Porcelain Inlays and Onlays are used when a restoration is too big for a filling but not so seriously damaged that it requires a crown. They are often used to strengthen the side of a tooth that has been compromised by decay or damage or to reinforce a back molar against the crushing forces exerted on it through regular biting and chewing.
An Inlay is similar to a filling as it lies inside the tips (cusp) of the biting surface of the tooth. A cusp is the part of the molar or bicuspid that is pointed and is used to grind or tear food. An Onlay restores a larger portion of the tooth and it usually covers one or more cusps in order to protect them from fractures.
During the first visit any decay or old defective fillings are removed and an impression is made of the tooth. A shade guide is used to colour-match the rest of your teeth and the impression is sent to a dental laboratory where the onlay or inlay is custom crafted. While the Onlay/Inlay is being made, a temporary filling is placed over your tooth, until the permanent onlay/inlay is returned from the lab 7 to 10 days later. The onlay/inlay is bonded with a resin cement which prevents leakage from occurring. Onlays and inlays can be x-rayed, allowing the dentist to diagnose any hidden conditions in the future before they require a major procedure such as a root canal.
An inlay/onlay looks exactly like your natural tooth. Dental Studies have shown that teeth with bonded inlays or onlays have nearly the identical strength of your original tooth. Onlays and Inlays provide an aesthetic and durable solution that will last for years.
Porcelain crowns and onlays are used when you have a substantial part of your tooth missing or in decay. These teeth are best restored by a means that reinforces the strength of the tooth. Traditional dental crowns were always made with a metal foundation. With recent technological advances, porcelain crowns and onlays can be made of pure ceramic or reinforced resin, a durable and natural looking alternative.
Both onlay restoration, which covers a portion of the tooth and crown, which covers the entire tooth are bonded to the healthy structure of the tooth. This type of restoration can be x-rayed, so future problems can be detected long before it is too late and a root canal is necessary. There are still occasions when the durability of porcelain fused to metal or a full gold crown makes it the restoration of choice.