Method of producing block for dental prostheses, and method of producing dental prosthesis

A method of producing a block for dental prostheses before cutting to form a dental prosthesis, the method comprising:

• exposing a glass blank at a temperature lower than a temperature at which crystals of lithium metasilicate are generated, to an atmosphere at a temperature equal to or higher than a temperature at which crystals of lithium disilicate are generated and lower than a melting point of the crystals of lithium disilicate, to heat the glass blank so that a main crystalline phase of the glass blank is of lithium disilicate,
• wherein heating of the glass blank is performed so that, in a partially enlarged cross sectional view of the block in a field of view of 5 μm in a width direction and 5 μm in a depth direction, a proportion of a total area of crystals having a length of at least 0.5 μm and appearing within the field of view to an area of the field of view is at most 1%,
• wherein the block consists essentially of 60 mass % to 80 mass % of SiO2, 10 mass % to 20 mass % of Li2O, 5.2 mass % to 15 mass % of Al2O3, and
• at least one component selected from the group consisting of
• Na2O:
• at most 2.8 mass %,
• K2O:
• at most 10 mass %,
• CaO:
• at most 3 mass %,
• SrO:
• at most 10 mass %,
• BaO:
• at most 10 mass %,
• MgO:
• at most 3 mass %,
• Rb2O:
• at most 2.8 mass %,
• Cs2O:
• at most 2.8 mass %,
• Fr2O:
• at most 2.8 mass %,
• BeO:
• at most 3 mass %,
• RaO:
• at most 10 mass %,
• respective oxides of Zr, P and Ti, and
• a coloring material.