What qualifications are needed to be a licensed dentist?

Depends on where? Most countries require you attend an accredited dental school. And then you can hang your shingle out. In the USA not only do you need the dental education but you also have to pass national boards and a state or regional licensing board and preform procedures on live people or mannequins. And some even have written test about legal issues and radiation.
Many. But it really depends on where the license is issued. The local dental society of the locale you are referring to may be of further assistance.
Some. I am not a dentist but will take a stab at this until a dentist comes on line to give a better answer. 1. Completion of an accredited dental school; 2. Passing a licensing exam to insure minimal competence; 3. Continuing education requirements 4. Maintainging a license within the state they practice.
Depends. Every country is different. In the USA, you need complete the requirements at an accredited dental school, graduate, and pass the written board exams and a clinical board exam. Some states require doing a residency. After, you need to take a state test and submit your licensure application to the state board for approval.
DDs and state board . Graduate from dental school and pass the state boards.
School and exams. Graduating from an accredited dental school, passing the national boards, passing the state board exams and getting a dental license in he state you want to practice in.