If you have a dental cavity that's too large for a regular filling, but you don't want a crown, an onlay could be the best option for you. Onlays are molded dental fillings that cover the tooth's biting surface as well as filling in the area where a cavity was removed. When a dentist fits an onlay, they remove less of the tooth's healthy structure compared to when they fit a crown.
Is an Onlay a Filling?
An onlay is pre-molded to the shape of the tooth, which makes it different from a regular filling. As ACE Dental Education explains, to apply a regular filling, the dentist cleans out the cavity, then inserts a composite filling, and then using a light to harden the composite filling material. To fit an onlay, the dentist takes a dental impression of the jaw the tooth is located, and sends it away to a laboratory that makes the customized onlay filling. What's more, once the cavity is removed, an onlay is placed in the area where the decay was eliminated and covers the tooth's biting surface, while a regular filling is placed in the area where the cavity was taken out of the tooth surface.
Dentists can also apply inlays, which are pre-molded fillings that fit within the area where the decay was removed. Both onlays and inlays help strengthen teeth that are weak from large cavities and at risk from tooth fracturing.
Onlays and Crowns
Onlays and crowns cover the surfaces of teeth and help protect them from further decay, but onlays are more conservative treatments than crowns. The dentist only removes the decayed areas of the tooth to fit an onlay. To fit a crown, however, the dentist must also file away healthy tooth material until only a portion of tooth remains. The crown then fits over the portion of tooth that is left after dental treatment.
The procedure to fit an onlay usually requires two dental appointments. At the first visit, the dentist injects a local anesthetic into the gum to numb the tooth before drilling out the diseased areas of the tooth. They then take an impression of the tooth and send it to a dental laboratory that fabricates the onlay out of porcelain or resin. To prevent further decay while waiting for the finished onlay to arrive, the dentist applies a temporary filling into the tooth.
On the second visit, the dentist receives the onlay from the laboratory, bonds it to the tooth and checks that the patient's bite (occlusion) to make sure it is correct. Between the two appointments, patients should brush with a soft-bristled brush like Colgate 360° Enamel Health Sensitive Teeth toothbrush to keep the teeth and gums healthy.
When Is an Onlay the Best Option?
When a tooth isn't too weak due to a large cavity and some parts of the biting surface are healthy, an onlay may be the best treatment option. For some patients, however, so much healthy tooth structure has been lost that a crown is the only treatment that provides a strong, reliable restoration that isn't at risk of more dental complications. If retaining the healthy parts of your teeth is important to you, discuss the possibility of an onlay with your dentist before going ahead with treatment to fit a crown. Your dentist can explain whether an onlay is the best option for you.