Crowns

A dental crown is a tooth-shaped “cap” that is placed over a tooth. The cap restores the tooth’s shape and size, strength, and appearance.

The crowns, when cemented into place, cover the visible portion of a tooth.

When would a dental crown be needed?

A dental crown may be needed to:

• protect a weak tooth (for example, from decay) from breaking or to hold together parts of a cracked tooth
• restore a broken tooth or a severely worn down tooth
• cover and support a tooth with a large filling and not much tooth remaining
• hold a dental bridge in place
• cover misshaped or severely discolored teeth
• cover a dental implant
• cover a tooth treated with a root canal

What types of crown materials are available?

Permanent crowns can be made from all metal, porcelain-fused-to-metal, all resin, or all ceramic.

• Metals used in crowns include gold, palladium, nickel, or chromium. Metal crowns rarely chip or break, last the longest in terms of wear down, and only require a small amount of tooth to be removed. They can also withstand biting and chewing forces. The metallic color is the main drawback. Metal crowns are a good choice for out-of-sight molars.
• Porcelain-fused-to-metal dental crowns can be matched to the color of the teeth beside them. They have a more natural tooth color. However, sometimes the metal under the crown’s porcelain cap shows through as a dark line. Other drawbacks are that the crown’s porcelain portion can chip or break off and there is more wearing down of the teeth opposite them in the mouth. (The top and bottom tooth that come into contact when the mouth is closed.) These crowns can be a good choice for front or back teeth.
• All-resin dental crowns are less expensive than other crown types. However, they wear down over time and are more likely to break than porcelain-fused-to-metal crowns.
• All-ceramic or all-porcelain dental crowns provide the best natural color match than any other crown type. They are also a good choice for people with metal allergies. However, they are not as strong as porcelain-fused-to-metal crowns. They also may wear down the teeth opposite them in the mouth a little more than metal or resin crowns. All-ceramic crowns are a good choice for front teeth.
• Pressed ceramic crowns have a hard inner core. They replace the metal liner that is used in the all-ceramic crown-making process. Pressed ceramic crowns are capped with porcelain, which provides the best natural color match. They are also more long-lasting than an all-porcelain crown.

What steps are involved in preparing a tooth for a crown?

Two visits to the dentist are usually needed.

At the first visit, the tooth to receive the crown is examined and prepared. X-rays are taken of the tooth and bone around it. If decay is found or there is a risk of infection or injury to the tooth’s pulp, a root canal treatment may need to be done first. (Pulp is the soft tissue inside your teeth containing blood vessels, nerves, and connective tissue.)

To make room for the crown, the tooth to receive it is filed down across the top and sides. The amount of tooth filed away depends on the type of crown selected. All-metal crowns are thinner and don’t need as much tooth structure removed compared with all-porcelain or porcelain-fused-to-metal crowns. If too much tooth is missing, due to damage or decay, a filling material is used to “build up” enough tooth structure for the crown to cover.

After reshaping the tooth, a paste or putty is used to make a copy (also called impression) of the tooth that will be receiving the crown. Impressions of the teeth above and below the tooth to receive the dental crown are also made. This is done to make sure that the crown will not affect your bite.

The impressions are sent to a dental laboratory. The laboratory makes the crowns and usually returns them to the dentist’s office in 2 to 3 weeks. During this first office visit your dentist will make a temporary crown to cover and protect the prepared tooth while the permanent crown is being made.

At the second visit, the permanent crown is placed. First, the temporary crown is removed and the fit and color of the permanent crown is checked. If everything is okay, a local anesthetic (“numbing” drug) is sometimes used to numb the tooth and the new crown is permanently cemented in place