One of my favorite clinical products is retraction paste, but using it means we need to be aware of the technique sensitivity and issues that may arise.
So why do I love it? Retraction pastes are the best hemostatic agents we have available today. Unlike the liquid versions they can not be absorbed into the dentinal tubules and cause a discoloration of the prepped tooth over weeks to months. They are however alumina based, and can interact with VPS and polyether impression materials. When using retraction pastes it is essential that you very generously rinse and remove all residue of the paste, even at the base of the sulcus. Leaving residual material will cause your light body impression material not to set, or to set much more slowly than the recommended time.
I use these materials only when the clinical indications require it. I am still a big fan of a two cord technique, and only if I have some residual bleeding after the top cord has been placed do I use retraction paste. I place a small amount over the top cord. Hemostasis requires a full one minute of contact. Astringent retraction requires 2-5 minutes of contact. Then remember to rinse very generously and check for residual material before beginning the impression process.