I dreamt that my teeth were rotten, they were stained brown and when I tried to brush them they started to crumble. My current day life is full of adversity where I feel that I am the target of vitriolic and vindictive behaviour from certain colleagues, I feel as if I am in the middle of an ongoing battle that will last for quite a while.
Good morning, Sharon.
Teeth in dreams mean so many things. It is very helpful that you included what's going on in your waking life, because it gives us a strong hint how to proceed.
Teeth are, among other things, weapons. Every animal which has teeth, uses them as weapons as well as to eat - for some animals, the two are permanently entwined. With you being involved in a lengthy and nasty battle, your dream seems to be saying that your position looks very weak to you. You're trying to strengthen that position (brushing your teeth), but it seems as if you are only making things worse (they crumble).
The dream doesn't, unfortunately, give us many suggested tactics for your situation. The best I could glean from it is, perhaps you should "keep your mouth shut" for a while and see if things get better on their own. We often associate tooth decay with sweets; there may be someone who acts sweet around you but is in truth a backstabber - "rotten."