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Objectives: to evaluate the effect of addition of potassium titanate fibers (PTF) on the mechanical and optical properties of a dental porcelain processed by conventional sintering(S) or heat-pressing(HP). Methods: Disks (n=30, Ø12x1mm) of porcelain (Vintage-Halo, Shofu) were produced using S and HP methods with or without addition of 10 vol% of PTF. For the S method, porcelain was sintered in a conventional furnace. In the HP technique, refractory molds were produced by lost wax technique. The porcelain slurry was dry-pressed (3ton/30s) to form a cylinder with 12mm(diameter) and 20mm(height), which was heat-pressed for 5min/3.5bar. Flexural strength was determined by biaxial test (1MPa/s), porosity was determined in an image analyzer, and optical properties were determined in a spectrophotometer in the diffuse reflectance mode. Data were analyzed with ANOVA (alpha=0.05) and Weibull statistics. Results: The association of heat-pressing with fibers resulted in significantly higher strength compared to other groups. However, the highest Weibull modulus was obtained for the sintered group. Addition of fibers increased the porosity of both sintered and heat-pressed specimens. Heat-pressed specimens (without fibers) showed very low porosity. Addition of fibers made the porcelain more opaque as confirmed by the significantly higher contrast ratio and lower translucency of groups containing PTF. Conclusions: Though the addition of PTF increased the strength of the porcelain, its porosity was also increased and the material became more opaque. HP alone was proved an excellent technique to reduce the porosity of the porcelain tested.
Property | Sintered(S) | Sintered +Fibers (S+F) | Heat-pressed (HP) | Heat-pressed +Fibers (HP+F) |
Flexural strength(MPa) | 51.3±5.6c | 65.2±4.4b | 67.1±7.9b | 76.5±11.0a |
Weibull modulus | 13.0(9.5-17.5)a | 8.3(6.1-11.2)ab | 7.8(5.7-10.5)ab | 6.8(5.0-9.1)b |
Porosity(%) | 4.0 ± 1.1b | 10.4 ± 4.5a | 0.3 ± 0.2c | 10.4 ± 4.5a |
Contrast ratio | 0.70±0.0.5b | 1.0±0.03a | 0.40±0.02c | 0.70±0.04b |
Translucency parameter | 17.6±0.8b | 0.26±0.1 c | 28.8±0.3a | 17.8±1.6b |
Keywords: Biomaterials, Ceramics, Dental materials, Porcelain systems and Prosthodontics
See more of: Dental Materials 3: Ceramic-based Materials and Cements