Crowns & Bridges
A crown is a restoration which appears similar to a cap and is fitted over the remaining of the natural crown of the tooth.
What Types of Crowns Are Available?
Permanent crowns can be made from stainless steel, all metal (such as gold or another alloy), porcelain-fused-to-metal, all resin, or all ceramic.
- Stainless steel crowns are prefabricated crowns that are used on permanent teeth primarily as a temporary measure. The crown protects the tooth or filling while a permanent crown is made from another material. For children, a stainless steel crown is commonly used to fit over a primary tooth that's been prepared to fit it. The crown covers the entire tooth and protects it from further decay. When the primary tooth comes out to make room for the permanent tooth, the crown comes out naturally with it. In general, stainless steel crowns are used for children's teeth because they don't require multiple dental visits to put in place and so are more cost- effective than custom-made crowns and prophylactic dental care needed to protect a tooth without a crown.
- Metals used in crowns include gold alloy, other alloys (for example, palladium), or a base-metal alloy (for example, 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, metal crowns rarely chip or break. 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 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.
- 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.
- All-ceramic or all-porcelain dental crowns provide better 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.
- Temporary versus permanent. Temporary crowns can be made in your dentist's office, 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 a lab.
Why Is a Dental Crown Needed?
A dental crown may be needed in the following situations:
- To protect a weak tooth (for instance, from decay) from breaking or to hold together parts of a cracked tooth
- To restore an already broken tooth or a tooth that has been severely worn down
- To cover and support a tooth with a large filling when there isn't a lot of tooth left
- To hold a dental bridge in place
- To cover misshapened or severely discolored teeth
- To cover a dental implant
- To make a cosmetic modification
For children, a crown may be used on primary (baby) teeth in order to:
- Save a tooth that has been so damaged by decay that it can't support a filling.
- Protect the teeth of a child at high risk for tooth decay, especially when a child has difficulty keeping up with daily oral hygiene.
- Decrease the frequency of sedation and general anesthesia for children unable because of age, behavior, or medical history to fully cooperate with the requirements of proper dental care.
In such cases, a dentist is likely to recommend a stainless steel crown.
What Steps Are Involved in Preparing a Tooth for a Crown?
Preparing a tooth for a crown usually requires two visits to the dentist -- the first step involves examining and preparing the tooth, the second visit involves placement of the permanent crown.
First Visit: Examining and preparing the tooth.
At the first visit in preparation for a crown, 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 a crown begins, your dentist will anesthetize (numb) the tooth and the gum tissue around the tooth. 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 and require 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), your dentist will use filling material to "build up" the tooth to support the crown.
After reshaping the tooth, your dentist will use a 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 lab where the crown will be manufactured. The crown is usually returned to your dentist's office in two to three weeks. If the crown is made of porcelain, your dentist will also select the shade that most closely matches the color of the neighboring teeth. During this first office visit your 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 a temporary cement.
Second Visit: Receiving the permanent dental crown.
At the second visit, your dentist will remove the 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.
How Should I Care for My Temporary Dental Crown?
Because temporary dental crowns are just that -- a temporary fix until a permanent crown is ready -- most dentists suggest that a few precautions. These include:
- Avoid sticky, chewy foods (for example, chewing gum, caramel), which have the potential of grabbing and pulling off the crown.
- Minimize use of the side of your mouth with the temporary crown. Shift the bulk of your chewing to the other side of the mouth.
- Avoid chewing hard foods (such as raw vegetables), which could dislodge or break 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.
Dental bridges literally bridge the gap created by one or more missing teeth.
A bridge is made up of two crowns for the teeth on either side of the gap -- these two anchoring teeth are called abutment teeth -- and a false tooth/teeth in between. These false teeth are called pontics and can be made from gold, alloys, porcelain, or a combination of these materials. Dental bridges are supported by natural teeth or implants.
What Are the Benefits of Dental Bridges?
- Restore your smile
- Restore the ability to properly chew and speak
- Maintain the shape of your face
- Distribute the forces in your bite properly by replacing missing teeth
- Prevent remaining teeth from drifting out of position
What Types of Dental Bridges Are Available?
There are three main types of dental bridges:
- Traditional bridges involve creating a crown for the tooth or implant on either side of the missing tooth, with a pontic in between. Traditional bridges are the most common type of bridge and are made of either porcelain fused to metal or ceramics.
- Cantilever bridges are used when there are adjacent teeth on only one side of the missing tooth or teeth.
- Maryland bonded bridges (also called a resin-bonded bridge or a Maryland bridge) are made of plastic teeth and gums supported by a metal framework. Metal wings on each side of the bridge are bonded to your existing teeth.
What Is the Process for Getting a Dental Bridge?
During the first visit for getting a dental bridge, the abutment teeth are prepared. Preparation involves recontouring these teeth by removing a portion of enamel to allow room for a crown to be placed over them. Next, impressions of the teeth are made, which serve as a model from which the bridge, pontic, and crowns will be made by a dental lab. Your dentist will make a temporary bridge to wear to protect the exposed teeth and gums while the bridge is being made.
During the second visit, your temporary bridge will be removed and the new permanent bridge will be checked and adjusted, as necessary, to achieve a proper fit. Multiple visits may be required to check the fit of the metal framework and bite. This is dependent on each individual's case. If the dental bridge is a fixed (permanent) bridge, your dentist may temporarily cement it in place for a couple of weeks to make sure it is fitting properly. After a couple weeks, the bridge is permanently cemented into place.