In Vivo Evaluation of the Differences in Oxidative-reductive Processes in Saliva During Treatment With Conventional Brackets and Clear Aligners

The differences between production of free radicals and the antioxidant capacity of a system is called oxidative stress, this leads oxidative damages to macromolecules, including lipids and proteins.

Oxidative stress occurs in the tissues when the normal balance between ROS production (extracellular Reactive Oxygen Species) and the antioxidant defense shifts in favor of the first; this situation can result from an excess of ROS and/or the reduction of antioxidants. Some ROS types (e.g. superoxide and hydroxyl radicals, hydrogen peroxide, hypochlorous acid) are capable to directly damage proteins, carbohydrates, DNA and lipids; furthermore, ROS production and an altered redox state of tissues can modulate the expression of a variety of immune and inflammatory molecules through redox sensitive transcription factors (eg NF-kB, AP-1), causing thus indirect tissue damage such as inflammation.

Antioxidants agents are found in all biological species to protect against the potential harmful effects of processes or reactions that cause excessive oxidation. Therefore, biological antioxidants represent an important part of our diet and, together with intracellular antioxidants and antioxidant enzyme systems, may prevent various diseases. Antioxidant defense systems are very complex and for this reason it is essential to evaluate the quantity and / or activity of the different systems when evaluating their in vivo state.

Studies on the antioxidant defense systems present in saliva and their relationship with oral diseases are still few. Despite markers of oxidative stress have been found in saliva in presence of systemic and oral diseases, including inflammatory diseases such as gingivitis, periodontitis, caries and oral cancer.4, 15 During an orthodontic treatment, which often lasts for years, some components of the used orthodontic appliance can be released into the oral environment and saliva. The release of these components and their diffusion can cause various adverse effects in the body, such as allergic reactions, systemic toxicity, cytotoxicity, mutagenicity and carcinogenicity. Although there has been satisfactory development of orthodontic materials, the biocompatibility of these materials is usually not well known. The evaluation of these characteristics of orthodontic materials is as important aspect as their physiological or mechanical properties. However, the studies on these characteristics are limited, and they are mostly related to the cytotoxic effects of orthodontic adhesives. The total state of the oxidant (TOS) and the antioxidant (TAS) reflects the oxidative state and provides information on the body's antioxidant capacity. Oxidative damage to DNA can be detected by chemical, physical and enzymatic methods. 8-hydroxyoxiguanosin (8-OHdG) is an oxidized nucleoside which is excreted in body fluids for DNA repair. Several studies have shown that 8-OHdG in body fluids can act as a biomarker of oxidative stress and 8-OHdG is commonly used as a marker to evaluate oxidative DNA damage in disorders including chronic inflammatory diseases. Previous studies have in fact indicated a possible relationship between the salivary levels of 8-OHdG and the diseased periodontium. However, the levels of TOS, TAS and 8-OHdG in patients undergoing therapy with conventional brackets and with clear aligners has not yet been studied.