[The influence of different thermal expansion coefficient (TEC) between ceramic and metal on thermal stability of porcelain-fused-to-metal (PFM) crown].
The ceramic-crazing examination after firing and thermal shock test had been provided to evaluate the thermal stress of PFM crown. The results of the experiment indicate: (1) When P alpha-M alpha greater than 1.7 x 10(-6)/degrees C, the crazing of facial side of PFM crown had been happened, when P alpha-M alpha = 0.9-(-)1.0 x 10(-6)/degrees C, no cracks were discovered, when P alpha-M alpha less than -1.5 x 10(-6)/degrees C, the incisive angle of PFM crown bursts apart. (2) The thermo-shock resistance (delta T) of PFM crown was influenced strongly by TEC between porcelain and metal. The rule of thermo-shock resistance (delta T) of PFM crown is that under the experimental condition, the smaller the P alpha is, the higher the value of delta T is. (3) The high residual stress in PFM crown is an internal cause on the failure of ceramic layer, the transient tensile stress is an external factor. (4) The results of this study showed that the optimal difference of TEC between the two is approximately 0.7 x 10(-6)/degrees C.
Lei
Y C
YC
College of stomatology, West China University of Medical Sciences.
D003442:Crowns; D003722:Dental Alloys; D003776:Dental Porcelain; D006047:Gold Alloys; D013314:Stress, Mechanical; D013816:Thermodynamics
D003722:Dental Alloys; D006047:Gold Alloys; D003776:Dental Porcelain