Blood extraction was performed in the pre-surgical area using a vacuum system. A total of 20 ml of blood (4 samples of 5 ml) per patient was collected in sterile sodium citrate tubes. PRGF was obtained following Anitua`s technique. The tubes with citrated blood were centrifuged at 1,800 rpm for 8 min to obtain a concentrate of platelets suspended in plasma, which was separated into three fractions. Pipetting was carried out with extreme care in all steps, particularly in the last fraction where, in order to avoid inflammation, leukocytes present in the lowermost portion of the centrifuged plasma were not aspirated. PRGF was activated by adding calcium chloride 10%,immediately before infiltration. The proportion required for PRGF activation is 50 ml of activator per 1,000 ml of PRGF. Separation of plasma into three fractions and subsequent activation of the fractions for injection was performed in a laminar flow chamber.