Evaluation of degree of conversion, rate of cure, microhardness, depth of cure, and contraction stress of new nanohybrid
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B I O M A T E R I A L S S Y N T H E S I S A N D CH A R A C T E R I Z A T I O N Original Research
Evaluation of degree of conversion, rate of cure, microhardness, depth of cure, and contraction stress of new nanohybrid composites containing pre-polymerized spherical filler Lidia Fanfoni1 Matteo De Biasi1 Gabriele Antollovich1 Roberto Di Lenarda1 Daniele Angerame ●
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Received: 27 May 2020 / Accepted: 3 November 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The aim of the present study was to characterize nanohybrid and nanofilled composites in terms of degree of conversion (DC), rate of cure (RC), microhardness (Vickers hardness number; VHN), depth of cure, and contraction stress (CS). Ceram. X® universal- A3, duo enamel E2, and duo dentin D3 composites were compared to Tetric EvoCeram® and FiltekTMSupreme XTE composites of equivalent dentin and enamel shades under a 40 s photopolymerization protocol. DC was measured by infrared spectroscopy, calculating RC from the kinetic curve. Top and bottom VHN were determined using a Vickers indenter, and bottom/top surface ratio (Vickers hardness ratio; VHR) calculated. CS vs. time was assessed by a universal testing machine and normalized for the specimen bonding area. All materials showed DC < 60%, Ceram.X® composites reaching higher values than the other composites of corresponding shades. RC at 5 s of photopolymerization was always higher than that at 10 s. All the Ceram.X® composites and the lighter-shaded Tetric EvoCeram® and FiltekTMSupreme XTE composites reached the RC plateau after 25 s, the remaining materials showed a slower kinetic trend. Tetric EvoCeram® and FiltekTMSupreme XTE composites displayed the softest and the hardest surfaces, respectively. Differently from darker-shaded materials, the universal and the three enamel-shaded composites resulted optimally cured (VHR > 80%). The tested composites differed in CS both during and after light cure, Tetric EvoCeram® and FiltekTMSupreme XTE composites displaying the highest and the lowest CS, respectively. Only the Ceram.X® universal-A3 reached a CS plateau value. The tested composites exhibited material-dependent chemo-mechanical properties. Increasing the curing time and/or reducing the composite layer thickness for dentin-shaded composites appears advisable. Graphical Abstract
1 Introduction * Daniele Angerame [email protected] 1
University Clinical Department of Medical, Surgical, and Health Sciences, University of Trieste, Trieste, Italy
Composite restorative materials represent one of the many successes of modern biomaterials research since they replace biological tissue in both appearance and function. At least half of posterior direct restoration placements now rely on composite materials [1]. Composites consist of three distinct
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Journal of Materials Science: Materials in Medicine (2020)31:127
phases, each one with its role in dictating the material’s properties: the polymerizable resin, the filler
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