Final answer:
The dental material in question is amalgam, an alloy used for fillings that consists of mercury mixed with silver, tin, and copper. It's chosen for its durability, ease of use, and cost-effectiveness, although there are concerns due to mercury's toxicity.
Step-by-step explanation:
The type of dental material used in direct restorations consisting of an alloy of mercury and silver, tin, and copper in smaller amounts is known as amalgam (a). Amalgams are commonly employed by dentists to fill cavities because they are cost-effective, easy to manipulate, and durable. A dental amalgam is roughly 50% mercury by weight, which raises concerns due to the toxicity of mercury. Despite this, amalgam remains in use in some practices, mainly because mercury bonds well with the solid metal alloy powders of silver, tin, and copper, creating a stable filling material for dental restorations.