The evaluation of thermal expansion coefficient and leucite crystalization of repeatedly heat treated dental ceramics periodically contacted with saliva and distilled water

ABSTRACTTHE EVALUATION OF THERMAL EXPANSION COEFFICIENT AND LEUCITECRYSTALIZATION OF REPEATEDLY HEAT TREATED DENTAL CERAMICSPERIOD CALLY CONTACTED WITH SALIVA AND DISTILLED WATERLeucite crystallization and its effect on the coefficient of thermal expansionhave been investigated for two porcelain systems submerged in distilled water and artificalsaliva for certain periods.90 disk-like samples were prepared to measure leucite crystallization for theCeramco II and Finesse porcelains and two samples in rectangular prism shape to measurethe thermal expansion coefficient. These samples are grouped into two categories withrespect to their duration of submergence in the distilled water and the artificial saliva. Thenthese samples were tested using X-ray diffraction and the dilatometer.It is found that leucite crystallization increased in the oven-dried samplessubmerged in distilled water and artificial saliva and samples submerged in artificial salivaproduced more leucite crystallization as compared to those submerged in the distilled water.It is also determined that leucite crystallization increased the thermal expansion coefficient ofthe porcelain.