1. a Centre for Mechanical and Materials Technologies (CT2M), Universidade do Minho , P-4800-058 , Guimarães , Portugal
2. b IBB – Institute for Biotechnology and Bioengineering, Universidade do Minho , 4710-057 , Braga , Portugal
3. c Department of Periodontology , Katholieke Universiteit Leuven , B-3000 , Leuven , Belgium
4. d Dept MTM , Katholieke Universiteit Leuven , Leuven , B-3001 , Belgium