Beam Profile Characterization of a Dental Light Curing Unit Using a Spectrometer-Based Method

Abstract

The study aimed to characterize a broad spectrum light curing unit (LCU) by measuring the light beam profile output of the LCU using a spectrometer-based method and correlate it with a standard camera-based beam profile method. Materials and Methods: A broad spectrum LED LCU (Ascent OL5, CAO Group) was mounted above a spectrometer (MARC® Resin Calibrator, BlueLight Analytics) at exposure distances of 1.0, 1.5 or 2.5 mm. The position of the center of the LCU was aligned with the spectrometer's cosine corrector sensor, and then moved in 1-mm increments in the x-y plane, while concomitantly recording the irradiance. The recorded irradiance was systematically organized and reported in function of the distance from the center of the LCU exiting window. Using a standard camera-based beam profiler, a beam profile of the LCU was obtained and the above approach was emulated to the beam profile. For both methods, the irradiance decreases related to the value measured at the center position was analyzed by calculating the slope, using a linear correlation. Results: Both methods showed that moving away from the center showed decreased irradiation. The beam profile of the LCU is asymmetric. The inhomogeneity of the beam was slightly lower with farther distance from the LCU's light exciting window. Conclusion: The spectrometer-based method was able to characterize the beam profile of the LCU and can be used in the evaluation of LCUs.

Beam Profiling of Dental Light Curing Units Using Different Camera-Based Systems

“… 12 13 The camera-based beam profiler is an instrument that uses a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera-based detectors to measure the spatial distribution of light intensity in the cross-section of a light beam according to the conversion of the light photon flux to an electrical current-voltage signal. 14 With the use of bandpass filters, the wavelength distribution of the light beam could also be detected. However, one of the main obstacles of this method is the cost of the complete instrumentation for a camera-based beam profiling system.…”

The effect of ceramic light scattering on an inhomogeneous beam profile

“…However, these LED LCUs show more or less pronounced inhomogeneity of the beam profiles [21][22][23][24]. This means that not every point on an irradiated surface gets exposed to the same level of irradiation from the different wavelengths, especially in depth [25][26][27]. Since ceramics scatter the light because its direction is changed at the grain boundaries, one can assume that the local irradiances may vary less, once the light has passed through the ceramic, thus moving the beam profile more towards homogeneity.…”