[1] Univ London Imperial Coll Sci Technol & Med, Dept Mat, London SW7 2BP, England
[2] Nat Hist Museum, Dept Mineral, London SW7 5BD, England
[3] Northwick Pk Hosp & Clin Res Ctr, Northwick Pk Inst Med Res, Dept Surg Res, Harrow HA1 3UJ, Middx, England
[4] ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci, CH-8093 Zurich, Switzerland
[5] Univ Liverpool, Sch Dent Sci, Liverpool L69 3GN, Merseyside, England
[6] Univ Westminster, Dept Mol & Appl Biosci, London W1W 6UW, England
[7] UCL, Eastman Dent Inst, Div Biomat & Tissue Engn, London WC1X 8LD, England