When molded properly, the SmartGuard Anti-Snore Device will stay firmly on your teeth, evenwhen you relax your jaw and open your mouth while sleeping. The patent pending design preventsthe trays from disengaging with the teeth when you open your mouth because the upper and lowertrays are only connected via the Advancement Bars. The bars hold trays comfortably on your teetheven when your jaw is relaxed and open.