Four-surface fillings are fillings that cover four of the five tooth surfaces on one tooth. A four-surface filling can contain a mixture of metals including silver, copper, tin, and liquid mercury. Generally, this process takes about an hour depending on the amount of decay that needs to be removed prior to filling.

"B," which stands for buccal, is the surface of the tooth that faces the cheek.

D2388 Resin-bonded Composite. This code describes a composite resin placed on a posterior tooth, involving four or more surfaces.

Code D2391 (one-surface posterior resin-based composite) explicitly states that it should be “used to restore a carious lesion into the dentin.” The rationale for the requirement that the lesion extends into dentin can be questioned.