Teeth may be lost to a number of disorders including cavities, periodontal disease, or injury or may be removed when treatment fails. Missing teeth may cause cosmetic and speech problems and problems with the alignment of the teeth or upper and lower jaws. Missing teeth may allow remaining, nearby teeth to move.
Missing teeth can be replaced with several types of dental appliances. These appliances include bridges, crowns, implants, and dentures.
Bridges, Crowns, and Implants
The replacement for an extracted tooth may be a bridge or an implant. Severely damaged teeth may have a crown placed over them.
A bridge is a fixed partial denture in which teeth on either side of the missing tooth are covered with crowns. A bridge is made up of false teeth that are fused together and then attached to a crown that is cemented to natural teeth. A bridge is permanently attached and cannot be removed. More than one bridge can be used to replace missing teeth.
A crown is a cap (restoration) that fits over a tooth. Getting a properly shaped crown usually takes two visits to the dentist, although sometimes more visits are needed. On the first visit, dentists prepare the tooth by tapering it slightly, take an impression of the prepared tooth, and put a temporary crown on it. A permanent crown is then made in a dental prosthetics laboratory, using the impression. On the next visit, the temporary crown is removed, and the final crown is permanently cemented onto the prepared tooth. Many dentists now use digital scanners and crown-milling devices that help them design and mill a crown for same-day placement.
Usually, crowns are made of gold, ceramic, or porcelain fused to a metal structure. The porcelain coating can be used to mask the color of the metal. Although porcelain is harder and more abrasive than tooth enamel and may cause wear on the opposing tooth, newer ceramics are less apt to do so. Crowns made entirely of porcelain or similar material have a slightly greater tendency to break than do those made entirely of metal.
Implants may be used to replace missing teeth. If people do not have sufficient healthy bone in their jaw, bone grafts can be done to create an adequate bed for the implants. Implants are metal fixtures inserted into the jawbone. The metal is a special alloy to which bone cells can attach. After a period of time, usually 2 to 6 months, the implant becomes solid with the bone, and a post is attached. Then an artificial tooth (crown) is attached to the post. The resulting tooth can handle the force of normal chewing. Implants are considered more desirable now because they do not decay and they offer a fixed solution to removable partial dentures. People must keep the area around the implant very clean to prevent infection.
Crowns, Bridges, and Implants
Complete (full) or partial dentures are useful for people who have lost nearly all or all of their teeth. Complete dentures can be removed and are worn by people who have no teeth. Partial dentures can also be removed and are worn by people who need to have several teeth replaced but who cannot have or cannot afford bridges or implants.
Dentists carefully construct dentures so that they fit well and look natural. Typically, constructing dentures takes several months and involves a sequence of carefully planned steps. Once they have dentures, people should see their dentist at least once a year. The shape of the mouth and jawbones can change over time or as weight is lost or gained, in which case the dentures may have to be refitted or replaced.
Dentures can improve appearance and speech, but they are far from a perfect solution. They do not fully restore the feeling of natural teeth and restore less than 20% of the chewing ability provided by natural teeth. Dentures can also cause discomfort and interfere with tasting.
Dentures must be kept clean. They should be removed after each meal and cleaned with nonabrasive, nonwhitening toothpaste or baking soda on a soft toothbrush or denture brush. Also, the mouth should be cleaned to remove food debris. Dentures should be removed before going to sleep, cleaned carefully, and kept in a safe place. Soaking dentures overnight in a cleaning solution can be helpful but is not necessary if dentures are cleaned well with a toothbrush.
Problems with dentures
Occasionally, the gums beneath dentures become red and inflamed and have a velvety appearance (denture sore mouth). The inflammation may not be painful. People who have infections caused by the yeast Candida may have poorly fitting dentures, poor oral hygiene, and dentures that move excessively, and, most frequently, people who wear their dentures 24 hours a day are at increased risk of inflammation. People who have an overgrowth of yeast have cottonlike patches or ulcerlike sores on their gums that can often easily be treated with drugs. If inflammation persists, the dentist may order a biopsy to test for oral cancer and other tests to look for systemic conditions such as diabetes.
Refitted or new, well-made dentures almost always improve the situation. Improving oral hygiene and more effective denture cleaning may also help reduce tissue inflammation. Some people may need to remove the dentures for extended periods and use antifungal mouth rinses and overnight soaks for the dentures. A dentist can prescribe a variety of topical antifungals to treat the yeast (Candida) infection that is contributing to inflammation beneath the dentures.
Dental Appliances and Surgery
Typically, all removable dental appliances are removed before general anesthesia or throat surgery to prevent them from breaking or being swallowed or inhaled into the lungs. During a procedure, dental appliances are stored in water to prevent changes in shape. Sometimes, however, anesthesiologists (doctors who give people anesthesia during surgery) have people leave their appliances in place so that they are better able to pass an airway tube. Leaving appliances in during a procedure also keeps the face in a more normal shape so that the anesthetic mask fits better and prevents the gums from being injured by natural teeth in areas where no teeth exist.