Translucency and Radiopacity of Five Resin Composites

Objective: Determine the translucency and radiopacity of five commercially available composites and to assess correlation between the properties. Methods: Experiment was conducted according to ISO guideline 4049.  Five composites: Aelite LS(AE), Filtek LS(FS), GC Kalore(KA), Empress Direct Enamel(EE), Empress Direct Dentin(ED) (n=10/material; shade A2), were packed into an aluminum mold (10-mm diameter, 1-mm thick) and light cured for 80 seconds(40 sec each side).  Color was measured according to the CIELAB color scale relative to the standard illuminant D65 against a white background and a black background using a reflection spectrophotometer with a 8mm (MAV) diameter target mask. Using color data, translucency and contrast ratio were calculated for each sample. For radiopacity, five specimens (1 for each composite) were placed in random order with an aluminum step wedge (20-mm x 50-mm, 10 0.5-mm steps) on an occlusal film and exposed at 70kV, 7mV, 0.339 sec from a target-film distance of 360-mm.  After immediately being processed (10 radiographs), the radiographic optical densities of the specimens and aluminum step wedge were read with a photographic transmission densitometer (aperture 1-mm).  Aluminum equivalent was calculated using regression analysis and  One-way ANOVA (p<0.05) and Tukey multiple comparison tests (p<0.05) were used for statistical analysis. Results: All five composites were significantly different for translucency; EE(22.09)>KA(18.39)>FS(17.50) >ED(14.41)>AE(11.81). For contrast ratio, AE was the highest (0.91) >ED(0.89)>KA (0.806)=FS (0.805))>EE(0.78). ED had the highest radiopacity in AlEq (3.61) >KA(2.84)>EE(2.18)>FS(1.32)=AE(1.26). Overall there was a very weak correlation between radiopacity Al Equiv and translucency (0.084) or contrast ratio (0.053), but this correlation was material specific (0.31 to -0.60). Conclusions: EE was the most translucent material but had relatively low radiopacity; AE was the most opaque material but the least radiopacity.  ED had the highest radiopacity, but relatively low translucency.  The correlation of radiopacity and translucency was material specific.