Dental Inlay Vs. Onlay

Dental terminology varies slightly on the definition of fillings, inlays and onlays, but there are several discerning characteristics that will help you understand the differences. An onlay is the more invasive and expensive procedure, while inlays and fillings are typically less invasive. Inlays and onlays are most often used for "posterior" teeth, namely the teeth with flat surfaces in the back of your mouth that you use to chew. An inlay or onlay procedure involves the creation of a cast that is bonded to your tooth with various types of cement. Alternatively, fillings are created by molding the filler material to your tooth and allowing it to harden. Always ask your dentist to explain his definition of the procedure to make sure you understand specifically what is recommended for your tooth.

Tooth Surface

• The primary difference between an inlay and an onlay is the tooth surface covered. An onlay covers more surface area of the tooth than an inlay and wraps over at least one edge of your tooth. An onlay can wrap over multiple tooth edges and even cover the entire chewing surface. An inlay does not wrap over the edge of your tooth, but remains within the "cusps" or bumps at the edges of your tooth surface.

Tooth Weakness

• An onlay is frequently recommended if your dentist finds structural weakness in the tooth as well as damage to the bite surface that spreads over the cusps. An onlay is aesthetically preferable to a crown, since more of your natural tooth will be preserved in an onlay procedure and less of the bonding material will be visible. A decayed tooth can be fortified and protected by bonding it with an onlay. An inlay will often be used in place of a filling if the tooth is weak or the decay in the center of the tooth is extensive. Again, bonding a tooth with an inlay can fortify the tooth, which can lower the need for future dental work on the tooth at a later date.

Procedure Time

• Depending on your tooth decay, an onlay might take slightly longer to complete than an inlay. With both an inlay or an onlay, your dentist will perform the same procedure of cleaning out the decay, creating the cast, hardening the cast (either in a machine on site, or at a lab) and then bonding the cast to your tooth. The procedure can be completed in one or two visits, depending on whether your dentist has the hardware to create the cast in the office or needs to send the cast away to be made. Since an onlay covers more surface area of your tooth, it might take longer for your dentist to clean and prepare the tooth to be bonded, but overall the two procedures are similar.

Visibility

• An inlay will be less visible than an outlay because it is located at the center of your tooth and does not wrap over the edges of your tooth. Many dentists use porcelain or ceramic to create inlays and onlays, which can be created in shades that match the color of your tooth enamel. The resulting cast is frequently barely visible to the casual observer and preferable to amalgams or gold.

Alternative Procedures

• An onlay is a less invasive option a dentist might recommend over a full crown, depending on the severity of your tooth decay. Since a full crown requires the removal of a significant portion of your tooth and placement of a full cast over the entire tooth, an onlay is an ideal alternative if your decay hasn't spread throughout the tooth. Alternatively, an inlay is sometimes interchangeable with a filling, depending on the extent of decay and weakness of your tooth.