Review (5/5): This works in hard to reach places.
OK the flavor is not a midnight snack, but it is worth it. In-between teeth was a problem with trays but with the pen, I put it directly where I need it. Personally I apply it, use a floss to maneuver it even more, leave on for a good half hour with my mouth open to not remove product from tooth then rinse it off and wipe tooth area with a hand towel as a gentle polish. I am getting compliments and feel great. Very excited. Takes some days for deeper stains but be patient and it WILL work.