Crowns and Onlays

When a tooth is badly damaged, as a result of injury or decay, it may no longer able to function with any efficiency and is likely a source of pain. Its loss of efficiency is due in large measure to an inability to properly contact, or occlude with opposing teeth. Any pain that may be present is usually caused by the exposure of its sub enamel structure, which includes the dentin and pulp, to air, as well as hot or cold food and drink.

In very simple terms, a crown is a cover or jacket intended to protect against direct exposure of the dentin and pulp and restore the functional tooth surface that comes in contact with other teeth.

An onlay acts in a similar way, but does not fully cover or "cap" the tooth. An onlay is generally used when there is direct exposure of the dentin or pulp, but the fundamental structure of the tooth is sound and capable of supporting the occlusal (opposing) forces of teeth that come into contact with it.

In addition to treating teeth that have been damaged, crowns may also be successfully  used to cosmetically cover misshapen or badly discolored teeth.

A specialized variation of a crown, known as a "bridge", involves "jacketing" two or more teeth with a single unit. Bridges may be employed to treat an array of situations discussed in a separate section of this site (see "Bridges" under the Treatment Menu in the right hand panel of this page).

Crowns may be prefabricated, or produced in a dental laboratory. Prefabricated crowns are composed of a variety of materials, acrylic or stainless steel being the most common. Prefabricated crowns are most often used as a temporary restoration until a permanent crown is manufactured. In some situations a prefabricated crown may even be used as a permanent restoration. The problem with prefabricated crowns, however, is that they rarely provide efficient occlusion with opposing teeth, and the structural bond tends to deteriorate over a relatively short period. Once the structural bond becomes compromised, forces act to weaken both the temporary crown and the tooth underlying it.

Crowns traditionally produced in a dental laboratory, perform much better than their prefabricated counterparts.  With proper hygiene they often last a life time. The fundamental difference (and reason for their permanency) is that they are designed to efficiently match occlusion of the opposing teeth, and are produced to precisely fit the prepared surface of the host tooth. In most cases, a tooth with a properly produced and seated crown is stronger than the tooth was when it was healthy.

Manufactured, crowns may be made of metal, porcelain, or porcelain fused to metal (PFM). Metals include gold alloy, palladium or a base-metal alloy of nickel or chromium. All metal or PFM crowns are generally reserved for teeth that have unusually high occlusionary forces applied by the opposing teeth, such as the back teeth in some patients. All-ceramic crowns, on the other hand, have become the restoration of choice by most patients. Not only do they easily handle normal occlusal forces, but appear entirely natural.

Typically, permanent crowns require two or more visits to complete. During the first appointment, the tooth surface is prepared, removing damaged tooth material and properly surfacing its structure to support the planned crown. A precision impression is then taken of the prepared surface, and a temporary crown or "cap" placed on the tooth until the next visit. The impression, together with oclussal models are then sent to the dental laboratory, where technicians skillfully craft and cast the crown and return it to the dental clinic  to be set.

During the second visit, the temporary crown is removed, and using special adhesives, the new crown seated.

The primary reason that two visits are required, is to provide time for the crown to be crafted to the specifications necessary for a lifetime of use. Metal and porcelain fused metal crowns continue to be manufactured almost exclusively by dental laboratories. However, with technological advances in computer digitalization and the development of modern porcelain restoration materials, high quality porcelain crowns may now be produced and placed during the patient's first visit.

CEREC Porcelain Crowns and Onlays

With the advent of CEREC technology, porcelain crowns with exact tolerances and specifications, can be produced in the clinic within minutes after the tooth has been prepped by the dentist.

Through the magic of computer imaging, the CEREC equipment measures the precise parameters of the tooth, both before and after preparation. A special imaging camera measures tooth surfaces and provides recommended depths and angles to ensure maximum strength when the crown is placed.

After the tooth is prepped, it is again imaged and  the crown contour designed for functionality and aesthetics.   Not only is it important that the tooth properly occlude with opposing teeth, but the forces applied to the tooth must be balanced, to avoid pressure spots.

With the contours established, the dentist will color select the porcelain to be used for the restoration and place it in the CEREC milling machine.
The milling machine uses roboticly controlled diamond cutting bits to reduce the porcelain block to the precise specifications programed by the dentist. The process usually takes between 10 and 15 minutes. When complete, the crown is ready to be placed.

During initial placement, the CEREC computer is again employed to image potential high spot, which are easily adjusted by the dentist. Using advanced adhesives, the crown is then set permanently in place. After a final polishing, the restoration is complete.

Deadwood Dental provides a full range restorations, from gold and porcelain to CEREC crowns produced right in our office. Each situation is different and only a careful examination and close consultation will determine what will work best for you.

Please feel free to discuss any questions you may have regarding the content in our website with either Dr. Hopper or Dr. Mills. Either will be more than happy to address any questions or concerns you may have.

You may reach the clinic at 605-578-3810 or 800-641-2035, or email us at: deadwooddental@mato.com