Mechanical properties and short‐term <i>in vivo</i> evaluation of yttrium‐oxide‐partially‐stabilized zirconia

TLDR

Yttrium‑oxide‑partially‑stabilized zirconia (YPSZ) is a new ceramic class that offers improved toughness relative to alumina. The material’s toughness arises from a martensitic‑like transformation of tetragonal grains to monoclinic at crack tips, and its in‑vivo performance was assessed by implanting cold‑isostatically pressed, sintered cylinders into rat paraspinal muscles for up to 12 weeks with histomorphometric comparison to alumina. YPSZ exhibited a bending strength of 900–1200 MPa, a Young’s modulus of 200 GPa, and a toughness of 9–10 MN m⁻³/², with a 0.5 µm grain size yielding 0.008 µm surface roughness; sterilization or 100‑day saline aging did not alter toughness, and in‑vivo implants showed no significant differences from alumina in membrane thickness or cellular distribution.

Abstract

Abstract Yttrium‐oxide‐partially‐stabilized zirconia (YPSZ) belongs to a new class of ceramics exhibiting an improved toughness when compared to alumina. The toughening mechanism is related to a martensitic‐like transformation of tetragonal metastable grains into a monoclinic state occurring at the crack tip. Specific tests showed that YPSZ exhibited a high bending strength (900–1200 MPa), a low Young's modulus (200 GPa), and a high toughness ( K IC = 9–10 MN/m 3/2 ). Its average grain size of 0.5 m̈m allows a surface roughness as low as 0.008 m̈m. Sterilization or aging in saline solution at room temperature for 100 days did not affect the toughness of this material. Cylindrical YPSZ samples, manufactured by cold isostatic pressing and sintering, were implanted in the paraspinal muscles in the rat up to 12 weeks. The tissue reaction was evaluated with reference to alumina (ISO requirements) by means of quantitative histomorphometry. No significant differences were found between YPSZ and alumina for both the membrane thickness and cell distributions surrounding the implants.