I'm not a novice to at home whitening I've tried many brands but it had been a couple of years since my last treatment. I decided to give Opalescence a whirl and I'm liking the results. I've used this twice to date and my teeth are NOT as sensitive as they were with other products AND the "wear" time is not as long. Those are TWO HUGE bonuses in my eyes! I do want to mention that it is REALLY recommended that you use 'dentist molded' teeth trays, their fit is far superior to those heat and bite trays you can do yourself (especially for those suffering from "burning gums") and one last tip is not to over fill the trays. Just one tiny little dot in each tooth of the tray is enough. One syringe will get at least 3 applications worth of top & bottom trays.