Sweet Gum Twig Toothbrush?

My grandmother used to make a toothbrush from sweet gum twigs. A friend of mine showed me that you could take your finger nail and slightly cut one of the twigs then come back the next day or several days later and there would be a large glob of light green jelly like liquid or gum formed that he would eat. I tried the gum and it tasted pretty good. I just wanted to verify if indeed it was a young sweet gum that he was doing this to or some other plant? Can you verify that it was or was not a sweet gum? Thanks.

By Floyd Hardee from Ayden, NC