Call your veterinarian and ask if it's okay if you go there once every other day or so, and just sit in the waiting room. Bring a treat you know he loves. Sit in the waiting room until he calms down and take the treat(s), then leave ONLY when he's calm and relaxed. Don't leave when he's anxious. If the veterinarian and the people who work there are okay with it, make them come and give him treats, praise, then leave. He should soon come to feel like this is a place where he gets treats and attention. At home, work with him on getting his teeth checked, his ears and the rest of his body. Once he's comfortable with this, put him on a table and continue the work there. The floor and a table can make all the difference in whether a dog is comfortable or not. Good luck!