No. The chances of harm are very low because dental x-rays have limited exposure and we always protect the children or adults before they take an x-ray. They will wear aprons and their neck will be protected as well. There is also a shield for certain x-rays that reduce the remission a person gets. The second thing is that most dental x-rays are digital and the amount of radiation that is required to get a quality image is much less than a traditional x-ray. That’s why dental x-rays are very safe even if we do it for children.
To add on, I would say the age that x-rays are usually taken when children are around 7 to 8 years old because we want to monitor teeth that are coming out. Usually when children are older, they are able to cooperate and keep still.