2.3. Activation of PRP was performed by adding 10% of CaCl2 (final concentration 22.8 mM), 10% of autologous thrombin, 10% of a mixture of CaCl2 + thrombin, and 10% of collagen type I (final concentration 4 μg) (Mascia Brunelli SpA, Milan). PRP without activation and PPP were used as control.