Dentistry is an art as well as a science; dental crowns offer a perfect example of this. A dental crown or “cap” is a covering that fits over a damaged, decayed or unattractive tooth. It can even replace a tooth entirely as part of dental bridgework.
Crowns are synthetic caps, usually made of a material like porcelain, placed on the top of a tooth. A crown completely covers a tooth above the gum line. This is in contrast to a dental veneer, which only covers a tooth’s front surface and needs natural tooth structure to support it. Therefore, if a tooth is missing a significant amount of structure above the gum line, a crown would be the restoration of choice.
Crowns are typically used to restore a tooth’s function and appearance following a restorative procedure such as a root canal. When decay in a tooth has become so advanced that large portions of the tooth must be removed, crowns are often used to restore the tooth.
Crowns strengthen damaged teeth, allowing them to function normally again. When crafted from today’s high-tech porcelains (dental ceramics), crowns are virtually indistinguishable from natural teeth. They can even be designed to improve upon a tooth’s original appearance.
Crowns are also used to attach bridges, cover implants, prevent a cracked tooth from becoming worse, or an existing filling is in jeopardy of becoming loose or dislocated. Crowns also serve an aesthetic use and are applied when a discolored or stained tooth needs to be restored to its natural appearance.
There are other materials besides porcelain that we can use to make dental crowns, depending on what qualities are most important. For durability, cast gold can’t be beaten. However, this is not always the most aesthetic choice — especially towards the front of the mouth. Other possibilities include porcelain-fused-to-metal crowns (PFM), which have a metal interior for strength and a porcelain exterior for a more natural appearance, and all-porcelain crowns with zirconia, representing the strongest ceramic. We would be happy to discuss the pros and cons of these various options with you.
Crowning or capping a tooth will usually take two to three visits. At the first visit, your tooth is prepared to receive its new crown. First, it is shaped to fit inside the new covering—a tooth must usually be reduced in size to accommodate a crown. This will involve some drilling to give the tooth a uniform shape. The tooth and the surrounding area will be numbed beforehand. If there is very little tooth structure left, to begin with, the tooth may have to be built up with filling material, rather than filed down, to support the crown.
After the tooth is prepared, impressions of your teeth are taken, either digitally or with reliable, putty-like impression materials, and sent to a special dental laboratory to create a custom-designed crown. There, the impressions will be used to make models of your teeth for the creation of a crown. The models will serve as guides to the highly skilled lab technicians, who will ensure that your new crown is designed to enhance your smile and function well within your bite.
In some cases, before you leave the office, a temporary crown will be attached to your tooth to protect it until the permanent crown is ready. At the second visit, your permanent crown will be attached to your tooth with either a resin that hardens when exposed to a special light source, or a type of permanent cement.
With proper care, a good quality crown could last up to eight years or longer. It is very important to floss in the area of the crown to avoid excess plaque or collection of debris around the restoration.
Certain behaviors such as jaw clenching or bruxism (teeth grinding) significantly shorten the life of a crown. Moreover, eating brittle foods, ice or hard candy can compromise the adhesion of the crown, or even damage the crown.
Bridges are natural-looking dental appliances that can replace a section of missing teeth. Because they are custom-made, bridges are barely noticeable and can restore the natural contour of teeth as well as the proper bite relationship between upper and lower teeth.
Crowns can be used in a bridge to create a lifelike replacement for a missing tooth. The bridgework spans the space of the missing tooth and requires at least three crowns. Two of those crowns will be placed over healthy teeth on either side of the missing tooth; these healthy teeth are referred to as abutment teeth. The two crowned abutment teeth become supports for a third crown placed in between them; that third crown is referred to as a pontic. If more than one tooth is missing, more crowns will be needed to bridge the gap in between the abutment teeth.
The number of abutment teeth necessary to replace missing teeth is influenced by the number of missing teeth, the size, and length of the abutment tooth roots, the amount of bone support each abutment tooth has, as well as where in the mouth the missing tooth is located. For example, if you have three missing teeth, four abutment teeth may be necessary, thereby creating a seven-tooth bridge. Engineering and designing of the bridge require an understanding of how to replace teeth, as well as the biology of the supporting gum and bone tissue.
Bridges are sometimes referred to as fixed partial dentures because they are semi-permanent and are bonded to existing teeth or implants. There are several types of fixed dental bridges (cannot be removed), including conventional fixed bridges, cantilever bridges, and resin-bonded bridges. Some bridges are removable and can be cleaned by the wearer; others need to be removed by a dentist. There are also appliances called implant bridges are attached to an area below the gum tissue or the bone; porcelain, gold alloys or combinations of materials are usually used to make such bridge appliances.
Bridgework requires the same conscientious care as a normal crown and your natural teeth. Be sure to brush and floss between all of your teeth — restored and natural — every day to reduce the buildup of dental plaque. When you have crowns or bridges, it is even more important to maintain your regular schedule of cleanings at the dental office. Avoid using your teeth as tools (to open packages, for example). If you have a grinding habit, wearing a nightguard would be a good idea to protect your teeth and your investment.