Question: how long do you leave opalescence 20 on?
Answer: Use no more than 1/3 to 1/2 of the syringe per tray. Brush teeth before inserting tray. Lightly tap tray to adapt sides to teeth. Unless directed otherwise by your dentist, wear Opalescence 10% for 8–10 hours or overnight, Opalescence 15% for 4–6 hours, Opalescence 20% for 2–4 hours, and Opalescence 35% for 30 minutes.