Purity: Touching Separated Bones or Teeth
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 517:
Performing this ghusl is not obligatory for touching a bone that has not been given ghusl and has separated from a dead or living person. Similarly, [performing this ghusl is not obligatory] for touching a tooth that has separated from a dead or living person.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)