Hi, Smittojess
It does appear that double canines are quite common with Yorkies and not something to worry about. I keep giving Gabi rawhide chews to hasten their departure. I may wiggle them once and awhile to see if they are loose, but I think eventually they will come out on their own. Do not know if you have had Yorkies before, but they are notorious finiky eaters. Gabi just now started eating her kibble again after I stopped giving her anything else.
One other thing I would like to mention about your vet recommending a teeth cleaning at 12 months

...way too soon for that. I presume he was planning on doing this under anethesia and then pull the baby teeth while your baby was out. I have been using a safe and natural tooth spray for Gabi since she was 3 months old. It is called Denta Sure and you can buy it on line. It works great on keeping her teeth tartar free and breath fresh. I just spray it in both sides of her mouth everyday . She doesn't mind it at all. Just thought I'd pass this info on to you.