More than 90% of adults have had a cavity before, and more than one-quarter currently have an untreated cavity that needs to be repaired. These cavities can be repaired with fillings, but fillings aren't the only way to fix tooth decay. Dentists can also use inlays and onlays to repair cavities. Here's what you need to know about these restorations.

What are inlays and onlays?

Inlays and onlays are restorations made of composite resin, porcelain, or even gold. They are prepared outside of your mouth and then cemented in place, like crowns, instead of being allowed to harden inside your mouth like regular fillings.

Inlays and onlays are very similar. Inlays don't cover the biting surfaces of your tooth, just the center portion of the tooth. Onlays cover part or all of your biting surface and are used for larger areas of decay.

When are these restorations used?

Inlays and onlays are used to fix tooth decay in your back teeth, where the teeth need to withstand the forces of chewing and aesthetics don't matter as much. Decay in the front teeth won't be fixed in this way, since tooth-colored fillings or crowns will look better.

Inlays and onlays are also good for severely decayed teeth that would be at risk of breaking if a filling was placed. Fillings can weaken your teeth by as much as 50%, leading to problems like cracks and breakage over time, since they can put pressure on your teeth when you chew.

How does getting inlays or onlays compare to getting a filling?

Most adults are familiar with the procedure for getting a cavity filled. Your dentist uses a drill to remove the decayed portions of your tooth, and then fills the resulting hole. The hole can be filled with composite resin or other materials like dental amalgam, ceramic, or gold. These materials are applied in layers, then hardened with a special light. As each layer hardens, another layer is applied, until finally, the cavity is filled.

Getting inlays or onlays is a bit different. Your dentist will still need to use a drill to remove the decayed part of your tooth, but instead of applying a filling material right away, your dentist will take an impression of your tooth. A laboratory will then use this impression to create the inlay or onlay. Once the restoration is ready, you'll go back to the dentist to have it cemented in place over top of your cavity.

How long do they last?

Inlays and onlays are very strong. They last longer than traditional fillings, so you won't need to worry about having them replaced for quite a while. They can last for as long as 30 years if you look after them. Biting hard objects or allowing more cavities to develop in the area can weaken your restoration and cause it to need to be replaced earlier.

Do they cost more than traditional fillings?

Traditional fillings can cost anywhere from $75 to $200 per tooth, depending on a wide range of factors like your location, your dentist, the size of the cavity, and the type of material the filling is made of. Inlays and onlays are more expensive, and can cost anywhere from $650 to $1200 per tooth. Inlays and onlays are more complicated for dentists to place, but they're also a better product: remember that these restorations last longer than traditional fillings and don't weaken your teeth.

Inlays and onlays are used as an alternative to traditional fillings for people with severe tooth decay. These restorations won't weaken your teeth like traditional fillings do, and they last longer; so next time you get a cavity, ask your dentist about getting inlays or onlays instead. 

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