Methods:In order to evaluate the effectiveness of LCUs, two experiments were performed. First, thermal analysis was performed by a differential scanning calorimeter(DSC). The LED LCU and the halogen LCU were used in this study for curing three composites(SureFil, Z-250, and AEliteFLO). The heat of cure(J/g), maximum rate of heat output(watt/g) and peak heat flow time of composites by different LCUs were obtained from the DSC curves. Second, the degree of conversion were obtained in the composites cured according to the above curing mode with a FTIR.
Results: 1.The heat of cure was not statistically different among the LCUs(p>0.05). 2. The composites cured by the LED(Exp) LCUs were statistically more slowly polymerized than by the halogen LCU and by the LED(Std) LCU(p<0.05). 3. The quantity of heat of the halogen LCU was significantly greater than that of the LED LCU(p<0.05). 4. The composite resin groups cured by the LED(Exp) LCUs had significantly higher degree of conversion than by the halogen LCU and by the LED(Std) LCU(p=0.0002).
Conclusions:From this DSC study, no statistically significant differences in the heat of cure were found between samples cured with the LED LCU or the halogen LCU, respectively, although the light intensity of the LED LCU was lower than that of the halogen LCU. The composites cured by the LED(Exp) LCUs were statistically more slowly polymerized than by the halogen LCU and the LED(Std) LCU. The effectiveness of cure of soft-start regimen in LED(Exp)LCUs was found in the degree of conversion obtained from the FTIR study.