Gary,
Not all dentists are created equal. I pesonally view dentists, ENT's, surgeons and oncologists as a team. If everyone knows the play book scenarios like yours should not happen.
There is a simple way to diagnose thrush.
Swab the area, wipe it on a microscope slide, stain the sample (various stains are available), wash the slide and have a look. Fungal hyphae appear stained. If we see this it's a positive diagnosis and then we treat it. I use Nystatin suspension for small localized areas, diflucan for larger areas, and for the stubborn cases ( this may disgust some people) both of the above plus antifungal vaginal suppositories.
Unfortunately most dentists don't have a microscope in their offices, and forget their microbiology, so they refer an otherwise simple procedure and cause a lot of anxiety for patients.

ENT's, great guys!! I personally feel that if I can perform this simple procedure and confirm a diagnosis in less than 20 minutes I should not contribute to their already bogged down schedules. If it's not thrush then I refer the patient.

I'm not trying to step on toes and I know it's not an ideal world. The mouths I treat are brought in by people who deserve the same care that I would expect regardless of my knowledge.

Cheers all,

Mike