title: Benefits and drawbacks of zinc in glass ionomer bone cements.
abstract: Glass polyalkenoate (ionomer) cements (GPCs) based on poly(acrylic acid) and fluoro-alumino-silicate glasses are successfully used in a variety of orthopaedic and dental applications; however, they release small amounts of aluminium, which is a neurotoxin and inhibits bone mineralization in vivo. Therefore there has been significant interest in developing aluminium-free glasses containing zinc for forming GPCs because zinc can play a similar structural role in the glass, allowing for glass degradation and subsequent cement setting, and is reported to have beneficial effects on bone formation. We created zinc-containing GPCs and characterized their mechanical properties and biocompatibility. Zinc-containing cements showed adhesion to bone close to 1 MPa, which was significantly greater than that of zinc-free cements (<0.05 MPa) and other currently approved biological adhesives. However, zinc-containing cements produced significantly lower metabolic activity in mouse osteoblasts exposed to cell culture medium conditioned with the cements than controls. Results show that although low levels of zinc may be beneficial to cells, zinc concentrations of 400 µM Zn(2+) or more resulted in cell death. In summary, we demonstrate that while zinc-containing GPCs possess excellent mechanical properties, they fail basic biocompatibility tests, produce an acute cytotoxic response in vitro, which may preclude their use in vivo.
authors.affiliation: Unit of Dental Physical Sciences, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK. d.brauer@qmul.ac.uk
authors.forename: Delia S
authors.initials: DS
authors.lastname: Brauer
authors.forename: Eileen
authors.initials: E
authors.lastname: Gentleman
authors.forename: David F
authors.initials: DF
authors.lastname: Farrar
authors.forename: Molly M
authors.initials: MM
authors.lastname: Stevens
authors.forename: Robert G
authors.initials: RG
authors.lastname: Hill
mesh_terms: D016475:3T3 Cells; D000535:Aluminum / Q000737:chemistry; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D001843:Bone Cements; D001842:Bone and Bones / Q000378:metabolism; D002448:Cell Adhesion; D002712:Chlorides / Q000494:pharmacology; D019245:Compressive Strength; D005899:Glass Ionomer Cements / Q000737:chemistry*; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D011312:Pressure; D013314:Stress, Mechanical; D015032:Zinc / Q000737:chemistry*; D017967:Zinc Compounds / Q000494:pharmacology
chemical_list: D001672:Biocompatible Materials; D001843:Bone Cements; D002712:Chlorides; D005899:Glass Ionomer Cements; D017967:Zinc Compounds; C016837:zinc chloride; D000535:Aluminum; D015032:Zinc