A perceptibility curve comparison of Ultra-speed and Ektaspeed Plus films

The purpose of this study was to evaluate the subjectively assessed contrast difference between Kodak's Ultra-speed and Ektaspeed Plus dental radiography films (Eastman Kodak, Rochester, N.Y.) through the use of perceptibility curves.

Four series of 22 radiographs were exposed at 70 and 90 kVp with each film type by means of a Gendex 1000 dental radiography unit (Gendex Corp., Milwaukee, Wis.) for times ranging from 0.05 to 5 seconds at 10 ma. The test object consisted of a 7-mm-thick rectangular aluminum block with 10 circular depth cuts, each 2 mm in diameter, which created wells varying in depth from 50 to 500 microns. The corresponding films were processed concurrently (for 4.5 minutes) in total darkness with fresh Kodak Readymatic solutions (Eastman Kodak) held at a constant temperature of 28 degrees C. The resulting radiographs were viewed in a predetermined random order under ideal conditions by 10 dentists. The evaluators recorded the maximum number of perceptible images on each film. A pair of perceptibility curves were generated at 70 and 90 kVp by plotting the log relative exposure versus the mean number of perceptible images.

There was no statistical difference between the two film types with respect to the mean number of perceptible images, as analyzed by Wilcoxon's signed rank test (p = 0.22; p = 0.44).

There is no subjectively assessed contrast difference between Kodak s Ultra-speed and Ektaspeed Plus films at 70 and 90 kVp.