Inlays, onlays and crowns are called indirect restorations, because the restoration is fabricated outside of the mouth, instead of being built in layers directly onto the teeth like a filling.
The dentist takes impressions of the teeth, then the restoration is shaped to match the part of the tooth it will replace. The restoration is attached with dental cement.
An indirect restoration is called an inlay if it covers part of a tooth, without extending to a cusp (pointed tip of tooth). It is an onlay if it extends to replace a tooth’s cusp. And if it completely covers the top surface of the tooth, it is called a crown or cap.
Inlays, onlays and crowns are more effective than fillings in reinforcing teeth to withstand biting forces. Indirect restorations are also more resistant to further decay. If a tooth’s original structure is too compromised to support a filling, an indirect restoration can provide fantastic, long-lasting, beautiful results.