Surface Microhardness of a Nanofilled Resin Composite: A Comparison of a Tungsten Halogen and a Light-Emitting Diode Light Curing Unit, in vitro

Abstract - Surface microhardness numbers (VHN) have been measured and compared for disk specimens (thickness 1.5 mm) of a commercial nanofilled resin composite cured using a range of exposure times with a quartz tungsten halogen (QTH) and light-emitting diode (LED) light-curing unit (LCU), respectively. Each LCU requires different minimum exposure times to optimise VHN with respect to the internal controls but yield bottom surface / top surface VHN ratios > 0.95 with these optimised exposure times. Both LCUs produce comparable VHNs for the top surfaces at short exposure times but the QTH LCU requires increased exposure time for comparable results with the bottom surfaces. Overall, the LCUs are capable of producing comparable VHN numbers and VHN ratios within the parameters investigated.

KEY WORDS: Resin Composite; Nanofilled, Surface Microhardness; Light-Activation; Tungsten Halogen; Light Emitting Diode; Exposure Times