 L-PRF preparation and placement 
STERILE
Using a 10-ml syringe, 9 ml whole venous blood sample was drawn quickly from
the brachial vein and placed into two sterile tubes without the use of an
anticoagulant (20-22 seconds on average). These tubes were then immediately
centrifuged (in less than a minute) at 2,700 rpm (about 400-g centrifugation
force, based on our estimations) for 12 minutes
