1. Faculty of Dentistry; McGill University; H3A 2B2 Montreal Quebec Canada
2. Institute of Glass and Ceramics, Department of Materials Science; University of Erlangen-Nuremberg; 91058 Erlangen Germany
3. Otto-Schott-Institute; University of Jena; 07743 Jena Germany
4. Division of of Orthopaedics, Department of Surgery, Faculty of Medicine; Montreal General Hospital; H3G 1A4 Quebec Canada