Platelet-rich preparations to improve healing.  Part II: platelet activation and enrichment, leukocyte inclusion, and other selection criteria. 
Multiple platelet-rich preparations have been reported to improve wound and bone healing, such as platelet-rich plasma (PRP) and platelet rich fibrin (PRF).  The different methods employed during their preparation are important, as they influence the quality of the product applied to a wound or surgical site.  Besides the general protocol for preparing the platelet-rich product (discussed in Part 1 of this review), multiple choices need to be considered during its preparation.  For example, activation of the platelets is required for the release and enmeshment of growth factors, but the method of activation may influence the resulting matrix, growth factor availability, and healing.  Additionally, some methods enrich leukocytes as well as platelets, but others are designed to be leukocyte-poor.  Leukocytes have many important roles in healing and their inclusion in PRP results in increased platelet concentrations.  Platelet and growth factor enrichment reported for the different types of platelet-rich preparations are also compared.  Generally, TGF-β1 and PDGF levels were higher in preparations that contain leukocytes compared to leukocyte-poor PRP.  However, platelet concentration may be the most reliable criterion for comparing different preparations.  These and other criteria are described to help guide dental and medical professionals, in large and small practices, in selecting the best procedures for their patients.  The healing benefits of platelet-rich preparations along with the low risk and availability of simple preparation procedures should encourage more clinicians to incorporate platelet-rich products in their practice to accelerate healing, reduce adverse events, and improve patient outcomes.