Light Energy Transmission Through Various Thicknesses of a CAD-CAM Material

Introduction: The amount of light energy that reaches the cement depends on light irradiance of the light curing unit (LCU), the thickness and the shade of the restoration. Objectives: The objective of this study was to quantify the amount of energy transmission through one shade of a CAD-CAM material in five different thicknesses using one light-emitting diode (LED) LCU. Methods: An LED LCU (Elipar S-10; 3MESPE, Seefeld, Germany) was mounted on a Marc™ Resin Calibrator (BlueLight Analytics Inc., Halifax, NS, Canada) and tested at 0.0mm with no specimen (group1). The LCU was set for 10 seconds of exposure following manufacture’s recommendation. Three specimens measuring group2) 0.5mm; group3) 1.0mm; group4) 1.5mm; group5) 2.0mm and group6) 3.0mm of A2-HT shaded blocks of a resin-nano ceramic CAD-CAM material (Lava Ultimate) were fabricated. The amount of light transmission was calculated for all thicknesses. Measurements were repeated three times for each specimen. Means and standard deviations were calculated. Results were analyzed with ANOVA followed by Tukey HSD test (α=0.05). Results: Means and standard deviations of light transmission (mW/cm²) were: group1 (1971.88±4.73); group2 (1121.96±80.68); group3 (660.36±40.96); group4 (439.48±10.93); group5 (298.70±16.87) and group6 (138.74±6.51). There was a statistical significant difference of light transmission through all different thicknesses. Conclusions: Within the limitations of this study, results determined that the energy delivered at the intaglio of a restoration made from the studied material in one particular shade decreases as the thickness of the restoration increases. Attention should be paid to prolong light curing times (even with LED curing units providing high irradiances) when light curing resin cements through thick resin-nano ceramic restorations.