What are inlays and onlays?
             Inlays are more like fillings than onlays. As mentioned, they’re made in a dental lab after your dentist has removed the decay. Inlays are generally more durable and far out-last fillings. They can be fabricated from tooth-colored composite resin, porcelain or gold. They are also more conservative than crowns. Generally, much less tooth structure is removed in the preparation of inlays than crowns.

            Onlays are essentially identical to inlays with the exception that one or more cusps have been included in the preparation. In other words, decay or trauma has affected the cusps, necessitating their replacement. Onlays may be composed of the same materials as inlays - tooth - colored composite resin, porcelain or gold. They are sometimes also referred to as partial crowns.

            Inlays and onlays are used to replace damaged areas of the tooth, and can be made of porcelain, gold or composite resin. An inlay, which is similar to a filling, is used inside the cusp tips of the tooth. An onlay is a more substantial reconstruction, similar to the inlay but extending out over one or more of the cusps of the tooth.

            Traditionally, gold has been the material of choice for inlays and onlays, however porcelain has become increasingly popular due to its strength and white-colored, which can closely match the natural color of your teeth.

How are they applied?
            Inlays and onlays require two appointments. During the first visit, the filling being replaced or the damaged or decaying area of the tooth is removed, and the tooth is prepared for the inlay or onlay. To ensure proper fit and bite, an impression of the tooth is made by the dentist, and sent to a lab for fabrication. The dentist will then apply a temporary filling on the tooth and schedule the next appointment.
            At the second appointment, the temporary filling is removed and we will make sure that the inlay or onlay fits correctly. Once the correct fit is achieved, the inlay or onlay is bonded to the tooth with a very strong resin and polished to a smooth surface.

Procedure

• Usually an anesthetic will be given to numb the area;
• Inlays and onlays are applied in two visits. On the first
• Visit, any old filling material and/or decay will be removed;
• An impression will be taken to record the shape of the tooth being repaired and the teeth around it.
• A temporary filling will be applied to protect the tooth while you wait for your restoration to be made;
• At the second appointment after your restoration has come back from the lab, your dentist will cement it in place; small adjustments may need to be made so that the tooth is comfortable to bite on.
  

Considerations

            Depending on their size and location, fillings can reduce the strength of a tooth by up to 50%. Inlays and onlays, on the other hand, can actually increase the strength of the tooth by up to 75%. Inlays and onlays are fabricated outside of the mouth and therefore are capable of being made much stronger than typical fillings. They typically last between 10 to 30 years.

Porcelain Inlays (Ceramic Inlays)

Ever more patients express the wish to replace their old amalgam fillings with a biocompatible and durable material. From an aesthetic view, ceramic inlays are regarded as the top of all available alternatives. For many years, gold inlays have been the tried and tested solution and have a long lifespan. Today, aesthetic awareness has led to a decline in their use.

Before – amalgam filling	After – ceramic inlay and onlay

What are the advantages of porcelain inlays?

Ceramic inlays have no metal core and are therefore translucent. They are bonded to the tooth using a special adhesive method, leaving no marginal gaps. A chemical bond is created between tooth and ceramic, restoring weakened teeth to their original strength. The high translucency yields an exceptional aesthetic quality. Ceramic is exceedingly biocompatible. For example, allergies such as to certain alloys are unknown.

Ceramic inlays are long-lasting. The following diagram shows the longevity comparison between composite fillings and ceramic inlays.