Degree of Conversion of Composite Resin with LED Curing Lights

Objectives: To compare the degree of conversion (DC) of composite resin polymerized with LED and halogen curing lights. Methods:  50 hybrid (Z-100, shade A3, 3M EPSE) and 50 microfilled composite resin (A-110, shade A3D, 3M/ESPE) specimens were fabricated in a 8x2mm acetyl-polymer mold (n=5).  The 2 mm specimens were polymerized for five seconds from a distance of one and five millimeters with four newer generation LED curing lights: Allegro (Den-Mat); FLASHlite 1001 (Discus Dental); UltraLume LED 5 (Ultradent); LEDemetron1 (Kerr/Demetron); and a halogen curing light: Optilux 501 (Kerr/Demetron).  Power was measured with a power meter (PowerMax 5200, Molectron).  DC was determined (Perkin-Elmer FTIR Spectrometer) at ten minutes.  DC was calculated for top and bottom surfaces.  Bottom DC was expressed as a percentage of maximum top DC.  Results: Data analyzed by 3-way ANOVA; Tukey’s; a=0.05.  The LEDemetron obtained the highest DC ratio with both composite types at a curing distance of 5mm. Conclusions:  Overall, the latest generation LEDs provided similar or better DC ratios than the halogen curing light at a curing distance of 5mm.  Table: letters denote significant differences by columns.