Aggressive free radicals and ROS substances participate in many stamotological diseases. In the mouth these are formed or transported due to inflammation from white blood cells, in reperfusion after ischemia, cell necrosis, after bleeding in the presence of several metals (Cu, Fe, Hg etc.), due to UV light on mucous membrane, in high glucose level, due to inhalation of injuring, agents smoking, due to pain, from osteoclasts, after some metabolic pathways, due to tooth bleaching etc. The consequence is lipoperoxidation, peroxidation of proteins and DNA with possible mutations and AGE substances are formed. We must take free radicals into account in periodontitis, gingivitis and other inflammations, in carious dentin matrix, in tumors, tissue aging etc. The protection against free radicals is offered by antioxidants, better is their mixture. The most important ones include sodium ascorbate, selenium, glutathione, vitamin E, nicotinic acid and pyridoxamin.The determination of the total antioxidant capacity of saliva may be useful.

        Key words: stomatological diseases - free radicals - tissue damage - antioxidants