Hi Tiffany,
The best way to serialize and whiten any tooth is hydrogen peroxide.
The 3% stuff in the brown bottles works just fine, it just takes a little longer to whiten than the professional strength (35%). You can find 3% at any grocery store or pharmacy, you can even get it a most dollar stores. It works safely on any bone and can take 6-14 days depending on how stained or greasy they are.
Bone has a natural tendency to yellow over time, but that will happen sooner with things that are handled because of the natural oils in a persons skin.
To avoid the 'premature aged' look, I recommend using clear spray paint.
If you want it to look shiny like a polished bone use a couple coats of glossy. If you prefer a more natural texture, use a flat or mat finish. Enamel, lacquer, acrylic... (even if it comes from the dollar store) it all works just fine.
THINGS NOT TO DO:
Do not boil...
It will cause the enamel to crack on teeth - it also makes bone brittle and harder to work with.
Do not use the peroxide you can get at beauty supply stores...
Yes it is stronger. However it also contains an acid that will break down the bone and etch tooth enamel causing the products you make to have a shorter lifespan (not a big problem for decorative items, but definitely not good for things meant to be handled frequently like jewelry).
Hope this helps, have a great day!
- Arora