You haven't been brushing your teeth with fluorine enough, therefore your teeth have began to decay.
What is fluorine and how does it help my teeth?
Well you see....
Fluorine help resist tooth decay and helps maintain the bone health. You can consume fluorine in fluoridated drinking water and toothpaste. If you do not consume enough of this nutrient then your teeth will begin to decay.
Oh I get it now. I need to consume fluorine so that I have strong bones and my teeth don't decay.
Yes, so I suggest you go brush your teeth now so that they don't decay.