Sometimes a simple filling is not always the best course of action. When over 50% of a tooth's biting surface is damaged by trauma or decay your dentist may feel that either an inlay or an onlay is the best from of treatment.
Inlays and onlays are made of porcelain, gold, or a composite resin that is cast in sections that are bonded to the damaged area of a tooth. An inlay, which is similar to a filling, lies inside the cusp tips of the tooth. An onlay is more extensive than an inlay and covers one or more cusps of the damaged tooth.
Until recently inlays and onlays have been made of gold, but advances in dental technology have made porcelain a better choice for two important reasons. Firstly, the materials that are used to make the porcelain now yield a material that is stronger and more durable than gold. Secondly, properly trained prosthodontists can mix the material to match the tooth to which it is affixed.
An inlay or onlay will require to visits to your dentist. During the first appointment the decay or old filling is removed and the tooth is prepared for the inlay / onlay. Your dentist will then make an impression of the tooth, and send that impression to a dental laboratory which will use it to construct, a porcelain, or gold inlay / onlay.
This inlay / onlay will be made to fit exactly into your tooth. Before you leave his office your dentist will place a temporary sealant on your tooth to protect it until the inlay is made and schedule a second appointment
During the second visit your dentist will remove the temporary sealant then will ensure that the inlay / onlay fits properly in the tooth. Once it is determined that the inlay / onlay fits correctly, and that it does not interfere with your bite, it is bonded into the tooth with a strong bonding resin, and polished smooth.
When considering an inlay or onlay, there are some things that you and your dentist should consider. In many cases fillings can reduce the strength of the tooth by up to 50%. Inlays and onlays can actually increase the strength of the tooth by up to 75% because they are bonded directly into the tooth with special resins. Consequently, they can last for up to30 years, and are often a good alternative to a crown.