The ADA is aware of a recent study that associates yearly or more frequent dental X-rays to an increased risk of developing meningioma, the most commonly diagnosed brain tumor. The ADA's long-standing position is that dentists should order dental X-rays for patients only when necessary for diagnosis and treatment. Since 1989, the ADA has published recommendations to help dentists ensure that radiation exposure is as low as reasonably achievable.
American Dental Association Statement Here
Dental X-ray examinations provide valuable information that helps your dentist evaluate your oral health. With the help of radiographs (the term for pictures taken with X-rays), your dentist can look at what is happening beneath the surface of your teeth and gums. If you have questions about your dental X-ray exam, talk with your dentist.
The amount of radiation that we are exposed to from dental X-rays is very small compared to our daily exposure from things like cosmic radiation and naturally-occurring radioactive elements (for example, those producing radon).
According to the American Thyroid Association, routine X-ray exposure (eg, dental X-rays, chest X-rays, mammograms) does not cause thyroid cancer.
Any dentist or dental hygienist, who in the performance of dental services, X-rays the mouth or teeth of a patient shall during the performance of such X-rays shield the torso and thyroid area of such patient including but not limited to the gonads and other reproductive organs with a lead apron thyroid collar, or other similar protective garment or device. Notwithstanding the provisions of this subdivision, if in the dentist's professional judgment the use of a thyroid collar would be inappropriate under the circumstances, because of the nature of the patient, the type of X-ray being taken, or other factors, the dentist or dental hygienist need not shield the thyroid area."