Google has a couple of versions that seem like a match.
> The day I lost my very first tooth,
> Was halfway through grade four,
> I'd run my tongue along the gap,
> Where my tooth had been before,
> I remember I want home crying,
> And showed it to my mum,
> She told me that a brand new tooth,
> Would grow up in my gum,
> In a while the gap would stop feeling strange,
> I wouldn't notice the tooth was gone,
> The only reason I missed it now,
> Was because it was there for so long,
> Then slowly but surely over the weeks,
> In the gap a new tooth grew,
> And now it makes me wonder,
> If people are like teeth too.