They are fillings that have been used for many years and are also known as gray or silver fillings. It is a filling material obtained by using a certain amount of mercury. It is known to be very durable. It is resistant to food and drink. Average lifetime is 5 years. However It has been proven through research that mercury metal has a toxic effect on the human body. For this reason, it is not a material that is used very often in recent years. It is not aesthetic because it reflects the color of tooth enamel as black.