What does “Inlays and onlays” mean?
Inlays and onlays restore part of a damaged tooth with a separately made restoration. An inlay fits within the prepared defect, while an onlay also covers one or more cusps—the raised parts of the chewing surface.
The key difference is cusp coverage
An inlay restores the tooth by fitting into the prepared defect. An onlay extends onto the cusps of the chewing surface to cover and protect weakened or damaged cusps. Identifying which cusps are covered helps explain the difference in treatment extent.
Material and coverage are separate decisions
Inlays and onlays can be made from metal or tooth-coloured materials. The same material can be used for different coverage, so the word ceramic does not tell you whether a restoration is an inlay or an onlay. Its shape and the way it restores the remaining tooth matter alongside material selection.
Assess whether a partial restoration is appropriate
Not every damaged tooth can be treated with an inlay or onlay. Another restoration, such as a crown, may be needed depending on how much of the remaining tooth requires coverage. Once the appropriate extent is determined, the restoration is made and secured to the tooth.
Frequently Asked Questions
Is an onlay always better than an inlay?
No. An onlay is considered when cusp coverage is needed. The important question is what the particular tooth needs restored, rather than ranking one type above the other.
Are all ceramic restorations onlays?
No. Ceramic is a material, whereas inlay and onlay primarily describe coverage. Both types can be made from ceramic.
Questions when comparing inlays and onlays
Learn what the term means and how it relates to your dental condition.
- Sufficient understanding
Are there cusps that need to be covered?
Explanation and evidenceCheck the planned coverage in relation to the remaining cusps and the location of damage.
NHS Business Services Authority · Distinguishing inlays and onlays - Preservation of natural teeth
Is a partial restoration or a crown needed?
Explanation and evidenceCompare suitable shapes based on the remaining tooth and the protection it needs.
American College of Prosthodontists · Inlays and Onlays
