ROS (reactive oxygen species) have become increasingly worthy of attention because of their central role in the progression of many inflammatory conditions. They are described as oxygen free radicals and any other non-radical oxygen derivative involved in the production of oxygen radicals. ROS are involved in normal cellular metabolism and are continuously generated by cells in most tissues. Another category of substances called antioxidants exist in the cell that can effectively delay or completely inhibit ROS-induced oxidation. Under physiological conditions, ROS production is drastically increased largely due to the immune system cells and the phagocytosis process through the metabolic pathway. Consequently, high levels or increased activities can not be balanced by the antioxidant defense system, which leads to oxidative stress and tissue damage. ROS can directly damage the tissue by their action against DNA, proteins and oxidation of important enzymes. At the same time, they can act as signaling pathways or as mediators of inflammation.
In recent years, numerous clinical and experimentional studies have demonstrated a strong association between oxidative stress and periodontitis. A better understanding of this association can lead us to a detailed knowledge of the pathogenic mechanisms of this disease, and so can guide us towards a more structured therapy.