Red...
I think it sounds like root surface sensitivity exacerbated by being on the ventilator. Most of us breathe through our noses, but those who breathe through their mouth have issues with sensitivity. The reason being, the air coming across our teeth and gums dries everything out, and the natural "barrier", saliva, isn't allowed to stay on our teeth and protect them. During intubated surgery, you are forced into a mouth breathing state, and consequently your teeth and gums suffer temporarily.
The suggestion of a desensitizing toothpaste is a good one. The instructions on those say you should not use it more than 2 weeks unless your dentist agrees. This is so the toothpaste doesn't mask anything more serious. Try the toothpaste temporarily. Stop using it after 2 weeks and see if everything is ok.
If you're really concerned, call your dentist or hygienist and ask them. You don't want any dental work right now...your heart is just too susceptible to any germs.
I'm not a dentist or a hygienist, but I've been working for a dentist for 7 years and I listen a lot!
Again talk to your dentist, he'll/she'll be able to tell you more.