Small breeds like YT unfortunately have dental problems…If he has just stinky breath, you can clean his teeth with some soft tooth-brush and special toothpaste made for dogs once a week. You can also prevent the tartar giving him special chewing bones. If he already has a dental scale, sooner or later you’ll be forced to visit your vet. Do not try to clean his teeth on your own (in this state), it’s vet’s job.
I know, it’s expensive (but that’s owning a pet:), but necessary far-between. (depends on each dog, once a year – 3 times a year)
Here is a link about prices>>>http://www.costhelper.com/cost/pets/dog-...
And you do not have to bring him to the groomers, that you can do on your own and save some cash:)

Your vet will do the cleaning. Yorkies are no more expensive to care for than any other dog. In some ways they are less expensive. For some reason some dogs get a build up of tartar on their teeth. If you can regularly brush her teeth, it would help. My yorkie doesn’t like the toothbrush and tries to eat it, so I take a washcloth and go over her teeth. Since my hand is holding the washcloth she won’t bite my hand. If the tartar is allowed to build up too much, it can cause health problems for a dog, the same as a human. Your Yorkie is worth the extra care you might need to give. There are some dog biscuits you can buy that might help by making her chew a bit more.

you can have the vet clean it’s teeth or do it yourself; it will extend the life of your dog by preventing diseases to form and it’s not necessary to take to the groomers.

No you take him to a vet for the teeth cleaning. Yes, animals are expensive and people should do research before they buy them so they know what to expect.