As with any procedure there is some risk involved but the positives outweigh the negatives when it comes to most dental procedures, IMO. Given your buddy's age I would recommend bloodwork prior to the procedure this will allow the vet to see how the internal organs are functioning. Ask them what type of anesthetic they use (Iso is wonderful). A good dental will do wonders for the heart, liver and kidneys for it will help prevent the spread of nasty bacteria to these organs. The most obvious reason though is healthy teeth and gums - imagine what your mouth would be like if you went long periods between cleanings and check ups.

Years ago I had an old diabetic cat, Scooter, who suffered from kidney and heart disease (diagnosed at age 8). I had his teeth cleaned annually and he did well each time. This may have been overkill in some eyes but I was of the mindset that his annual cleanings were saving his internal organs. He lived to be 17. I'll never know if this really helped but I believe it did.