Polymerization efficiency of LED curing lights

Area of Science:

• Dental Materials Science
• Photopolymerization Technology
• Biomaterials Engineering

Background:

• Dental resin composites require light curing for polymerization.
• Quartz tungsten halogen (QTH) lights have been traditionally used, but light-emitting diode (LED) technology offers potential advantages.
• Comparing the curing efficiency of different light sources is crucial for optimizing clinical outcomes.

Purpose of the Study:

• To compare the curing efficiency of three commercial LED curing lights against a QTH light using hardness testing.
• To analyze the power density and spectral emission of LED and QTH lights within specific wavelength ranges.

Main Methods:

• Depth-of-cure specimens were prepared using two composite types (microfill and hybrid) and four curing lights (3 LED, 1 QTH).
• Knoop hardness measurements determined bottom/top Knoop hardness (B/T KH) percentages after 24 hours.
• Power density and spectral emission (380-520 nm and 450-500 nm) were measured for each light source.

Main Results:

• LED lights' emission spectra better matched the photoinitiator camphorquinone absorption spectrum (450-500 nm).
• Despite better spectral match, LED lights required significantly longer exposure times (39-131 seconds) compared to the QTH light (21-42 seconds) for adequate polymerization.
• QTH light exhibited higher power density between 450-500 nm than the tested LED lights.

Conclusions:

• First-generation LED curing lights demonstrated lower polymerization efficiency than the QTH light for both hybrid and microfill resin composites.
• Longer exposure durations are necessary with these LED lights, potentially impacting clinical chairside time.
• Further advancements in LED technology are needed to match or exceed the performance of QTH lights in dental applications.