Probably not.
If it was a digital x-ray, the radiation is even further reduced by 50-80% compared to traditional film x-ray in which they have to develop them in fixer/developer. The x-rays were probably a routine amount of x-rays for a dental check for an initial visit.
Although there's no conclusive evidence of any thyroid problems etc from radiation, a collar to protect the neck wouldn't have been a bad thing but its not necessary or required by law as far as I know
oh and they did put a led apron over me but i didnt have anything to cover my neck should i be worried?