Correlation Between Composite Translucency and Depth of Cure and Radiopacity

Objectives: To evaluate the correlation between the translucency and depth of cure and radiopacity of commercially available flowable and packable composites.
Methods: Twenty composites were included in the study (see table). Translucency specimens (n=6) (1mm thick) were placed against calibrated white and black backgrounds and L*a*b* values were taken using a spectrophotometer (CM-700d; Konica Minolta). The translucency parameter (TP) was measured as the difference in color using ΔE00. The depth of cure specimens (n=6) were prepared by inserting composite into a cylindrical metal mold with a 4mm diameter and 10mm length. Specimens were cured for 10 or 20 seconds with a curing light (Elipar S10, 1100mW/cm2). The maximum length of cured and intact composite was measured with digital calipers and halved to determine depth of cure. Radiopacity specimens (n=6, thickness=1mm) were radiographed with a digital x-ray device (Planmeca; Prostyle Intra) set at 70 kVp for 0.32 seconds along with an aluminum step wedge at a distance of 400mm. Image analysis software (GIMP) was used to measure the gray scale levels of the composites using the Histogram function and to compare intensity values to the step wedge. Linear correlation between mean translucency and depth of cure and radiopacity were measured by Pearson’s correlation using SPSS.
Results: The mean +/-standard deviation of the translucency, depth of cure and radiopacity are presented in the attached table. There was a strong significant positive linear correlation between translucency and depth of cure for 10sec (r=0.79, p<0.01) and 20sec (r=0. 85 p<0.01). There was not a correlation between translucency and radiopacity (r=-0.38 p=0.09).
Conclusions: Translucency is a good indicator of the depth of cure but not radiopacity of a resin composite.