Tongue has a light green coat on it dentist said not cancer or oral thrush what could it be then he said use tongue scraper it has helped some?

Biofilm: A coating on the tongue is a common finding. Of course the mouth is not a sterile site, and food passes through - so of course bacteria/microbes may find refuge there. (Think of bad breath). A bacterial mat or biofilm could form. RINSING with water frequently might help-it will dilute out nutrients therefore depriving microbes of food. Then you have BRUSHING (brushing the tongue) to dislodge them.