PubMed · 3267830
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R Herrmann. 1988. [Ceramic inlay (I)].. https://pubmed.ncbi.nlm.nih.gov/3267830/
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The adhesion between titanium and dental porcelain is related to the diffusion of oxygen to the reaction layer formed on cast-titanium surfaces during porcelain firing. The diffusion of oxygen could be suppressed by coating the titanium surface with a thin gold layer. This study characterized the effects of gold coating on titanium-ceramic adhesion. ASTM grade II CP titanium was cast into a MgO-based investment (Selevest CB, Selec). The specimen surfaces were air abraded with 110-microm Al(2)O(3) particles. Gold coating was applied on titanium surfaces by three methods: gold-paste (Deck Gold NF, Degussa-Ney) coating and firing at 800 degrees C for three times, single gold-paste coating and firing followed by sputter coating (40 mA, 500 s), and sputter coating (40 mA, 1000 s). Surfaces only air abraded with Al(2)O(3) particles were used as controls. An ultra-low-fusing dental porcelain (Vita Titankeramik, Vident) was fused on titanium surfaces. Specimen surfaces were characterized by SEM/EDS and XRD. The titanium-ceramic adhesion was evaluated by a biaxial flexure test (N = 8), and area fraction of adherent porcelain (AFAP) was determined by EDS. Numerical results were statistically analyzed by one-way ANOVA and the Student-Newman-Keuls test at alpha = 0.05. SEM fractography showed a substantial amount of porcelains remaining on the gold-sputter-coated titanium surfaces. A new Au(2)Ti phase was found on gold-coated titanium surface after the firing. Significantly higher (p <.05) AFAP values were determined for the gold-sputter-coated specimens compared to the others. No significant differences were found among the other groups and the control. Results suggested that gold coatings used in this study are not effective barriers to completely protect titanium from oxidation during the porcelain firing, and porcelain adherence to cast titanium can be improved by gold-sputter coating used in the present study.
OBJECTIVE: To characterize the high temperature viscoelastic properties of several dental ceramics by the determination of creep functions based on mid-span deflections measured in a beam-bending viscometer (BBV). METHODS: Six groups of beam specimens (58 x 5.5 x 2.5 mm) were made from the following materials: (1) IPS Empress2 body--a glass veneer ceramic (E2V); (2) an experimental glass veneer (EXV); (3) Vita VMK 68 feldspathic body porcelain--a low-expansion body porcelain (VB); (4) Will-Ceram feldspathic body porcelain--a high-expansion body porcelain (WCB); (5) Vita feldspathic opaque porcelain--a medium-expansion opaque porcelain (VO); and (6) Will-Ceram feldspathic opaque porcelain--a high-expansion opaque porcelain (WCO). Midpoint deflections for each specimen were measured in a BBV under isothermal conditions at furnace temperatures ranging from 450 to 675 degrees C. Non-linear regression and linear regression analyses were used to determine creep functions and shear viscosities, respectively, for each material at each temperature. RESULTS: The shear viscosities of each group of dental ceramics exhibited bilinear Arrhenius behavior with the slope ratios (x) ranging from 0.19 for WCB to 0.71 for EXV. At the higher temperature ranges, activation energies ranged from 363 kJ/mol for VO to 386 kJ/mol for E2V. SIGNIFICANCE: The viscoelastic properties of dental ceramics at high temperatures are important factors in understanding how residual stresses develop in all-ceramic and metal-ceramic dental restorations.
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.