1. Department of Biomaterials, Institute of Surgical Sciences , Box 412, Göteborg, 405 30, Sweden
2. Department of Prosthetic Dentistry/Dental Material Science, Faculty of Odontology, Göteborg University , Box 450, Göteborg, 405 30, Sweden
3. Department of Prosthetic Dentistry, Faculty of Odontology, Centre of Oral Health Sciences, Malmö University , Malmö, 205 06, Sweden