Final answer:
The metal used to control the rate of set of the amalgam is zinc. It helps prevent impurities and porosity in dental fillings, enhancing workability and durability. The option (B) is correct.
Step-by-step explanation:
The metal used to control the rate of set of the amalgam is zinc (b). In dental amalgams, zinc acts as a scavenger for oxygen and other impurities that might otherwise lead to porosity in the set material. This control of the set rate is important for the workability and longevity of the dental filling.
Typically, a dental amalgam is composed of a mixture of metals that includes mercury, silver, and a small amount of tin, copper, and sometimes zinc. The mercury is mixed with an alloy powder to create the amalgam which is then used to fill cavities in teeth. Dentists choose amalgam for its low cost, ease of manipulation, and durability, despite concerns over mercury’s toxicity. Therefore, option (B) is correct.