Which best describes the purpose and consistency of a dental cement used for the final seating of a porcelain-fused-to-metal crown?

The correct answer focuses on the primary consistency of the dental cement used for the final seating of a porcelain-fused-to-metal crown. When seating this type of crown, the cement’s purpose is primarily for cementation, which means it should be able to adequately fill the space between the crown and the tooth structure, ensuring a stable bond.

Primary consistency indicates a thicker, more viscous mixture, which is ideal for achieving an effective seal and stability upon application. This thickness helps to prevent washout and provides better retention for the crown. A primary consistency allows the cement to maintain its position without slumping or collapsing under the weight of the crown, facilitating proper seating.

In contrast, the other options introduce terms like "base" and "secondary" consistency, which emphasize different properties or uses for dental materials. A base consistency typically refers to materials used for thermal insulation or to support dentin and pulp, not suitable for crown cementation purposes. Secondary consistency would imply a thinner mixture that may not provide the same level of retention or seal required for a durable crown fixation.

Thus, the use of cementation with primary consistency aligns perfectly with the requirements for secure and long-lasting placement of porcelain-fused-to-metal crowns.