LILIANA POROJAN, MIHAELA BIRDEANU, SORIN POROJAN MULTIDISCIPLINARY APPROACH ON THE CORROSION BEHAVIOR OF WELDED NICKEL-FREE AND NICKEL-CONTAINING STAINLESS STEEL ORTHODONTIC WIRES The oral environment is responsible to the degradation of metal wires, with consequent release of metal ions in the oral cavity during corrosion, and welded joints are known as areas that are particularly susceptible to corrosion. The aim of the study was to achieve the corrosion behavior of welded Ni-free and Ni-containing stainless steel (SS) orthodontic wires. The morphology and the topography of the laser welded samples were investigated by scanning electron microscopy and atomic force microscopy. The electrochemical measurements calculated the values for corrosion potential, corrosion current and corrosion rate, for different pH values. Immersion in acidic solution had minimal effect on the corrosion on the joint regions. Ni-free SS wires proved to have a better corrosion resistance, improved by laser welding. Ni-containing SS wires are positive influenced by laser welding, relative to the corrosion behavior.