A filling is a way to restore a tooth damaged by decay back to its normal function and shape. When a dentist gives you a filling, he first removes the decayed tooth material, cleans the affected area, and then fills the cleaned out cavity with a filling material. There are a variety of different materials that can be used for filling. We will only address the two most common filling materials, which are amalgam and composite resin
Amalgam fillings: These are the traditional dark metal fillings. Dental amalgam is strong and long lasting but it has some disadvantages. It doesn’t bond with the tooth structure, it rather depends on retentive features in the cavity design to be maintained. It is dark colored, and it contains elemental mercury. It releases low levels of mercury vapor that can be inhaled during placement. Dentists that are exposed to high levels of mercury vapor are at risk of adverse effects in the brain and the kidneys that’s why it's not preferable nowadays
Composite fillings: are newer than amalgam fillings and are constantly improving. They bond with the tooth structure, they have very good strength, and they are tooth colored. The composite resin has a consistency of modeling clay. In order for it to harden, the dentist shines a bright blue light on it. Through a series of chemical reactions, the composite resin hardens into a very strong material that looks very much like a natural tooth.