Dental fillings are metal amalgams or composite resins used to fill a cavity.
Dentists use dental fillings to restore teeth damaged by dental caries (tooth decay). Dental caries are caused by microorganisms that convert sugars in food to acids which erode the enamel of a tooth, creating a hole or cavity. The dentist cleans out the decayed part of the tooth and fills the opening with an artificial material (a filling) to protect the tooth's structure and restore the appearance and utility of the tooth.
As in any dental procedure, the dentist and dental assistant will need to use sterile techniques. Gloves and masks are essential as well as the sterilization of equipment and tools. This not only helps prevent the spread of infectious diseases like AIDS and hepatitis, but also the common cold.
The patient's reaction to anesthesia is the other main concern of the dentist and dental assistant when performing dental fillings. Nitrous oxide should be avoided with pregnant patients, and local anesthetics should be used with caution, though they are considered safe. Local anesthetics like Novocain and lidocaine have been in practical use for decades with few side effects reported. Some patients, however, are allergic to these drugs.
Though dentists are encountering fewer and smaller cavities in their patients, there is still a need for dentists to fill cavities. Old fillings suffer wear and need to be replaced. Patients are demanding more restorative work on their teeth, sometimes opting for full mouth restorations that involve installing crowns, bleaching teeth or applying veneers, and replacing dark metal fillings with tooth-colored ones that create a monochomatic view in a patient's mouth.
Once the decay is removed and the tooth is prepared, the dentist has a wide choice of dental filling materials to choose from.
The most common and strongest filling material is amalgam. It is a silver filling that is usually placed on the rear molars which endure more stress during chewing. Amalgam fillings—used for large, deep cavities—are strong and very resistant to wear. Amalgam has been in use since 1833.
Amalgam is a mixture (which is what the word means) of several metals, including liquid mercury (35% silver, 15% tin or tin and copper, a trace of zinc, and 50% mercury). When it is prepared, it has a malleable consistency which can easily be shaped to fit the prepared tooth. It hardens to a durable metal.
Despite its durability, many dentists and patients avoid amalgam fillings. Dentists have found that amalgam has a tendency to expand with time. As a result, teeth become fractured from the inside, often splitting the tooth. Patients often avoid amalgam for strictly aesthetic reasons. Amalgam fillings darken over time and make teeth look as if they are decayed.
The biggest reason amalgam has lost favor is a health concern due to its 50% mercury content. Although the American Dental Association (ADA) has pronounced amalgam safe in the quantity and composition of amalgam, some patients and dentists are disturbed by various reports of illness in relation to the mercury in amalgam fillings. Mercury is a toxic material. Some states are required to dispose of mercury waste as if it were a hazardous product. There is also an added risk of inhaling mercury particles when old fillings are removed.
Gold fillings or inlays are created outside of the mouth by a dental technician and then cemented into place. They are also used to fill the back molars. Gold fillings are very durable. Like amalgam, however, they are not as aesthetically pleasing as tooth-colored fillings.
Composite fillings, often called white fillings, are made of a plastic resin and finely ground glass. They must be applied to the tooth surface in thin layers. Dentists try to match the color of composites with neighboring teeth for a more natural look, making the filling appear invisible. Composite resin fillings often are made smaller than amalgam fillings and require less tooth preparation, thereby saving more natural tooth surface.
Composite fillings are bonded to the tooth so that the tooth becomes stronger than it was before. They are also less sensitive to temperature changes in the mouth that can damage the tooth; therefore there is less chance that the tooth will shatter because of the filling.
These fillings may not be suitable for large cavities in molars. Though composite durability increased in the 1990s, a porcelain inlay or crown may be the best choice for a durable, natural-looking restoration of a molar.
The major drawback of composite resin fillings is cost. They average one-and-a-half to two times more than the price of amalgam fillings. They also can be stained from drinking coffee and tea. Large composite fillings tend to wear out sooner than amalgam fillings.
Composite fillings can last seven to 10 years, which is similar to the lifespan of amalgam fillings.
Resin ionomers are new, tooth-colored filling materials that contain a resin and fluoride. They are very suitable for children and for older adults who suffer from root decay that occurs as a person ages. These fillings seal the tooth and also protect it from future decay because of the fluoride that they release.
During a routine checkup, the dentist may find a cavity in a tooth with a metal tooth probe. A new diagnostic tool, the DIAGNOdent, can detect evidence of cavities and pre-cavity conditions on the tooth's surface. A low-powered laser, the DIAGNOdent is able to detect decay so early that a dental cavity can be avoided. These pre-cavity areas can be protected with a sealant, thereby preventing further decay.
Cavities found since the 1990s are relatively small and not very deep, there may be no need to anesthesize the area where the dental work will be done. High-speed drills often are able to clean out the decay quickly and with little discomfort. If the cavity is not very deep, the drill may not reach the sensitive nerves in the teeth which usually cause pain. Children and some adults may need anesthesia in any case. The dentist and the dental assistant need to be aware of the patient's history and if the patient reacts adversely to local anesthesia.
There are some dentists who use electronic dental anesthesia (EDA), a device that sends electrical charges to the gum through electrodes. Sometimes this is enough anesthesia for the procedure. At other times, EDA numbs the area where the anesthesia is administered, so that the patient doesn't feel the needle as it goes into the gum. Some dentists also provide soothing music to calm patients during the procedure. Other dentists will use local anesthesia in combination with nitrous oxide-oxygen analgesia to minimize discomfort through the drilling phase of a filling.
Dental lasers that generate a low-powered beam of light are being used to cut away decay, but without the whine of the drill and without using anesthesia. Though a bit slower than the conventional drill, lasers are very efficient at preparing a tooth to receive a filling. Unfortunately, lasers cannot yet remove old fillings or prepare a tooth surface to receive a crown.
Air abrasion is another way to remove decay without using anesthesia. Air abrasion machines produce a spray of air and powder. There is no vibration or heat. Because it has no vibration, it avoids microfractures in the tooth that sometimes occur with drills. Air abrasion removes only a small amount of the tooth's structure. Therefore, it is suitable for small cavities and the repair and replacement of old fillings. It also can repair chipped teeth and clean discolored or stained teeth.
After the cavity is cleaned of decay, the walls of the tooth are shaped and are ready to receive a filling material. If a composite resin filling is used, the tooth next needs to be etched so that the resin will adhere to the tooth. The tooth then is filled, shaped, and polished. The composite filling then must be hardened by shining a special light on it.
The dentist and dental assistant should advise the patient that the teeth, lips, and tongue may be numb for several hours after the procedure, if a local anesthetic was used. Some patients experience sore gums or a sensitivity to hot and cold in the tooth that has just been filled. Normally, patients are advised to avoid chewing hard foods directly on new amalgam fillings for 24 hours. Composite fillings require no special caution since they set immediately. If patients experience continued pain or an uncomfortable bite, they should call their dentist.
Some patient's have allergic reactions to local anesthesia.
Amalgam— A mixture of metals, primarily mercury used to make large, durable fillings. Also called silver fillings.
Anesthesia— A condition created by drugs that produces a numb feeling. General anesthesia produces unconciousness whereas a local anesthesia produces numbness around the site where the drug was introduced.
Composite filling— A resin material that is tooth colored and is used to fill a tooth once decay has been removed. It is used most often in front teeth, but may be used in any tooth for aesthetic reasons.
Crown— An artificial covering prepared by a lab technician to fit over a damaged tooth or one weakened by decay.
Dental caries— Tooth decay caused by microorganisms that convert sugars in food to acids which erode the enamel of a tooth.
Dental laser— A device that generates a low-powered beam of light that is used in place of a dentist's drill to cut away decay from a tooth or remove gum tissue.
Enamel— The hard outer surface of a tooth.
Fillings restore a tooth's function and appearance. They permit the patient to continue to eat and chew properly and last for several years. Normal fillings will need to be replaced over a patient's lifetime. Since fewer dental caries had been observed since the last decade of the twentieth century, dentists are initially filling fewer teeth, but are replacing fillings as they fail and sometimes systematically, especially if the patient decides to cosmetically enhance his or her teeth. Since many of the initial cavities are quite small, patients are opting for more aesthetically pleasing filling materials even if they are not as durable.
Health care team roles
When the dentist discovers a cavity, filling options are discussed with the patient. The dental assistant prepares the dentist's workstation and lays out the specific instruments that are needed. The dental assistant prepares the filling material according to the manufacturer's directions and assists the dentist in preparing the tooth for filling and in the filling procedure itself. The dental assistant cleans the patient's mouth and returns the procedure room to order. All of the instruments that have been used are sterilized by the dental assistant.
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