Five licensed dentists excluding all authors viewed the radiographs independently and in random sequence. A total of 30 radiographs were used (10 from each film type). 10 K-files had been placed at various lengths within 4 canals were studied in a cadaver section. Three human maxillary posterior teeth for which No. Radiographs were exposed to achieve a standard background density of approximately 2.0. We sought to compare observer measurement error and subjective ratings for International Standards Organization D-, E-, and F-speed direct exposure dental x-ray films used to determine endodontic working lengths.
