A dental filling material used for over 150 years, commonly known as "silver fillings." It is an alloy made of mercury, silver, tin, and copper.
While extremely durable and cheap, they are unsightly (dark grey) and require removing more healthy tooth structure than modern composite fillings. Many patients choose to replace them for better aesthetics.
Leading health organizations (ADA, FDA) consider it safe for adults, but we avoid it for pregnant women or those with metal allergies.
Metal expands and contracts with heat, which can eventually cause the natural tooth to crack (Fractured Tooth Syndrome).