Localised irradiance distribution found in dental light curing units

Area of Science:

• Dental materials science
• Photopolymerization technology
• Optical metrology

Background:

• Dental light curing units (LCUs) are crucial for polymerizing dental resins.
• Accurate characterization of LCU output is essential for predictable polymerization.
• Previous characterization methods often provide averaged output values, masking spatial variations.

Purpose of the Study:

• To measure and map the localized irradiance and wavelength distributions from various dental LCUs.
• To establish a reliable method for characterizing the spatial output of LCUs.
• To assess the uniformity of light energy delivery across the LCU tip.

Main Methods:

• Utilized an integrating sphere spectrometer system to measure power, irradiance, and spectral emission at LCU tips.
• Employed a beam profiler camera to record localized irradiance distribution across 45 distinct 1mm² areas.
• Recorded spectral emission from various regions across LCU tips using a 4-mm aperture.

Main Results:

• All tested LCUs exhibited inhomogeneous localized irradiance distributions.
• Plasma-arc (PAC) units showed the most uniform irradiance distribution.
• Polywave LED (poly-LED) units displayed highly uneven irradiance and spectral emission patterns.

Conclusions:

• Single irradiance values or spectral ranges are insufficient to describe LCU output.
• Spatial mapping of irradiance and spectral emission is necessary for accurate LCU characterization.
• Inhomogeneous light output, especially from poly-LEDs, may lead to incomplete resin polymerization and restoration failure.