My 9 months old can`t sleep through the night.?

Is she teething? That is what is sounds like. In which case there isn't much you can do other than comfort her, and give her infant Tylenol before bed. My 21 month old still doesn't sleep through the night, waking up between 3 and 6 times a night. My son didn't consistently sleep through until he got in his last baby tooth at 2 years and 2 months old