First Tooth Baby Ponies
Yes, we already know that there were no first tooth baby unicorns. I don't know why, but I can tell you this: baby unicorns were rare compared to other baby ponies. Not very many appeared on TV either. They only came up with two baby unicorn poses overtime. The Baby Glory pose got redone for baby unicorns from Year 5, yet they were screwed up. A few unicorns had an earth pony or pegasus for a baby while Twice As Fancy earth ponies sometimes had unicorns for babies. Since Baby Glory wasn't from Year 5, they probably decided not to give baby unicorns a first tooth. I hope this all makes sense.
"Tsuppari is my former name."