I work in the OR so anesthesia does not scare me like it does to some people. He's small but he really isn't that tiny. Mine will not allow me to brush so I have no tips for brushing teeth. But that baby tooth needs to go! Bogey just had a dental yesterday and I picked in up in a couple of hours. It was the 3rd time he was under general anesthesia and did well. He is a rescue and over a year old when I adopted him. He was just about 5 lbs and had to be neutered according to his adoption contract. At the same time he had a couple of puppy teeth removed. Before the dental was done his breath was HORRIBLE from the retained teeth. So I really do understand. Recently, he had an ear infection and also anal gland infection. The vet told me "ears and rears" mean allergies and suggested adding fiber and changing his diet to a limited ingredient. But my girl was on Royal Canin Hydrolized Protien so I just switched him to that instead. So I totally get the issues you are having and it's the reason that I'm pushing the dental and food change.
__________________ “Never argue with a fool, onlookers may not be able to tell the difference.”  Mark Twain |