Assessment of radiopacity of restorative composite resins with various target distances and exposure times and a modified aluminum step wedge.
OBJECTIVE
ANSI/ADA has established standards for adequate radiopacity. This study was aimed to assess the changes in radiopacity of composite resins according to various tube-target distances and exposure times.


METHODS
Five 1-mm thick samples of Filtek P60 and Clearfil composite resins were prepared and exposed with six tube-target distance/exposure time setups (i.e., 40 cm, 0.2 seconds; 30 cm, 0.2 seconds; 30 cm, 0.16 seconds, 30 cm, 0.12 seconds; 15 cm, 0.2 seconds; 15 cm, 0.12 seconds) performing at 70 kVp and 7 mA along with a 12-step aluminum stepwedge (1 mm incremental steps) using a PSP digital sensor. Thereafter, the radiopacities measured with Digora for Windows software 2.5 were converted to absorbencies (i.e., A=-log (1-G/255)), where A is the absorbency and G is the measured gray scale). Furthermore, the linear regression model of aluminum thickness and absorbency was developed and used to convert the radiopacity of dental materials to the equivalent aluminum thickness. In addition, all calculations were compared with those obtained from a modified 3-step stepwedge (i.e., using data for the 2nd, 5th, and 8th steps).


RESULTS
The radiopacities of the composite resins differed significantly with various setups (p<0.001) and between the materials (p<0.001). The best predicted model was obtained for the 30 cm 0.2 seconds setup (R(2)=0.999). Data from the reduced modified stepwedge was remarkable and comparable with the 12-step stepwedge.


CONCLUSIONS
Within the limits of the present study, our findings support that various setups might influence the radiopacity of dental materials on digital radiographs.
Dentistry Student Research Committee (DSRC), Dental Materials Research Center, Dentistry School, Babol University of Medical Sciences, Babol, Iran.
Arash
A
Poorsattar Bejeh Mir
Morvarid
M
Poorsattar Bejeh Mir