Halogen-based visible light curing units are the most common curing lights used in dentistry. However, they are prone to decreased output over time mainly due to degradation of the halogen bulb and the internal filter. Other technologies have been advocated, including plasma-arc lights and lasers. Recent literature suggests that light-emitting diodes (LEDs), specifically gallium-nitride blue LEDs, offer another means of polymerizing light-activated materials. One advantage of LED-based lights is that they produce a spectral output that falls within the absorption spectrum of the camphorquinone photoinitiator without the need for a filter. LEDs also have a useful life of thousands of hours without reduction in output. Objective: To determine the ability of two commercially available LED curing lights and one combination LED/Halogen curing light to adequately polymerize two types of resin composite. Methods: A PTFE mold (2-mm high, 8-mm internal diameter) was used to prepare 5 hardness test specimens for each combination of exposure time, composite type (Silux Plus [microfill], Z100 [hybrid]), and curing light (Zap Dual Curingä Light, LumaCureä, VersaLuxä). After 24 hours, Knoop hardness (KH) measurements were made for each side of each specimen, means were calculated, and a bottom/top KH percentage was determined. A value of at least 80% was used to indicate satisfactory polymerization. A linear regression of KH percentage versus exposure time was performed and the resulting equation used to predict the exposure time required to produce a KH value of 80% for the test conditions. Results: Summarized in table below.

Curing Time (seconds) Required for Adequate Polymerization (80%KH)
	Z-100	Silux Plus
ZAP	39	83
LumaCure	53	103
VersaLux	61	131

Conclusion: The LED curing lights and the combination LED/Halogen curing light in this study required longer exposure times than most halogen-based curing lights to adequately polymerize the hybrid and the microfill resin composites.

Back to the Dental Materials: VIII - Others-Non-metallic Program
Back to the IADR/AADR/CADR 80th General Session (March 6-9, 2002)

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