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Comment by tsomctl | Hacker News Reader

> Titanium is one of the few metals that human bone is able to grow around firmly, allowing it to be used widely in medicine and dentistry.

How good are we at concentration gradients in alloys? For a replacement joint, say, could the part that the bone bonds to be mostly titanium, and then the bearing portion be this new alloy?

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The article says the material has better biocompatibility than currently used alloys, so biocompatibility wouldn't be a motivation to do that.

Still have to think about other measures of strength and the processes required to make parts out of it.

More: The paper mentions bonding the material to the surface of ceramic materials to save weight.

Although I've only spent a few weeks in an ortho rotation in med school, I think pretty good. Many implants are coated with silver to help prevent infections. I've never heard of such silver layers ever "peeling off" or somesuch, so it seems the silver/titanium mix is effective.

The silver oxidizes and disappears after a while (few weeks?) though, right? (probably by design)

It's been quite a long time since I studied this, but the primary problem with materials in implants is the quality of being bioinert. Many titanium alloys are not bioinert. Any combination would have to be tested separately.

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.

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

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.

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