Discrimination between restorative dental materials by their radiopacity measured in film radiographs and digital images.

The aim of this study was to investigate the possibility of differentiating between various dental restorative materials by means of their radiopacity. Ten extracted molars and ten canines/anterior teeth were selected for the study. In the molar group a class II cavity and in the canines/anterior teeth group a class III cavity were cut by airrotor. The cavities were coated with vaseline before filling with five molar- and three anterior tooth restorative materials in the following sequence: for molars: amalgam, light-cured composite, glass ionomer cement, reinforced glass ionomer cement and light-cured composite. After each filling sequence radiographs were taken of the teeth on conventional film (Ektaspeed Plus) and by two digital systems: a storage phosphor plate (Digora) and a ccd-based sensor (Sidexis). Density was measured in the films with a densitometer in three areas of "air", in three areas of the class II fillings and one area of the class III fillings. The same areas were measured in the digital images where the program calculated automatically the mean grey shade values. The density values obtained from the filling areas were taken as a proportion of the values obtained from the areas of "air". Statistically significant differences in material density when related to "air" density (Wilcoxon's test) were observed between all materials in film (p < 0.01 for molars and p < 0.02 for canines/anterior teeth). For Digora only half of the materials differed significantly which was also the case for the Sidexis system (none of the CF materials were significantly different). In conclusion, the molar filling materials could be distinguished with a high probability in film while the two digital systems were less reliable. The results may be useful in forensic dentistry.