The sticky, viscous formula of Opalescence gel does not leach from the tray like other whitening agents, and the sticky gel holds the comfortable tray securely in place. Opalescence gel contains PF (potassium nitrate and fluoride). Twenty percent water content prevents dehydration and shade relapse, making Opalescence gel one of the most reliable whitening gels available. Opalescence gel is recommended for whitening discolored teeth prior to placement of composite, veneers, and/or crowns. It is effective in breaking down some or all internal tooth discolorations due to congenital, systemic, pharmacologic, traumatic, etc., factors as well as aging. It is successful with fluorosis and even tetracycline staining. 16% PF, mint flavor. Contains 8pcs 1.2ml syringes, 1pc 20ml whitening toothpaste, 1pc tray case and 1pc shade guide.