Microleakage and surface hardness of resin based restorative materials cured with LED and QTH curing units

Abstract EN

Light-emitting diode, or LED, technology provides certain advantages over halogenbased light polymerization of resin-based composites.

Methods: The halogen-based light curing units (Optilux Radiometer Model 100, SDS Kerr; Donbury, CT, USA) and LED LCUs (Blue phase meter, Ivoclar/Vivadent ) were used to polymerize filtek supreme (3M/ESPE Dental Products, St Paul, MN.

USA) and Z 100 (3M/ESPE Dental Products, St Paul, MN.

USA) resin-based composite.

For microleakage tes, 28 human molar teeth had standardized class V cavities prepared on the buccal surface with the occlusal margins in enamel and the cervical margins located 1 mm apical to the CEJ.

The teeth were divided into two groups of 14 teeth each.

Group 1 was restored with filtek supreme, while group 2 with Z 100.

Each group was divided to two subgroups (n= 7) according to the mode of curing of the restorations.

subgroup 1a, 2a, were cured with QTH while subgroup 1b, 2b were cured with LED.

The teeth were subjected to 500 thermocycles, stained with 2% solution of basic fuchsine dye for 24 hours, and then sectioned buccolingual longitudinally through the center of the restoration.

Dye penetration at tooth/restoration interface was scored based upon the extent of the dye using a binocular Stereomicroscope at magnification of X 100.

For surface hardness test, a total of 40 discs was fabricated using a split cylindrical teflon mould (3 mm height and 6 mm diameter) united by a metal ring (n= 10).

Hardness was measured using a Vickers microhardness tester.

Results: Chi-square test revealed no significant differences in the microleakage scores among the light curing modes and restorative material at the occlusal/enamel margins.

The nanofilled restorations tended to display less microleakage when cured with LED at the apical/dentin margins compared to QTH, but the differences were statistically significant (P= .006).

Duncan test revealed that the surface hardness test for the microhybrid composite resin was significantly greater than nanofilled resin when cured with QTH curing unit.

Conclusions: The light output of commercially available diodes for resin-based composite polymerization still requires improvement to rival the adequacy of cure of halogen-based LCUs.

Additional studies are necessary.