What health issues would prevent a dental? Sounds to me like the health issues have been changed...in other words, not a problem The infection from his teeth certainly are not good for his heart, not to mention his kidneys.
I totally understand being worried about doing a dental as I have had to make such decisions on my senior pups. I have one who I felt was never going to have another one and now I am so glad I did it. That was my George .. here is his thread about his recent dental.
http://www.yorkietalk.com/forums/yor...ds-dental.html
If you can afford to do a dental with a specialist, I highly recommend a consult with one. My vet did not want to do a dental on George either.
Keep us posted on the lab work. With diabetes if he has it, I would think that would be another reason to avoid any infection such as in the mouth.
Prayers for Prince...