Objective: This study developed and tested a simple method to calculate the radiopacity (Rp) of composite and adhesive materials. The method's ability to accurately calculate Rp was tested by comparing calculated versus experimental values for two systems. One system was a simple methacrylate-based composite made using tantalum metal as a filler, and the other was the first radiopaque, nano-filled adhesive, Adper Scotchbond SE (3M ESPE).
Method: The calculation requires as input the elemental composition, the mass absorption coefficient of each element present, and the material density of the composite's constituent parts. The output of the calculation is the radiopacity in millimeters aluminum equivalent thickness. Experimental Rp values were determined by ISO 4049:2000(E) part 7.14 on disks of tantalum-filled composite or on disks of neutralized adhesive and primer.
Results: The number of experimental samples, experimental and calculated Rp values, p-values from the one-sample t-test, and percentage errors (difference between calculated and experimental divided by experimental) are listed in the table below.
Sample | N | Expt. Rp (mm Al) | Calc. Rp (mm Al) | p-value | % error |
10 wt% Ta composite | 3 | 0.94±0.06 | 0.99 | 0.349 | 5.3 |
20 wt% Ta composite | 3 | 2.12±0.04 | 2.03 | 0.044 | 4.2 |
30 wt% Ta composite | 3 | 3.48±0.09 | 3.31 | 0.075 | 4.9 |
40 wt% Ta composite | 3 | 4.40±0.1 | 4.91 | 0.014 | 11.6 |
Adper Scotchbond SE | 3 | 1.03±0.16 | 1.28 | 0.073 | 24 |