Ceramic glass and lithium silicate tetravalent metal oxide with

Lithium silicate glass-ceramic containing a tetravalent metal oxide selected from ZrO2, TiO2, CeO2, GeO2, SnO2 and mixtures thereof, between 67.0 and 79.0 wt% SiO2, at least 12, 1% by weight of Li2O, from 0 to 6.0% by weight Al2O3, less than 0.1% by weight of La2O3, less than 1.0% by weight of K2O and less than 2.0% Na2O weight.