Dental Crowns
A cap, crown or more accurately a fixed partial denture is the name given to a restoration that replaces the part of the tooth that is above
the gumline. Preparing a tooth for a crown has a relatively high biological cost as the removed tooth structure cannot be regrown.
However, when a tooth is severely damaged, a crown can be a beautiful and long-lasting solution to restoring a tooth.
Dentistry has been compared to cosmetic (plastic) surgery where the goal is to provide an undetectable end result. Creating a natural-looking, long-lasting, comfortable crown to restore a damage tooth begins with a critical evaluation of what caused the tooth to fail. To achieve an optimal result, many things are considered.
Is the tooth a good candidate for a crown?
On many occasions, patients have presented to our office with a tooth or teeth where decay or trauma has reduced the amount of tooth structure available to place a crown. The term “ferrule effect” has been used to describe the minimum amount of tooth structure above the bone that a crown must be supported by in order to keep the tooth from fracturing. Many times, a crown that has “come off” lacks an adequate 1.5 to 2.0 mm “ferrule”. Approaches to regaining an adequate ferrule include limited orthodontic or periodontal treatment. An indication that a tooth may have an inadequate ferrule would be if a crown unexpectedly falls off. Often the remainder of the tooth is fractured off and remains inside of the crown.
Another consideration when restoring a tooth with a crown is the concept of biological width. Biological width is the space that the body needs to transition from an “inside” tissue such as bone to an “outside” tissue such as epithelium (gum tissue). In his famous paper, Tarnow determined that amount to be 2mm measured from the margin or edge of your crown to the top of your bone tissue. An indication of a tooth that may have an inadequate biological width is red, swollen and bleeding gums where your crown and gums meet. Another cause of these symptoms may be an “open margin” or crown that does not fit tightly to your tooth.
There are many types and grades of crowns. A crown may be made of all gold, porcelain fused to gold, zirconium, porcelain fused zirconium, pressed empress, di-lithium silicate or all porcelain (feldspathic). Which material to choose depends on may factors unique to each patient. Each choice has its benefits and disadvantages. It is important to have a discussion of which material choices best suits your need