I've never thought of it this way, and you are right from both a technological and biological perspective.
Biologically we are wonderful containers of nutrients, but we have an army only the very sneaky or militant can overcome. Once that army stands down we are rapidly colonized - which is why we must be so careful with food/meat storage.
Realizing that, it's easy to see why autoimmune diseases are so devastating.
Presumably they sheath these devices in inert plastics or something in an attempt to counteract all this?
Fun fact: Gold teeth caps are really good for you, though maybe not your love life. Gold has very very similar mechanical parameters to your dentin.
Overall, bioengineers are making great strides into these compounds. We are developing new heart stents that coil and expand in response to heat or can just be injected and will solidify and expand wherever they are needed. A cool development sector is in 'smart' hip replacements. They have nano-pores in the titanium to induce bone growth into the implant and create a better and more healthy bond.