Hello and welcome to Just Answer. I am a licensed veterinarian and would be happy to answer your questions.
Yes, I would have to tell you that the symptoms you describe would have me concerned also for a few reasons. First, I would not usually expect that dental issues would show up so acutely, so I would be worried if his teeth that ended up being extracted were really the cause of his symptoms or an incidental finding. Secondly, really the only side effect I would expect from the Zeniquin would be GI, and since his appetite is good, I wouldn't think that to be involved.
You didn't mention why the teeth were extracted, but in almost all cases, pain meds are not needed for longer than 5 days as usually the extraction is removing the source of the pain. If there is continued pain in the mouth, it should be investigated. Even if he doesn't act like his mouth is sore, it would be good to have the incision site checked to make sure it has healed.
From what you have described and being almost 2 weeks post procedure, I would definitely have him at least examined and perhaps some basic bloodwork rechecked. Being an older dog, the organs I would be most worried about would be his kidneys, both from the bloodflow changes during a general anesthetic and the history of being on Rimadyl for years. There should not be too much to worry about as long as his blood pressure was maintained and there remained a good perfusion of his kidneys during the procedure, but it is simple enough to check out with a blood test. Rimadyl can also cause GI irritation and or ulcers, but I wouldn't expect he would be eating well if that were the case. It may be that he is just taking a little longer than normal, but most dogs I work with are up and back to normal within a few days. It certainly warrants some further looking into now. I hope this helps. Please let me know if you have any further questions.
Thank you for your detailed reply. I should have mentioned 2 4th premolars had complete root resorption and canine tooth had died with infection above the tooth. Based on the dentist, he stated all of the extractions were 'complicated extractions'. Originally when I took him to the emergency clinic, they felt he was in back pain (but the symptoms they observed were no different than what he has shown for sometime. So it wasn't clear if it was his back or his mouth (or both). It seemed like his mouth was giving me more symptoms, so off the dentist. It's possible what I'm seeing now is add-on back pain but I can't be sure. It was recommended I get an mri for his back also so I had to decide what to go with first. Honestly, I don't see any new symptoms with his back but maybe it is. My regular vet could not get a pain response on his back when she examined him although he is very stiff in his hips and has been for a long time. I want to be sure I give him enough time to heal from his dental surgery and make sure I'm allowing enough time for that to resolve before I dive into yet another path. Based on how comments, it sounds like I might need to start looking at other possibilities.
They said he did very well under anesthesia but I agree I would like to see his bloodwork now.
Any final thoughts before I 'Accept' are appreciated!!