I’ve recently becoming lucid at moments when i wake up during the night, and i am aware of my conscience “crossing” the line between the awake and the dreaming world. You can feel you mind “wooooosh” as it falls asleep. But the problem is, usually when this happens, i wake up in the morning with a terrible tooth-ache. My frontmost upper teeth hurts a lot. Does someone know anything about this? Doest anyone feel the same thing? I’ve heard a lot of people dream of their teeth falling, or feel like their jaw is being compressed or something (i feel that too).
Maybe something is stressing you out and you are grinding your teeth have a close look at them to see if they are getting worn down.
I’ve never experienced what you have. it might just be something to do with diet or if you are young your teeth might be ready to fall out.
Other than that, you may want to see a dentist/doctor if they don’t stop hurting.
I get something like that too. Do your teeth just hurt when you wake up or all the time. If the former than you’re a clencher like me. It doesen’t happen too often to me so I can’t give you much advice but if you do it every morning your teeth are going to get ground into dust. If the latter than perhaps you should take a good look at your teeth and if required go to the dentist.
It just happens when i wake up, and it hurts for some hours then it’s just gone. 
Can you explain more about this ‘clencher’ thing?
It means that sometimes when asleep, you press you teeth together and grind them. A good while ago I awoke from this two or three times (not related to LDing though) and couldn’t stop it for a few secs because I hadn’t regained full control over my body. I almost thought a tooth would break under the strain. Definitely not something you want to experience. It can be caused by inner conflicts / stress and such, and in my case it went away after a while.
If this is, in your case, connected to lucid dreaming, I’d consider leaving the topic or checking if you’re really comfortable with it. Maybe you have some fears concerning LDs. LDing is all very nice, but I’d put my health first. I am not a doctor, though. If this toothache is serious, I’d go see a dentist, even if it goes away in the afternoon.
MedO