Dasequin is for arthritis. Vet & I talked about it during his dental pre-op. I brought up how he now walks with an overall stiffness sometimes. It helps with the fluid in the joints, I believe. All in an effort to prevent him from becoming worse.
For what it's worth, I think some of his occasional lethargy is from the arthritis, plus the crap floating around from his teeth, plus higher BGs. I definitely notice less activity when he's riding in the 300s now. All these things add up to a 17 year old cat "slowing down," which vet says is normal, but which of those things can I help with? All of them really. And we are going at the arthritis with both barrels since I do not want his quality of life to decline. Actually with multiple barrels.
I know he's not going to run up on the cat tree any longer. But the fact he shows no interest even in doing that anymore bothers me. Vet also thinks from some things I describe (such as sitting in bathroom crying in his own way, "Let me out." and not sitting at patio door saying, "Let me out.", both complete opposites of what he used to do - sit in bathroom patiently with no meows and sit at patio door meowing that he wants out.) that he may be changing mentally, becoming senile, basically. His main communication now is "mer, mer" when he's lying down and I speak to him, so he still communicates some, but his level has decreased dramatically. You've seen his "Let me in," video, right? He's no longer vocally demanding like that.