[Methodologic and systemic reasons for failures of metal ceramics].
Only by the use of scanning electron microscope in investigations concerning the metal-porcelain interface of ceramic masses upon metal frames (approx. 160 crowns since 1967), essential differences in the reason of mistakes have been revealed recently. Primarily, methodic mistakes are to be declared relevant. Independent of their veneering origin, they contribute to fractures within the ceramic layer or to crack-offs of the fired ceramic masses from the metal frame. Obviously, the systemic causes for mistakes in metal ceramics revealed to be dependent on the groups of veneers. Veneering involves non-manageable reasons for mistakes. These qualities in the material are the coefficient of thermal expansion or the share of palladium in the veneer. Very often, palladium is responsible for the formation of bubbles in the ceramic layer, and thus it is the reason for the development of cracks. The so-called pure titanium is quite extraordinary, when covered with ceramic mass, because the so-called alpha case layer cannot be bridged, despite 10 years of permanent research in that field. The clinical critical examination of systemic mistakes, however, proves to be mild. Clinical reasons for mistakes in metal ceramics remain disregarded in this paper.
Eichner
K
K
Freie Universität, Berlin.
D003442:Crowns; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003801:Dental Veneers; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D010165:Palladium; D014025:Titanium
D016876:Metal Ceramic Alloys; D003776:Dental Porcelain; D010165:Palladium; D014025:Titanium