Abrasive Machining of Glass-Infiltrated Alumina with Diamond Burs
L Yin, L K. Ives, S Jahanmir, E D. Rekow, E Romberg
The abrasive machining characteristics of a glass-infiltrated dry-pressed alumina used for fabrication of all-ceramic dental crowns are investigated using a high-speed dental handpiece and diamond burs containing supercoarse (180 m), fine (40 m), and ultrafine (10 m) grit sizes. The material removal rate, surface roughness, and extent of edge chipping are measured as a function of grit size. It is found that the removal rate increases substantially with increasing bur grit size, while it decreases gradually with continued machining for all grit sizes. The observed reduction in removal rate is primarily due to wear of the diamond grit and accumulation of debris on the bur (i.e., bur loading). Both surface roughness and edge chipping damage are found to be sensitive to diamond grit size, but insensitive to bur loading and grit wear. It is concluded that micro-fracture and dulling of diamond grit edges are the dominant wear mechanisms and after prolonged use bur life expires due to severe wear and grit loss.