Moldable, Pressable, Castable, Stackable The mid 1980's brought much excitement with the promise of stronger esthetic porcelain crown systems. For all I knew they were blown into the shape of teeth by glass blowers. They did however, pave the way for more recent advances which have lead to stronger ceramic products available today.
Stresses can cause micro cracks which in turn weaken the porcelain.
Attempts to increase the fracture toughness of dental porcelains has included modifying existing products as well as developing new products. Unfortunately, the relationship between improved fracture toughness and clinical performance has not been demonstrated yet in research. The strengthening effect comes about as the crystal or alumina particles cause an increased resistance to micro crack initiation, propagation, and size. This certainly rings true as one begins to probe the complex issues connected with evaluating the strength of dental ceramics. Even the current research literature produces contradictory information regarding strengths of these systems.