A tooth is irradiated with light (5), in particular with visible light for identifying tooth-colored tooth filling residues (3) of the tooth. The light with which the irradiation procedure is effected includes at least one wavelength component that is absorbed or scattered by the tooth filling material differently from the tooth material in such a way that the tooth filling material differs from the tooth material in respect of its brightness or in respect of its color. Thus the identification of tooth filling residues (3) can be effected in such a way that the dentist can recognise the tooth filling residues (3) with the naked eye, or possibly with the assistance of simple technical aids such as for example a color filter.