Aluminum-free glass-ionomer bone cements with enhanced bioactivity and biodegradability

Al-free glasses of general composition 0.340SiO2:0.300ZnO:(0.250-a-b)CaO:aSrO:bMgO:0.050Na2O:0.060P2O5

(a, b=0.000 or 0.125) were synthesized by melt quenching and their ability to form glass-ionomer cements

was evaluated using poly(acrylic acid) andwater.We evaluated the influence of the poly(acrylic acid)molecular

weight and glass particle size in the cementmechanical performance.Higher compressive strength (25±5 MPa)

and higher compressive elasticmodulus (492±17 MPa) were achieved with a poly(acrylic acid) of 50 kDa and

glass particle sizes between 63 and 125 μm. Cements prepared with glass formulation a=0.125 and b=0.000

were analyzed after immersion in simulated body fluid; they presented a surface morphology consistent with

a calcium phosphate coating and a Ca/P ratio of 1.55 (similar to calcium-deficient hydroxyapatite). Addition of

starch to the cement formulation induced partial degradability after 8 weeks of immersion in phosphate buffer

saline containing α-amylase. Micro-computed tomography analysis revealed that the inclusion of starch increased

the cement porosity from 35% to 42%. We were able to produce partially degradable Al-free

glass-ionomer bone cements with mechanical performance, bioactivity and biodegradability suitable to be applied

on non-load bearing sites and with the appropriate physical characteristics for osteointegration upon partial

degradation. Zn release studies (concentrations between 413 μM and 887 μM) evidenced the necessity to

tune the cement formulations to reduce the Zn concentration in the surrounding environment.