An apparatus for the generation of metallic and metal oxide nanoparticles for use in the treatment of periodontal disease has a discharge chamber with a controlled flow of water, the water flowing through a plasma gap formed by electrodes, the electrodes having a pulsed voltage applied to create a plasma discharge, the pulse duration chosen to maximize the generation of nanoparticles from the electrodes which are in the range of 10 nm to 50 nm. The discharge chamber flow rate and pulse duration is controlled to maintain a particular temperature differential across the plasma gap to additionally optimize the nanoparticles population for the desired 10 nm to 20 nm size range having negative surface electric charge. The nanoparticles thereby formed may thereafter be applied to a subject in need thereof as an irrigation treatment, or as a paste applied directly to a region of periodontal disease.