Abstract: The invention relates to a method for the preparation of a glass ceramic or a glass, which comprise cerium ions and are suitable in particular for the preparation of dental restorations, the fluorescence properties of which largely correspond to those of natural teeth. The invention also relates to a glass ceramic and a glass which can be obtained using the method according to the invention, the use thereof as dental material and in particular for the preparation of dental restorations, as well as a glass-forming composition which is suitable for use in the method according to the invention.