Objectives: The aim of this study was to evaluate the influence of restorative material thickness and exposure time of dental film, on the radiopacity. Methods: Disks of six restorative materials measuring 5.0 mm in diameter with different thickness (2.0, 4.0 or 6.0 mm) were prepared using a Teflon ring molds (N=5 per material). One disk each material with different thickness was radiographed (Spectro, 70kV, 8mA/Dabi-Atlante, Brazil) using oclusal dental films (Insight, Kodak) with two exposures time (T1=0.4s and T2=0.8s). After development, the radiopacity of all the materials was determined by an image analysis program (Adobe Photoshop 6.0), using the histogram function after scanning (HP Deskjet 4C/T) and digitalization of all radiographs (N=10). Three-way ANOVA and Tukey test were used to determine differences in the gray values (a=5%). Results: The data was expressed in gray mean values (SD):

	Permite-C SDI		Z100 3M-ESPE		Prodigy Kerr		Fill-Magic Vigodent		ArtGlass Kulzer		Durafill VS Kulzer
Exposure time Thickness	T1	T2	T1	T2	T1	T2	T1	T2	T1	T2	T1	T2
2 mm	198.4 (1.34)	185.8 (2.16)	140.8 (3.89)	88.8 (4.14)	127.6 (2.30)	76.2 (2.58)	107.8 (3.11)	65.4 (2.79)	102.8 (2.77)	62.8 (1.64)	73.2 (1.30)	61.0 (2.65)
4 mm	197.6 (2.07)	183.4 (2.19)	169.4 (2.30)	134.4 (1.94)	162.8 (2.04)	122.8 (3.42)	146.0 (2.73)	95.4 (3.57)	141.4 (2.79)	89.4 (3.50)	81.4 (2.30)	61.8 (2.17)
6 mm	200.6 (2.40)	189.4 (3.36)	184.6 (2.07)	161.0 (1.00)	181.2 (1.92)	155.8 (2.28)	169.4 (1.94)	134.4 (1.51)	164.0 (2.12)	125.2 (2.49)	90.2 (2.86)	62.4 (2.61)

There were statistically significantly differences among materials, thickness and exposure times (p<0.05). Conclusions: The material thickness can influence positively on the radiopacity in polymeric materials and increased exposure time can decrease the radiopacity values. Supported by CNPq 140665/2002-1 and 140999/99-0.