Dream interpretation is complicated.
Your subconscious runs thousands of permutations of events throughout your evening. You remember only the last one. The stranger the dream the more combinations you've considered that night. The ones you remember are often the ones that woke you up and are therefore the more disturbing combination of events. In general, the "script" is often a very abstract representation of your conscious day. So taking it too literally is not recommended. Losing your teeth, could be a memory of childhood when the loss of your baby tooth was something your mother would help you with and praise you for having finally worked it loose without swallowing. Possibly rewarding you with a visit from the Tooth-Fairy. All warm memories of a loving parent. Dreaming you lost your tooth as an adult could be a desperate attempt to somehow return to those more innocent days and caring moments, but mixed with the reality that you can't give up your adult teeth and therefore you can't get back what you've lost, when a beloved parent passes.