Onlays
What happens when a tooth is too damaged to support just a filling, but is not damaged enough to warrant a full dental crown? Filing down the entire top of a tooth for a crown when it doesn’t need one removes more natural tooth structure than necessary. However, placing a large dental filling in a badly damaged tooth can weaken the remaining structure and leave it very susceptible to fractures, causing worse problems in the future. In cases such as this, a dental restoration called an ‘onlay’ is usually selected.
Onlys fall somewhere between a filling and a crown, and allow large cavities to be restored while keeping as much natural tooth structure as possible.
An onlay is a custom-made restoration that only covers some of the cusps of the tooth, as opposed to a crown which covers all of them, which is why they are sometimes referred to as ‘partial crowns’.
INLAYS
You may also have heard of a restoration similar to an onlay, called an ‘inlay’. These are the same kind of restoration, but they cover different areas of the tooth. A dental inlay fills the space in the middle of the tooth between the cups, whereas an onlay covers the middle area and one or more outer chewing cusps. Because of the extensive coverage onlays provide, only they are referred to as ‘partial crowns’.
They can be made from metal, composite (resin) material or ceramic/porcelain (the latter two are matched to the natural tooth colour). They ARE more resistant to fractures and damage than traditional cavity fillings and are Stain-resistant.
Procedure
Inlays and Onlays are made in a dental laboratory and generally require two dental appointments.
During the first appointment after the tooth is prepared, impressions are taken which are sent to the lab for the onlay to be custom designed from.
You will receive a temporary filling to wear while your permanent onlay is being made.
When you come back for your second appointment, the temporary is removed and the permanent restoration is cemented.
