When a large cavity or an old filling needs to be replaced, different restoration options are considered depending on how much sound tooth tissue remains. Inlays and onlays are custom-made restorations, produced in a laboratory or digitally, that sit between a standard filling and a crown.
The difference between an inlay and an onlay
- Inlay: A restoration that fills the space between the cusps on the chewing surface of the tooth.
- Onlay: A restoration that covers a larger part of the tooth, including one or more cusps.
Both aim to preserve as much tooth tissue as possible.
When are they considered?
- Teeth with a defect too large for a standard filling but enough sound tissue not to need a crown
- Replacing large, old fillings
- Strengthening back teeth after root canal treatment (in suitable cases)
- Fractured cusps
Materials
- Ceramic (porcelain)
- Composite resin
- Metal alloys in some cases
Ceramic inlays and onlays are often chosen because they match the tooth colour and resist wear.
How are they placed?
- The decay or old filling is removed and the tooth is prepared.
- An impression or an intraoral digital scan is taken.
- The restoration is made in a laboratory or with digital design and milling systems; a temporary filling is placed in the meantime if needed.
- After fit, bite and colour are checked, the restoration is bonded to the tooth.
Advantages
- More of the sound tooth tissue is preserved
- Good marginal fit thanks to custom manufacture
- Durability in back teeth
- Aesthetic material options
Limits
- May need more appointments than a standard filling.
- If the tooth structure is very weak, a crown may be more suitable.
- The bonding technique requires precision.
Care
Inlays and onlays are brushed and flossed like natural teeth. Regular check-ups help detect new decay at the margins early. For information on the signs of decay, see our article on the signs of tooth decay.
