The effect of composition and annealing on the properties of aluminum free GPCs: A preliminary evaluation

• We examined the reactivity of Zn–Br–Ge glasses in polyalkenoate cements.
• Reactivity was altered by glass annealing and varying Zn:Ge ratio.
• GPC properties were evaluated to quantify the effects of varying glass reactivity.
• Annealing extended GPC setting reaction but strength varied with glass composition.
• A large tipping point in handling properties was observed as Zn:Ge neared 1:1.

Glass polyalkenoate cements (GPC) comprising zinc borogermanate glass may have clinical potential as injectable bone cements. However significant improvements in setting characteristics are required, i.e. significant extension of working/setting times into clinical relevant ranges is required without compromising strength. Achieving such features may be possible via reducing the zinc to germanium ratio of such glasses coupled with an annealing process. The reactivity of non-annealed and annealed experimental glasses with Zn:Ge ratios between 1:0.64 and 1:1.11 were compared by measuring GPC working times, setting times, and compressive strengths. The working and setting time results were impressive, and ranged from 2–15 and 5–31 min, respectively, influenced by both Zn:Ge ratio and annealing. Interestingly, abrupt and significant changes in handling properties were observed in both non annealed and annealed GPCs as the Zn:Ge ratio passed 1:1. The strongest composition comprised an annealed glass with a 1:0.74 ratio, which demonstrated 30 MPa at 1 day increasing to 39 MPa at 30 days. The influence of glass annealing on GPC strength was found to be compositionally dependent. These experimental GPCs demonstrated handling characteristics sufficient for use as injectable bone cements