Robust spectrometer-based methods for characterizing radiant exitance of dental LED light curing units

Objectives Firstly, to assess light output, from a representative range of dental light curing units (LCUs), using a new portable spectrometer based instrument (checkMARC™) compared with a “gold standard” method. Secondly, to assess possible inconsistency between light output measurements using three different laboratory-grade thermopile instruments. Methods The output of four blue-dental LCUs and four polywave blue-and-violet-LCUs was measured with two spectrometer-based systems: a portable spectrometer instrument and a benchtop Integrating Sphere fiber-coupled spectrometer system. Power output was also recorded with three thermopiles according to ISO 10650-2. Beam profile images were recorded of LCU output to assess for spatial and spectral beam uniformity. Results Power recorded with the portable spectrometer instrument closely matched the ‘gold standard’ Integrating Sphere apparatus calibrated according to International Standards. Radiant exitance for the eight LCUs differed significantly between the three thermopiles. Light source to thermopile sensor distance influenced recorded power significantly (p <0.05), indicating the severe limitations of thermopiles for absolute measurements. Polywave LCU beam profiles demonstrated output spectral heterogeneity. Significance Spectrometer-based methods are capable of overcoming the limitations inherent with thermopile-based measurement techniques. Spectrometer based measurements can fulfill the intention of ISO 10650.