Dentally speaking, a bridge is the common word for a fixed partial denture. It is used to replace one or more missing teeth.
Bridges placed in esthetic areas of the mouth are usually made in PFM, or Porcelain Fused to Metal. The metal framework underneath is made of a high-palladium gold alloy in most cases. This makes the gold appear to be white gold in color.
The shortest span bridge is a cantilever bridge. This is created by preparing one tooth for a crown, then creating a two-unit bridge, effectively creating two teeth with one tooth's worth of roots. This can be dangerous, however, in the molar area of the mouth, and is usually restricted to the anterior portion of the mouth in order to avoid preparing more teeth than is necessary. Each prepared tooth is called an abutment.
Most commonly, a bridge will have two abutments, and be three units, or teeth, long. Two of the teeth will receive crowns, and the crowns will suspend a third, artifical tooth between them.
It is important to floss beneath any bridge, to prevent periodontal disease from setting in and causing eventual loss of the teeth.
A bridge might be created under the guideance of a prosthodontist, a dental specialist who has extensive training in this field, and is able to take on more complex cases, such as full mouth restorations.