The invention discloses porous, bioactive glass and glass ceramic morsels or pellets to be used as tissue graft substitute materials and processes for obtaining the same wherein the bioactive glass and glass ceramic morsels or pellets are made up of natural agents like phosphate, calcium, sodium and other elements which are not alien to the human or animal body. The said preparation process encompasses various steps like quenching sintering, foaming, and sol-gel casting which render the glass morsels or pellets unique bioactivity and enhanced porosity which may facilitate tissue repair and augmentation during tissue graft replacement.