Y‐TZP (YZ) and Al2O3‐doped Y‐TZP (AYZ) bioceramics with addition of different contents of a refractory bioglass were fabricated. The influence of the glass addition and sintering temperature on the ...densification behavior, microstructure, and mechanical properties of YZ and AYZ was studied. The developed ceramics contained small amounts of ZrSiO4 and Ca2P2O7 phases within the ZrO2 matrix. The incorporation of glass to YZ promoted the ZrO2 phase partitioning and enhanced the ZrO2 grain growth at all the sintering temperatures, whereas the glass addition in AYZ prevented the Y2O3 redistribution between ZrO2 grains and limited the ZrO2 grain growth at 1300–1400°C. The hardness of the samples with glass was not significantly altered by using either YZ or AYZ. A slight increase in the fracture toughness with increasing glass content was found for YZ, while the fractured toughness of AYZ decreased by the glass addition. The more pronounced ZrO2 phase partitioning of YZ with glass decreased the flexural strength, whereas AYZ maintained almost unaltered its flexural strength at a high level by the glass incorporation.
Well‐dispersed concentrated aqueous suspensions of Al2O3‐doped Y‐TZP (AY‐TZP), AY‐TZP with 5.4 vol% of CaO–P2O5–SiO2 (CaPSi) glass (AY‐TZP5) and 10.5 vol% CaPSi glass (AY‐TZP10), with ammonium ...polyacrylate (NH4PA) dispersant were prepared to produce slip cast compacts. The rheological properties of 35 and 40 vol% slips were studied. The densification, microstructure as well as hardness and fracture toughness were investigated as a function of CaPSi glass content at 1300°C‐1500°C. The optimum NH4PA concentration of 35 vol% AY‐TZP5 and AY‐TZP10 slips at pH ~9 was found to be about 43% and 67% greater than that of AY‐TZP slips; this behavior was related to the greater amounts of Ca2+ ions leached out from the CaPSi glass surface. The viscosity of stabilized 40 vol% slips with NH4PA attained a minimum value at 5.4 vol% CaPSi glass addition, and resulted in a more dense packing of cast samples. AY‐TZP5 can be sintered at a lower temperature (1300°C) compared to that of AY‐TZP. AY‐TZP5 exhibited a fine microstructure of tetragonal ZrO2 (grain sizes below 0.3 µm), and ZrSiO4–Ca2P2O7 particles homogeneously distributed within the zirconia matrix. It presented similar fracture toughness and a slightly lower hardness compared to those of AY‐TZP.
3mol% yttria-partially stabilized zirconia (Y-TZP) powder and a sol-gel derived CaO- P2O5- SiO2 (64S) bioglass, were used to produce Y-TZP- 64S slip cast compacts. The compacts with 10.5 and 19.9vol% ...64S were sintered at different temperatures up to 1500°C using 5 and 10°C/min heating/cooling rates. The densification behaviour, crystalline phase formation and zirconia grain growth were investigated as a function of sintering temperature and 64S glass content. Ca3(PO4)2 along with SiO2 as a major phase were obtained from thermal decomposition of the 64S glass at 950–1500°C. Both 64S additions, 10.5 and 19.9vol%, promoted the sintering process at a lower temperature with respect to Y-TZP (1500°C); the SiO2 phase markedly increased the Y-TZP solid state sintering rate at the intermediate stage. The rapidly cooling at 10°C/min inhibited the t-m transformation of Y-TZP and markedly reduced that of Y-TZP- 64S at 1300–1500°C. Sintered Y-TZP with 10.5vol% 64S, nearly fully densified at 1300–1400°C, was constituted by polygonal ZrSiO4 particles and elongated Ca2P2O7 particles uniformly distributed in the tetragonal zirconia fine grain matrix. This ceramic exhibited similar hardness to that of Y-TZP sintered at 1500°C; the in situ formation of calcium phosphate will have the potential to improve the Y-TZP biological properties without significantly affecting its hardness.
Abstract
Y‐TZP (YZ) and Al
2
O
3
‐doped Y‐TZP (AYZ) bioceramics with addition of different contents of a refractory bioglass were fabricated. The influence of the glass addition and sintering ...temperature on the densification behavior, microstructure, and mechanical properties of YZ and AYZ was studied. The developed ceramics contained small amounts of ZrSiO
4
and Ca
2
P
2
O
7
phases within the ZrO
2
matrix. The incorporation of glass to YZ promoted the ZrO
2
phase partitioning and enhanced the ZrO
2
grain growth at all the sintering temperatures, whereas the glass addition in AYZ prevented the Y
2
O
3
redistribution between ZrO
2
grains and limited the ZrO
2
grain growth at 1300–1400°C. The hardness of the samples with glass was not significantly altered by using either YZ or AYZ. A slight increase in the fracture toughness with increasing glass content was found for YZ, while the fractured toughness of AYZ decreased by the glass addition. The more pronounced ZrO
2
phase partitioning of YZ with glass decreased the flexural strength, whereas AYZ maintained almost unaltered its flexural strength at a high level by the glass incorporation.
A quantity of 3 mol% yttria‐partially stabilized zirconia (Y‐TZP) with 10.5 and 19.9 vol% 64S bioglass compacts was sintered at different temperatures up to 1500°C. The influence of 64S glass ...addition on the sintering kinetic, flexural strength, and osteoblast cell response of Y‐TZP ceramics was investigated. The addition of 64S glass increased the initial sintering rate through the decrease in the activation energy and the increase on the order of diffusion with respect to those previously reported for Y‐TZP. Y‐TZP at 1500°C exhibited the highest flexural strength. Within Y‐TZP ceramics with 64S additions, a maximum flexural strength occurred for 10.5 vol% 64S at 1400°C, its flexural strength was able to approach that of Y‐TZP at 1500°C. The polished sintered surfaces became rougher as the 64S content increased. Cell viability experiments on the less nanoroughness Y‐TZP and Y‐TZP with 10.5 vol% 64S surfaces revealed their good biocompatibility; on the contrary, the high level of nanoroughness of Y‐TZP with 19.9 vol% 64S significantly reduced cell survival. However, the matrix mineralization was not adversely affected by the surface roughness; larger amounts of calcium phosphate phases on Y‐TZP‐19.9 vol% 64S surfaces appeared to promote the osteogenic potential of UMR‐106 cells.
Zirconia based materials are widely used as dental materials because of their good mechanical properties and aesthetic, but there is a need of enhancing its biological response for clinical use. In ...that sense, a bioactive glass is added to zirconia matrix with the aim of improving the material biocompatibility. The effect of the raw powders synthesis method for dense zirconia/bioactive glass biomaterials was investigated. Two paths were developed to obtain zirconia-based composites with 2.5, 5 and 10 wt% addition of a bioactive glass (referred as 64S): the traditional powder mixture method, and a core-shell powder through sol-gel particle nanocoating. Particle size distribution and SEM images were performed for the powders characterization. Sol-gel coating was analyzed with TEM images and FT-IR spectra. The sintering process was studied with an optical dilatometer up to 1450 °C, and the density of the samples was calculated with the Archimedes method, in the range of 1100–1500 °C. The final crystalline phases were studied with Rietveld quantification through XRD analysis and the microstructure with SEM/EDS analysis. Vickers indentation method was used to evaluate the hardness. Biological properties were studied with murine fibroblast cell line L929 and were analyzed by fluorescence microscopy. Results showed that samples obtained by the sol-gel particle coating method enhanced the sintering process, with a sintering temperature in the range 1300–1400 °C; they showed a more homogeneous and pore-free microstructure with a higher retention of the t-ZrO2 phase after cooling, in comparison with the samples obtained by the powder mixture method. The Vickers hardness of composites obtained by the core-shell particles had values above 11 GPa, and composites with 2.5 and 5 wt% 64S, sintered at 1400 °C, presented Vickers values of ∼13 GPa. Furthermore, biocompatibility was promoted with the addition of 64S glass, independently of the raw powders synthesis method.
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Y‐TZP containing Ca2P2O7 are promising bioceramics with potential applications in dental implants and dentistry. These ceramics were developed by the introduction of a refractory sol‐gel derived ...CaO‐P2O5‐SiO2 bioglass into Y‐TZP; Ca2P2O7, and ZrSiO4 phases were formed in situ after sintering. The aging process of Y‐TZP with different glass additions was studied. The effect of glass addition on the flexural strength and osteoblastic cell response of non‐aged and aged Y‐TZP was investigated. Y‐TZP exhibited the most pronounced tetragonal (t) to monoclinic (m) transformation of zirconia (ZrO2) during aging; the addition of glass contents between 5 and 20 vol% improved the aging resistant of Y‐TZP. Y‐TZP flexural strength markedly decreased with increasing aging time; in contrast, the ceramics with glass did not alter their flexural strength upon aging. An increase in the Ca2P2O7 content with increasing glass up to 10 vol%, promoted both the cell viability and the osteogenic differentiation of UMR‐106 cells on non‐aged and aged samples. The high micro‐roughness of Y‐TZP with 20 vol% glass after aging, limited the proliferation and the osteogenic potential of the cultures. Y‐TZP with 10 vol% glass had the best combination of properties in terms of flexural strength and osteoblast cell response.
Abstract Well‐dispersed concentrated aqueous suspensions of Al 2 O 3 ‐doped Y‐TZP (AY‐TZP), AY‐TZP with 5.4 vol% of CaO–P 2 O 5 –SiO 2 (CaPSi) glass (AY‐TZP5) and 10.5 vol% CaPSi glass (AY‐TZP10), ...with ammonium polyacrylate (NH 4 PA) dispersant were prepared to produce slip cast compacts. The rheological properties of 35 and 40 vol% slips were studied. The densification, microstructure as well as hardness and fracture toughness were investigated as a function of CaPSi glass content at 1300°C‐1500°C. The optimum NH 4 PA concentration of 35 vol% AY‐TZP5 and AY‐TZP10 slips at pH ~9 was found to be about 43% and 67% greater than that of AY‐TZP slips; this behavior was related to the greater amounts of Ca 2+ ions leached out from the CaPSi glass surface. The viscosity of stabilized 40 vol% slips with NH 4 PA attained a minimum value at 5.4 vol% CaPSi glass addition, and resulted in a more dense packing of cast samples. AY‐TZP5 can be sintered at a lower temperature (1300°C) compared to that of AY‐TZP. AY‐TZP5 exhibited a fine microstructure of tetragonal ZrO 2 (grain sizes below 0.3 µm), and ZrSiO 4 –Ca 2 P 2 O 7 particles homogeneously distributed within the zirconia matrix. It presented similar fracture toughness and a slightly lower hardness compared to those of AY‐TZP.
Yttria-partially stabilised zirconia (Y-TZP) of 3 mol-% with 5.4, 10.5 and 19.9 vol.-% 64S bioglass compacts was sintered at 1300-1500°C. The influence of 64S content and sintering temperature on the ...mechanical properties and aging behaviour of Y-TZP ceramics were studied. Among Y-TZP ceramics with 64S additions, maximum hardness and flexural strength values were found for Y-TZP with 10.5 vol.-% 64S at 1400°C. Y-TZP with 19.9 vol.-% 64S at 1500°C presented the highest fracture toughness; crack deflection and pinning by ZrSiO
4
particles combined with zirconia microcracking contributed to the fracture toughness. Y-TZP at 1500°C was extremely susceptible to hydrothermal degradation and its flexural strength markedly decreased after aging. On the contrary, Y-TZP with 10.5 vol.-% 64S at 1400°C remained almost unaltered; it maintained its flexural strength at a high level during aging, becoming the most promising ceramic in terms of mechanical properties and aging behaviour.
