Endodontic measurements in digital radiographs acquired by a photostimulable, storage phosphor system

Digora is a newly developed digital system for intraoral radiography utilizing photostimulable storage phosphor image plates. The aim was to test the quality of the system in respect to the visibility of endodontic files and root apices at different exposures. In teeth from five dry mandibular jaw sections, Hedstrom files no. 15 were placed with the file tip at varying distances from the apex. The specimens were covered with soft tissue equivalent material and placed behind a 2-cm thick polymethyl methacrylate cylinder filled with water. Distance from focus to image plate was 30 cm. Exposures were made at 60 kV and 7 mA at 7 timer settings from 16 ms to 1000 ms in 50% increments. All images were viewed from the monitor by each of 8 observers allowed to use available contrast enhancement facilities to obtain subjectively good image quality. Utilizing built-in measurement functions, distances from file tip and root apex, respectively, to a reference line were measured in 0.1 mm. For measurements between file tip and reference line, and root apex and reference line, there was no statistically significant difference between measurements made at the lowest exposure, compared to the second lowest exposure but there was a statistically significant difference compared to the 5 highest. Measurements at the second lowest exposure were not significantly different from those obtained at the 5 highest exposures. Interobserver variability expressed as standard deviation between observers showed the largest value for measurements obtained at the lowest exposure. The mean observed distances between the tip of the file and the root apex were calculated and showed no statistically significant differences between different exposures. We concluded that the Digora intraoral image plate system provided reliable endodontic measurements even at very low exposures.