It's not in my water thank goodness. I use my tap water for bathing, brushing teeth, making hot drinks and cooking. But I always drink spring water.
It is possible to find fluoride free toothpaste. There used to be one in my supermarket, then stock of that grew smaller and smaller, until it was hidden away, and big names like Colgate completely dominated the shelves! Now they don't have it. If asked the store would probably say there wasn't enough demand for it.
I know...hardly surprising.
Still, it's possible to buy those toothpastes elsewhere.
But they hardly ever are the "whitening" kind. And this obsession with everyone having 18-year old's teeth and the perfect Hollywood smile means that the fluoride containing ones will be preferred by most.
(Up until the 80s having teeth that worked and were fairly healthy was always good enough!)
It certainly helps, if you have to use a fluoride toothpaste to brush a few times with plain water after using it, and rinse rinse rinse!
I just took a look...there is so much info online about fluoride detox. Just typing in "detox from fluoride" should bring up many results.