My Little Pony: Friendship is Magic - If there's a potion that magically makes ponies' teeth grow back...

Because:
1- Zecora wasn’t there at the time and maybe without twi and the mane 6 nopony would ever talk to her.
2- because your ''girls'' aren't that young and potions may work different on old ponies
3- the ingredients may not be cheap…

No, man, they're generation is just racist towards zebras. Obviously.