Differences Between Dental Crowns and Bridges

Dental crowns and bridges are types of fixed partial prosthetic devices. They are termed “fixed” because they are cemented to the tooth.  They are partial because they replace one or more (but not all) teeth. Unlike your ordinary dentures—the ones which you can remove from your mouth and clean daily—crowns and bridges can only be removed by a dentist using special tools and instruments.

Contrary to what most people think, crowns and bridges are different from each other. A crown is generally used to cover a damaged tooth whereas bridges are for replacing one or more missing teeth. Bridges require putting crowns, called bridge abutments on the teeth adjacent to the ones missing.

GENERAL INFORMATION

As previously mentioned, a crown is used to cover a tooth. Most of the time, it is used on a damaged tooth or as cover for a dental implant. A single crown refers to a one-unit restoration used to cap a tooth that has been damaged or weakened by cavities, fractures or large fillings. The main difference from an ordinary filling is that a crown fits mostly or completely over the tooth while a filling is a material used to plug up small cavities. Fillings are for teeth that have minimal to moderate damage. Crowns are reserved for cases where the remaining tooth structure is not enough to support a filling. In most cases, teeth with extensive damage are those with large fillings that need to be replaced and those that have undergone root canal treatment. A crown serves as the final restoration of most root canal-treated teeth. A crown may also be placed on healthy teeth if these teeth are needed to support a bridge.

A dental bridge is a multiple-unit restoration used in cases of a missing tooth or multiple teeth. An artificial tooth called a pontic replaces a missing tooth. The support for the pontic is derived by placing crowns, called bridge abutments, on the teeth next to the space occupied by the missing teeth. At least one tooth is needed for support. A dental bridge works pretty much the same way as an actual bridge. The pontic serves as the beam (span) while the adjacent teeth with crowns are the poles that anchor and support the beam.

Unlike fillings, which are done in the dental clinic, construction of both crowns and bridges are done in a dental laboratory.

TREATMENT ANALYSIS

Crowns protect teeth that are weakened by decay or any other type of damage by holding or reinforcing the remaining tooth structure. Crowns reduce the chances of tooth fracture, which may eventually lead to intense pain and eventual tooth loss. In many instances, crowns are also used to improve the appearance of a patient’s smile.

Bridges offers the same benefits as crowns along with replacing missing teeth. Furthermore, they prevent the remaining teeth from drifting into the space left by the missing ones. The materials used for fabricating crowns and bridges include metal alloys, porcelain or a combination of both. Crowns and bridges made up of entirely metal are termed all-metal or all-ceramic if they are made completely of porcelain. A combination of both metal and porcelain is referred to as porcelain-fused-to-metal (PFM) crowns and bridges.

An all-metal restoration is an option if the teeth to be restored or replaced are located in the posterior (back) area. Esthetics is not critical in this area but durability of the material is important. In the posterior area, the biting force is greater compared to the anterior (front) area and requires a material that is strong enough to withstand such force.

If both esthetics and durability are required, dentists recommend PFM crowns and bridges. PFM restorations are actually much better than their all-metal counterparts when it comes to restoring or replacing anterior teeth.

On the other hand, all-ceramic is the material of choice in cases where esthetics is of prime importance. The six front teeth and the teeth next to the canine (aka the premolars) are readily visible when the patient smiles so all-ceramic crowns and bridges are suitable for these. In the past, the  problem with all-ceramic restorations was their brittleness. Unlike metal, porcelain has low resistance to fractures and can break when subjected to heavy forces. Now, new all-ceramic restoration materials are available that allow them to withstand heavy forces. This makes them a good choice for restoring front and back teeth.

ESTIMATED COSTS

The price varies according to region, materials used, laboratory fees and the dentist’s skills and experience. But in general, a good quality crown is usually in the $1200 range. All-metal restorations are the cheapest, followed by PFM. All-ceramic restorations are the most expensive.

For bridges, most dentists charge on a per-unit basis. For instance, if you have only one missing teeth and two crowns for support, that’s a total of 3 units. If the dentist charges $1000 per unit, you’re looking at a total of $3000 for the entire bridge. The number of units depends on how many teeth are missing. In general, the number of teeth that supports the bridge must exceed the number of teeth that will be replaced. In other words, the more teeth are missing then the longer the bridge will be and more remaining teeth will be needed for support.

For instance, a patient with only one missing tooth will require a 3-unit bridge (one unit for the pontic, two units for the support). But if the patient has 2 missing teeth, the bridge will most likely consist of 5 units (2 units for the pontic, 3 units for the support).

LIMITATIONS AND RISKS

The only disadvantage of crowns and bridges over ordinary fillings is the amount of tooth structure that needs to be removed. Greater removal is required for crowns and bridges because the dentist has to make room for the crown to fit. Reduction of gum tissue may sometimes be needed if the tooth is too short to receive a crown. Otherwise, the dentist will only alter the tooth and leave the gums untouched.

If the adjacent tooth is healthy and the patient does not want to have it altered, the dentist may recommend dental implants instead of a bridge. An implant is a stand-alone restoration that does not require support from the adjacent teeth. It derives support from the underlying bone so surgery is required to put it in place. It is more expensive than a bridge but it produces superior results.

RECOVERY

The area may be sore for a few days following treatment. It is not serious in nature and will go away after a few days. The patient will be instructed to chew on the opposite side for 1-2 weeks following treatment. Oral hygiene instructions will also be provided. Bridges require special cleaning aids like super floss and interdental brush. These cleaning aids will help the patient clean underneath the bridge thoroughly as it may not be possible to do so by using only a toothbrush.

RESULTS

The life expectancy greatly depends on the condition of the teeth before being restored and how well the patient takes care of their teeth. In general, 10-15 years is a good average life expectancy. If done properly, crowns and bridges will restore normal function as if the patient never lost his teeth in the first place. The patient will be able to speak and chew normally.

Crowns and bridges are stain-resistant. In fact, they are more stain resistant than the natural teeth. If stains are ever present, they are only superficial and can be removed by the dentist or hygienist. Crowns and bridges are not affected by bleaching either. So if the patient is planning to undergo teeth whitening, it is best to do it prior. That way, they can choose the shade that matches their already-whitened teeth. If crowns and bridges were done first, then the only way to whiten them is to replace them.

FINAL THOUGHTS

Restoring that perfect smile is now easier than ever. With the advancements in cosmetic dentistry, patients won’t have to hide their smiles because there is always a solution to their problem. To find out if crowns and bridges are recommended for you, consult with your dentist.

Written by Cosmetic Town Editorial Team -AA

Based on an exclusive interview with Dr. Jim Spurgeon in Norman, OK