Obtenção e avaliação de ligas de NiTi tratadas a laser: perspectiva para aplicação em implantes dentários.

Abstract

The nickel-titanium (NiTi) alloys has been widely used in devices of the area medical and dental treatment due to their properties of biocompatibility, shape memory effect and superelasticity. The implantology has sought biomaterials that offer in addition to the mechanical resistance, proper relationship between bioactivity/biocompatibility when in contact with biological tissues. This way, the present study aimed to obtain and analyze NiTi alloys under the LASER action with and without deposition chemistry of apatite, in order to evaluate the mechanical properties, physico-chemical, morphological and biological, for application in dental implants. We obtained from three alloy compositions: equiatomic (NiTi- A), with a higher concentration of Ni (NiTi-B) and with the greatest concentration of Ti (NiTi- C). Part of the samples had their surfaces irradiated by LASER (Yb:YAG), in normal atmosphere, with and without coating of apatite by Method Biomimetic employing the solutions SBF (Simulated Body Fluid) 0 and 6. The samples were characterized by the techniques of X-Ray Diffraction (XRD), Energy Dispersive Spectroscopy X-ray (EDX), optical microscopy (OM), Scanning Electron Microscopy (SEM), Wettability, Differential Scanning Calorimetry (DSC), Vickers microhardness, Dynamic Mechanical Analysis (DMA) and Cytotoxicity Analysis. The XRD analysis showed decrease in crystallinity of the samples subjected to surface modifications, characteristic of the formation of titanium oxides and apatite layer. The spectroscopy revealed an increase in the concentration of oxygen and carbon in the alloys after ablation, suggesting that the laser energy favors the diffusion of oxygen atoms and results in the formation of oxides of titanium. The coated samples showed a molar ratio of Ca / P of 1.0, characterizing the formation of a film of apatite of low crystallinity. NiTi alloys irradiated with or without the apatite, showed changes in surface morphology and wettability properties that contribute to an increased interaction of the biomaterial with the biological environment and reduction in the time of osseointegration. The DSC results revealed distinct phase transformations, where a temperature close to the body (37 ⁰ C) NiTi samples A, B and C had to austenitic / martensitic, austenitic and martensitic predominantly, respectively. In relation to mechanical properties, the NiTi-C alloy had the lowest value of Vickers hardness (HV 273.14 + 4.15) due to the type monoclinic crystal structure (martensite) present. The DMA analysis, alloys showed tensile modulus below 21.5 GPa, close to the bone. The cytotoxicity assays demonstrated the feasibility of NiTi alloys, especially when subjected to laser treatment alone and associated with the biomimetic coating in SBF-6. Therefore, based on the results presented, we conclude that NiTi-C alloy surface-modified showed mechanical properties, morphology and biological characteristics favorable for application as biomaterial, besides being economically viable for dental implants.