I certainly understand your fears, i too went through the same thing with my Ash, he is around 13 yrs old maybe older, i was worried how it would go,everything went fine,however he was at a point it was necessary to have his dental done, or he was going to suffer, and have repeated infections in his mouth, he ended up loosing two teeth,and of course with older cats they always do a full blood test, and hydrate the cat before hand, also my Ash has a heart murmur so that was even more of a concern for me,they are very professional and make sure they give him just the right dosage, and he sailed through it, alas we discovered he had early CRFailure,but still it is better to know than not,however it was not due to Ash's teeth that he has CRF, which i was worried about, just simply his old age,good luck i am sure kitty will be just fine.