A new technique for measuring the radiopacity of natural tooth substance and restorative materials.

A technique was developed which utilized a visible-light spectrophotometer to measure the transmission of light through a radiograph. This was used to compare readings produced by an aluminium step-wedge and the material of which radiopacity was under investigation. This enabled the radiopacity of the material, be it tooth substance or restorative material, to be measured accurately. The radiopacity, on average, of fresh enamel was found to be 2.1 mm Al/1 mm enamel and that of dentine to be equivalent to 1.0 mm Al/1 mm dentine.