Which instrument is commonly used to smooth the surface of a finished amalgam restoration?

The burnisher is designed specifically for the purpose of smoothing and polishing surfaces of dental materials, including finished amalgam restorations. Its rounded, smooth surface helps achieve a lustrous finish by compacting the material and reducing surface irregularities. This is crucial because a well-polished restoration can prevent plaque accumulation, reduce wear, and improve the overall aesthetic appearance of the tooth.

The other instruments listed serve different purposes. An excavator is primarily used for removing carious material and debris from teeth. A matrix band is utilized to create a temporary boundary for filling materials within a cavity preparation, which helps in forming the shape of the restoration. A carver is used for shaping and trimming excess material of restorative materials but does not provide the smooth finish characteristic of a burnisher. Thus, the burnisher is the appropriate choice for achieving the desired smoothness of a finished amalgam restoration.