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Inlays and onlays are indirect restorations, which means they are made outside of the mouth in a dental laboratory. They treat decayed or damaged teeth caused by poor oral hygiene or trauma. Both restorations are typically used when a patient’s cavity is too large for a simple filling. Although, based on the severity of a patient’s cavity, a dentist will determine the best restoration type depending on several factors:
A dental inlay fills a prepared cavity in a tooth with a solid, custom-formed material rather than with a conventional cavity filling, such as amalgam. Depending on the patient’s cavity size and depth, inlays are either cast into shape (gold) or milled into shape (porcelain) before placement. When a patient has a deep cavity, a dentist molds an inlay to fit into the grooves of the affected tooth. The restoration does not extend over the cusps of teeth.
Onlays are larger than inlays but smaller than dental crowns. Similar to inlays, dental onlays fill a cavitated tooth with a solid, custom-made material rather than a traditional cavity filling. The main difference between inlays and onlays is that onlays cover at least one cusp of a tooth. In other words, onlays restore larger cavities that extend beyond the grooves of teeth.
There are many advantages to inlays and onlays. For example, they are:
“Inlays and onlays can increase a tooth’s strength by up to 75 percent.”
Inlays and onlays are made from metal alloys and ceramics:
In the past, gold inlays and onlays were the material of choice because of their durability and shaping capabilities. Since gold is extremely strong, it protects weakened teeth cusps caused by cavities and trauma. Today, with the introduction of tooth-colored restorations, gold is less common.
Ceramic refers to inlays or onlays made of porcelain. In dentistry, porcelain is used to create tooth-colored restorations that mimic the color, shape, and function of natural teeth. Ceramic inlays are placed with a resin-based cement and are handled the same way as porcelain veneers.
Composite inlays and onlays are used to fill cavities that are too large for traditional fillings. They are an alternative to gold or ceramic restorations because they still perform the same functions (treating damaged or decayed teeth).
Often times, inlays and onlays replace fractured or damaged cavity fillings. If there is already an existing filling in the tooth, the dentist removes it prior to placement. Any cavitated tooth tissue is also removed, which leaves a “hollowed out” cavity in the tooth. The dentist also prepares and shapes the tooth. This allows for easier placement of the new restoration once it’s created.
During the first appointment, a mold is taken of the cavitated or damaged tooth. The material used to fabricate the inlay or onlay (gold, ceramic, or composite) is decided by the dentist and patient. If ceramic material is chosen, the shade of the filling is also determined during this visit.
While the inlay is being prepared in the dental laboratory, a new temporary filling is placed to seal the cavity, prevent further decay, and protect the tooth from thermal stimulation (cold or hot liquids).
Once the restoration is made, it is sent to the dentist and prepared for placement. During this appointment, a dentist administers a local anesthetic if the patient requests it to reduce pain and increase comfort. Usually, dentists can remove the temporary filling and place the permanent without causing much discomfort. The temporary filling material is pulled off of the cavity and the inlay or onlay is cemented into the patient’s tooth.
Both porcelain and composite inlays and onlays can now be made in-office through CAD/CAM technology and milling machines like CEREC. It's the same technology that dentists use to make "same-day" crowns. In this case, the patient would undergo steps one and two, skip step three, and then go straight to step four all within the same visit.
The recovery time for inlays and onlays only takes a few days. Although, as with other restorative dental treatments, they are susceptible to plaque and oral bacteria buildup over time.
To reduce the chance of disease, dentists recommend the following tips:
Oral Hygiene — inlays require extensions into the interdental areas of the dental arch to replace parts of a tooth. These are difficult areas to clean and require regular interdental cleanings, such as flossing and the use of an interdental toothbrush. Basic oral care practices are also necessary, such as brushing twice a day and rinsing with mouthwash to kill bacteria.
Diet — patients should reduce sugar intake after inlay or onlay placement. Dentists also recommend avoiding highly acidic foods and drinks. This includes candy, coffee, dairy, dark fruits, and processed food.
Check-Ups — the restorations are routinely checked by the dentist. They will examine the tooth and gums for signs of leakage, damage, and disease. It is crucial to visit a dentist regularly after receiving an inlay or onlay.
The cost of an inlay or onlay depends on the restorative material and the dentist’s location. Since inlays and onlays treat cavities, decay, or trauma-related dental conditions, insurance covers part of the procedures. Usually, inlays and onlays fall under "major" dental procedures and get up to 50 percent coverage. The patient's portion is only a couple hundred dollars. The prices below reflect the procedure costs without insurance:
$650-$1200 (per tooth)
$650-$1200 (per tooth)
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Freedman, George A. Contemporary Esthetic Dentistry. Elsevier, 2012.
Blue Ocean Publishing Group. The Million Dollar Smile, Changing Lives with Cosmetic Dentistry. 2018.
Hollins, Carole. Basic Guide to Dental Procedures. John Wiley & Sons, Inc., 2015.