Does an additional UV LED improve the degree of conversion and Knoop Hardness of light-shade composite resins? Maria Cecília Caldas Giorgi¹ Flávio Henrique Baggio Aguiar1 Luís Eduardo Silva Soares2 Airton Abrahão Martin2 Priscila Christiane Suzy Liporoni3 Luís Alexandre Maffei Sartini Paulillo1 ABSTRACT Objective: The purpose of this study was to evaluate the degree of conversion (DC) using FT- Raman spectroscopy and the Knoop hardness (KHN) of composites cured by second and third-gen- eration LED light curing-units (LCU), Radii Cal and Ultralume 5. Methods: Three composites (Filtek Supreme XT, Filtek Z350, and Esthet X) were selected for this study. KHN testing (n=10) was performed with 10 indentations for the top (T) and bottom (B) surfaces. For DC (n=10), both the T and B surfaces were analyzed. Results: For KHN, the three composites differed in hardens. There was a “LCU-surface” interac- tion, in which Radii Cal showed signiﬁcantly greater hardens in the B surface. For DC, there was a “composite-surface-LCU” interaction. For the “composite” factor, there was no signiﬁcant differ- ence between the groups, except for Supreme XT-Radii Cal (T or B surfaces). For the “LCU” factor there was a signiﬁcant difference for Supreme XT T surface, Ultralume 5 obtained a higher DC. For the Z350 T surface, a signiﬁcant difference in the DC in which Radii Cal obtained better results. For the “surface” factor, all groups presented T surfaces with a higher DC than the B surfaces, the sole exceptions involved Esthet X-Radii Cal and Z350-Ultralume 5. Conclusion: Knowledge regarding composite composition and the characteristics of LCUs are important for effective polymerization. (Eur J Dent 2012;6:396-401) Key words: Composite resin; UV LED; degree of conversion 1 Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas (UNICAMP), Piracicaba (SP), BRAZIL 2 Laboratory of Biomedical Vibrational Spectroscopy (LEVB), Research and Development Institute (IPD), Vale do Paraíba University (UNIVAP), São José dos Campos (SP), BRAZIL 3 Department of Restorative Dentistry, School of Dentistry, Taubaté University (UNITAU), Taubaté (SP), BRAZIL Corresponding author: Dr. Flávio Henrique Baggio Aguiar Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas (UNICAMP), Piracicaba (SP), BRAZIL Tel: +55 19 21065337 Email: aguiar@fop.unicamp.br INTRODUCTION Since light-cured composite resins have be- come an integral part of modern dentistry, polym- erization lamps have become a key instrument in dental practice.1 Both the light source and the resin composite play an important role in ensuring adequate polymerization. Until the development of light-emitting diode (LED) curing units, the com- monly used LCUs for almost 40 years were the quartz-tungsten-halogen (QTH) LCUs.2,3 The ad- vantages of LED LCUs include the narrow spectral emission of gallium nitride blue LEDs. This emis- sion spectrum is centered at 470 nm and covers 396 European Journal of Dentistry