The present invention is directed to a process for producing a sintered lithium disilicate glass ceramic dental restoration out of a porous 3-dim article, the process comprising the step of sintering the porous 3-dim article having the shape of a dental restoration with an outer and inner surface to obtain a sintered lithium disilicate ceramic dental restoration, the sintered lithium disilicate glass ceramic dental restoration comprising—Si oxide calculated as SiO2 from 55 to 80 wt.-%, —Li oxide calculated as Li2O from 7 to 16 wt.-%, —Al oxide calculated as Al2O3 from 1 to 5 wt.-%, and—P oxide calculated as P2O5 from 1 to 5 wt.-%, wt.-% with respect to the weight of the dental restoration, the sintering being done under reduced atmospheric pressure conditions, the reduced atmospheric pressure conditions being applied at a temperature above 600° C. The present invention is also directed to a kit of parts comprising a porous 3-dim article having the shape of a dental milling block and a respective instruction of use.
