Quartz Tungsten Halogen (QTH) and Light Emitting Diode (LED) are common light curing units which are used to polymerize resin-based materials. LEDs have narrower spectrum of visible light which may cause insufficient polymerization. The object of this study was to compare the effect of Quartz Tungsten Halogen (QTH) and Light Emitting Diode (LED) on microhardness of Light-Cured Resin-Modified Glass Ionomer (LCRMGI).
Methods:
In this experimental study, 20 samples of a LCRMGI with 5mm diameter and 2mm thickness were prepared in two groups, of which 10 were cured with QTH and 10 with LED unit. Microhardness test was done by Vickers Digital microhardness device in 6 points of each sample, 3 points on top surface and 3 points on bottom surface. The mean values of microhardness of top and bottom surfaces of each sample and the ratio of microhardness of bottom to top surface were calculated in each group. Statistical analysis was done with T-test and Paired T-test.
Results:
The mean values of microhardness of top surface of LCRMGI cured with QTH and LED were 30.1 and 27.6 VHN, respectively and the difference was significant (P<0.05). However, the difference of the microhardness of bottom surface was not significant between the two units. Both units caused the bottom to top surface ratio of more than 80% which is accepted as sufficient polymerization of a resin-based material.
Conclusions:
LED caused sufficient curing of Resin-Modified Glass Ionomer like QTH even though the top surface of the samples cured with it had significantly higher microhardness.