ObjectiveThe aim of this study was to evaluate the effect of multiple layers of an
infection control barrier on the micro-hardness of a composite resin. Material and MethodsOne, two, four, and eight layers of an infection control barrier were used to
cover the light guides of a high-power light emitting diode (LED) light curing
unit (LCU) and a low-power halogen LCU. The composite specimens were
photopolymerized with the LCUs and the barriers, and the micro-hardness of the
upper and lower surfaces was measured (n=10). The hardness ratio was calculated by
dividing the bottom surface hardness of the experimental groups by the irradiated
surface hardness of the control groups. The data was analyzed by two-way ANOVA and
Tukey's HSD test. ResultsThe micro-hardness of the composite specimens photopolymerized with the LED LCU
decreased significantly in the four- and eight-layer groups of the upper surface
and in the two-, four-, and eight-layer groups of the lower surface. The hardness
ratio of the composite specimens was <80% in the eight-layer group. The
micro-hardness of the composite specimens photopolymerized with the halogen LCU
decreased significantly in the eight-layer group of the upper surface and in the
two-, four-, and eight-layer groups of the lower surface. However, the hardness
ratios of all the composite specimens photopolymerized with barriers were <80%.
ConclusionsThe two-layer infection control barrier could be used on high-power LCUs without
decreasing the surface hardness of the composite resin. However, when using an
infection control barrier on the low-power LCUs, attention should be paid so as
not to sacrifice the polymerization efficiency.