Tooth replacements and restorations

A tooth restoration is any artificial substance or structure that replaces missing teeth or part of a tooth in order to protect the mouth's ability to eat, chew, and speak. Restorations include fillings, inlays, crowns, bridges, partial and complete dentures, and dental implants. Restorations have somewhatdifferent purposes depending on their extensiveness. Fillings, inlays, and crowns are intended to repair damage to individual teeth. They replace tooth structure lost by decay or injury, protect the part of the tooth that remains,and restore the tooth's shape and function. Bridges, dentures, and implants are intended to protect the shape and function of the mouth as a whole.

Fillings are restorations that are done to repair damage caused by tooth decay (dental caries). To stop the decay process, the dentist removes the decayedportion of the tooth using a high-speed drill or an air abrasion system, shapes the cavity walls, and replaces the tooth structure with a filling of silver amalgam, composite resin, or gold. The filling is placed in the cavity asa liquid or soft solid. It sets within a few minutes and continues to hardenover the next several hours. Silver amalgam is commonly used to fill cavitieson the biting surfaces of the back teeth, because it is strong enough to withstand the tremendous pressures exerted by grinding and chewing. Composite resin is typically used to fill cavities in front teeth and any other teeth that are visible when the patient smiles, because its color can be matched to the tooth surface. Gold as a filling material is far less common, but is beingincreasingly used. Although it is more expensive and less easily applied, itdoes not trigger the sensitivity reactions that some patients have to silveramalgam.

An inlay resembles a filling in that it fills the space remaining after the decayed portion of a tooth has been removed. The difference is that an inlay is shaped outside the patient's mouth and then cemented into place. After thedecay is removed and the cavity walls are shaped, the dentist makes a wax pattern of the space. A mold is cast from the wax pattern. An inlay, usually ofgold, is made from this mold and sealed into the tooth with dental cement.

The crown of a tooth is the portion that is covered by enamel. A restorativecrown replaces this outer part to protect the tooth. This protection becomesnecessary when a tooth cracks or has its entire structure weakened by decay.As with a filling or inlay, the dentist first removes the decayed portion ofthe tooth. The tooth is then prepared for a crown. It may be tapered on the outside edges to a peg, reinforced with a cast metal core, or rebuilt with both a cast metal core and a post. A wax impression of the prepared tooth and the teeth next to it is made. The new crown is made to fit this mold. The crownmay be made of gold or stainless steel alone, metal with a veneer of tooth-colored porcelain or resin, or of porcelain or resin alone. The finished crownis then placed over the prepared tooth, adjusted, and cemented into place.

Bridges are a type of restoration that is done when one or more permanent teeth are lost or pulled. Bridges are nonremovable appliances of one or more artificial teeth (pontics) anchored by crowns on the adjacent teeth (abutment teeth). The abutment teeth carry the pressure when the patient chews food.

A partial denture is similar to a bridge in that it fills a gap left by missing teeth with artificial teeth on a metal frame. A partial denture is removable, however. It attaches to a crown on the abutment tooth with a metal claspor precision attachment. A partial denture is primarily used at the end of arow of natural teeth, where there is only one abutment tooth. The pressure exerted by chewing is shared by this abutment and the soft tissues of the gum ridge beneath the appliance.

Dental implants are a means of securing crowns, bridges, and dentures in themouth. A hard plastic or metal fixture is implanted through the soft tissue into the bone. Over time, the bone grows around this fixture, firmly anchoringit. The exposed end of this fixture is covered with a crown and may serve asa stable abutment for a bridge or denture.

Complete dentures may be worn when all of the top or bottom teeth have been lost. A complete denture consists of artificial teeth mounted in a plastic base molded to fit the remaining oral anatomy. It may or may not be held in place with a denture adhesive. A partial or complete denture may take several weeks of getting used to. Inserting and removing the denture will take practice.Speaking clearly may be difficult at first--the patient may find it helpfulto read out loud for practice. Eating may also feel awkward. The patient should begin by eating small pieces of soft foods. Very hard or sticky foods should be avoided. Patients with dentures must work on good oral hygiene. Specialty brushes and floss threaders may be used to remove plaque and food from around crowns and bridges. Dentures should be removed and brushed daily with a specially designed brush and a denture cleaner or other mild soap. The patientshould see the dentist for an adjustment if there is any discomfort or irritation resulting from a restoration. Otherwise, the patient should see the dentist at least twice a year for an oral examination.

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