What Is a Crown?
Your teeth have only a very limited ability to heal themselves. When a fracture or a cavity occurs in a tooth, the standard treatment involves removing any decay that may have formed in that fracture and then filling the resulting hole with a material that’s strong enough to stand up to chewing forces and durable enough to last from 10 to 15 years.
In some instances, however, the tooth is too damaged for a simple restorative filling. Cracked teeth, for example, are typically too unstable to support conventional fillings, and placing a filling in a cracked tooth may actually cause the tooth to break further. A tooth can also be so badly worn down that filling it is unfeasible. In such cases, a dentist will typically recommend the placement of a crown, which is a kind of cap that’s fitted over the damaged tooth and cemented into place.
Crowns are also used in conjunction with dental implants as well as when a tooth has been treated with a root canal. Additionally, crowns are placed on teeth that will be used as abutments for a dental bridge.
What Is a Dental Bridge?
A dental bridge is an oral prosthesis that’s engineered to be a replacement for a missing tooth or teeth. A missing tooth is more than just a cosmetic issue. Remaining teeth may shift position in a patient’s mouth, which can affect the bite and hamper the performance of effective oral hygiene regimens. Missing teeth can also cause the underlying jawbone to shrink, which can lead to the appearance of premature aging.
A dental bridge is cemented into place using the two teeth on either side of the oral space as anchors for the prosthesis. These teeth are known as “abutments,” while the artificial replacement tooth is known as a “pontic.”
What Are Crowns and Dental Bridges Made From?
Crowns can be made from ceramic materials like porcelain, from composite resins, from metal alloys or from some combination of these three materials. Dental bridges are typically made from porcelain or from metal over which a porcelain veneer has been fused.
• Metal crowns
Prefabricated metal crowns are generally used on a temporary basis to protect a tooth while a permanent crown is being created. Occasionally, metal crowns made of gold- and base-metal alloys will be used on back molars that aren’t visible because metal stands up well to biting and chewing forces.
• Porcelain and metal crowns
Metal crowns can be overlain with porcelain to match the color of a patient’s natural teeth.
• Resin crowns
Resin may be the most cost-effective material for making a crown, but resin crowns are prone to fracture.
• Ceramic crowns
Ceramic crowns look most closely like a patient’s natural teeth, but they wear down opposing teeth and have less ability to withstand chewing forces.
Fitting the Crown or Dental Bridge
Typically, a tooth on which a crown will be placed will need to be reshaped in some fashion in order to support the crown. The tooth may need to be filed down with a drill, or if a large portion of the tooth is missing, it may need to be built up with filling material. Once that process is complete, the dentist will make an impression of the patient’s mouth to help ensure that the new crown will fit comfortably without negatively impacting the patient’s bite. If the new crown is to be made from porcelain or some other type of ceramic, the dentist will also choose a shade that matches the shade of the natural teeth most closely. Once the patient’s mouth is prepped, and the new crown has been manufactured, the dentist will fix the crown into place using a permanent cement.
Preparing a patient’s mouth for a dental bridge placement is a more complicated process than preparing a patient’s mouth for a single crown since two teeth will need to be shaped, prepped, and fitted with crowns, and a new dental prosthesis will need to be created. Essentially, however, the steps involved in the process are the same.
Issues with Crowns and Dental Bridges
Even when a crown is an excellent fit, a small margin typically develops around its edge where the gum recedes from the artificial material from which the crown was crafted. If bacteria creep into this space, the underlying tooth is susceptible to decay. Occasionally, too, a crown will fall off because not enough cement was used in the fitting process or because the natural tooth surface has suffered from decay. Ceramic crowns can also chip, particularly if a patient grinds or clenches his or her teeth frequently. With proper oral hygiene and regular dental checkups, however, a patient can expect his or her new crown or dental bridge to last between five and 15 years.