Aim:

The aim of this in vitro study was to examine the Vickers hardness (VHN) of composite restorations with different color shades in different depths using different polymerization methods.

Materials and Methods:

80 cylindrical occlusal composite restorations (Tetric Ceram [Vivadent], diameter 3mm, depth 3,5 mm, shades A1 and D3) with margins in enamel were placed in decapitated human molars using bulk technique. 10 specimen per group were cured for 40 s using halogen light curing units (H) (1) Elipar Trilight [3MESPE] and (2) Astralis10 [Vivadent], and blue light emitting diodes (L) (3) Elipar FreeLight [3MESPE] and (4) ELight [GC]. Specimen were stored in water (dark, 24 h, 37°C). After polishing (1200 grit), VHN was determined superficially and for 40 specimen in 3mm depth. Statistical analysis was performed using Mann-Whitney-U-Test (p£0.05).

Results:

VHN expressed as medians (25/75% Quantiles) was:

Color shade	depth	(1)Elipar Trilight (H)	(2)Astralis10 (H)	(3)Elipar FreeLight (L)	(4)Elight (L)
A1	Occlusal	Not tested	44(39/50 )	Not tested	48(45/50)
A1	3mm	63(60/65)	62(59/65)	71(66/84)	58(55/62)
D3	Occlusal	Not tested	43(41/49)	Not tested	44(42/48 )
D3	3mm	62(58/63)	59(57/61)	60(56/66)	57(55/58)

VHN was significantly higher for all polymerization units and both colors in 3mm depth compared to the surface, whereas on the surface no significant influence of both, curing methods and color shade was found. In 3 mm depth, and for color shade A1, data for curing units were significantly different from each other, except (1) vs. (2), whereas for color shade D3 no differences were found, except (1) vs. (4).

Conclusion:

VHN was influenced by depth, probably due to the oxygen induced inhibition of the polymerization. Differences of VHN values between curing units could not be found for type, but for individual systems.