Hello aspirant,
Hope you are doing good
So, as per your query, Yes you can opt to do the internship, or else you can also opt not to do it after completion of the BDS course. Even students can take a gap of 6 months. However it is generally not considered that much necessary to ir.
Students who generally do it soon as after completion of the course will be having thorough knowledge of the subject and can adapt to the atmosphere easily, and learn the things more efficiently than those who took the break. Therefore it is generally advised to do it as soon after the completion of the course.
Good luck!!