A process for the preparation of multi-coloured dental restorations is described, in which glasses and glass ceramics with various compositions are given the shapes of dental restorations and colour changes are effected in the glasses and glass ceramics by irradiating them with artificial electromagnetic radiation and subjecting them to a heat treatment.

A method of forming a multi-colored glass substrate comprises: irradiating a first region of a glass substrate with a first high energy source to form a first irradiated glass substrate; and subjecting the irradiated glass substrate to a first heat treatment to form a first heat treated glass substrate, wherein the first heat treated glass substrate comprises a second region having a different transmittance color coordinate in the CIELAB color space, as measured at an article thickness of 1.33 mm under F2 illumination and a 10° standard observer angle, than the first region.

Embodiments of the present disclosure are directed to methods for inducing color change in glass and glass-ceramic articles. According to one embodiment, color change may be x-ray induced in glass or glass-ceramic articles. The method for x-ray inducing color change may include exposing the glass or glass-ceramic article to x-rays at a temperature of up to 200 C. to induce a colored area in the glass or glass-ceramic article. The glass or glass-ceramic article may comprise: 50-85 mole % SiO.sub.2; 5-25 mole % Al.sub.2O.sub.3; 0-15 mole % P.sub.2O.sub.5; 0-15 mole % B.sub.2O.sub.3; 5-25 mole % R.sub.2O, wherein R.sub.2OLi.sub.2O+Na.sub.2O+K.sub.2O.

Embodiments of the present disclosure are directed to methods for inducing color change in glass and glass-ceramic articles. According to one embodiment, color change may be x-ray induced in glass or glass-ceramic articles. The method for x-ray inducing color change may include exposing the glass or glass-ceramic article to x-rays at a temperature of up to 200 C. to induce a colored area in the glass or glass-ceramic article. The glass or glass-ceramic article may comprise: 50-85 mole % SiO.sub.2; 5-25 mole % Al.sub.2O.sub.3; 0-15 mole % P.sub.2O.sub.5; 0-15 mole % B.sub.2O.sub.3; 5-25 mole % R.sub.2O, wherein R.sub.2O=Li.sub.2O+Na.sub.2O+K.sub.2O.

Embodiments of the present disclosure are directed to methods for inducing color change in glass and glass-ceramic articles. According to one embodiment, color change may be x-ray induced in glass or glass-ceramic articles. The method for x-ray inducing color change may include exposing the glass or glass-ceramic article to x-rays at a temperature of up to 200 C. to induce a colored area in the glass or glass-ceramic article. The glass or glass-ceramic article may comprise: 50-85 mole % SiO.sub.2; 5-25 mole % Al.sub.2O.sub.3; 0-15 mole % P.sub.2O.sub.5; 0-15 mole % B.sub.2O.sub.3; 5-25 mole % R.sub.2O, wherein R.sub.2O=Li.sub.2O+Na.sub.2O+K.sub.2O.