Abstract
Zirconium oxide ceramic was proposed for different biomedical applications. It is used in orthopedic as hip and knee prostheses and in dentistry due to the good mechanical, biological high corrosion and wear resistance properties, addition to the aesthetic property owing to tooth like color. Zirconia stabilized with Y2O3 has the best properties for these applications. The present work aims to study the effect of (5 and 10)Wt.% hydroxyapatite (HA) as additives to 3 mol% yttria stabilized zirconia (3YSZ) nano powder matrix. The green body samples were shaped by powder technology using cold pressing then sintering at (1300 and 1400)ᵒC. The 3YSZ/ HA nanocomposites samples were characterized by XRD to investigate phase stability with varying percent's of HA and different sintering temperatures, the mechanical properties (maximum bending strength and hardness) were investigated as a function of the HA content, the changes of the thermal expansion coefficient for composite samples were investigated using Dilatometer. The experimental results proved that additions of (5 and 10)Wt.% HA to 3YSZ matrix reduce both hardness and max. bending strength, while increasing sintering temperature from 1300ᵒC to 1400ᵒC leading to an increase in the hardness and bending strength for all composite samples. The results of thermal expansion test showed a reduction in the thermal expansion coefficient with presence of HA%, however the coefficient of 3YSZ/ 10%HA is closer to 3YSZ from 3YSZ/ 5%HA. EDS analysis shows improvement in the bioactivity of inert 3YSZ with HA% additions represented by increasing Ca and P ions on the composite samples after immersing in SBF for 6 days.
Highlights
Zirconia-based ceramics have exceptional mechanical properties including, outstanding biocompatibility, aesthetics and heat conductivities that introduced it in dental and orthopedic applications over the last decades[1], zirconia was classified as bioinert, which hampers their implantation in direct contact with bone
The volume of monoclinic unit cell is 4% more than the volume of tetragonal unit cell, this leads to the creation of ceramic flaws if no stabilizing oxides were used [2], many researches focused on using 3 mol% yttria stabilized zirconia (3YSZ) for prosthodontic applicationsand orthopedic implants, because this material exhibit the best combination of strength, toughness and hardness [3, 4]
The outcomes of this work demonstrates that the addition of (5,10)% HA to 3YSZ matrix led to a reduction in the bending strength and vickers hardness
Summary
Zirconia-based ceramics have exceptional mechanical properties including (fracture toughness, strength and hardness), outstanding biocompatibility, aesthetics and heat conductivities that introduced it in dental and orthopedic applications over the last decades[1], zirconia was classified as bioinert, which hampers their implantation in direct contact with bone. The disadvantage of HA is the poor mechanical strength (brittleness and low fracture toughness) that leads to limited fitness in loadbearing applications [6,7].In most applications of biomedical materials the mechanical properties are especially important, as well as the chemical reactivity of their surfaces for this reasons using bioactive ceramic such as HA has attracted a great attention for enhancing the biocompatibility of many strong biomaterials through the use of composite or as coating layer to achieve osseo integration and accelerate new bone formation beside high strength which is required for load-bearing applications such as dental/orthopedic implants [8]. The flexure strength, hardness, thermal expansion coefficient and XRD analysis were examined for the composites (3YSZ/ HA) samples as a function of the HA wt.% content using (1300, 1400) o C as different sintering temperatures
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