Effect of Li<sup>+</sup>/Na<sup>+</sup> exchange on mechanical behavior and biological activity of lithium disilicate glass-ceramic.

Li, X C; Li, D; Zhang, S F; Jing, L; Zhou, W H; He, L; Yu, S; Meng, M · J Mech Behav Biomed Mater · 2022

biomechanical · Level V

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Abstract

Lithium disilicate (LD) glass-ceramics with a stoichiometric composition were ion-exchanged in pure NaNO<sub>3</sub> or mixed NaNO<sub>3</sub> + KNO<sub>3</sub> molten salt baths below the glass transition temperature (T<sub>g</sub>). The microstructures, surface morphologies, mechanical properties and bioactivities of the ion-exchanged glass-ceramics were studied in detail. It was found that the strength and toughness of LD glass-ceramic could be enhanced from 175 MPa to 0.96 MPa m<sup>1/2</sup> before ion-exchange to 546 MPa and 4.31 MPa m<sup>1/2</sup> respectively under a lowered ion-exchange temperature because the less stress relaxation. In addition, a gradient of Na<sup>+</sup> rich layer in the surface of glass-ceramic was induced by Li<sup>+</sup>/Na<sup>+</sup> exchange, which could be beneficial to the formation of HA (Hydroxyapatite) with nano-size porous after soaking in SBF (Simulated Body Fluid) solution and exhibited better bioactivity compared with the original LD glass-ceramic. The results might provide a reference for the strengthening and biological activation of LD glass-ceramics in bone restoration applications.

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