Dental inlay, dental onlay vs filling

Last Updated: 4.12.2023

Author: George Ghidrai, MD  

When a tooth is too damaged to support a traditional filling but not damaged enough for a dental crown, you end up somewhere in the middle:

• Capping a damaged tooth unnecessarily with a dental crown removes more tooth structure than needed
• On the other hand, a large dental filling can weaken the remaining structure of the tooth, causing the tooth to break, crack or eventually need a root canal treatment

Inlays and onlays are often used in place of traditional dental fillings to treat tooth decay or similar structural damage.

Whereas dental fillings are molded into place within the mouth during a dental visit, inlays and onlays are fabricated indirectly in a dental lab before being fitted and bonded to the damaged tooth by the dentist.

What is the difference between an inlay and an onlay ?

There is not a big difference between dental inlays and dental onlays :

• A dental inlay fills the space in between the cusps, at the center of the tooth's surface

• A dental onlay works like an inlay but covers one or more cusps or the entire biting surface of the tooth. An onlay is required when the extent of the damage is greater.

Materials

Inlays and onlays can be made from gold, porcelain or composite resin materials.

• If aesthetics is not a concern (for example, with back molars), gold is the best option

• Porcelain inlays and onlays offer the best aesthetics and are often used in visible front areas

• Composite inlays and onlays may be a good choice for people who grind their teeth and/or those with a misaligned bite (malocclusion)

Gold and porcelain inlays are much more expensive.

Procedure

Typically, an inlay or onlay procedure is completed in two dental visits. During the first appointment, the dentist prepares the tooth by removing any tooth decay.

Once the tooth is prepared, an impression is made of the tooth's structure and then sent to a dental laboratory, where the inlay or onlay is fabricated.

The dentist may place a temporary dental filling to preserve the tooth. During the second dental visit, the temporary filling is removed and the inlay or onlay is fitted and cemented onto the tooth.

Benefits

• Aesthetics

  Porcelain inlays and onlays are not likely to discolor over time as tooth-colored resin fillings often do.

• Conservative preparation

  Inlays and onlays preserve as much healthy tooth as possible while restoring decayed or damaged areas, helping to ensure functional longevity.

• Perfect fit

  Composite fillings can shrink during the curing process, whereas prefabricated porcelain or gold inlays and onlays will not, which ensures a precise fit.

• Strength and stability

  Inlays and onlays are extremely stable restorative solutions that usually last longer than fillings. An onlay can protect the weak areas of the tooth, which will actually strengthen the damaged tooth.

• Cavities between teeth

  In case of a cavity between teeth, it is a good idea to consider an inlay rather than a direct composite filling.

  Inlays are better at sealing teeth to keep out bacteria; they are easy to clean, will not stain and offer exceptional longevity.

Drawbacks

• Inlays and onlays need more time to be completed

  Inlays and onlays need at least two visits to be completed, which can take two or more weeks. By contrast, a dental filling is placed by the dentist in a single appointment.

• Higher cost

  Inlays and onlays (especially gold and porcelain) are much more expensive than direct fillings. The cost of a dental inlay or onlay procedure can depend on many factors, including the dentist performing the procedure, geographic location or the tooth or teeth being worked on.