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Open AccessArticle

Vickers Hardness and Shrinkage Stress Evaluation of Low and High Viscosity Bulk-Fill Resin Composite

1
Department of Biomedical and Neuromotor Sciences, DIBINEM, University of Bologna, Alma Mater Studiorum, Via San Vitale 59, 40125 Bologna, Italy
2
Department of Surgical Science, CIR Dental School, University of Turin, Via Nizza 230, 10126 Turin, Italy
3
Department of Medical Sciences, University of Trieste, Strada di Fiume 447, 34149 Trieste, Italy
4
Institute for Maternal and Child Health—IRCCS “Burlo Garofolo”, Via dell’Istria 65/1, 34137 Trieste, Italy
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Polymers 2020, 12(7), 1477; https://doi.org/10.3390/polym12071477
Received: 9 June 2020 / Revised: 28 June 2020 / Accepted: 29 June 2020 / Published: 30 June 2020
The aim of this in vitro study was to evaluate the hardness and shrinkage stress (SS) of six bulk-fill resin composites. To evaluate microhardness (MH), ten 6 mm specimens were prepared using a metal mold for each selected bulk-fill resin composite and irradiated from the top side for 40 s using an LED light. After 24 h of storage, Vickers MH was evaluated on the upper, lower and lateral sides of the specimens. SS evaluation was then performed with a universal machine, which evaluated the contraction force generated by a bulk-fill composite specimen placed between two metal cylinders during and after light curing. The results were evaluated with a one-way ANOVA test with a post-hoc Bonferroni test and linear regression analysis (p < 0.05). All materials showed a significant MH decrease between the top and bottom surfaces. However, the bulk-fill materials tested performed differently when considering lateral depth progression. ANOVA tests for SS evaluation showed that both SDR and Venus Bulk Fill had significantly lower stress during irradiation than other tested materials. Further, MH decrease became significantly lower from the top surface at different depths in each tested group. Among the different resins, Venus Bulk Fill and SDR showed not only inferior hardness, but also a significant reduction in SS. View Full-Text
Keywords: bulk-fill composite; microhardness; shrinkage stress; composite resins bulk-fill composite; microhardness; shrinkage stress; composite resins
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MDPI and ACS Style

Comba, A.; Scotti, N.; Maravić, T.; Mazzoni, A.; Carossa, M.; Breschi, L.; Cadenaro, M. Vickers Hardness and Shrinkage Stress Evaluation of Low and High Viscosity Bulk-Fill Resin Composite. Polymers 2020, 12, 1477.

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