Without a letter of invitation from a Polish university and a promise of financial support, there is little to discuss here. You're talking in such vague and speculative terms that it is impossible to give a useful answer.
As for getting permission to practice dentistry in Poland, chances are very slim that you will find an employer willing to go through the hassle of hiring you, that the work office will be willing to accept your documentation, and that nostrification will not be frustratingly difficult and drawn out so that you eventually give up.
As for part-time work, forget about it. That just ain't gonna happen.
Sorry, but from the way your question is written, you have invested very little time in finding out about these questions on your own, to the point that you are completely unable to ask questions here that can receive useful answers.
As a general answer, it is highly unlikely that you will be allowed to practice dentistry in Poland without going through a very long, very difficult, very costly and very frustrating nostrification process. Nor is it likely that, even after going through that process, anyone will go through the hassle and expense of getting work permission for you.
As for academic research in dentistry that does not involve actually practicing dentistry, you would have to apply for a grant on your own to do research in Poland, or find some professor in Poland who is willing to apply for a grant for you, or let you share in their own limited grant funding.
The place to start is with dental associations in Turkey. They should have grant advisors on staff to help you with the process. The dean's office at your university in Turkey may also be able to answer some questions, or direct you to someone who can.
Last of all, you have to arrange all of this BEFORE you come to Poland, and it could take months, or even years.
