These are cast restorations which are used when there are particularly large holes in teeth, where a normal filling material is not strong enough. This is normally when the typically have too much damage or decay in the tooth structure to be successfully treated using a filling, but have sufficient healthy tooth remaining to avoid the need for a crown. Normally, the materials they are made of are alloys, composites or porcelain, which are treated and cast so as to provide sufficient strength to protect the tooth.. This allows the dentist to conserve more of the patient's original tooth structure.
The clinical indications being for this is when the need arises to repair rear teeth with mild to moderate decay or cracked and fractured teeth that are not sufficiently damaged to need a crown, here then other clinical indication can come into play as well. These include that the treatment options are very durable, they can help to strengthen teeth more than the usual filling materials, also they can increase the life span of teeth as which may be reduced normally by the teeth being broken down.
The difference between an inlay and onlay are that the dental inlay is similar to a filling and fits inside the cusp tips (top edges) of the tooth, whereas a dental onlay is more extensive and extends over the cusps of the treated tooth.
The procedure for an inlay/onlay procedure is the same as that for the crown, where the tooth is first prepared, then dental impressions are taken of the prepared tooth surface. This is sent to the technician with the relevant information about the material, shade of the tooth and the bite. The technician will then make an inlay/onlay with the relevant material and then a fit appointment is booked where the inlay/onlay is fitted with a special dental adhesive cement.