Objective: The purpose of this study was to identify the causes of excessive exposure in those dental practices that were found to use exceptionably high levels of radiation in bitewing radiography.
Study design: Using the parameters of the Dental Exposure Normalization Technique survey, certified radiation equipment safety officers conducted on-site inspections of 186 intraoral x-ray machines in 77 dental facilities.
Results: In 23 facilities, the safety officers identified 43 units (23.1%) that delivered entrance exposures greater than 10% in excess of the upper limit of recommended exposures. For each of 27 (63%) of these units, the cause of the elevated exposure was clearly identifiable.
Conclusions: The factors contributing to increased exposure, listed from most frequent to least frequent, were as follows: improper processing, kilovoltage miscalibration, use of D-speed techniques with E-speed film, use of newly installed units with default timer settings that were too high, exposure timer failure, and insufficient half-value layer. Only 18% of the facilities surveyed reported using E-speed film.