Unfortunately, metal implants in the body still cause long-term problems and inflammation in the surrounding area. Otherwise, they could have used laser sintering to make a adamantium skull.
Metal implants are routine, and usually the "best of the alternatives" in implant design. The body generally tries to isolate metal implants, making them mostly inert, although this does depend a bit on which metal.
The main problems with metal implants are that the can shed ions that accumulate in some people, and that wear particles can cause psuedo-tumors. This is mainly a problem with metal-on-metal joint surfaces (ie in knee or hip replacements). Some more info here: http://en.wikipedia.org/wiki/Hip_replacement#Risks_and_compl...
I actually would have thought that titanium would be the go-to for orthopeadic plates in the skull. I would have thought plastics aren't stiff enough and ceramics too brittle.
I wonder if the increased thermal conductivity of titanium over plastic was a consideration. I can see how having a skull plate that heats/cools much faster than surrounding bone could be a problem.
