Our dreams mustn't be took literally, since they are made by symbols. In your case : falling teeth. However the meaning of symbols is different for each person, it's individual. So the true question is : '' What is YOUR own perception about it ? (when you dream about that).
It's because an interpretation can't be generalized, that all the books and websites supposed interpret our dreams are fake. Since they generalize something that is individual.
A psychoanalyst who helps people to interpret their dreams, always will use their personal perceptions / feelings about them, never his/her own ones.
In clear, when you dream about something and if you don't have the opportunity to see a psychoanalyst, ask to yourself what it makes you think? Don't pay attention at what thinks someone else : whichever / across a book, website etc...