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DENTAL MATERIALS BEAM PROFILE CHARACTERIZATION OF A DENTAL LIGHT CURING UNIT USING A SPECTROMETER-BASED METHOD Jean-François Roulet 1a* , Mateus Garcia Rocha 2b , Chiayi Shen 1c , Marwah Majid Khudhair 1d , Dayane Carvalho Ramos Salles de Oliveira 2e Department for Restorative Dental Sciences, Center for Dental Biomaterials, College of Dentistry, University of Florida, 1395 Center Drive Gainesville, FL-32610, USA 2 Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Areiao 13419-110, Piracicaba SP, Brazil 1 Dr med dent, Dr hc, Professor, Director of Center for Dental Biomaterials DDS, MSC, PhD, Researcher c PhD, Professor d DDS, Preceptor e DDS, MSC, PhD, Post-Doctoral Researcher a b ABSTRACT DOI: 10.25241/stomaeduj.2018.5(2).art.1 Aim: 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. Keywords: light curing units, beam profile, spectrometric analysis. 1. Introduction Light curing has revolutionized the placing of composite restorations [1]. Furthermore, light curing is used for multiple other applications such as cementing dental fixed prostheses, including indirect restorations made from ceramics or composites, sealing fissures, and bonding orthodontic brackets. Nowadays, market available light curing units (LCUs) are very well build and really intuitive which make dentists assume that light curing is a simple procedure, however it is not. First, to be cured properly, a resin-based composite (RBC) must be exposed to a visible light energy at the proper wavelength range (blue or blue and violet) and a radiant exposure ranging from 8-16 J/cm 2 [2], which means that, depending on the irradiance the RBC is receiving, exposure times up to 60 s are required [3]. The key problem is that dentists believe that a single irradiance value of LCU reported and stated by the LCUs’ manufacturer homogeneously reaches the entire RBC surface, which is not the case [4]. It starts with the correct positioning of the LCU on top of the RBC, controlled by the dentist only. Very large differences have been documented when comparing the light curing of untrained vs trained dentists [5]. Furthermore, the dentist should be aware that 84 OPEN ACCESS This is an Open Ac- cess article under the CC BY-NC 4.0 license. Peer-Reviewed Article Citation: Roulet J-F, Rocha MG, Shen C, Khudhair MM, de Oliveira DCRS. Beam profile characterization of a dental light curing unit using a spectrometer-based method. Stoma Edu J. 2018;5(2):84-91. Academic Editor: Nicoleta Ilie, Dipl. Eng,  PhD, Professor, University Hospital, Ludwig- Maximilians-Universität München, Munich, Germany Received: May 17, 2018 Revised: May 24, 2018 Acccepted: June 11, 2018 Published: June 12, 2018 *Corresponding author: Jean-François Roulet, DMD, PhD, Dr hc, Center for Dental Biomaterials, College of Dentistry, University of Florida 1395 Center Drive, Room D9-26, Gainesville, FL 32608 Gainesville, FL 32608, USA Tel: [phone]; Fax: [phone], e-mail: [email protected] Copyright: © 2018 the Editorial Council for the Stomatology Edu Journal. the irradiance of an LCU diminishes as the distance increases from the light output window [6] and, besides that, the cleanliness aspect of the LCU light tip is fundamental, because any residual RBC stuck onto the light exiting window may also reduce the light irradiance, which is a huge problem that affects the geometry of the light tip which may create shadows [7,8], and thus the depth of the cure may be reduced. Furthermore, depending on their composition (filler, resin mix, pigments and opacifiers), RBCs absorb more or less light [9], which reduces the depth of the cure as well. Based on this knowledge, recommendations for dentists about how to light cure were formulated by a group of researchers, industry representatives, editors and dentists [10-12]. This group is very active and has published recommendations in dental journals, newsletters and websites of associations worldwide. Multiple studies have shown that the LCUs as used in practices do not yield the light intensity output stated by the manufacturers [13-16]. The outcome of light curing can be influenced as well by factors which are governed by the design of the LCU and of course by the RBCs themselves [9,17]. The characteristics of the LCUs have a strong influence on the incident irradiance received by a material due to a multitude of Stoma Edu J. 2018;5(2): 84-91. http://www.stomaeduj.com