Published scientific research is not much but the few researches do say they help. No harm as long as you dont drink or aspitlrate the oil. Usually sesame or coconut oils are used
Health Tips
For oil pulling therapy, a tablespoon of oil is taken in the mouth, sipped, sucked, and pulled between the teeth for 10–15 min. The viscous oil turns thin and milky white in consistency. The oil should not be swallowed as it contains bacteria and toxins. Oil pulling must be followed by tooth brushing and rinsing of the mouth. It is better to perform oil pulling in the morning on an empty stomach.