Parasuram was one of the avatars of Vishnu. He went to see Shiva and Ganesh was at the door. So Parasuram began to fight with Ganesh. Parasuram had received the axe from Shiva, the Parasu. He was Parasu-Ram. He had the axe in his hand. And the axe was amog, it was infallible. Whatever he would strike would be instantly cut in two.
When he fought with Ganesh, Ganesh was just this little boy. And Parasuram had defeated all the kings of the earth twenty-one times. He had a great ego. He had come to see Shiva. Ganesh said, “Shiva is inside and he told me to stand outside so no one can come in.”
And Parasuram said, “I am a devotee of Shiva and and no one has the authority to keep a devotee away from his ishta deva, away from his chosen form of worship. I am a pure devotee. You stand aside.” Ganesh said, “no one comes into the inner sanctum of Shiva’s abode without wisdom. You must first honor wisdom.” The devotee said, “stand aside.”
They got into an altercation and Ganesh was predominant in the altercation, Ganesh was defeating him and then Parasuram got so mad he threw his axe and cut his tooth. So he became Ekadanta.
The other story is Shani Deva. You know Shani, he is Saturn, the planet. He came to see Shiva and he got into the same type of argument with Ganesh and he cut Ganesh’s tusk with his trident, the Trishul. Those are the two who both cut Ganesh’s tooth.