Depth of Cure and Temperature Rise with LED Curing Lights

Objectives: This study compared the depth of cure and temperature rise of a composite polymerized by LED lights to a tungsten halogen light. Methods: Seven LED lights and a tungsten halogen (Optilux 400, control) were evaluated. Depth of cure (DOC) of Heliomolar (A1) was measured using the scraping method in ISO 4049 when cured for 40s. When DOC obtained was significantly lower than the control, cure time was increased in 10s intervals. Power density was measured using ISO 10650. A thermocouple was used to measure the temperature rise within the composite, 3 mm from the light tip, when cured for 40s at 37°C.

Results:

Power Density DOC Temperature increase

mW/cm²
n=5
t, s*
n=5
mm
n=5
°C
n≥3

Optilux 400 391 (5) 40 2.43 (0.08)^a 6.2 (0.1)^a

L.E. Demetron 1 447 (3) 40 2.70 (0.06)^b 6.4 (0.5)^a

Ultralume LED 2 308 (2) 40 2.38 (0.08)^a 4.5 (0.2)^c

Flashlite 246 (5) 40 2.39 (0.13)^a 5.2 (0.4)^b

Elipar Freelight 217 (2) 40 2.52 (0.13)^a 4.8 (0.3)^b,c

Cool Blu 173 (1) 40 2.52 (0.13)^a 4.6 (0.2)^b,c

GC E-Light 119 (2) 50 2.41 (0.08)^a 4.9 (0.1)^b,c

Hilux LED 79 (1) 110 2.41 (0.10)^a 3.2 (0.2)^d

*time required to achieve DOC statistically similar or greater than control. Different superscripts show significant differences (alpha =0.05).

For DOC, all tested LED lights except GC E-light and Hilux LED were found to meet the control level within the same cure times. All LED lights except L.E. Demetron 1 had smaller temperature increases than the control. Temperature rise appeared to correlate (R²=0.73) with power density. Conclusion: While most LED lights tested met the ISO 4049 guidelines for DOC, some caution is recommended because the recommended time may not be sufficient to meet this criterion. Supported by ADAF and NIST.