1. Department of Oral and Dental Science, Biomedical Engineering and Biomaterials Science Section, University of Bristol, Lower Maudlin Street, Bristol BS1 2LY, U.K., H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, U.K., Interface Analysis Centre, Oldbury House, University of Bristol, 121 St. Michael's Hill, Bristol BS2 8BS, U.K., and Department of Materials Science and Engineering, Technisches Institut, Friedrich-Schiller-Universität Jena, Löbdergraben 32, D-07743...