inlays and onlay in BellevueAn inlay is an indirect restoration, a filling material that is made outside of the mouth.  Its material can consist of either porcelain, gold, or cured resin composite. Fabricated in a dental laboratory it is used when there is medium loss of tooth structure that is too large to be restored by a filling.  An inlay and onlay can also be used to establish proper chewing forces with the opposing dentition by a matching bio material.

An onlay is similar to an inlay, except that this indirect restoration extends to replace one or more cusps of the tooth.

A crown in comparison is an onlay that covers ALL cusps of the tooth.


An inlay is sometimes used when a tooth due to decay, cavity, or fracture needs a restoration that a traditional direct restoration (ie. composite or amalgam filling) would affect the tooth’s structural integrity.  An inlay can also be more advantageous compared to a composite restoration as the latter tends to shrink during light curing/polymerization, which may cause issues with marginal integrity; the former does not as the inlay is custom made by a dental laboratory.  Recent composite advances though, have made marginal adaptations much improved and less of an issue.

An inlay is also superior to the direct resin/amalgam restorations in that material choice has superb resistance to decay, precision marginal integrity and fit, improved cleansing ability, and often times better gingival health if the material is placed subgingivally (beneath the gum line).


An onlay is used when the tooth needing a restoration has one or more cuspal involvement, but not all cusps affected (i.e. a singular cusp fracture). The onlay is a more conservative restoration than a crown, while maintaining all the benefits of an inlay as described above.  And similar to an inlay, an onlay can be made out of porcelain, gold, or composite.


After the tooth is sufficiently prepared and decay and unsupported fractured structure removed, an impression is taken and sent to a dental laboratory or milling machine for a custom make.  Your dentist may decide to place a temporary material and have you return at a subsequent date to place the final prosthetic restoration.  The restoration is ultimately cemented or bonded to the tooth.

If you have any questions about inlays and onlays, contact us at (425) 614-1600.

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