Please cite this article in press as: Shortall AC, et al. Robust spectrometer-based methods for characterizing radiant exitance of dental LED light curing units. Dent Mater (2015), http://dx.doi.org/10.1016/j.dental.2015.02.012 ARTICLE IN PRESS DENTAL-2522; No. of Pages 12 d e n t a l m a t e r i a l s x x x ( 2 0 1 5 ) xxx–xxx Available online at www.sciencedirect.com ScienceDirect jo ur nal home p ag e: www.intl.elsevierhealth.com/journals/dema Robust spectrometer-based methods for characterizing radiant exitance of dental LED light curing units Adrian C. Shortall a , Christopher J. Felix b , David C. Watts c,* a The Dental School, St. Chad’s Queensway, Birmingham B4 6NN, UK b Bluelight Analytics Inc., 24-2625 Joseph Howe Dr, Halifax, NS B3L 4G4, Canada c The University of Manchester: School of Dentistry and Photon Science Institute, Manchester M13 9PL, UK a r t i c l e i n f o Article history: Received 10 February 2015 Received in revised form 25 February 2015 Accepted 26 February 2015 Available online xxx Keywords: Dental Light curing unit Thermopile Spectrometer ISO 10650-2 Radiant exitance Irradiance Spectral radiant power a b s t r a c t Objectives. Firstly, to assess light output, from a representative range of dental light curing units (LCUs), using a new portable spectrometer based instrument (checkMARC TM ) com- pared 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. © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. 1. Introduction 1.1. The challenge of photo-polymerization in dentistry Effective photo-polymerization is a prerequisite for the long term clinical success and quality of light-activated ∗ Corresponding author at: University of Manchester School of Dentistry, Oxford Road, Manchester M13 9PL, UK. Tel.: +44 1612756749. E-mail address: David.Watts@manchester.ac.uk (D.C. Watts). resin-based composite (RBC) restorations. Amongst the factors which influence the polymerization efficiency of (multi-)methacrylate RBCs, the light curing unit (LCU) is a key extrinsic variable [1,2]. Whilst quartz tungsten halogen (QTH) LCUs have been the mainstay of dental practice for decades [3] blue light emitting diode (LED) units have replaced them http://dx.doi.org/10.1016/j.dental.2015.02.012 0109-5641/© 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.