Crowns & Bridges
What is a crown?
A crown or cap is an artificial tooth made of porcelain or metal and porcelain placed over an tooth to increase its strength and improve appearance.
It is done in two appointments. In the first appointment, the tooth is reduced by one to two millimeters on all sides and an impression is taken. A temporary crown is then made to protect the area between the first and second appointment. The impression is sent to a lab which will fabricate the final crown.
At the second appointment, which is usually around 2 weeks after the first appointment, the temporary crown is removed and the permanent crown is cemented. Some adjustment to the height of the crown may be necessary.
Teeth are crowned most often because there is little natural tooth structure remaining. A crown helps prevent this remaining tooth structure from fracturing. This is common in teeth that have had root canal treatments because they often have large fillings.
What are crowns made of?
Crowns can be made of gold, porcelain, or porcelain fused to metal (gold and other metals).
Gold crowns are an excellent choice because they are very close in hardness to teeth. They also require less reduction of tooth structure then other crowns. The problems with them include the esthetics and cost (due to the high cost of gold!)
Porcelain crowns are great for esthetics because they look very natural. They require more reduction because of the need for more porcelain to resist fracture. The problems with them are that they do tend to fracture. They are not generally good in areas where there is high stress such as molars.
Porcelain fused to metal crowns are often the best choice because they have the strength of the gold crowns but are covered with porcelain to provide better esthetics. The esthetics are not quite as good as porcelain crowns but close.
Do crowns fail?
There are some issues that can occur after a crown is placed.
The most common problems would include cavities around the margins. While the crown cannot get a cavity there is natural tooth structure around the edges of your gums that can decay. This may often lead to the crown needing to be redone.
Another major problem can be the fracture of porcelain on both porcelain crowns and porcelain fused to metal crowns. Unfortunately it is not easy to bond materials back to porcelain so depending on the esthetic concerns, crowns may need to be redone.
How do we replace missing teeth?
There are three main ways to replace missing teeth.
- Full or partial dentures
- Fixed bridges
- Implants
The simplest option is usually a denture. This involves taking impressions of the mouth and the fabrication of either a full or partial denture. Partial dentures can generally be made of acrylic or metal and acrylic. The acrylic or plastic dentures are less expensive (about half the cost) but do not function well. They usually look good but do not stay in very well when the patient is trying to eat. A partial denture with a metal framework, which is not visible, is thinner (and more comfortable) and is easier to eat with. These are always the best option cost wise because they can replace a lot of teeth for almost the same price. They are not usually a good option when only one tooth is missing because the patient will usually not bother with it. Of the three options, this is also the least comfortable option.
The next option is a fixed bridge. Bridges are when missing teeth are replaced between two existing teeth to fill in the space. The most common bridge would be a conventional bridge which has a crown on the tooth in front of the space and a crown on the tooth behind the missing tooth. These usually will look almost exactly like real teeth and function like them also. The difficulty with this type of restoration is that they require you to clean underneath the bridge because they need to be slightly away from the gum tissue. The other disadvantage can be if the teeth supporting the missing tooth are in good condition because it involves reducing these teeth for the supporting crowns. In some cases, a Maryland bridge can be done which involves much less reduction of tooth structure and is also less expensive.
The best option (and most expensive) is dental implants. They function almost identically to natural teeth. The implant is usually done in two steps. The first step, a screw is placed into the bone and allowed time to heal into the bone (osseointegration). After that a crown is attached to the screw. These are the easiest two clean because they function just like real teeth. The success rate on implants is also the highest of any procedure in dentistry. The problem is the cost. A single implant can cost around $3500-$4000.