I may get yelled at for this but...

If by any chance you can get your hands on some chlorohexadine you may be able to use it on his mouth. i would probably do a search on using it in an oral cavity but i have used it on an iguana whose head had been terrorized by mites, a ball python with severe lacerations on its underside and on a burmese python that got bit by a rat. It takes some time and about three daily applications but it has always worked for me. Generally i diluted it in water and applied it with a syringe, no needle of course and generally tried to keep the area clean. I am by no means a vet but this is my personal advice.
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My Kids:
The Scaled:
0.1 Savannah Monitor
2.5 Leopard Geckos
0.1 Green Iguana
1.4 Tokay Geckos
1.1 Bearded Dragons
0.1 Golden Gecko
1.0 Burmese Python
1.0 Het. Albino Ball Python
1.0 Lavender Albino Cali King
1.0 Black RatSnake

The Furred:
0.1 Ferret
1.0 Chinchilla
0.1 Hedgehog
1.0 Sugar Glider
0.1 Rat
1.0 Cat

The Feathered:
1.0 Citron Cockatoo
0.1 Goffins Cockatoo
1.0 Cockatiel