Dental Inlays & Onlays
Gum Disease

What are Dental Inlays & Onlays?

Dental inlays and onlays are indirect dental restorations used to replace decayed enamel on the chewing surface of molars or premolars. They resemble dental fillings but they are fabricated indirectly in a dental lab and then placed in the mouth. Dental inlays & onlays are usually used for restorations that are too extensive for a filling but not so much to require a crown.

When dental inlays and onlays are used?

Dental inlays & onlays are used by several dentists for the treatment of tooth decay of the chewing surface of molars or premolars and for restoring structural damage due to other causes such as an accident or fracture. They are suitable in cases where the extend of damage does not permit the use of a traditional dental filling, but does not necessarily require a full coverage crown.

Dental inlays and onlays, also known as indirect fillings or partial crowns, under certain conditions can provide a better alternative to dental fillings or crowns both in aesthetics and functionality. Both types are usually used when a large area of the biting surface is affected by tooth decay. The choice between filling, inlay, onlay or crown depends on the size and position of the damaged tooth area.


A dental inlay is an indirect restoration where the restoring material is placed inside the center of the chewing surface of the tooth, between the cusps. Cusps are the elevated areas (bumps) of the top surface of back teeth. Molars and premolars may have 3-5 cusps. If the restoration does not involve the area of a cusp, it is called an inlay.


Dental onlays serve the same purpose as inlays, but they are usually larger and they are designed to cover different areas of the tooth. Onlays are used to treat dental cavities or fractures that involve at least one or more cusps, without having to use a dental crown. In some cases they can also be used when the entire chewing surface of the tooth must be restored.

Advantages of Dental Inlays and Onlays

Both inlays and onlays provide similar benefits to other restoration types as fillings and crowns:

  • Stop the progress of tooth decay
  • Protect the tooth from further damage and infection
  • Restore the structural integrity and strength of the tooth
  • Restore mouth functionality and chewing ability

When dental inlays or onlays can be used, they can provide several benefits versus other restoration alternatives as fillings or crowns:

  • Dental inlays (and onlays) strengthen teeth much more than dental fillings. When large dental fillings are used, the remaining tooth structure may be weakened and the tooth may crack or break.
  • They last longer than conventional fillings.
  • Hot or cold foods may cause changes to the size of amalgam fillings due to expansion and contraction, that may weaken the tooth by time and cause a fracture. The materials used for dental inlays and onlays are not sensitive to temperature changes.
  • Dental inlays have minimum risk of restoration shrinkage compared to composite resin fillings. In some cases a composite resin filling may shrink after it has been hardened into place. This can affect the fit of the filling on the tooth leaving small gaps or abnormalities across the edge of the filling. Even a hair-like gap between the filling and the enamel may cause tooth sensitivity and provide a point of entrance for bacteria that can cause a new cavity. Dental inlays and onlays are prepared and hardened in the lab, so they do not shrink further when they are bonded in place providing a precise fit with the tooth.
  • Most dental inlays are made of porcelain that provides a better aesthetic and more natural result than tooth colored fillings (that may discolor over time).
  • Dental inlays and onlays require the removal of less healthy tooth structure when preparing the tooth compared to dental fillings and dental crowns. The preservation of more healthy tooth structure while restoring tooth decay helps to increase the longevity of the treated tooth.
  • The only drawback in selecting a dental inlay versus a large filling is that it is more expensive and requires at least two appointments.
  • Dental onlays cost less than dental crowns but they are not as durable as crowns.

Inlays and Onlays: The Procedure

Dental inlays and onlays are indirect restorations prepared in the lab and not directly in the patient’s mouth as fillings, therefore their placement is a procedure that normally needs two dental visits.

The first part of the procedure that includes the preparation of the tooth is similar to that for a traditional dental filling. The tooth is numbed with a local anaesthetic and the dentist removes the decayed tooth tissues and any material of old dental fillings. The tooth surface is shaped in a way that will provide the best stability for the restoration.

The rest of the procedure is different from that for a filling, but quite similar to that for a crown. After the tooth is prepared the dentist will take an impression of the tooth, and the mold will be sent to the dental laboratory where the inlay or onlay will be fabricated. The impression must include the tooth to be treated, the adjacent teeth and the tooth in the opposite jaw in order to design the restoration in a way that offers a perfect occlusion (bite). The tooth is covered with a temporary restoration that will protect it until the second visit.

Several materials can be used for fabricating the final restoration, such as gold, porcelain or composite resin materials. Porcelain is the best option when aesthetics are a priority, gold is the most stable material, while composite resin is the most economic solution. Composite resin is also suggested instead of porcelain if the patient has a grinding or malloclusion problem. In these cases porcelain has a higher risk of fracture over resin made inlays or onlays. Gold is a more durable material recommended for large restorations on back molars that have to withstand most of the forces of biting. Porcelain offers the most natural result and it is preferred for restorations that can be visible.

During the second visit, the temporary restoration is removed and the inlay or onlay is bonded onto the tooth. The dentist will then smooth any abnormal edges in order to ensure a perfect fit with the existing tooth structures. The biting surface may also require some minor adjustment to ensure perfect occlusion (bite).

Direct Inlays and Onlays - When a dental office has the appropriate equipment, the inlay or onlay can be done in a single visit. New techniques have made it possible to place dental inlays or onlays as direct restorations. The use of 3D computer imaging (CEREC®) can substitute the need of taking impressions and using a mold of the teeth. Using special equipment the dentist can prepare the porcelain restoration right in his dental office, eliminating the lab waiting period and the need for a second appointment. The restorative material can be shaped into the prepared tooth, then removed and hardened in a special oven on-site, after which it is permanently cemented or bonded onto the tooth.

Aftercare – After a tooth is restored with an inlay or onlay, it requires the same care as every other tooth. Good oral hygiene, daily brushing and flossing and regular dental examinations are necessary to prevent dental problems in the future.

Complications related to Inlays and Onlays

Complications after the placement of inlays or onlays are rare. In some cases the restoration will not bond properly to the tooth, usually due to the cement being diluted or washed out by saliva. The most common symptom of this problem is tooth sensitivity. You should call your dentist if the treated tooth continues to be sensitive for more than a few days following the procedure.

Not every case is suitable for an inlay or onlay. In cases of extensive damage when there is concern about the structural integrity of the tooth, a full crown may be more suitable than an onlay. Your dentist will evaluate the tooth’s condition and determine the best solution for you.

Inlays/Onlays Cost

Both inlays and onlays offer several advantages versus traditional dental fillings but they are more expensive. Dental onlays are a cost efficient way to treat large dental cavities at a lower price than dental crowns, preserving as much of the tooth structure as possible.

Dental inlays and onlays cost in average about $900, with prices ranging between $650 to $1200 per tooth. Onlays typically cost more than inlays because they are normally used to cover larger area of the tooth. The cost of the restoration depends mainly on:

  • the location of the tooth - back teeth cost more because they are larger and more difficult to prepare.
  • the extent of damage to restore, that affects how much restorative material will be needed.
  • the type of material to be used - gold is more expensive than porcelain, while composite resin is the most affordable choice.
  • other social-economic factors - the expertise of the dentist and geographical location of the dental office and lab.

Most insurance policies cover some or all of the costs associated with inlays and onlays as they are considered as restorative procedures, unless they are placed to replace existing old fillings for aesthetic reasons. In this case inlays and inlays are considered as cosmetic treatment and they are not covered by dental insurance. Depending on the terms of your insurance policy, your provider may cover the cost of an inlay only up to the cost of an amalgam filling which is what is known as the Least Expensive Alternative Treatment (LEAT).

Dental inlays and onlays offer an intermediate solution between fillings and crowns for restoring tooth decay localized on the biting surfaces of teeth. They can provide a durable, well-fitting, lasting and aesthetic alternative to repairing a damaged tooth.

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