DreamsMaster: A tooth in a dream may represent one’s appearance or image, and it may also represent one’s sense of strength.
If the tooth was in the front of your mouth, putting on someone else’s false tooth could symbolize wearing another’s identity instead of being true to yourself. That your own tooth fell out after you took off the false tooth could mean that you’re at risk of losing your own identity completely if you continue to hide behind someone else’s.
If the tooth was a molar in the back of your mouth, then instead of the dream message having to do with assuming a false identity, it’s possible the message is about borrowing on someone else’s strength. Losing your own tooth after taking off the false one could symbolize that you’ve come to rely so heavily on another’s strength, that you no longer trust your own.