Exploring the unexpected influence of the Si:Ge ratio on the molecular architecture and mechanical properties of Al-free GICs

Abstract

Germanium (Ge)-based glass ionomer cements have demonstrated the ability to balance strength with extended setting times, a unique set of characteristics for aluminum-free glass ionomer cements. However, the mechanical properties of current Ge-based glass ionomer cements significantly deteriorate over time, which jeopardizes their clinical potential. This work explores the effect of incrementally decreasing the Si:Ge ratio in the glass phase of zinc-silicate glass ionomer cements to identify potential mechanisms responsible for the time-induced mechanical instability of Ge-based glass ionomer cements. The influence of Ge was evaluated on the basis of changes in mechanical properties and molecular architecture of the cements over a 180-day period. It was observed that the compressive strength and modulus of the cements were sustained when Si:Ge ratios were ≥1:1, but when Si:Ge ratios are <1:1 these properties decreased significantly over time. These mechanical changes were independent of structural changes in the glass ionomer cement matrices, as the level of metal-carboxylate crosslinks remained constant over time across the various Si:Ge ratios explored. However, it was noted the temporal decline of mechanical properties was proportional to the increased release of degradation byproducts, in particular Ge that was released from the cements in substantially greater quantities than other glass constituents. Unexpectedly, the slowest setting cement (Si:Ge 1:1) was also the strongest; behavior that is uncommon in Si-based glass ionomer cements, supports the potential of Ge-containing glass ionomer cements as injectable bone cements in applications such as percutaneous vertebroplasty.

Hydroxyapatite decreases cytotoxicity of a glass ionomer cement by calcium fluoride uptake in vitro

“…A possible explanation for this toxicity reduction is a chemical interaction that occurs between HAp and CaF 2 , triggering an ion exchange and consequently the removal of fluoride from the local environment. This phenomenon confirms that GICs have the ability to bind chemically with tooth structures after a setting reaction (23-25).…”

Properties of zirconia-containing glass-ionomer cement

“…The other constituents were polymeric materials which do not present peaks in an XRD pattern but appear as wide bands due to their amorphous structure. Other studies also showed that SiO 2 is the major component of this material [36][37][38][39][40]. On the other hand, ZrO 2 presented a crystalline structure, with characteristic peaks in the XRD pattern (Fig.…”

Development of Novel Adhesives for Sternal and Radial Fixation

“…Recent investigation regarding the incorporation of germanium (Ge) at the expense of Si has shown great promise for clinical applications. By formulating GPCs using a glass composition of (mole fraction): SiO2 -0.24, GeO2 -0. offering excellent clinical handling properties while maintaining mechanical strengths similar to Ge-free cements (> 50 MPa) [116]. In addition, the incorporation of Ge has been suggested to reduce the release of Zn to negligible levels (< 10 ppm) [116].…”