Implementation of titanium anodization to produce an anatase surface layer

The world's population is growing and a greater need for surgical implants will accompany this growth. By the year 2030, it is estimated that the number of hip replacements will increase by 174%, and the number of knee replacements will increase by 673%. With greater demand for implants, the number of device associated problems will increase. The two main complications associated with orthopedic and dental implants are infection and mechanical loosening. In 2002, it was estimated that 4.3% of 2.6 million orthopedic implants inserted became infected. Couple this fact with the continuing evolution of antibiotic-resistant bacteria, which renders conventional antibiotic therapies increasingly ineffective, there is an urgent need for approaches beyond antibiotic prophylaxis to address the implant-associated problems. The surgical and non-surgical procedures currently utilized to correct these complications can be costly and painful for the patient. The current study attempted to address the infection and mechanical loosening potential issues through a novel pulsed-anodization treatment on commercially pure titanium. The anodization treatment produced a modified surface oxide that may act as an antimicrobial surface while not adversely affecting the known biocompatibility of titanium.;Titanium is one of the most commonly used metals for orthopedic and dental implants due to their mechanical strength and ductility, corrosion resistance in physiological conditions, and its biocompatibility. Titanium spontaneously forms a protective surface oxide in the presence of oxygen, which is usually naturally formed in the amorphous condition. However, titanium dioxide can also be formed into three crystalline allotropes: anatase, rutile, and brookite. Anatase and rutile are the two most common forms and have been recently studied due to their reported photocatalytic properties. Photocatalytic activity is the ability to catalyze oxidation/reduction reactions when exposed to light of a certain wavelength. Literature has shown that activated anatase, rutile, or a combination of the two has the ability to react with the cell membranes of bacteria and suppress their activity.;Anodization is an electrochemical method of surface modification used for colorization marking and improved bioactivity on orthopedic and dental titanium implants. Anodization techniques have recently been researched as a method of producing crystalline oxides, nano dimensioned topographies, and greater levels of bioactivity. The oxide layer produced by anodization is thicker and denser than the natural forming titanium oxide. The processing parameters under which the oxide is formed determine its thickness, density, homogeneity, surface roughness, and crystallinity.;A pulsed anodization waveform was optimized for anatase formation in sulfuric acid electrolytes for both gold and dark green colored samples. The surface properties evaluated were oxide crystallinity, pore size and distribution, wettability, and surface roughness. Near-UV activation was carried out at a wavelength of 365 nm for various time periods before antimicrobial and bioactivity testing. The bactericidal effect was evaluated on both methicillin resistant Staphylococcus aureus and Streptococcus sanguis , which are commonly associated with orthopedic and dental infections. The bioactivity levels were evaluated through apatite formation in simulated body fluid soak tests.;The results showed that anodizing titanium to both gold and dark green colors 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 5 0.01 to 1 pm2. Near-UV activation of the anodized surfaces showed a transition from a more hydrophilic surface to a hydrophobic surface with increasing exposure time. The surface roughness analysis showed that the pulsed anodized samples had nano sized roughness features that may be beneficial for cellular attachment.;The bactericidal effect results showed that the thicker dark green oxides created with the pulsed anodized method was superior in reducing the bacterial attachment both 24 and 48 hours of exposure. Evaluation of the photocatalytic activity of the crystalline titanium dioxides through near-UV activation was inconclusive as the effect was not shown against MRSA but was shown to have a significant effect against S. sanguis. The bioactivity testing in simulated body fluid results showed that the thicker dark green anodized samples had a similar bioactivity level as the titanium control while the gold anodized samples showed a slight reduction.;In conclusion, the crystallinity, pore size distributions, wettability, and the nano sized surface roughness produced through pulsed anodization of commercially pure titanium in sulfuric acid resulted in a significant reduction in the bacterial attachment and may be beneficial for bone cell attachment and proliferation.