Abstract
Prosthetic materials become brittle by repeated heat shock such as sudden heating and cooling.Especially, porcelain is brittle under heat shock.Heat resistance of porcelain was tested by the thermal cycle method and the effect on the mechanical properties of porcelain such as bending strength, deformation and surface stress value was examined.The thermal shock of porcelain-fused-to metal with increase the number of thermal cycles got weak in the bending strength and the bending elasticity coefficient became small and the toughness became gradually small.The surface stress of porcelain-fused-to metal became small by the effect of the thermal cycles and the deformation get to be shaped like an ellipse shape by being free from stress.The thermal shock resistance of chemically strengthened porcelain is stronger than that nontreatment.
