NIIOM has a digital dental x-ray system using phosphor plates and a digital scanner. The system is used for measuring radio-opacity of dental materials according to ISO standards, such as ISO 6876 (Endodontic materials) and ISO 4049 (Polymer-based restorative materials). By making a specimen of the specific material and place it beside an aluminium step wedge, the x-ray picture is used to calculate the radio-opacity of the material.

The radio-opacity is found by recording the grey values of the material compared to the grey values from the aluminium step wedge. The radio-opacity of the material is expressed in equivalent aluminum thickness.

X-ray machine with test plate.
Test specimen and aluminium step wedge.