Such dreams are usually connected with fear from responsibilities or fear from the next life steps.
If you are in the front of some new life path that might be more difficult then you are aware, you might get the "warning" about it in the state of dream. Even if your present circumstances are bothering you, and require change (and you do not want to apply that change) you might get the "warning" that change is necessity, otherwise you will loose your courage, vital energy and will not be able to cope with problems that may arise.
Teeth are psychologically connected with our readiness to cope with life.
Your body also can get such warning if your body requires some nutrients (as Calcium, vitamin C etc).
There is nothing mysterious about dreams - they are here to give us certain subconscious messages about our body, emotions and life itself.