Microstructure and strength analysis of ultrasonically shaped ceramics
Hahn, R.; Löst, C.
Schweizer Monatsschrift für Zahnmedizin 103(7): 844-850
1993
ISSN/ISBN: 0256-2855 PMID: 8356419 Document Number: 406355
In this study, the influence of a new ultrasonic shaping procedure on the surface quality, microstructure, bending strength and fatigue behaviour of a feldspathic porcelain was investigated. A total of 120 standardized (ISO 6872) autoglazed, ground, lapped and ultrasonically machined porcelain test bars were analyzed. Another 24 equiformat experimental alumina ceramics, which were ultrasonically machined, as well as 24 nontreated fload glass specimen served as controls. It could be shown that the porcelain removal process with diamond grinding wheels yielded a rough surface microrelief and lead to structural subsurface damage, decreasing bending strength and fatigue behaviour. In contrast, ultrasonic shaping resulted in a smoother surface and prevented damage to the subsurface layer of the machined brittle porcelain, although, the smoothest surfaces were achieved by lapping. Both bending strength and fatigue behaviour of the conventional dental porcelain were increased by ultrasonic machining. However, the fracture toughness of the experimental alumina was substantially higher and was not subjected to a decrease in fatigue.