Dental work at basic and can I be disqualified for dental issues if I’ve already passed meps?

Once you get there, you will receive a dental exam. The dental clinic at basic will not do a lot of work in order to ensure that you can complete training. Once you get to your duty station, you will receive all required dental work. You will not be disqualified for a couple of cavities.

Doubtful- just see a dentist at 1st duty station.

No. All of what you have described is minor, at least as far as the military goes. MEPS knows about these from the repeated x-rays they have taken of your mouth. And even if they did not? Mouth issues are something can arise fairly quick and be taken care of just as quickly. Worst case scenario you ship for basic, you get there and during in processing they do a quick dental screen and see all this and take care of it, thus delaying your start of BCT by a bit. The Army does not care. You signed a multi year contract. You get cleared/off profile and then you go into rotation for a BCT class and you soldier on. Not a big thing or anything to worry about.