Effect of different light sources on degree of conversion, hardness and plasticization of a composite

Bruno de Castro Ferreira Barreto, Anderson Catelan, Ricardo Coelho Okida, Gisele Fernanda Gonçalves, Gisele Rodrigues da Silva, Paulo Henrique dos Santos, Tathy Aparecida Xavier, Flávio Henrique Baggio Aguiar, Carlos José Soares

Abstract


Clinical performance of composite resins depends largely on their mechanical properties, and those are influenced by several factors, such as the light-curing mode. The purpose of this study was to evaluate the influence of different light sources on degree of conversion (DC), Knoop hardness (KHN) and plasticization (P) of a composite resin. Disc-shaped specimens (5 x 2 mm) of Esthet-X (Dentsply) methacrylate-based microhybrid composite were light-cured using quartz-tungsten-halogen (QTH) Optilight Plus (Gnatus) or light-emitting diode (LED) Ultraled (Dabi Atlante) curing units at 400 and 340 mW/cm2 of irradiance, respectively. After 24 h, absorption spectra of composite were obtained using Nexus 670 (Nicolet) FT-IR spectrometer in order to calculate the DC. The KHN was measured in the HMV-2000 (Shimadzu) microhardness tester under 50 g loads for 15 s, and P was evaluated by percentage reduction of hardness after 24 h of alcohol storage. Data were subjected to t-Student test (alpha = 0.05). QTH device showed lower P and higher KHN than LED (p < 0.05), and no difference between the light-curing units was found for DC (p > 0.05). The halogen-curing unit with higher irradiance promoted higher KHN and lower softening in alcohol than LED.

Keywords


Composite resins; Polymers; Hardness; Dental materials

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DOI: http://dx.doi.org/10.19177/jrd.v1e22013134-139

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Journal of Research in Dentistry, University of Southern of Santa Catarina, Santa Catarina, ISSN 2317-5907

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