1. Carmem Silvia Costa Pfeifer, graduate student, University of São Paulo, School of Dentistry, Department of Dental Materials, São Paulo, Brazil
2. Roberto Ruggiero Braga, associate professor and chair, University of São Paulo, School of Dentistry, Department of Dental Materials, São Paulo, Brazil
3. Jack Liborio Ferracane, professor and chair, Oregon Health and Science University, Division of Biomaterials and Biomechanics, Portland, OR, USA