I could be wrong, but if it was candida in my mouth, wouldn't the thrush be all over my mouth?
No. I only ever had whiteness on top of my tongue.
Here's the weird thing though about the candida, I don't have any symptoms of it other than my tongue. And when I took the stool test I had already been off the strict strict candida diet for a month. I have been eating about 120-150 grams of carbs a day from things like quinoa, sweet potatoes, brown rice pasta without any issue. I know some people eat those items on their candida diet, but I was incredibly strict and just stuck to meat/veggies for 4 months.
IMO, intestinal candidiasis is not an overgrowth of Candida, as is popularly believed, but a fungal infection of the bowel wall with hyphal Candida. A stool test only checks for the yeast form of Candida, which, IMO, is commensal. A stool analysis does not diagnose pathognic fungal/hyphal Candida. So, IMO, stool tests are useless for Candida.
Interesting that you mentioned Biotene as I found a bottle of it unopened at my mom's house and started using it a couple nights ago. I'll use it and take note of how my tongue looks shortly before and and after.
Use the Biotene regularly after each meal. It will not have an instant effect, but after a few days you may notice your tongue is less white. I doubt Biotene has enough lactoferrin in it to clear up a white tongue, but you may notice improvement. Biotine has been shown to clear up resistant oral thrush when added to a triazole antifungal.
If I do have a candida issue, would a probiotic help get rid of the tongue coating?
Unlikely. I tried acidophilus and it did nothing to my white tongue.