A wax-up for a removable partial denture (RPD) framework is made on what type of cast?

The correct answer is that the wax-up for a removable partial denture (RPD) framework is made on a refractory investment cast. This type of cast is specifically designed to withstand high temperatures and is essential in the lost-wax casting process typically used in dental prosthetics.

When fabricating an RPD, a wax pattern is first created on a refractory cast. This wax pattern is then used to form a mold where molten metal will be cast to produce the final framework of the removable partial denture. The refractory material allows for the accurate replication of the wax pattern when it is subjected to the heat of the metal pouring process.

This choice emphasizes the importance of using a material that can endure the heat required to create a stable and precise framework, ensuring that the final product fits well and functions effectively in the patient's mouth. The accuracy and resilience of the investment cast are critical for achieving the desired outcomes of durability and functionality in dental appliances.