Donkeys that cannot eat properly will not thrive! They too can suffer with teeth problems which can affect their ability to chew and swallow food and if your donkey is losing weight, teeth are something to be considered.
An adult donkey has approximately 40 permanent teeth, he loses his "milk" teeth between the ages of 2 and 4yrs. His teeth can be used as a guide to assess his age.
The majority of dental problems will be uneven wear, rough sharp edges, loose teeth, infections and congenital problems. Loss of weight, a reluctance to eat, dribbling, quidding (inability to chew food adequately/ falling from mouth) and bouts of colic can all be indicators of tooth problems.
Teeth should be checked yearly from about 5yrs of age (your vet will do this). Sharp edges may need to be rasped and any "hooks" removed.
If however your donkey displays more serious problems then you should consider asking an equine dentist to visit. This is very specialised work and he/she will visit your donkey bringing along everything that is required to carry out what is necessary including a Hartman's gag which is essential in keeping the donkey's mouth open (and the dentist's hands safe!).
Donkeys love to gnaw especially wood and this is a normal behavioural occupation. Its a good idea to provide a largish branch or stump from which they will strip off the bark. This is good for their teeth and provides mental stimulation.
There have been some donkeys, albeit elderly who have managed without any teeth in latter years. Such animals would require intensive care/feeding and such a situation is not desirable. Prevention is better than cure!