The doxycycline periodontal system (Atridox) has the antibiotic doxycycline and is used to treat periodontal disease. Doxycycline works by stopping the growth of bacteria. Your dentist puts the doxycycline periodontal system into deep gum pockets next to your teeth. These dissolve naturally over 7 days. The time release of this medication may continue even after it has dissolved.