Mixing it Up

At some point in the not-too-distant future, our body’s natu- ral defense mechanism no longer will fend off foreign in- vaders. Modern medicinal saviors such as vascular stents, guidewires, metallic joints, intramedullary rods, bone plates and sur- gical screws no longer will trigger an automatic seek-and-destroy response from the 25.2 billion-strong army of B-cell lymphocytes that patrol our biological byways. At some point, Werner E.G. Mül- ler trusts, our man-made rescue missions will go undetected, easily slipping past the legions of battle-ready white blood cells and reach- ing their destination without so much as a figurative second glance.

Müller’s vision is ambitious but all not that far-fetched. Thou- sands of drugs and medical devices currently receive a free pass from the body’s dendritic gatekeepers to help debug disease: Hips, knees, ankles, teeth, heart valves, pacemakers, nails and pins routinely are implanted in our anatomies without much immunologic resistance. This impunity usually is granted on behalf of the material compo- sition of the implants—titanium-based products almost always receive preferred guest status, while those containing chromium, nickel or cobalt often are treated as imposters (up to 13 percent of patients are “sensitive” to one or more of the latter three, rendering them less-than-ideal candidates for implantation).

Titanium 6AL4V and 6AL4V ELI, alloys composed of 6 percent aluminum and 4 percent vanadium, are the most common types of medical grade titanium. The alloys’ durability, flexibility, superb bio- compatibility and high strength-to-weight ratio makes them opti- mal substitutes for dead roots of teeth, worn out or damaged joints, malfunctioning rib cages, deteriorated vertebrae and deformed areas of skull. Additionally, titanium is radiolucent (nearly invisible in X- rays, magnetic resonance imaging and computed tomography im- ages), binds easily to bone and organic tissue (due to its high dielec- tric constant) and sports a protective oxide film that forms naturally in the presence of oxygen, even in trace amounts. That film, accord- ing to the Boulder, Colo.-based International Titanium Association, is highly adherent, insoluble and chemically non-transportable, thus preventing adverse reactions to biological tissue.

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