An inlay or onlay is a custom-made restoration that sits inside or over a damaged back tooth. They are made in a dental laboratory from porcelain, ceramic, or gold, and are bonded securely to the tooth.
An inlay fits within the cusps (bumps) of the tooth, filling the central part of the chewing surface.
An onlay extends over one or more cusps of the tooth — covering a greater area than an inlay but less than a full crown.
They are sometimes called "indirect fillings" because they are made outside the mouth and then fitted.
When might I need an inlay or onlay?
An inlay or onlay may be recommended when:
A tooth has too much damage for a simple filling but does not need a full crown
A large filling has broken down and needs replacing
A tooth has cracked or fractured in its chewing surface
Greater durability than a direct composite filling is needed for a heavily used back tooth
Inlays and onlays versus fillings and crowns
Inlays and onlays sit between direct fillings and full crowns on the scale of how much tooth structure is involved:
Filling — placed in a single appointment directly in the mouth. Quickest and lowest cost. Best for small to medium cavities.
Inlay / onlay — laboratory-made, two appointments, more precise fit. Better for larger restorations in back teeth. More durable than large direct fillings. Preserves more tooth structure than a crown.
Crown — covers the entire tooth. Required when too little healthy tooth remains for an inlay or onlay.
What does the procedure involve?
Getting an inlay or onlay takes two appointments:
First appointment:
The tooth is numbed with local anaesthetic
Decay or old filling material is removed and the tooth is shaped to receive the inlay or onlay
An impression or digital scan is taken and sent to the laboratory
A temporary filling protects the tooth while the inlay or onlay is made (usually 1–2 weeks)
Second appointment:
The temporary filling is removed
The inlay or onlay is checked for fit and bite, then bonded permanently to the tooth
Risks and possible complications
Common:
Sensitivity in the tooth for a few days to weeks after fitting
Occasional bite adjustment needed
Uncommon:
The tooth may require root canal treatment if the pulp is affected — this risk is discussed before treatment if applicable
Debonding of the restoration
Porcelain inlays and onlays typically last 10–20 years with good oral hygiene and regular check-ups.
Questions to ask your dentist
Why is an inlay or onlay more appropriate than a large filling for my tooth?
What material do you recommend — porcelain, ceramic, or gold?
Is there a risk this tooth could eventually need a crown?
How should I care for my restoration to make it last as long as possible?
This leaflet is for general information only and does not replace professional dental advice. It is intended to support — not replace — the discussion with your dentist about your individual options, risks, and treatment plan. Treatment outcomes vary between patients depending on individual circumstances. Your dentist will confirm exact fees and what is suitable for your specific circumstances before you agree to any treatment.