Impact of light-cure protocols on the porosity and shrinkage of commercial bulk fill dental resin composites with differ
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Impact of light-cure protocols on the porosity and shrinkage of commercial bulk fill dental resin composites with different flowability Daina Dayana Arenas Buelvas 1 & João Felipe Besegato 2 & Bruno Luiz Santana Vicentin 1 Márcio Grama Hoeppner 1 & Avacir Casanova Andrello 3 & Eduardo Di Mauro 1
3
& Eduardo Inocente Jussiani &
Received: 12 May 2020 / Accepted: 17 August 2020 # The Polymer Society, Taipei 2020
Abstract This research aimed to probe the degree of conversion (DoC), porosity and polymerization shrinkage strain (PSS) from three different commercial bulk fill resin composites (BFRCs) with different flowability submitted to two different irradiation protocols. Samples (n = 3) of Tetric N-Ceram (TNF), Opus Bulk Fill (OBF) and Filltek Bulk Fill Flow (FBFF) were studied by FT-IR (for DoC) and micro-CT (for porosity and PSS analysis) after submitted to the following light-cure protocols: P1 (1000 mW/cm2 for 20 s) and P2 (3200 mW/cm2 for 6 s). All data were statistically treated. The material’s viscosity interfered on its porosity, as well as in the response to the irradiation protocol. Furthermore, data showed that the greater the polymerization shrinkage strain the lower the porosity. On the other hand, the lower the DoC the greater the polymerization shrinkage strain. We conclude that samples of high viscosity composites submitted to extended curing time with lower irradiation showed best physical characteristics for clinical use. The low viscosity FBFF and high power light-cure protocol should be used carefully since it presented the poorest results, which may result in undesirable clinical outcomes. Keywords X-ray computed microtomography . Degree of conversion . Viscosity . Polymerization shrinkage stress . Dental materials
Introduction The restorative technique with conventional photopolymerizable dental resin composites is limited by the thickness of the resin mass to be used (2 mm), resulting in increased clinical time and eventual bonding failure between increments. In order to make the technique faster and safe, Bulk Fill resin composites (BFRC) that allow restoration with one increment up to 5 mm were developed [1–4]. The BFRCs are becoming popular in clinical
* Bruno Luiz Santana Vicentin [email protected] 1
Laboratório de Ressonância Paramagnética Eletrônica (LARPE), Departamento de Física, Universidade Estadual de Londrina, C. P. 6014, Londrina, PR 86051-990, Brazil
2
Departamento de Odontologia Restauradora, Universidade Estadual de Londrina, Londrina, PR, Brazil
3
Laboratório de Física Nuclear Aplicada (LFNA), Departamento de Física, Universidade Estadual de Londrina, Londrina, PR, Brazil
practice because of their advantages compared to the incremental technique [5, 6]. The main mechanism used by manufactures to produce such characteristics are the use of new methacrylatebased monomers [5], increased translucency, new photoinitiator systems [7] and inclusion of different inorganic filler particles (glass fibers) [1]. As in conventional resins, the BFRCs are
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