Postprocessing of all-zirconia restorations in digital dental radiographs: a quality assurance predicament

The aim of this study was to describe a quality assurance issue, that is, the production of nondiagnostic high-contrast radiographs when imaging teeth restored with all-zirconia crowns on bitewing radiographs.

All-zirconia crowns were imaged with DIGORA Optime photostimulable phosphor (PSP) plates (Soredex/Orion Corp., Helsinki, Finland). To assess the differences in software processing, the PSP plates were scanned into third-party software as well as directly into the twain and native software provided by the manufacturer. Gamma correction, histogram stretch, and scanner resolution settings were adjusted. Vertical bitewings were acquired to increase anatomic coverage.

Scanning into third-party software or directly into the twain and native software did not improve contrast. Shifting the lower limit of the histogram stretch to 3 with a gamma correction of 2 resolved the problem. Neither scanner resolution setting nor vertical bitewings improved contrast.

The nondiagnostic high-contrast radiographs result from imaging software not effectively displaying the available gray scale. The software processing error appears to be initiated by the high-attenuation characteristics of zirconia. Consequently, radiographs with a high ratio of zirconia crown to normal anatomy are particularly susceptible.