Hardness and Cure Depth 12 Composites with LED Curing Light

Improved LED composite resin curing lights have been introduced with fewer LEDs than previous versions.  How well these lights cure a variety of composite resins with different photoiniators is unknown.  Objectives: This study measured top and bottom hardness of 2mm thick specimens and compared depth of cure of 12 composite resins (shade A2) (Z-100, Filtek Supreme, Herculite, Point4, TPH Spectrum, EsthetX, Durafill VS, Gradia Direct, Heliomolar, Filtek Flow, Tetric Flow). Methods: 5mm diameter and 2mm thick specimens were made by packing composite resin into a flexible mold, covering composite with a Mylar strip and a glass slab and curing the composite for 10sec.  After curing, the specimens were removed from mold, and stored for 24 hours. Top and bottom hardness was measured using a Barcol hardness tester. Depth of cure was measured by placing each composite into a split rectangular mold 8mm in depth.  The mold was filled with composite resin, covered with Mylar strip and a glass microscope slide and cured for 10sec.  Specimens were separated from the molds and the unpolymerized composite was removed. Depth of cure was measured by dividing the length of the cured composite by 2.   The power density for the E light measured at (620 mW/cm²) with Power Max Radiometer.  Two-way ANOVA was used with factors for Light Source and Material. Tukey's HSD post-hoc analysis were used to determine significant inter-group differences (p=. 05).  Results: All composite resins tested cured 2mm specimens so that the bottom hardness was greater than 80% of the top hardness.  Heliomolar HB had the least depth of cure (p<0.05). Z-100 the greatest depth of cure.  Conclusions: Depth of cure depends upon the curing light and the individual composite. The GC E Light resulted in greater depth of cure when compared to Optilux 500 (p<0.05) for all composite resins tested.