Cavities are not always sensitive or painful. The first picture shows a broken silver or amalgam filling and a large cavity is present where the filling has broken away. The
patient was unaware that there was a problem. If this problem was not addressed the cavity would have progressed and more extensive treatment would be required. Cavities that progress to the nerve of the tooth require root canal treatment.
In this case the broken filling and cavity were repaired with a composite resin restoration this preventing the need for more extensive treatment. Regular dental examinations allow the detection of such problems before they require major dental treatment.