poor baby - GOOD luck with him - and sometimes you can use a little syringe to give them water - he sounds like he was really needing a good home and he found one with you - GOOD LUCK with him - when a yorkie is in that kind of shape at only 5 years old - (no teeth and worms) he's had a very hard life....
that just breaks my heart to know how neglected or abused he must have been
bless his heart - I hope he gets to feeling better.