Henny Youngman is famous for an old chestnut he has used for years.  In response to the query, "How is your wife?” he replies, "compared to what?" “Compared to what” holds the key to an understanding of the significance of x-ray exposure in dentistry. For, although we all know radiation is in general undesirable, what then is dentistry's contribution to the overall picture?

Dental x-ray (Gonadal Exposure) compared to background and other sources of radiation:

The Gonadal radiation absorbed by an individual in a normal day from fall-out, sun, TV, etc. is approximately .3mR/day (1972).

People who live in mountainous areas may absorb up to .5mR/day. 

Wrist watch dial, 1 mR/hr. to wrist.

Pilot’s absorption from instrument panel, 1 mR/hr. 

Coincidentally, ..3mR is the gonadal dosage from a full mouth set of dental x-rays taken at 65kvp at 10 ma, and at a distance of 8 inches and is tantamount to watching TV in the evenings for 4 weeks.  (Journal of American Dental Association).