Hacker News Reader

This. Anytime you have metal in the body, you want to make sure it's not going to leach into the bloodstream and cause heavy metal toxicity, like mercury or amalgam fillings do.

View on HN

Not only leach. Even titanium alloys used in implants have narrow specifications. For example, the Ti6Al4V that is used in implants differs from the used in airplanes by the amount of Iron on it. From 0.05% to 0.5% makes your body react to it and reject the implant.

Gonna need a link for that. Here's one: http://www.quackwatch.com/01QuackeryRelatedTopics/mercury.ht...

Mercury/amalgram fillings isn't the best example, but biocompatibility is still the primary constraint.

Mayo clinic has a good overview and timeline regarding the discovery process for cobalt-chromium, which was previously thought to be a good all-around implant material:

https://medlineplus.gov/ency/article/002495.htm

Reply on news.ycombinator.com