South Kensington
- 20 Old Brompton Road, London SW7 3DL
- Open seven days a week
- 020 7183 2362
Treatment comparison · Wimpole Street, Marylebone
Crown or onlay: full coverage or a more conservative repair?
An onlay sits in the space between a filling and a crown. Like a crown it is made in a laboratory from strong ceramic and bonded to the tooth; unlike a crown it covers only the damaged part, typically one or more of the raised cusps, and leaves the healthy walls untouched. For a good many damaged molars it offers most of the protection of a crown while keeping more of the tooth you were born with.
Decision guide
Which is right for you?
Choose Onlays if…
- One or two cusps are broken or undermined but the rest of the tooth is strong.
- You want to keep as much natural enamel as possible.
- The tooth has not been root-treated and shows no crack lines.
- Your dentist is confident there is enough sound tooth for the onlay to bond to.
Choose Dental crowns if…
- The tooth has a crack, or damage extends across most of its surfaces.
- The tooth has had root canal treatment.
- Very little enamel remains above the gum.
- You clench or grind heavily and the tooth needs to be encased rather than partly covered.
At a glance
Side by side
| Feature | Onlays | Dental crowns |
|---|---|---|
| Purpose | Restore moderate damage while preserving healthy walls | Rebuild and enclose a badly compromised tooth |
| Coverage | The chewing surface and one or more cusps | All surfaces above the gum |
| Strength | High; bonded ceramic supports the damaged cusps | Very high; the whole tooth is held together |
| Expected lifespan | Around 10 to 20 years | Around 10 to 25 years or more |
| Appearance | Ceramic matched to the tooth | Ceramic matched to the tooth |
| Time needed | Two visits, one to two weeks apart | Two visits, one to two weeks apart |
| Fee per tooth | From £995 | From £995 |
| Tooth preparation | Only damaged areas and a little surrounding enamel | Every surface reduced by a millimetre or two |
| Best suited to | Large cavities and broken cusps in otherwise sound teeth | Cracked, root-treated or structurally depleted teeth |
In the chair
What the treatment involves
Onlays
The tooth is numbed and any decay or old filling removed. Rather than reducing the whole tooth, the dentist smooths and shapes only the damaged region so a ceramic piece can seat cleanly on it. A scan or impression is taken and a temporary filling placed. In the laboratory the onlay is milled or pressed to fit the preparation and match the shade. At the second visit it is tried in, the fit and contacts checked, and it is bonded with adhesive cement that effectively fuses ceramic and tooth.
Dental crowns
After numbing, decay and old restorations are cleared and the tooth is reduced on all sides and across the top to create room for the crown. Where little tooth remains a core build-up restores a base to work from. A scan or impression follows, a temporary crown is fitted, and the laboratory fabricates the crown in ceramic, zirconia or metal-ceramic. The definitive crown is checked for fit, bite and shade at the second visit and cemented permanently.
Fees
Cost and longevity at Wimpole Street
Onlays and crowns at Wimpole Street will both start from £995 per tooth, so cost does not usually drive the choice. Both involve two appointments and laboratory work, and both are available in porcelain, zirconia and other materials depending on the position of the tooth and how hard you bite.
Onlays typically last ten to twenty years and crowns ten to twenty-five. An onlay leaves more options open: if it ever fails, a crown remains possible because the tooth walls were kept. A crown is the more robust restoration for a tooth that is already fragile, and in those circumstances its longer lifespan justifies the extra reduction.
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
Onlays
Strengths
- Removes far less healthy tooth than a crown
- Ceramic bonded to enamel strengthens the remaining cusps
- Same materials and fee as a crown
- Keeps the crown option in reserve for the future
- Margins often sit above the gum, which is kinder to gum health
Trade-offs
- Not enough protection for cracked or root-treated teeth
- Relies on adequate enamel for a strong bond
- Slightly more technique-sensitive to fit than a crown
- Two visits, like a crown
Dental crowns
Strengths
- Most complete protection against fracture
- Works on teeth with very little structure left
- Long track record across all materials
- Standard recommendation after root canal on a molar
Trade-offs
- Sacrifices sound enamel that cannot be regained
- Margins sit at or below the gum and need careful cleaning
- If a crown fails, the remaining options are more limited
- Higher risk of the nerve becoming irritated because more tooth is cut
FAQ
Common questions
No. A filling is placed soft in the mouth and set in place; an onlay is made outside the mouth from high-strength ceramic, fitted precisely and bonded. It is closer to a partial crown than to a filling in strength and longevity.
An inlay sits within the cusps, filling a cavity in the middle of the chewing surface. An onlay extends over one or more cusps to replace them. Both are laboratory-made; the onlay simply covers more.
Because the tooth needs it. If a crack is present or the tooth has been root-treated, partial coverage leaves weak areas exposed to biting force. A crown encloses everything and reduces the chance of a split.
They come close. Ten to twenty years is typical for a bonded ceramic onlay, against ten to twenty-five for a crown. In a suitable tooth the difference is small, and the enamel saved is worth having.
Yes, and this is one of its main advantages. Because the walls of the tooth were preserved, there is still enough structure to prepare for a crown should the onlay ever wear out or the tooth deteriorate.
Yes. Onlays and crowns are routine restorative work at every Medical & Dental clinic and will be offered in Marylebone from 1 October 2026. In the meantime, the same dentists see patients in South Kensington and the City.
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
