Objective: To determine the effectiveness of Prototype LED Curing Light Units (PLED) #1 and #3 (Discus Dental) on curing dental resin composites compared to other curing lights.  PLEDs were compared with L.E.Demetron 1 (Demetron) (DLED) for depth of cure.  Method:  A2 anterior shade MatrixxÔ composite (Discus Dental) was used.  Four time intervals (10 sec., 20 sec., 30 sec., 40 sec.) were tested.  Teflon split molds (4 mm. dia., 6 mm. long) were used for sample preparation.  ANSI/ADA Standard No. 27 was followed for testing.  Five resin composite samples were prepared per group.  A least squares random effects model was conducted for the analysis.  Tukey-Kramer's HSD test was employed for all post-hoc comparisons. Results: Levels not connected by same letter are significantly different.

Time (sec)	Instrument					Mean (mm)	SD
30	PLED -1	A				3.02	0.01
30	PLED -3	A				3.01	0.01
40	DLED	A				3.01	0.01
20	PLED -1	A				3.01	0.02
20	PLED -3	A				3.01	0.01
40	PLED -3	A				3.00	0.01
40	PLED -1	A				3.00	0.01
30	DLED	A				2.90	0.07
20	DLED		B			2.26	0.11
10	PLED-3			C		1.72	0.07
10	PLED -1			C	D	1.65	0.05
10	DLED				D	1.60	0.05

Conclusion:  All groups were clinically acceptable based on ANSI/ADA Standard No. 27.  Prototype LED curing-light units produced the highest depth of cure values.  Exposure time of 20 seconds or more provides the most reliable depth of cure for both Prototype LED curing lights.  Support provided by Discus Dental.