Behavior of rat bone marrow stem cells on titanium surfaces modified by laser-beam and deposition of calcium phosphate.

OBJECTIVES: The aim of this study was to evaluate the behavior of rat bone marrow stem cells seeded on a Ti-15Mo alloy surface modified by laser-beam irradiation followed by calcium phosphate deposition. MATERIALS AND METHODS: A total of four groups were evaluated: polished commercially pure titanium (cpTi): Ti-P; laser irradiation + calcium phosphate deposition on cpTi: Ti-LCP; polished Ti-15Mo alloy: Ti15Mo-P; and laser irradiation + calcium phosphate deposition on Ti-15Mo alloy: Ti15Mo-LCP. Before and after laser irradiation and calcium phosphate deposition on the surfaces, physicochemical and morphological analyses were performed: Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDX). The wettability of the samples was evaluated by contact angle measurement. In addition, the behavior of osteoblast-like cells to these surfaces was evaluated for cell morphology, adhesion, proliferation and viability, evaluation of alkaline phosphatase formation and gene expression of osteogenesis markers. RESULTS: Surfaces wet-abrade with grit paper (P) showed oriented groves, while the laser irradiation and calcium phosphate deposition (LCP) produced porosity on both cpTi and Ti15Mo alloy groups with deposits of hydroxyapatite (HA) crystals (SEM). EDX showed no contamination after surface modification in both metal samples. A complete wetting was observed for both LCP groups, whereas P surfaces exhibited high degree of hydrophobicity. There was a statistical difference in the intragroup comparison of proliferation and viability (p < 0.05). The ALP activity showed higher values in the Ti15Mo alloy at 10 days of culture. The gene expression of bone related molecules did not present significant differences at 7 and 14 days among different metals and surface treatments. CONCLUSION: Ti15-Mo seems to be an alternative alloy to cpTi for dental implants. Surface treatment by laser irradiation followed by phosphate deposition seems to positively interact with bone cells. CLINICAL RELEVANCE: Ti-15Mo alloy surface modified by laser-beam irradiation followed by calcium phosphate deposition may improve and accelerate the osseointegration process of dental implants.

Ti-15Mo Alloy Decreases the Stress Concentration in Mandibular Angle Fracture Internal Fixation Hardware.

OBJECTIVES: Comparison of the mechanical stability of 2.0 plates made of commercially pure titanium (cpTi) and a titanium-molybdenum (Ti-15Mo) alloy and two methods of internal fixation employed mandibular angle fractures, using 3D finite element analysis. MATERIALS AND METHODS: Four groups were evaluated. For the cpTi: group Eng 1P, one 4-hole plate and 4 screws 6 mm long, in the tension zone of the mandible; group Eng 2P, two 4-hole plates, one in the tension zone of the mandible and the other in the compression zone, both were fixed with 8 screws 6 mm long. The same groups were created for the Ti-15Mo alloy. A 100 N compressive load was applied to the occlusal surface of the mandibular first molar on the plated side. RESULTS: When considering the von Mises equivalent stress (σ vM) values for the comparison between both groups with one plate, a decrease of 10.5% in the plate and a decrease of 29.0% in the screws for the Ti-15Mo group was observed. Comparing the same groups with two plates, a decrease of 28.5% in the screws was shown for the Ti-15Mo alloy group. No significant differences were observed when considering maximum and minimum principal stresses (σ max, σ min), and maximum principal strain (ε max) to the mandibular bone. The Ti-15Mo alloy plates substantially decreased the stress concentration in the screws for both internal fixation techniques and in the plate for the Ti-15Mo 1 plate group. CONCLUSION: From a clinical standpoint, the use of Ti-Mo alloy with reduced stiffness will decrease the stress shielding between the hardware and bone, influencing the outcome of the treatment.

Electrochemical behavior and corrosion resistance of Ti-15Mo alloy in naturally-aerated solutions, containing chloride and fluoride ions.

The electrochemical behavior and corrosion resistance of Ti-15Mo alloy to applications as biomaterials in solutions 0.15 mol L(-1) Ringer, 0.15 mol L(-1) Ringer plus 0.036 mol L(-1) NaF and 0.036 mol L(-1) NaF (containing 1,500 ppm of fluoride ions, F(-)) were investigated using open-circuit potential, cyclic voltammetry, and electrochemical impedance spectroscopy techniques, X-ray photoelectron spectroscopy and scanning electron microscope. Corrosion resistance and electrochemical stability of the Ti-15Mo alloy decreased in solutions containing F(-) ions. In all cases, there were formation and growth of TiO2 and MoO3 (a protector film), not being observed pitting corrosion, which might enable Ti-15Mo alloys to be used as biomedical implant, at least in the studied conditions, since the electrochemical stability and corrosion resistance of the passive films formed are necessary conditions for osseointegration.

Electrochemical stability and corrosion resistance of Ti-Mo alloys for biomedical applications.

Electrochemical behavior of pure Ti and Ti-Mo alloys (6-20wt.% Mo) was investigated as a function of immersion time in electrolyte simulating physiological media. Open-circuit potential values indicated that all Ti-Mo alloys studied and pure Ti undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the chloride-containing solution. It also indicated that the addition of Mo to pure Ti up to 15wt.% seems to improve the protection characteristics of its spontaneous oxides. Electrochemical impedance spectroscopy (EIS) studies showed high impedance values for all samples, increasing with immersion time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The fit obtained suggests a single passive film present on the metals' surface, improving their resistance with immersion time, presenting the highest values to Ti-15Mo alloy. Potentiodynamic polarization showed a typical valve-metal behavior, with anodic formation of barrier-type oxide films, without pitting corrosion, even in chloride-containing solution. In all cases, the passive current values were quite small, and decrease after 360h of immersion. All these electrochemical results suggest that the Ti-15Mo alloy is a promising material for orthopedic devices, since electrochemical stability is directly associated with biocompatibility and is a necessary condition for applying a material as biomaterial.

Electrochemical impedance spectroscopy characterization of passive film formed on implant Ti-6Al-7Nb alloy in Hank's solution.

The influence of potential on electrochemical behavior of Ti-6Al-7Nb alloy under simulated physiological conditions was investigated by electrochemical impedance spectroscopy (EIS). The experimental results were compared with those obtained by potentiodynamic polarization curves. All measurements were carried out in Hank's aerated solution at 25 degrees C, at pH 7.8 and at different potentials (corrosion potential, 0 mV(SCE), 1000 mV(SCE), and 2000 mV(SCE)). The EIS spectra exhibited a two-step or a two-time constant system, suggesting the formation of a two-layer oxide film on the metal surface. The high corrosion resistance, displayed by this alloy in electrochemical polarization tests, is due to the dense inner layer, while its osseointegration ability can be ascribed to the presence of the outer porous layer.

Avaliação da formação do biofilme de Candida albicans sobre superfície de titânio revestida com hidroxiapatita por meio de microscopia eletrônica de varredura / Assessment of Candida albicans biofilm formation on commercially pure titanium hydroxyapatite coated surfaces by means of scanning electron microscope

Neste estudo, a formação de biofilme por Candida albicans na superfície de corpos-de-prova de titânio comercialmente puro (Ti-cp) revestidos com hidroxiapatita foi observada por meio de microscópio eletrônico de varredura. O biofilme foi formado após 45 dias de incubação do corpo-de-prova de Ti-cp revestido, em meio de cultura líquido inoculado com as células leveduriformes, contido em tubo de poliestireno com tampa de rosca e esterilização. Após a remoção do biofilme com solução de EDTA 10%, pontos de corrosão foram observados na superfície rugosa/porosa do Ti-cp revestido com hidroxiapatita

Placas de aço inoxidável 316L aplicadas no reparo de fratura experimental diafisária do rádio e ulna de cäes / Reparing radial and ulnar diaphysial experimental fracture of dogs employing stainless steel plates 316L

O objetivo do presente trabalho foi o de estudar a resistência à corrosäo em placas de aço inoxidável 3l6L, com diferentes tipos de acabamento e tratamento superficial, e a possível interferência dessa reaçäo corrosiva na consolidaçäo óssea. Utilizaram-se placas semi-acabadas, polidas, tratadas com jatos de microesferas de vidro e passivadas, as quais foram aplicadas na epífise distal do rádio de cäes. Foram utilizados 12 animais, divididos em dois grupos, nos quais, após osteotomia bilateral do rádio e ulna, foram realizadas osteossínteses do rádio, totalizando 24 procedimentos. Avaliou-se a evoluçäo clínica e radiográfica das regiöes que receberam os implantes aos 30, 60, 90, 180, 240 e 360 dias. Os animais do grupo 1 (GI) foram sacrificados aos 180 dias e os do GII aos 360 dias para estudo histológico e de microscopia eletrônica de varredura do local da osteotomia sob a regiäo dos implantes metálicos e para estudo da resistência à corrosäo no organismo, pelos implantes metálicos, por meio de análises química e metalográfica (microscopia óptica e eletrônica de varredura e espectroscopia de espalhamento de energia por raios X). Os animais recuperaram a funçäo dos membros operados 24 horas após a cirurgia. Radiograficamente, verificou-se a consolidaçäo óssea em todos os animais. Macro e microscopicamente näo foram observados sinais de corrosäo nos implantes metálicos, exceto em uma placa passivada, aplicada no rádio esquerdo de um animal, na qual a corrosäo foi detectada pela microscopia óptica e eletrônica de varredura. Este estudo permite concluir que as placas de aço inoxidável 3l6L, independente do acabamento superficial a que foram submetidas, näo sofreram corrosäo ou reaçöes adversas e foram efetivas no tratamento das fraturas experimentais do rádio e ulna de cäes

Metallurgical evaluation of a copper-based alloy for dental castings.

The present study was designed to evaluate the metallurgical properties of an experimental, low-cost copper-zinc-aluminum-nickel alloy for dental castings. Some specimens were subjected to heat treatment after induction casting. The extent of corrosion was determined by measuring weight loss of specimens stored in a sodium sulfite solution. In the as-cast specimens, tests demonstrated the presence of three phases: the first consisted of copper-zinc-aluminum, the second was similar but lower in copper and aluminum, and the third consisted of an intermetallic compound of manganese-nickel-phosphorus. After heat treatment, the first phase remained relatively constant, the second was converted to Cu3Al, and the third increased in volume. The weight loss from the as-cast specimens was eight times that of the heat-treated specimens. It was concluded that the heat treatment substantially changed the microstructure and improved the corrosion resistance of the experimental alloy.

[Effect of heat treatment on the structure of a Cu-Zn-Al-Ni system dental alloy]. / Efeito do tratamento térmico na estrutura da liga odontológica do sistema Cu-Zn-Al-Ni.

This article characterizes the structural phases present in the copper-based metallic alloy system "Cu-Zn-Al-Ni" developed for dental use, and relates those phases to other properties. The characterization was obtained after casting (using the lost wax process), and after heat treatment. In order to obtain better corrosion resistance by changing the microstructure, the castings were submitted to 30, 45 and 60 minutes of heat treatment at the following temperatures: 750 degrees C, 800 degrees C, and 850 degrees C. The various phases were analyzed using X-ray diffraction and scanning electron microscopy (SEM). The results after heat treatment showed a phase (probably Cu3Al), that could be responsible for the improvement in the alloy's resistance to corrosion as compared to the as-cast structure.

[Determination of casting contraction of alternative copper based alloys]. / Determinação da contração de fundição de ligas alternativas à base de cobre.

This study is about the cast contraction of 10 alternative alloys developed in the Dentistics Department of the Faculdade de Odontologia de Bauru that were compared with type III and type IV gold alloys and alternative commercial alloys.