; needs a dry field, so slightly longer | Packed and carved; quicker and tolerant of some moisture |
| Fee at Wimpole Street | From £185 (small), £260 (medium) or £305 (large) | Generally lower per filling |
| How long it lasts | Around 5 to 15 years depending on size and position | Around 10 to 15 years, sometimes longer |
| If it chips | Can often be repaired by adding more composite | Usually replaced in full |
| Best suited to | Smaller and moderate cavities anywhere in the mouth | Large cavities in molars under heavy load |
In the chair
What the treatment involves
White (composite) fillings
After the tooth is numbed, the decay is removed with the smallest possible opening, since composite does not need the cavity to be shaped for grip. The tooth is isolated to keep it dry, then the surfaces are etched with a mild acid gel, rinsed and coated with a bonding agent. Composite in a shade chosen to match the tooth is placed in increments of a few millimetres, each hardened with a blue light before the next, which limits shrinkage and keeps the seal tight. The surface is carved to restore the natural contours and grooves, the bite is checked and the filling is polished. The tooth can be used as soon as the anaesthetic wears off. A typical appointment lasts thirty to fifty minutes depending on the size.
Silver (amalgam) fillings
The tooth is numbed and the decay removed, then the cavity is shaped so that it is slightly wider at the base than at the opening; these undercuts are what hold the amalgam in, since the material does not bond to tooth. A lining may be placed over deep areas to protect the nerve. Freshly mixed amalgam is carried into the cavity in small portions and firmly packed to eliminate voids, then carved to the shape of the tooth while still soft and burnished smooth. The material reaches most of its strength within a few hours and full hardness over about a day, so you are asked to avoid chewing on that side until then. Placement is generally quicker than composite and less affected by saliva or bleeding.
Fees
Cost and longevity at Wimpole Street
White composite fillings at Wimpole Street will start from £185 for a small filling, £260 for a medium one and £305 for a large one, the price reflecting the time taken to layer and shape the resin. Amalgam is generally cheaper per filling, although the difference on a single tooth is modest.
Longevity is closer than the old reputation suggests. Amalgam has historically lasted 10 to 15 years or more in large back-tooth cavities, while composite spans roughly 5 to 15 years, with small and medium fillings placed under good conditions now performing much like amalgam. Two further considerations tilt the balance: composite fillings can usually be repaired rather than replaced when an edge chips, and because less tooth is removed at the outset, the tooth has more reserve for whatever restoration it needs in later life.
All prices are indicative and are confirmed in a written treatment plan at your consultation. Fees are the same at every Medical & Dental clinic.
Weighing it up
Strengths and trade-offs
White (composite) fillings
Strengths
- Indistinguishable from the tooth
- Bonds to enamel and dentine
- Requires removal of less healthy tooth
- Suitable for front and back teeth
- Chips can often be repaired in place
- Contains no mercury
Trade-offs
- Higher fee than amalgam
- Needs a dry field, so placement is more exacting
- May wear faster in very large molar cavities
- Can pick up stain over many years
- Slightly longer appointment
Silver (amalgam) fillings
Strengths
- Very durable under heavy chewing forces
- Lower cost per filling
- Quick to place and forgiving of moisture
- Track record of well over a century
- Reliable in large, deep molar cavities
Trade-offs
- Grey and clearly visible
- More tooth removed to create retention
- No bond to the tooth; relies on cavity shape
- Contains mercury and is restricted for some groups
- Can tarnish, and may expand and contract with temperature
- Chips generally mean full replacement
FAQ
Common questions
The bond between resin and tooth forms only on a clean, dry surface. Saliva or blood on the etched enamel weakens the seal and shortens the life of the filling, which is why the dentist uses a rubber sheet or cotton rolls and suction throughout. Amalgam is more forgiving because it does not rely on a bond.
Current UK and EU guidance advises against amalgam for children under fifteen and for women who are pregnant or breastfeeding, unless the dentist judges it strictly necessary. Patients with kidney disease or a known sensitivity to the metals involved are also steered towards alternatives.
Usually only if the amalgam is cracked, leaking, has decay beneath it or the tooth is sensitive. Removing an intact filling takes away more tooth each time, so purely cosmetic replacement is weighed carefully. Where a filling does need redoing, composite is the normal replacement.
The debris is collected by high-volume suction and captured by an amalgam separator fitted to the surgery drainage, as required by regulation, so it does not enter the water system. It is then disposed of as hazardous waste.
Often, but the dentist may suggest an inlay, onlay or crown instead, since a large composite carrying heavy load wears and flexes more than a laboratory-made restoration. The choice depends on how much of the tooth remains and how it meets the opposing teeth.
Our South Kensington and St Paul’s clinics place fillings now at the same fees and with the same clinicians. Routine check-ups and any future fillings can move to Wimpole Street once it opens on 1 October 2026.
Marylebone, W1
Wimpole Street opens 1 October 2026
Register your interest and we will contact you when the Marylebone diary opens. If you would rather not wait, the same clinicians can see you at South Kensington or St Paul's now.
Related treatments at Wimpole Street
Opening 1 October 2026
Wimpole Street is not yet seeing patients. Until then, please book or call our South Kensington clinic on 020 7183 2362 or our St Paul's clinic on 020 7183 3709. Questions about the new clinic: wimpolestreet@md.co.uk.
Until we open
Need an appointment before 1 October 2026?
The same clinical team already works from two other Medical & Dental clinics. Book at either one now and, if you prefer, move your ongoing care to Wimpole Street once the doors open.
St Paul's, City of London
- 5 Ave Maria Lane, London EC4M 7AQ
- Open Monday to Friday
- 020 7183 3709
