Which of the following materials is appropriate to mix on a paper mixing pad?

The most appropriate material to mix on a paper mixing pad is amalgam. Amalgam, which is a mixture of metals including silver, mercury, tin, and copper, is typically mixed on a paper pad due to its easy cleanup and the fact that it does not react with the paper. This surface allows for a uniform mixing which is essential for achieving the correct consistency and properties of the amalgam, ensuring optimal performance once placed in a cavity preparation.

Other materials, such as composite resin and glass ionomer, may have specific mixing requirements that involve the use of glass or porcelain mixing surfaces to avoid adhesion to the mixing surface and to ensure proper mixing and handling characteristics. Zinc oxide-eugenol can also be mixed on paper, but it might not provide the ideal moisture control that a glass slab would offer, as it can be sensitive to moisture and can set improperly if mixed in the wrong environment. Hence, while several materials have mixing pads they can work with, amalgam is particularly suited to this method for effective results.