In a dream, seeing a mountain or an edifice or a mausoleum breaking into pieces or being destroyed without an outside interference or blasting, it means fading of one’s name or evanescence of one’s remembrance after his death or disappearance of one’s traces or references. Crumbling in a dream also means fulfilling one’s promise.... Islamic Dream Interpretation
This dream might have a physical origin in people gritting or grinding their teeth during sleep. Freud suggested that dreams of teeth falling out are related to fears of castration, but women have this dream as often as men, suggesting that tooth troubles in dreams are related to hidden anger, with a dreamer acting out the clenching of teeth. Other dream analysts believe the dream reflects anxiety about appearance and how others perceive you. Teeth can also represent a means of assimilating knowledge so it can be used. Teeth are the first instruments of the digestive system, so in dreams they represent the acquisition of knowledge.
Losing teeth is a common symbol in a dream, indicating a change in the way the dreamer assimilates what is learned.... The Element Encyclopedia