Dogs tooth

[jappa1]

HI people
I don't even know if I am on the right page but my 4yr old dog has got a brown 'fang' tooth, other teeth are white. doesn't seem to be causing her pain and I have tapped it to see if I can get a reaction of any sort from her (to see if she has feeling in it). I have read that the tooth is fractured and once brown will not be causing her any pain, don't know if this is true or not. I only spotted her tooth when checking her mouth recently but don't know how long its been like that....any suggestions other than the vet? (I am making an appointment at the vets this week)