Pedro, problem with teeth and gums? +photo

[filip]

Hello,

I am here on behalf of my eight year old miniature Dachshund Pedro.
I've noticed recently some strange discoloration on his teeth. He is a jumpy dog and it is difficult to get a look inside his mouth. So, I took a quick photo of the inside of his mouth, as you can see the result is not very attractive.

I was wondering if this is a serious problem, and if I should consult a vet. We don't have much money and this little dog has problems with cooperating with vets so I wanted to get some opinions before hand. Are we just taking bad care of his teeth and is this normal with age? Or should we be worried?

Thank you for your time,
-filip