Light Energy Transmission and Microhardness of Various Bulk-fill Composite Materials

Objectives: Introduction: Bulk fill materials are used in thick increments. The depth of cure of a composite depends on many factors including the amount of light energy, the thickness and the shade of the restoration.
Objectives: The objectives of this study were to quantify the amount of energy transmission through four bulk fill composite resin materials in three different thicknesses using one light-emitting diode (LED) LCU and subsequently measure surface microhardness of top and bottom surfaces of the specimen.
Methods: 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 group1)0.0mm; group2)1.0mm; group3)3.0mm and group4)5.0mm with no specimen. The LCU was set for 10 seconds of exposure following manufacture’s recommendation. Three specimens measuring group5)1.0mm; group6)3.0mm and group7)5.0mm of four different composite resins a)Z250 (3MESPE); b)Filtek Bulk Fill (3MESPE); c)Tetric EvoCeram Bulk Fill (Ivoclar Vivadent) and d)Sonic Fill(Kerr) of A2 shade were fabricated in a Teflon mould. The amount of light transmission was calculated for all thicknesses. Surface microhardness was measured at the top and bottom surface in a Microharness tester (422MVD; Wilson Instruments, Norwood, MA, USA). Measurements were repeated three times for each surface. Means and standard deviations were calculated. Results were analyzed with ANOVA followed by Tukey HSD test (α=0.05).
Results: Results: Means and standard deviations of light transmission (mW/cm²) and microhardness (HV) are shown in Table 1 and 2 respectively. There was a statistical significant difference of light transmission and surface microhardness through all different thicknesses (p<0.05).
Conclusions: Conclusions: Within the limitations of this study, results determined that the energy delivered at the bottom surface of an increment decreases as the thickness 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 increments of bulk fill composites.