Glass Ionomer Bone Cements

Glass ionomer cements are commonly used in dentistry, and the use of glass ionomer cements for orthopaedic applications is of interest, as they could overcome some of the limitations of poly(methyl methacrylate) (PMMA), such as shrinkage during polymerisation or an exothermic setting reaction. While acrylic cements cannot form a chemical bond to bone and mechanical stability is achieved by mechanical interlocking only, glass ionomer cements chemically bond to hydroxyapatite, which is the mineral phase of bone, and to surgical metals.

Glass ionomer cements set by an acid-base reaction between an acid-degradable glass and a polymeric acid such as poly(acrylic acid) (PAA). Dental ionomer cements contain aluminium, which plays an important role in both glass degradation (hydrolysis of Si-O-Al bonds) and in stability of the cements (cross-linking of PAA chains by Al3+). However, as aluminium is a neurotoxin and also negatively affects bone mineralisation, new aluminium-free ionomer cements offer an alternative for orthopaedic applications.

Cell test zinc cements
Osteoblasts growing on zinc-containing glass ionomer cements. (Brauer et al., Biomedical Materials 6(4) (2011) article #045007)

Zinc toxicity
Cell metabolic activity in the presence of zinc ions. (Brauer et al., Biomedical Materials 6(4) (2011) article #045007)


Collaborations

Dr Eileen Gentleman, Department of Craniofacial Development & Orthodontics, King's College, London, UK
Dr David Farrar, Smith & Nephew Research Centre, York, UK (now with Xiros Medical Devices, Leeds, UK)
Dr Izabela Radecka, School of Applied Sciences, University of Wolverhampton, Wolverhampton, UK