Estudo da toxicidade de ligas de NI-TI: uma contribuição para o uso de ligas nacionais e a ortodontia.

Abstract

The present work focused on the study of the properties concerning the chemical composition, microstructure, thermic behavior and cytotoxic in three Ni- Ti alloy compositions. Their characterization resides in the combination of properties such as: the superelasticity and the shape memory effect. These properties can be put to excellent use in various biomedical applications and technology. However, the high content of ions (nickel and titanium) and their release require a special attention, once they can bring about allergic, toxic or even carcinogenic effects, harmful to the human organism. In odontology, the Ni- Ti is widely used to make orthodontic accessories. But any material used in the oral cavity, during a certain time, is supposed to corrosion and it is very important that the professional choose materials more biocompatible. Therefore, this work evaluated and characterized the morphology of surface and cytotoxic of three national Ni-Ti alloy compositions. The characterizations were made by Optical Microscopy (M.O), Scanning Electron Microscopy and Energy Dispersive Spectroscopy (SEM/EDS), Differencial Scanning Calorimetry (DSC) and Rezasurin Test (cytotoxic test). Near ambient temperature optical microscopy has shown the typical Ni-Ti alloy martensitic structure and the electron microscopy has shown the improving of the grain boundary in all the compositions. The DSC have shown that none of the alloy is completely austenitic, but total or partially martensitic at ambient temperature (25ºC). Besides, at mouth temperature (37º) only the high nickel content alloys are completely austenitic, being more applied in orthodontic. The EDS have shown typical spectrum to these alloys without significant differences among the compositions. The Rezasurin Test has not shown any significant statistic difference among the samples either.