Hi, I have a 2year old German Shepherd, we noticed last night that her lower canine tooth is discoloured, not tartar, but a greyish sort of colour, we are very particular on what she chews, and we always feed her a dental stick after her dinner, Any ideas?
Thank you, Maggie

A grey tooth means that it's probably dead. The enamel doesn't really chip off -- you can get a slab fracture, but that causes bleeding and tenderness. A nutritional deficiency won't affect the color of the tooth (at least not after it's formed), and wouldn't affect just a single tooth like that.

It's very possible that these teeth are painful, even if the dog does not show signs. Sometimes the dogs behavior changes after bad teeth are removed or fixed, indicating that it was affecting them even though they weren't aware of it at the time. There's also a chance of infection, which can affect the heart and kidneys as well as the mouth.

I would recommend having a vet check it out. It's really one of those things that could be nothing, or could be potentially serious.