I believe our dreams are a way of our mind trying to make sense of everything that was fed it since the last time you were asleep.
But… it doesn’t have the “real world” as a background… so it is putting together bits and pieces from everywhere.
It could be a toothache. Maybe the nerves on your face were tense or itchy or felt “sharp” and your mind interpreted that as having teeth all over your face.
Maybe your belly felt hunger and you were being shown teeth because you were so hungry you could eat with your whole face.
For interpreting dreams, I usually start with physical causes. If there are none, then I would go back into what you were worried about during the day that just passed.
and then deeper if that doesn’t have any results.