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To improve the mechanical strength of denture base resin, several types of noble metal cluster were introduced into PMMA, and the mechanical properties and color changes were evaluated. Complex salts of gold, silver, platinum, and palladium were used as the raw materials of noble metal clusters, and after adding each cluster to MMA, polymerization and thermal treatment were performed to produce PMMA-noble metal cluster complexes. Bending deflection, bending strength, and Vickers hardness were measured, and the formation conditions of metal clusters were investigated using EPMA, SEM, and TEM. Furthermore, color changes between before and after metal cluster creation were measured. The bending deflection increased with the addition of silver and platinum, and decreased with the addition of palladium. The bending strength was lowest with the addition of gold, highest with the addition of palladium. Vickers hardness increased with the addition of palladium. Color differences increased with increasing thermal treatment temperature.

Three types of bending tests -the 3-point bending test, 4-point bending test and biaxial flexural test-were performed to examine the correlations among the testing methods for dental hard resins (HRs). The results for 5 HRs showed that the bending strengths in descending order were: biaxial flexural strength>3-point bending strength>4-point bending strength. Regression analysis of the test methods indicated that the coefficients of determination were large for all test methods; the largest was for the combination of the 4-point bending test and biaxial flexural tests. The Weibull moduli ranged from 5.42 to 10.61, and a similar descending-order trend was found in the Weibull characteristic strength (S0) of the test methods. The biaxial flexural test method is thus a valid test of the flexural strength of dental hard resins.

Pyrolysis of methane over pitch based carbon fibers at 1173–1273 K produced rather selectively C2 hydrocarbons (selectivity up to 67%) at a stational conversion of 20% with limited deposition of carbon (18%).

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