Objectives: The aim of this study was to compare the knoop micro hardness of a hybrid composite resin between a halogen and two LED curing units.

Methods: A composite with two colours (A2 and A3, Tetric Ceram, Vivadent, Germany), one halogen lamp (Elipar Highlights, ESPE 3M) with 40 sec polymerization time, and two LED curing units (Ultralume 5, Ultradent, USA; Smartlite, Dentsply, Germany) with 10 sec and 20 sec, were used, respectively. Totally 10 groups were prepared, 10 samples each. The composite cylinders were fabricated in 8mm thickness. After the polymerization, every sample was embedded in acrylic resin and separated in the middle in the vertical axis. On the section plane Knoop microhardness was measured.

Results: For all polymerization units tested, measurements could be done only up to 3.5 mm deepness. For both colours, the difference between the units was found statistically significant (A2: p=0,0009 and A3: p=0,0141, ANOVA). Tukey's studentized Range test showed that for A2, halogen (40sec) has a statistically better curing performance, comparing to Smartlite (20sec) and Ultralume (20 sec). The same test for A3, showed no significant difference between the Halogen and the Smartlite, but both of them were significant better comparing to Ultralume.

	A2 mean±SD			A3 mean±SD
Depth	Halogen	Smartlite	Ultralume	Halogen	Smartlite	Ultralume
0,5mm	41,2±4,8	31,1±4,0	33±6,5	40,3±6,0	37,8±6,0	31,7±4,9
1,5mm	34,9±5,64	28,8±5,81	30±6,1	35,4±5,7	32,4±3,57	26,5±3,7
2,5mm	34,5±4,3	26,5±4,8	27,2±4,6	36,8±9,9	32,5±4,9	26,4±5,52
3,5mm	27,9±4,0	21,9±4,8	23,6±5,7	30,6±5,4	27,9±5,0	21,78±5,3

 

Conclusions: For the color A2, halogen lamp was found to be better compared to the LED units while between the two LEDs no significant difference was found. For A3, between Smartlite and halogen lamp no significant difference was shown.