This study evaluates effects of repeated baking processes on the mechanical and physical properties of single and triple applications of opaque, body and enamel porcelains fused to three different metal substrates (precious metal, semi-precious metal and non-precious metal).The vintage halo porcelain system was employed and fused to metals. Fused samples were subjected to three-point bend tests to evaluate bend strength and modulus of elasticity.It was found that, by increasing repeated baking cycles, (1) body and enamel porcelains increased bend strengths but opaque porcelain did not show any changes, (2) all triple-layered porcelains fired to metals increased bend strengths, and (3) all three porcelains and metal substrates did not exhibit changes in thermal expansion percentage.It was concluded that repeating baking procedures up to 10 cycles did not exhibit any adverse effects on the final properties of porcelain-fired to metals, rather it was noticed that mechanical strengths increased by increasing cycles.
The thermal expansion rate, coefficient of thermal expansion, and high temperature strength of two types of commercially available alloy for metal-bond porcelain, KIK-HII (KIK) and Degubond-J2 (J2) , were evaluated up to the liquidus point ternperature using a thermo-mechanical analyzer. Furthermore, microstructure in the solid-liquid coexisting region was observed for evaluation.Our results revealed the following findings: 1 . For KIK, solidus point was 1,209.3±3.2t, liquidus point was 1,308.3±7.1t, and melting expansion rate was 0.41± 0.16%. 2 . For J2, solidus point was 1,198.3 ± 0.6t , liquidus point was 1,253.0±4.4C, and melting expansion rate was 4.50 ± 0.80 %. 3. At high temperature, the mechanical characteristics of KIK greatly differed from those of J2. The risk of causing deformation during porcelain baking was suggested for KIK. Removal of segregation during casting was considered difficult in J2.
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