My Sadie is at the Vet's today having her first dental. She's two years old. I try to brush her teeth every day but I brush them at least every other day (probably 4-5 times a week). I use the Petzlife gel and I add a supplement to her water. I've pretty much done everything I can except floss them.
Last Friday when I was brushing her teeth I saw a little blood so I explored. I found a loose tooth. When I looked further, the same tooth on the other side was also loose. I almost cried because I know I'm already doing everything I can to preserve her teeth. I took her to the vet on Saturday and he said that she has a small amount of tarter but not enough to cause her to lose teeth. He believes that the loose teeth are actually retained baby teeth and perhaps the adult teeth under them are malformed and never pushed them out. He said that without the loose teeth he wouldn't have suggested doing a dental on her yet. He's going to add a sealer while after he gets them good and clean. I just called and she came through it fine. I can pick her up in an hour. Whew! I'll find out more about what caused the loose teeth when I talk to my vet.
She did have several retained baby teeth pulled when she was spayed. These are in the middle bottom of her mouth. I think they are pre-molars.