Nanopore formation on the surface oxide of commercially pure titanium grade 4 using a pulsed anodization method in sulfuric acid.

Titanium and its alloys form a thin amorphous protective surface oxide when exposed to an oxygen environment. The properties of this oxide layer are thought to be responsible for titanium and its alloys biocompatibility, chemical inertness, and corrosion resistance. Surface oxide crystallinity and pore size are regarded to be two of the more important properties in establishing successful osseointegration. Anodization is an electrochemical method of surface modification used for colorization marking and improved bioactivity on orthopedic and dental titanium implants. Research on titanium anodization using sulphuric acid has been reported in the literature as being primarily conducted in molarity levels 3 M and less using either galvanostatic or potentiostatic methods. A wide range of pore diameters ranging from a few nanometers up to 10 µm have been shown to form in sulfuric acid electrolytes using the potentiostatic and galvanostatic methods. Nano sized pores have been shown to be beneficial for bone cell attachment and proliferation. The purpose of the present research was to investigate oxide crystallinity and pore formation during titanium anodization using a pulsed DC waveform in a series of sulfuric acid electrolytes ranging from 0.5 to 12 M. Anodizing titanium in increasing sulfuric acid molarities showed a trend of increasing transformations of the amorphous natural forming oxide to the crystalline phases of anatase and rutile. The pulsed DC waveform was shown to produce pores with a size range from ≤0.01 to 1 µm(2). The pore size distributions produced may be beneficial for bone cell attachment and proliferation.

Titanium alloys for fracture fixation implants.

This paper is intended to provide an overview of the composition, mechanical properties, biocompatibility, and clinical applications for titanium alloys that are used for fracture fixation implants. A new class of titanium implant alloys has emerged in recent years that exhibits a beta microstructure and a unique combination of mechanical properties. Important information regarding notch sensitivity testing and clinical significance is also discussed. Attributes such as stress corrosion cracking resistance, fatigue strength, and wear characteristics are also essential for specific clinical applications, but are beyond the scope of this presentation.

Stainless steel in bone surgery.

Today, stainless steel is one of the most frequently used biomaterials for internal fixation devices because of a favorable combination of mechanical properties, corrosion resistance and cost effectiveness when compared to other metallic implant materials. The biocompatibility of implant quality stainless steel has been proven by successful human implantation for decades. Composition, microstructure and tensile properties of stainless steel used for internal fixation is standardized in ISO and ASTM material specifications. Metallurgical requirements are stringent to ensure sufficient corrosion resistance, nonmagnetic response, and satisfactory mechanical properties. Torsional properties of stainless steel screws are different from titanium screws. Stainless steel bone screws are easier to handle because the surgeon can feel the onset of plastic deformation and this provides adequate prewarning to avoid overtorquing the screw. New nickel-free stainless steels have been recently developed primarily to address the issue of nickel sensitivity. These stainless steels also have superior mechanical properties and better corrosion resistance. The Ni-free compositions appear to possess an extraordinary combination of attributes for potential implant applications in the future.

Torsional properties of implant grade titanium.

The purpose of this research was to evaluate the torsional strength and ductility of CP titanium in the as received condition, heat treated below the alpha----beta transition temperature, and glass bead blasted. Results were compared to as-received samples of implant quality 316L stainless steel. Little or no effect of any of the treatments was noted. The torsional strength of all titanium samples was comparable to 316L stainless and the torsional ductility of the titanium was significantly greater than 316L stainless (p less than .01). These results are significantly different than those obtained when torsion testing bone screws of the same material. A hypothesis is proposed for the differences in these results.

Implant materials for fracture fixation: a clinical perspective.

The optimum management of traumatic skeletal fractures may involve the installation of high quality surgical implants by a skilled orthopedic surgeon. Satisfactory clinical results are very dependent on the ability to maintain stable fracture fixation. Well designed contemporary implants rely on precise control of material composition and properties to achieve a well tolerated level of biological response. Metallic materials, such as 316L stainless steel, pure titanium, and titanium alloys, demonstrate an acceptable combination of strength, ductility, corrosion resistance, and biocompatibility. Polymers, composites, and biodegradable materials may offer selected opportunities for fracture fixation. An understanding of relevant clinical factors is essential to evaluate potential applications for advanced materials.