No teeth

Dazhane🌹 • April 24th.. the day my life changed 👑❤🍼
My son is 9 months and he has been drooling terribly since he was 5 months and chewing on all toys. 
But he's has no teeth, not even signs of teeth, he had his 9 month check up yesterday and his doctors said she'll get worried if he's one and still doesn't have any teeth. 
She thinks they may just come in all at onetime! I really hope!! 
Has this happened to any mommies ?