PURPOSEThe purpose of this study was to compare the linear sintering behavior of presintered zirconia blocks of various densities. The mechanical properties of the resulting sintered zirconia blocks were then analyzed.MATERIALS AND METHODSThree experimental groups of dental zirconia blocks, with a different presintering density each, were designed in the present study. Kavo Everest® ZS blanks (Kavo, Biberach, Germany) were used as a control group. The experimental group blocks were fabricated from commercial yttria-stabilized tetragonal zirconia powder (KZ-3YF (SD) Type A, KCM. Corporation, Nagoya, Japan). The biaxial flexural strengths, microhardnesses, and microstructures of the sintered blocks were then investigated. The linear sintering shrinkages of blocks were calculated and compared.RESULTSDespite their different presintered densities, the sintered blocks of the control and experimental groups showed similar mechanical properties. However, the sintered block had different linear sintering shrinkage rate depending on the density of the presintered block. As the density of the presintered block increased, the linear sintering shrinkage decreased. In the experimental blocks, the three sectioned pieces of each block showed the different linear shrinkage depending on the area. The tops of the experimental blocks showed the lowest linear sintering shrinkage, whereas the bottoms of the experimental blocks showed the highest linear sintering shrinkage.CONCLUSIONWithin the limitations of this study, the density difference of the presintered zirconia block did not affect the mechanical properties of the sintered zirconia block, but affected the linear sintering shrinkage of the zirconia block.
This study investigated the mechanical properties and initial cell response of bioactive glass infiltrated zirconia before and after sandblasting. One hundred zirconia specimens were divided into the following four groups: untreated zirconia (ZR), sandblasted zirconia (ZS), glass infiltrated zirconia (ZG), and sandblasted glass infiltrated zirconia (ZGS). Surface roughness, biaxial flexural strength, hardness and osteoblast cells proliferation were evaluated. ZGS group showed a slight decrease in hardness. However it has improvement in flexural strength (686.2 MPa). After sandblasting, the ZGS group had the highest surface roughness (R a = 1.24 μm) with enhanced osteoblast cells response. Our results indicated that sandblasting method can improve the mechanical properties of bioactive glass infiltrated zirconia with better osteoblast cell response. This new surface is promising for zirconia dental implant application in the future.
This study was to examine the effects of ferric oxide contents, which is one of the components of a newly developed glass, on the color and mechanical strengths of zirconia surfaces after glass infiltration. The composition of bioactive glass contained: SiO2–Al2O3–Na2O–MgO–BaO–CaO–Nb2O5–TiO2–Fe2O3. 84 presintered zirconia discs (diameter 15 mm, height 1.2 mm) were prepared. The experimental groups were divided into 6 groups by Fe2O3 contents of 0, 1, 1.5, 2.0, 2.5 and 2.9 wt%. Non-glass infiltrated zirconia was used as a control. Bioactive glass was coated on the presintered zirconia disc by a spin coating and infiltrated into zirconia by complete sintering at 1450°C for 2 hr. The color of the specimens was measured using a digital spectrophotometer and biaxial flexural strength and fracture toughness was compared. The colors of glass infiltrated zirconia were from yellow to yellowish orange according to ferric oxides contents and those were within the range of natural teeth colors. The mechanical properties of glass infiltrated zirconia were not inferior to those of zirconia. Glass infiltration with ferric oxide into zirconia can improve the color and mechanical properties of zirconia and be applicable for dental purpose.
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