1. Department of Restorative Dentistry, The University of Connecticut Health Center, Farmington, Connecticut 06032, USA
2. Department of Dental Materials, School of Dental Materials, School of Dentistry, The University of Michigan, Ann Arbor, Michigan 48109, USA
3. Department of Materials and Metallurgical Engineering, College of Engineering, The University of Michigan, Ann Arbor, Michigan 48109, USA