For use with customized take-home whitening trays, Opalescence PF offers many options for patients. With its easy syringe delivery, Opalescence PF is easily customizable for each patient's individual situation. The gel contains 20% water to prevent dehydration, and the sticky, viscous formula helps keep the gel and tray in place. Opalescence tooth whitening gel contains PF (potassium nitrate and fluoride) and formulated to prevent dehydration and shade relapse.