INFLUENCE OF MICROSTRUCTURE ON INDENTATION AND MACHINING OF DENTAL GLASS-CERAMICS

The influence of microstructure on the abrasive machining and indentat ion response for a series of dental glass-ceramics was characterized. The experimental materials prepared for this study contained crystalli ne mica platelets that ranged in diameter from about 1 to 15 mu m, whi le the volume fraction of mica remained essentially constant. Damage f ormation and material removal behavior were studied as a function of m ica platelet size using Vickers indentation, Berkovich instrumented in dentation, and abrasive machining. In the instrumented indentation exp eriments, the energy absorbed in indentation decreased with increasing platelet size when indentations of equal penetration depth are made i n each material. To characterize the grinding response, the normal and tangential forces for each material were measured as a function of th e depth of cut in surface grinding, The grinding forces and the specif ic grinding energy at fixed depths of cut decreased with increasing th e mica platelet size following the same trend observed in the fixed di splacement indentation tests. Since the same microfracture process was observed to occur in both indentation and grinding, the absorbed inde ntation energy is proposed as a quantity for predicting the machining response of these glass-ceramics.