Crowns and Bridges
When teeth are heavily decayed they may be too weak to survive with just a filling. By placing a crown, a tooth may be given a new lease of life. Even when a single tooth is lost, a denture may not be required as a bridge can be made which spans the gap with a tooth attached to those next to the space. Sometimes when a single small tooth is lost at the front of the mouth a simple bridge can be made which has ‘wings’ that are glued to the back of the adjacent teeth. This results in less tooth being damaged by the drill.
Crowns
A dental crown is a tooth-shaped “cap” that is placed over a tooth — to cover the tooth to restore its shape and size, strength, and improve its appearance.
The crowns, when cemented into place, fully encase the entire visible portion of a tooth that lies at and above the gum line.
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 pediatric dentist is likely to recommend a stainless steel crown.
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.
Bridges
A bridge allows the dentist to replace lost teeth without the use of a denture or dental implant. Basically a false tooth is held in place by being attached to a tooth next door. The disadvantage is that the teeth next to the space have to be prepared in a similiar way to a crown in order to accept the bridge. If these teeth already have crowns or big restorations then this is not a problem, the major concern however is when these teeth have small or no restorations (fillings). One compromise is the ‘acid etched bridge’, with this type a fine ledge is placed on the back of the adjacent teeth.One disadvantage of a bridge is that the patient should wait three months before placement as the ‘gum’ shrinks’ after a tooth is extracted. If the bridge was fitted early a gap would appear underneath the pontic (the false tooth). At the back of the mouth this may not be a problem, at the front of the mouth however this may appear as a black line along the gum.