treat like any other ivory, or handle material. as mentioned youll want to fill the hollow cavity in the tusk. pay attention to how much wall you leave when filling. as with any material youll want enough there to hold itself together, not split, and have room for trimming/finishing youll do to the outside. and im a big fan of pinning. I like to know my knife will stay together even if the epoxy doesn't.
which hippo tooth would you be working with? the smaller front teeth are a good size as they are just cut to length you want. the root end is hollow like the warthog, but the rest is solid. and, at 6"-8" there is plenty there to trim off the hollow end to work with mostly solid piece.
if one of the larger tusks, then you can cut them into slabs. just a tip..... ceramic belts for the sander, and 14tpi bimetal blade on the saw to cut that stuff. id once read it was the hardest of the ivories. well I sure found out. the large lower tusk I was working with was actually throwing sparks on the 36grit ceramic belt.
here are a couple of the hippo pieces. top one is hidden tang, and the bottom is full tang slab side
https://www.flickr.com/photos/oiseau...7629378096370/
https://www.flickr.com/photos/oiseau...7629378096370/