Repairing Ivory

[ALEX]

David, it also depends on kind of "break". Age cracks better to leave alone and not to fill. if something broke into several pieces - the above recommendation will work. apply the glue near the center, keep it away from edges, not let it come near edges when parts are pressed against each other as you'll need to join them so the gaps will be as small as possible, then fill them with any light and washable adheisive of ivory colour (I use All Purpose Filler or Worktop Joint filler). if done right - it'll be unnoticeable. the same for repairs, see below pix, not the best restoration as it can be seen (the gap still needs to be stained). the top part of the handle was broken and corner missing.
Good luck