Depth of Cure of Composite Using Halogen, LED and Laser

Objectives: To investigate the efficiency of light sources in the process of photoactivation. The evaluation of the depth of cure of composite-resin was done by two methods: degree of conversion (DC) and Vickers hardness (HV).

Methods: Samples (n=3) 1, 2 and 3mm in thickness were fabricated using Filtek Supreme-3M/ESPE. The groups were polymerized (40s) by: Halogen (Optilux 501/Demetron-Kerr), LED (Lec1000/MMOptics) and Argon laser (Innova100/Coherent) at a setting of 600mW/cm² and stored (37^oC, 24 hours). The DC was measured by Infrared Spectroscopy (FTIR) (Bomem MB-102), using potassium bromide mixed with ground powder of specimens. DC values were determined by using the percentage of carbon double bonds (1638cm^-1) present before and after polymerization in comparison with the aromatic peak reference (1608cm^-1). For HV, the specimens were measured through Leica VMHT Mot, at (50gf, 30s), making four indentations in the top (1 and 2mm) and bottom (3mm) of the specimens.

Results:

Depth	HALOGEN		LED		LASER
	DC% (sd)	HV (sd)	DC% (sd)	HV (sd)	DC% (sd)	HV (sd)
1 mm	39.0 (±1.0)	69.3 (±1.8)	35.6 (±1.1)	68.1 (±0.7)	32.3 (±3.2)	69.2 (±1.0)
2 mm	38.3 (±0.6)	64.8 (±0.2)	35.6 (±2.0)	64.7 (±0.4)	32.0 (±2.6)	66.5 (±1.8)
3 mm	36.3 (±0.6)	54.8 (±0.9)	31.3 (±1.5)	58.4 (±2.1)	27.0 (±1.1)	59.1 (±1.8)

The results were analyzed using two-way analysis of variance and Tukey test. The Pearson's test was used for correlation of the tests (p<0.05).The 3mm presented statistical difference in relation with 1 and 2mm for both tests. The light sources presented statistical differences, in the DC: the Halogen had better values, followed by LED and Argon laser. There was no positive correlation between DC and HV.

Conclusions: All light demonstrated the ability to polymerized the composite, but the Halogen light had better values than the others. The depth of cure decreased significantly in the 3mm.