1. Prosthodontics and Occlusion Department, University of Oviedo, Oviedo, Spain
2. Avsan Holdings Limited, Luton, Great Britain
3. Department of Mines Prospecting and Exploitation, University of Oviedo, Oviedo, Spain
4. Department of Business Administration, University of Oviedo, Oviedo, Spain
5. Department of Materials Science and Metallurgical Engineering, University of Oviedo, Oviedo, Spain