have excellent strength are corrosion resistant and they produce dental restorations which approximate humane coloration and are translucent and esthetically pleasing further lithium disilicate glass ceramic materials are advantageous in that they maintain their structural integrity during heat treating in that they do not slump or sag during proper heat treating other lithium disilicate glass ceramic materials which may be used in this invention are disclosed in u s pat no 5 219 799 issued jun 15 1993 lithium dissicate glass ceramic materials may utilize p 2 o 5 as a nucleating agent other nuculating agents are tio 2 and zro 2 glass ceramic compositions which may be useful in this invention are as per table i table i______________________________________li sub 2 o 8 12al sub 2 o sub 3 2 5 0sio sub 2 75 85na sub 2 o 0 2k sub 2 o 0 2p sub 2 o sub 5 1 5 5tio sub 2 0 2zro 0 3coloring oxide 0 5______________________________________ specific glass ceramic compositions which may be useful in the invention are as per table ii table ii__________________________________________________________________________composition 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17__________________________________________________________________________sio sub 2 81 0 84 0 84 0 83 0 62 0 84 0 81 0 83 0 83 0 81 5 80 0 86 0 84 0 81 0 82 0 82 0 81 0al sub 2 o sub 3 3 5 3 0 3 0 3 0 4 0 3 3 3 3 3 5 3 5 3 0 6 0 1 5 3 0 3 3 3 5 3 0li sub 2 o 11 0 10 5 10 5 10 5 10 5.