Blackening of unprotected dental X-ray films due to scattered radiation

Unexposed films awaiting exposure as well as exposed films awaiting processing are subjected to scattered radiation if kept unprotected in the dental X-ray clinic. The purpose of the present study was to analyze the influence of various storing principles, film speed, and distance from X-ray source upon the degree of film blackening. Test films were subjected to scattered radiation from 150 exposures. Maximum additional blackening (0.27 D) was recorded for type E films not protected by lead foil at the shortest distance studied (55 cm). At a distance of 200 cm blackening was reduced to 0.02 D and could be further reduced by utilizing the inherent protective effect of the lead foil. It is concluded that if dental X-ray films not in use are kept at a distance of 200 cm from the X-ray source and protected by lead foil additional blackening due to scattered radiation is negligible and further protective precautions are unnecessary.