That is quite a diverse set of professions you've suggested.
The only problem is that you really need an interest in a specific one. You won't be able to apply for one of each, and if you're choosing them on the assumption that they are 'vocational' degrees then your chances of success will be low.
For dentistry and psychiatry (Dr) you will need a specialist dentistry or medical degree, both of which require significant experience in the form of voluntary or work experience programmes before you even apply. This ensures that candidates really are interested and have fully researched their chosen profession. Obviously the medical degree will encompass the whole of human medicine so if you're only interested in psychiatry then it may be a very hard course.
For both you'll need either A-levels or Access with very high grades and GCSE's in English, Maths and Science (at least) at grade B or above. As someone has already eluded to there are only a couple of dentistry schools which accept Access courses, and there are more medical schools but entry is tough as these are some of the most oversubscribed courses that exist.
Social work would be much easier to get into, with grades required being much lower but pay seems dire.
I understand your desire to find a vocation, but you really need to research something that you are really interested and passionate about. Otherwise you're going to end up wasting more of your life chasing a vocation that isn't what you really want to do. The ones you mentioned are so varied and don't really share a common skills set, so you do need to spend some time finding what you really want to do. Hope you don't think this is too negative.