Background: The microbial factor plays a major role in the pathogenesis of the periodontal disease. The presence of the periodontal bacteria was demonstrated during numerous researches. The susceptibility of the host in the initial stage of the periodontal disease is considered a mandatory condition. Material and methods: For this study, there were 96 patients selected, men and women, aged between 41 and 73, diagnosed with severe marginal chronical periodontitis (severe CMP). The patients were divided into two lots – the control lot of 52 patients, who received a classical non-surgical periodontal treatment and the research lot of 44 patients, who received the same treatment complimented with systemic and topic ozone therapy. Results: The recent researches have shown the other risk factors, such as the formation of free radicals, which are formed internally and externally. Another very important factor, which accumulates free radicals and creates an appropriate environment for the development of the inflammatory phenomena, is the disruption of the microcirculation, which leads to the development of the chronic tissue hypoxia. The interaction of the free radicals with oxygen leads to the creation of the reactive oxygen species (ROS). The excessive production of the ROS is associated with the development of conditions that involve a wide range of affections and degenerative diseases, including periodontitis. The reduction of the oxidative stress plays a critical role in the complex treatment of the periodontal disease. In the last years, the traditional nonsurgical methods for treating periodontitis have lost their effect, because of the number of cases, showing resistance to the antibiotics and increased allergic reactions, in addition to the high number of contraindications and the side effects of the medications. All these factors lead to a new approach and new researches of alternative methods of treatment. Conclusions: The achieved result led to the rapid reduction of the inflammatory phenomena in the periodontal tissue ensuring a considerable decrease of the bacterial contamination in the periodontal sacks and a stimulation of the repairing processes, which led to the increasing of the health condition maintenance of the periodontal status when comparing it with the traditional treatment.