There are certain circumstances when it is not possible to restore a heavily broken down tooth with a conventional filling. In these cases a laboratory-made restoration called an inlay or onlay is fabricated. They are usually made from either gold alloy, reinforced composite material or porcelain.
They are normally used as a possible alternative to crowning, due to the desire to be as conservative as possible when it comes to losing any further tooth structure. They are only appropriate in certain cases as sufficient remaining structure and space must be available for their use. Each case is selected on it’s own merits and they are not “one shoe fits all”!
Treatment is carried out over two visits and the extra time, manufacturing procedures and complexity means that these are significantly more expensive than fillings but often it is the “last chance saloon” for any attempt to save the tooth in question. The “onlay” refers to cases where the cusps and biting surfaces of the tooth are covered with the replacement material. They are cemented onto the remaining tooth structure and give a much improved prognosis towards retaining your tooth for many years longer.