Naruto 643 Spoiler - The Shadow Within

The naruto 643 chapter starts off with a recap of the damage Naruto and Sasuke's combined attack did to Obito. And it seems it was rendered useless because Obito comes out unharmed, and all his little Black Particle balls come back to him, almost like a magnet. And then he kind of fans the fires away with his Jinchuuriki cloak it would seem.

Even in the midst of failure Tobirama is analyzing every little thing. He's starting to become my favorite Hokage. The first thing to note is that Minato's Edo Tensei arm isn't regenerating. And Tobirama then goes on to warn Minato that if he gets hit by Obito like that again he'll die once more and never return, his Edo Tensei will be finished...that makes me wonder what happened to Sarutobi...he took a direct hit to the face with that black particle stuff earlier.

Anyway, the reason why his arm can't regenerate is because Obito is using a technique that renders all Ninjutsu useless. It's called "Onmyoudon" according to the Mangapanda translations. And this mythical tecnique, or Obito's 'Black Particle technique' seems to be the root of it, whatever it touches turns to dust according to the Third Hokage: