David,I have hippo ivory, It is a LOT harder than elephant ivory,which is why it was used for false teeth. Washington's false teeth(which I have seen in the Smithsonian) were actually porcelain. The uppers and lowers were connected with little steel coil springs.
I was planning some day to make a set of hippo ivory false teeth for the Apothecary Shop in the museum. Didn't get to it. Got the hippo tusk,though. You can get them 2 feet long,really incredible to see teeth that large. The hard outer shell has to be ground off,but it isn't very thick.
We actually had this rather eccentric clock maker in Williamsburg. He was scared to death of the dentist. He finally got into such pain that he had to go to one. When the dentist started drilling on his "fillings",he began ruining burrs. He asked what the heck those fillings were. The clock maker told him he had filled his OWN TEETH with something called "Plastic Steel"!!!!
The clock maker lost a front tooth,but didn't want to pay for a bridge. He was very conscious of his appearance,though(actually,he looked like a cadaver!!) so,he got hold of a piece of ivory,made a tooth from it, and JAMMED it into place!! How he lived with that,I don't know!! Ivory will invariably turn yellow in the mouth. When it did,he's make another tooth and jam that one in place!!!!