Types of Dental Crowns

What is a dental crown?

A dental crown is a tooth-shaped "cap" that is placed over a tooth covering the tooth to restore its shape, size, strength, and to improve its appearance. When the crowns are cemented into place it fully encases the entire visible portion of a tooth that lies at and above the gum line.

Why is a dental crown needed?

At Crescent Dental Limerick a dental crown is used to do any of the following:

  • To restore an already broken tooth or a tooth that has been severely worn down
  • To protect a weak tooth from breaking or to hold together parts of a cracked tooth
  • To hold a dental bridge in place
  • To cover and support a tooth with a large filling when there isn't a lot of tooth left
  • To cover a dental implant
  • To cover misshaped or severely discolored teeth

Are there any risks involved?

If tooth decay is right next to the pulp, the pulp may not be strong enough to make healthy dentin. If this happens, the pulp may need to be removed by dentist or endodontist, or the whole root may have to be removed by an oral surgeon.

Some dental procedures can cause bacteria in the mouth to enter the bloodstream and cause infections in other parts of the body. People who have difficulty fighting off infections may need to take antibiotics before and after dental surgery. Such people include those who:

  • Were born with heart defects.
  • Have damaged or artificial heart valves.
  • Have liver disease (cirrhosis).
  • Have an impaired immune system.
  • Have a history of bacterial endocarditis.
  • Have artificial joints, such as a hip that has been replaced.

How well do dental crowns work?

A crown will work just like a healthy tooth. However, crowns can sometimes come loose over time and may need to be replaced or cemented in again. If the decay is near the centre of the tooth and bacteria invade the pulp, the pulp may die. If this happens, the crown may need to be removed and root canal treatment will be needed to eliminate the bacteria and dead pulp.

What types of crown materials are available?

Permanent crowns can be metal, porcelain-fused-to-metal, resin, or completely ceramic.

All-ceramic or all-porcelain dental crowns provide the best natural color match than any other crown type and may be more suitable for people with metal allergies. However, they are not as strong as porcelain-fused-to-metal crowns and they wear down opposing teeth a little more than metal or resin crowns. All-ceramic crowns are a good choice for front teeth.

Porcelain-fused-to-metal dental crowns can be color matched to your adjacent teeth unlike the metallic crowns. However, more wearing to the opposing teeth occurs with this crown type compared with metal or resin crowns. The crown's porcelain portion can also chip or break off. Next to all-ceramic crowns, porcelain-fused-to-metal crowns look most like normal teeth. However, sometimes the metal underlying the crown's porcelain can show through as a dark line, especially at the gum line and even more so if your gums recede. These crowns can be a good choice for front or back teeth.

Metals used in crowns include gold alloy, other alloys (e.g. palladium) or a base-metal alloy (e.g. nickel or chromium). Compared with other crown types, less tooth structure needs to be removed with metal crowns, and tooth wear to opposing teeth is kept to a minimum. Metal crowns withstand biting and chewing forces well and probably last the longest in terms of wear down. Also, they rarely chip or break. The metallic color is the main drawback. Metal crowns are a good choice for out-of-sight molars.

All-resin dental crowns are less expensive than other crown types. However, they wear down over time and are more prone to fractures than porcelain-fused-to-metal crowns.

Temporary versus permanent. Temporary crowns can be made in a dental practice whereas permanent crowns are made in a dental laboratory. Temporary crowns are made of acrylic or stainless steel and can be used as a temporary restoration until a permanent crown is constructed by the dental laboratory.

What steps are involved in preparing for a crown?

Preparing a tooth for a crown usually requires two visits. The first step involves examining and preparing the tooth and the second visit involves placement of the permanent crown.

Examining and preparing the tooth. At the first visit, your dentist may take a few x-rays to check the roots of the tooth receiving the crown and surrounding bone. If the tooth has extensive decay or if there is a risk of infection or injury to the tooth's pulp, a root canal treatment may first be performed.

Before the process of making your crown has begun, your participating dentist will inject a local anesthetic that will completely numb the teeth, gums, tongue, and skin in that area. Dental sedation may be used to reduce pain and help you relax. Next, the tooth receiving the crown is filed down along the chewing surface and sides to make room for the crown. The amount removed depends on the type of crown used (for instance, all-metal crowns are thinner, requiring less tooth structure removal than all-porcelain or porcelain-fused-to-metal ones). If, on the other hand, a large area of the tooth is missing (due to decay or damage), participating dentists will use filling material to "build up" the tooth enough to support the crown.

After reshaping the tooth, participating dentists will use impression paste or putty to make an impression of the tooth to receive the crown. Impressions of the teeth above and below the tooth to receive the dental crown will also be made to make sure that the crown will not affect your bite.

The impressions are sent to a dental laboratory where the crown will be manufactured. The crown is usually returned to your participating dentist in 1 to 2 weeks. If your crown is made of porcelain, your participating dentist will also select the shade that most closely matches the color of the neighboring teeth. During this first visit your participating dentist will make a temporary crown to cover and protect the prepared tooth while the crown is being made. Temporary crowns usually are made of acrylic and are held in place using temporary cement.

Receiving the permanent dental crown. At your second visit, a participating dentist will remove your temporary crown and check the fit and color of the permanent crown. If everything is acceptable, a local anesthetic will be used to numb the tooth and the new crown is permanently cemented in place. Your participating dentist will then have you bite on a piece of carbon paper that will indicate any high spots and reshape and polish the crown to fit the tooth.

What can I expect after treatment?

Your lips and gums may remain numb for a few hours until the anesthetic wears off. Avoid chewing on your numb lip or cheek to avoid injuring your mouth.

How should I care for my temporary dental crown?

Most dentists suggest that a few precautions be taken with your temporary crown.

  • Minimise the use of the side of your mouth with the temporary crown. Shift the bulk of your chewing to the other side of your mouth.
  • Avoid chewing hard foods (e.g. raw vegetables) which could dislodge or break the crown.
  • Avoid sticky and chewy foods (e.g. chewing gum, caramel) which have the potential of grabbing and pulling off the crown.
  • Slide flossing material out-rather than lifting out-when cleaning your teeth. Lifting the floss, out as you normally would, might pull off the temporary crown.

What problems could develop with a dental crown?

Allergic reaction. Because the metals used to make crowns are usually a mixture of metals, an allergic reaction to the metals or porcelain used in crowns is extremely rare.

Discomfort or sensitivity. Your newly crowned tooth may be sensitive immediately after the procedure as the anesthesia begins to wear off. You may experience some hot and cold sensitivity if the tooth that has been crowned still has a nerve in it. Your dentist may recommend that you brush your teeth with a toothpaste designed for sensitive teeth. Pain or sensitivity that occurs when you bite down usually means that the crown is too high on the tooth. Call your dentist if this is the case. He or she can easily fix this problem.

Loose crown. Sometimes the cement washes out from under the crown. Not only does this allow the crown to become loose, it allows bacteria to leak in and cause decay to the tooth that remains. Contact your dentist in the event that your crown feels loose.

Chipped crown. Crowns made of all porcelain can sometimes chip. If the chip is small, a composite resin can be used to repair the chip with the crown remaining in your mouth. The crown may need to be replaced if the chipping is extensive.

Crown that falls off. Sometimes crowns fall off. Usually this is due to an improper fit or a lack of cement. If this happens, clean the crown and the front of your tooth. You can replace the crown temporarily using dental adhesive or temporary tooth cement that is sold in stores for this purpose. Contact your dentist's office immediately. He or she will give you specific instructions on how to care for your tooth and crown for the day or so until you can be seen for an evaluation. Your dentist may be able to re-cement your crown in place; if not, a new crown will need to be made.

Dark line on crowned tooth next to the gum line. A dark line next to the gum line of your crowned tooth is normal, particularly if you have a porcelain-fused-to-metal crown. This dark line is simply the metal of the crown showing through.

What are "onlays" and "3/4 crowns"?

These are variations on the technique of dental crowns. The difference between these crowns and the crowns discussed previously is their coverage of the underlying tooth - the "traditional" crown covers the entire tooth; onlays and 3/4 crowns cover the underlying tooth to a lesser extent.

How long do dental crowns last?

Dental crowns last between 5 and 15 years. The life span of a crown depends on the amount of wear and tear the crown is exposed to, how well you follow good oral hygiene practices, and your personal mouth-related habits (you should avoid such habits as grinding or clenching your teeth, chewing ice, biting your fingernails and using your teeth to open packaging).

Does a crowned tooth require any special care?

While a crowned tooth does not require any special care, remember that simply because a tooth is crowned does not mean the underlying tooth is protected from decay or gum disease. Therefore, continue to follow good oral hygiene practices, including brushing your teeth at least twice a day and flossing once a day-especially around the crown area where the gum meets the tooth.

Is there anything else to think about?

It may be less costly and less complicated to have a tooth removed than to have tooth restoration. If the decay is near the pulp and the dentist thinks there is a chance that the pulp will die, tooth removal (extraction) may be recommended and a bridge or implant installed. If the pulp dies after the crown is placed, root canal treatment will be needed to remove the dead pulp.