Dental Crowns, Inlays, and Bri... Health Article

Bridges

Bridges are restorations that fill in a gap caused by missing teeth. They prevent the remaining teeth from shifting and provide a more stable surface for chewing. If the gap is not filled, the other teeth shift, affecting the patient's bite (occlusion), which sometimes produces pain in the jaw joint. As the teeth move and become crooked, they also become more difficult to keep clean. The risk of tooth decay and gum disease increases, also increasing the likelihood that additional teeth will be lost. A bridge is inserted to prevent this risk.

Bridges are appliances consisting of a metal framework and one or more artificial teeth (pontics) anchored to adjacent teeth. The abutment teeth carry the pressure when the patient chews food. Bridges can be removable or fixed (permanent). Removable bridges are attached to the abutment teeth by wires or precision attachments. Fixed bridges are attached to permanent crowns placed on abutment teeth. There are two types of fixed bridges—the crown-and-bridge design and the Maryland Bridge. A Maryland Bridge does not have crowns on it. The backs of the abutment teeth are reduced slightly and small wing-like appendages on the bridge are cemented to the back of the abutment teeth.

When the adjacent teeth are not strong enough to support a bridge, a two-implant bridge is required. This type of bridge takes longer for the permanent bridge to be fitted because of the necessity for the gums to heal. Posts are surgically implanted into the patient's bone and the gum closed. It takes several weeks for the bone to attach to the posts. The posts are re-exposed and the bridge is made to fit. It is then cemented in place.

Inlays

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 the decay 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 is made from this mold and sealed into the tooth with dental cement.

Inlays and their counterparts, onlays, are conservative alternatives to crowns. They don't require as much

tooth preparation and often are more durable than amalgam fillings. Inlays cover the grooves on the surface of the molar. Onlays wrap over the tooth, covering more of its surface.

Inlays used to be made entirely of gold for its durability. New inlay alloys of palladium, nickel, or chromium are frequently used. Metals have been the dentist's choice for inlays in molars. When inlays are required for teeth that will be seen when a patient smiles, tooth-colored composites and porcelains are used. Reinforced porcelain and Lucite porcelain are durable but still may not be suitable for patients who grind their teeth. Composites are also used in fillings.