Cavities or carries are caused when bacteria infiltrates the tooth structure. If left untreated it can result in tooth loss or the need for a root canal. To treat a cavity, the dentist removes all of the decay in the area of the cavity. A modern dental practice will fill the cavity with a very strong composite resin material that is tooth colored. Once the decay is removed and the cavity is filled the tooth is polished and looks just like the neighboring teeth. This is a fairly pain free procedure the most discomfort coming from the ‘pinch’ of the initial injection of the numbing agent. Silver fillings or amalgam are used much less frequently because they can expand and contract causing the tooth to crack and amalgam contains mercury.