Aspen Dental Group - Aspen Dental Services

Crowns and Bridges

A crown (also known as a cap, dental cap, or tooth cap) is used to repair a damaged tooth by fully covering (capping) the tooth; the crown is cemented in place and becomes the tooth's new outer surface. The crown is shaped and colored to look like a real tooth, and is strong, durable, and stable.

Teeth can sustain damage from a number of causes, including lost fillings, root canals, decay, and chipping and cracking of the enamel. Since a crown involves replacing the outer portion of a tooth, it should be used when there is significant damage to the tooth. Whatever is left of the outside of the tooth is ground away so the crown can be applied. In the interests of preserving as much of the original tooth as possible, a crown should not be used if a more conservative procedure will produce the same results and should not be used for cosmetic purposes alone.

There are different types of crowns, each having its advantages and disadvantages. The dentists at Aspen Dental Group are proficient in the use of them all and can advise you as to what is best for your situation. Following is information on the different types of crowns.

Metal Crowns

Metal crowns can be made of gold alloy, palladium alloy, or a base metal (such as nickel or chromium) alloy. Metal has many advantages over other materials used for crowns:

Metal is the strongest of the materials used for crowns and less of the tooth has to be removed for application as opposed to other crown materials.
Metal is very workable and is much easier than other crown materials to get a precise fit to the gum.
Although strong, metal is softer than other crown materials. This causes less wear to to opposing teeth, especially with molars which do the grinding. Since metal withstands these forces better, it rarely chips or breaks.

Due to all of the above, metal crowns usually last longer than other crowns. The only drawback to using metal is that it is unsightly which has led to the use of other materials. Metal crowns are usually used in the back of the mouth for molars.

Porcelain (Ceramic) Crowns

A crown of all porcelain has the distinct advantage over metal in that it can be matched to the color of the natural tooth. It is also excellent for patients with metal allergies. However, an all porcelain crown:

Is not as strong as metal so more of the tooth needs to be removed for application.
Is not worable the way metal is and as such more difficult to get a precise fit to the gum.
Is harder than metal so more wear occurs to opposing teeth, especially molars.
Being harder but not stronger, porcelain is more likely to chip or break and will not hold up to grinding forces as well as metal.

For these reasons all porcelain crowns are best used for front teeth.

Porcelain Fused To Metal Crowns

With this type of crown the metal rests on the gum and porcelain covers part or all of the metal. This creates a crown that is stronger than an all porcelain crown and is cosmetically pleasing making them an excellent choice for either front or back teeth.

These crowns retain most of the advantages of metal:

Less of the tooth is removed due to the metal.
Get a precise fit to the gum due to the metal.
Are much stronger than an all porcelain crown and can withstand heavy biting pressures.

However, some of the problems of porcelain still remain:

Still cause more wear to opposing teeth.
Still susceptible to chipping and breaking.

And although these crowns are far better cosmetically than all metal, they are still not as nice as all-porcelain due to the difficulty of replicating the translucency of natural teeth because of the underlying metal. Another problem is that the underlying metal can show through as a dark line at the gum line which becomes more pronounced if the gum recedes.

Crowns can also be used to hold a 'spacer' in place to span a gap between teeth.
This is known as a Bridge.

A completely missing tooth is not just a cosmetic problem but has implications for the rest of the mouth. Without the support of the missing tooth, adjacent teeth will float making them more susceptible to tooth decay and gum disease. Even though the root is gone, a crown can still be used in the space by supporting it from adjacent teeth forming a "bridge". Bridges are fixed to the teeth and cannot be removed from the mouth so they require commitment to serious oral hygiene on the part of the patient. Different types of bridges are used depending on where the tooth is missing and the condition of the adjacent teeth.

Traditional Bridge

A crown is placed on each of the adjacent teeth creating a structure to support a crown in the empty space. This type of bridge makes the most sense if the adjacent teeth need crowns as well. If the adjacent teeth are in good condition, a resin bonded bridge (see below) or an implant may be a better choice.

Cantilever Bridge

In a cantilever bridge only one tooth adjacent to the empty space is used for support. This type of bridge is used when there is only one tooth adjacent to the empty space (such as when the last molar in the back of the mouth is missing) or the empty space is in an area of less stress where only one tooth is necessary for support (such as when a front tooth is missing).

Resin Bonded Bridges

In this type of ridge the spanning crown is held in place y metal bands that are bonded to the adjacent teeth with a resin (type of plastic). A resin bonded bridge is best used when the adjacent teeth are in good condition and putting crowns on them is uncalled for. However, a resin bonded ridge is not as strong as a traditional bridge (see above) and is usually used in an area of less stress (such as a missing front tooth). If the missing tooth is a molar, an implant may be a better choice.