That should be fine with a large crack, but the kind usually seen on razors will allow the glue to enter, especially if it is cyanoacrylate, but not the ivory powder. If I wanted to try this, I would try to get the powder into the crack, and impregnate it with the cyanoacrylate afterwards. But Ace Hardware do a white epoxy glue, probably intended for bathroom items, which is actually slightly off-white, and all you would lose is the thought that there is ivory in there someplace.