Inlays & Onlays

Inlays Onlays

Reviewed By:
Andrew M. Sicklick, D.D.S.

Summary

Inlays and onlays are indirect dental restorations that reinforce an existing tooth that is too damaged to support a filling, but not damaged enough to require a crown. An inlay is placed on the chewing surface between the bumps (cusps) of a tooth, whereas an onlay covers one or more of the cusps.

Prior to an inlay or onlay procedure, local anesthesia is injected into the patient’s mouth to numb the area to be treated. Tooth decay or old fillings are then removed from the tooth and the area may be reshaped to ensure a good fit. An impression is taken of the area and a mold sent to a dental laboratory, where the custom inlay or onlay is created. A patient is fitted with a temporary inlay or onlay while waiting for the permanent one to be completed. The entire process may take two or more visits to the dentist.

Sometimes an inlay or onlay may be permanently affixed during a single visit. In these cases, restorative material is shaped into the prepared tooth, then removed and hardened in a special oven in the dentist’s office, after which it is cemented or bonded into the tooth.

Inlays and onlays offer better strength and durability than fillings, and cost less than crowns. Inlay and onlay procedures are usually completed without complications, although patients may experience some minor pain or discomfort immediately afterward. In some cases, the cement used to affix the inlay or onlay to the tooth may wash out or become contaminated with saliva during application. Patients should consult their dentist if the inlay or onlay becomes loose, cracks or falls out.

Teeth with inlays and onlays should receive the same type of oral hygiene as natural teeth, including brushing, flossing and regular dental examinations.

About inlays & onlays

Inlays and onlays are forms of indirect restoration used when a molar or premolar (bicuspid) is too damaged to support a basic filling, but not so severely that it needs a crown.

Inlays and onlays are prepared outside the patient’s mouth then cemented or bonded to the tooth. The inlay or onlay fits into the prepared tooth much like a puzzle piece. Inlays and onlays are intended to rebuild a large area of the chewing surface of a tooth, whereas fillings are direct restorations designed to fill a small hole in tooth enamel. Inlays and onlays are not as extensive as crowns, which cover most of the tooth.

An inlay is placed on the chewing surface between the bumps (cusps) of the tooth, while an onlay covers one or more of the cusps. Onlays, which are sometimes called partial crowns, may be used if more than half of the biting surface of the tooth is decayed or otherwise in need of repair.

Preparing and placing inlays and onlays is a multistep process. It involves:

  • Preparing the tooth (e.g., removing any decay)
  • Taking an impression of the area to receive the restoration
  • Preparing the inlay or onlay in a dental laboratory or with special equipment
  • Cementing or bonding the restoration to the tooth

If a dentist has the appropriate equipment on-site, this can be done in a single visit to the dentist. However, it more commonly takes two or more visits to complete the entire process. A temporary inlay or onlay is placed on the prepared tooth while a patient waits for the finished restoration to return from a dental laboratory.

Materials such as gold, composite resin or ceramics may be used to create inlays and onlays. Which material is chosen may be influenced by aesthetic appeal, strength, durability and cost. The material used plays a major role in determining how long these restorations will last, as some substances are tougher and better tolerated than others. Other factors that influence the longevity of an inlay or onlay include the strength of the tooth that is treated, the amount of chewing that occurs on the restoration and a patient’s willingness to maintain oral hygiene and to have regular dental examinations.

Before, during and after the procedure

Patients should follow any preparatory instructions provided by their dentist. Prior to the procedure, local anesthesia is injected into the patient’s mouth to numb the area to be treated. Patients may also receive nitrous oxide or some type of sedative to help them relax during the procedure.

The dentist begins by removing any decay or old fillings in the tooth to receive the inlay or onlay. Reshaping of the tooth may also be necessary to ensure a better fit of the inlay or onlay.

The next step is taking an impression of the tooth to be treated, the adjacent teeth and the tooth in the opposite jaw with which it makes contact when biting. In most cases, this is done using a special wax that is formed into a mold of the area to be restored. This mold is sent to a dental laboratory, which uses it to produce the permanent inlay or onlay. A temporary inlay or onlay is attached to the tooth before a patient leaves the dentist’s office to protect the tooth while waiting for the permanent inlay or onlay to be produced.

During the patient’s next visit, the dentist will remove the temporary inlay or onlay and clean the tooth. Then, the permanent inlay or onlay will be cemented or bonded into place and polished. Reshaping of the inlay or onlay may be necessary to ensure a proper bite.

When a dental office has the appropriate equipment, the inlay or onlay may be prepared on-site and permanently affixed in one visit. In this case, the material for the inlay or onlay is molded to fit the prepared tooth. Once a proper fit has been achieved, it is removed and hardened in a special type of oven before being cemented or bonded onto the tooth. Finally, the inlay or onlay is polished and shaped so that it is properly adjusted for the patient’s bite.  

Following the procedure, patients may experience some minor pain or discomfort. This usually can be alleviated with an over-the-counter pain reliever. However, patients should not take any pain medication without first consulting their dentist or physician.

Potential benefits and risks of inlays & onlays

Benefits of inlays and onlays include their strength, durability and cost. Inlays and onlays are used when a simple filling is not enough – when some or all of the chewing surface of a tooth needs to be rebuilt, but a crown is not yet necessary. Inlays and onlays are stronger and last longer than fillings, although they are less durable than crowns. They are less expensive and invasive than a crown, although they are more so than fillings.

In addition, inlays and onlays minimize the risk of restoration shrinkage, which can affect tooth sensitivity, strength and resistance to decay. In a small number of cases, composite resin fillings shrink slightly once they have hardened into place in the tooth. This leaves the area vulnerable due to microscopic gaps between the restoration and tooth. Because inlays and onlays are hardened outside the mouth, any shrinkage occurs prior to placement in the mouth and can be compensated for when cementing or bonding the inlay or onlay into place.

Inlay and onlay procedures usually are completed without complications. However, patients are urged to call their dentist if the tooth with the inlay or onlay remains sensitive for more than a few days following the procedure.

In some cases, cement used to affix the inlay or onlay to the tooth may wash out or become contaminated with saliva during application. This can loosen the inlay or onlay. Patients are urged to consult with their dentist if this occurs, or if an inlay or onlay cracks or falls out.

Teeth with inlays and onlays should receive the same type of oral hygiene as natural teeth, including daily brushing and flossing and regular dental examinations.

Questions for your doctor about inlays & onlays

Preparing questions in advance can help patients to have more meaningful discussions regarding their conditions. Patients may wish to ask their doctor the following questions related to inlays and onlays:

  1. Am I a candidate for an inlay or onlay? If so, which one?
  2. What are the advantages and disadvantages of this type of procedure?
  3. Would a filling or crown be more appropriate? Why or why not?
  4. What material will you use for my inlay/onlay?
  5. What are the benefits and risks of this material over other types of material available for inlays and onlays?
  6. Dental work makes me nervous. Can I get nitrous oxide or a sedative to help me relax during the procedure?
  7. Will the procedure be completed in one visit, or will I need to return?
  8. How long will it take for the permanent inlay/onlay to be prepared by a dental lab?
  9. Will I experience pain after the procedure? Are there over-the-counter painkillers you recommend to treat any discomfort I might have?
  10. What should I do if my inlay/onlay comes loose? Can it be cemented or bonded back onto my tooth, or will I need to have another one made?
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