It does seem a bit ridiculous for the inspector to issue this order, especially since your dog is not suffering from rotten teeth and it has nothing to do with the original complaint
Originally I assumed your dog had been in the shelter (got loose) or they were called by someone because of bad teeth. If all he could find wrong was tartar on an 11 yr old dog, then I think your doing pretty good
If you have your vets support, there shouldnt be any problems having the order removed.