Julian G Leprince1, William M Palin2, Julie Vanacker3, Joseph Sabbagh4, Jacques Devaux5, Gaetane Leloup6. 1. School of Dentistry and Stomatology, Université catholique de Louvain, Brussels, Belgium; Institute of Condensed Matter and Nanoscience, Bio- and Soft-Matter, Université catholique de Louvain, Louvain-la-Neuve, Belgium; Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium; CRIBIO (Center for Research and Engineering on Biomaterials), Brussels, Belgium. Electronic address: julian.leprince@uclouvain.be. 2. Biomaterials Unit, University of Birmingham, College of Medical and Dental Sciences, School of Dentistry, St Chad's Queensway, Birmingham B4 6NN, UK. 3. Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium. 4. Department of Restorative and Esthetic Dentistry, Lebanese University, Beirut, Lebanon. 5. Institute of Condensed Matter and Nanoscience, Bio- and Soft-Matter, Université catholique de Louvain, Louvain-la-Neuve, Belgium; CRIBIO (Center for Research and Engineering on Biomaterials), Brussels, Belgium. 6. School of Dentistry and Stomatology, Université catholique de Louvain, Brussels, Belgium; Institute of Condensed Matter and Nanoscience, Bio- and Soft-Matter, Université catholique de Louvain, Louvain-la-Neuve, Belgium; Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium; CRIBIO (Center for Research and Engineering on Biomaterials), Brussels, Belgium.
Abstract
OBJECTIVES: Bulk-fill composites have emerged, arguably, as a new "class" of resin-based composites, which are claimed to enable restoration in thick layers, up to 4mm. The objective of this work was to compare, under optimal curing conditions, the physico-mechanical properties of most currently available bulk-fill composites to those of two conventional composite materials chosen as references, one highly filled and one flowable "nano-hybrid" composite. METHODS: Tetric EvoCeram Bulk Fill (Ivoclar-Vivadent), Venus Bulk Fill (Heraeus-Kulzer), SDR (Dentsply), X-tra Fil (VOCO), X-tra Base (VOCO), Sonic Fill (Kerr), Filtek Bulk Fill (3M-Espe), Xenius (GC) were compared to the two reference materials. The materials were light-cured for 40s in a 2mm×2mm×25mm Teflon mould. Degree of conversion was measured by Raman spectroscopy, Elastic modulus and flexural strength were evaluated by three point bending, surface hardness using Vickers microindentation before and after 24h ethanol storage, and filler weight content by thermogravimetric analysis. The ratio of surface hardness before and after ethanol storage was considered as an evaluation of polymer softening. Data were analyzed by one-way ANOVA and post hoc Tukey's test (p=0.05). RESULTS: The mechanical properties of the bulk-fill composites were mostly lower compared with the conventional high viscosity material, and, at best, comparable to the conventional flowable composite. Linear correlations of the mechanical properties investigated were poor with degree of conversion (0.09<R<0.41) and good with filler content (R>0.8). Softening in ethanol revealed differences in polymer network density between material types. CONCLUSION: The reduction of time and improvement of convenience associated with bulk-fill materials is a clear advantage of this particular material class. However, a compromise with mechanical properties compared with more conventional commercially-available nano-hybrid materials was demonstrated by the present work. SIGNIFICANCE: Given the lower mechanical properties of most bulk-fill materials compared to a highly filled nano-hybrid composite, their use for restorations under high occlusal load is subject to caution. Further, the swelling behaviour of some of the bulk-fill materials may be a reason for concern, which highlights the critical requirement for a veneering material, not only to improve aesthetic quality of the translucent material, but to reduce the impact of degradation.
OBJECTIVES: Bulk-fill composites have emerged, arguably, as a new "class" of resin-based composites, which are claimed to enable restoration in thick layers, up to 4mm. The objective of this work was to compare, under optimal curing conditions, the physico-mechanical properties of most currently available bulk-fill composites to those of two conventional composite materials chosen as references, one highly filled and one flowable "nano-hybrid" composite. METHODS: Tetric EvoCeram Bulk Fill (Ivoclar-Vivadent), Venus Bulk Fill (Heraeus-Kulzer), SDR (Dentsply), X-tra Fil (VOCO), X-tra Base (VOCO), Sonic Fill (Kerr), Filtek Bulk Fill (3M-Espe), Xenius (GC) were compared to the two reference materials. The materials were light-cured for 40s in a 2mm×2mm×25mm Teflon mould. Degree of conversion was measured by Raman spectroscopy, Elastic modulus and flexural strength were evaluated by three point bending, surface hardness using Vickers microindentation before and after 24h ethanol storage, and filler weight content by thermogravimetric analysis. The ratio of surface hardness before and after ethanol storage was considered as an evaluation of polymer softening. Data were analyzed by one-way ANOVA and post hoc Tukey's test (p=0.05). RESULTS: The mechanical properties of the bulk-fill composites were mostly lower compared with the conventional high viscosity material, and, at best, comparable to the conventional flowable composite. Linear correlations of the mechanical properties investigated were poor with degree of conversion (0.09<R<0.41) and good with filler content (R>0.8). Softening in ethanol revealed differences in polymer network density between material types. CONCLUSION: The reduction of time and improvement of convenience associated with bulk-fill materials is a clear advantage of this particular material class. However, a compromise with mechanical properties compared with more conventional commercially-available nano-hybrid materials was demonstrated by the present work. SIGNIFICANCE: Given the lower mechanical properties of most bulk-fill materials compared to a highly filled nano-hybrid composite, their use for restorations under high occlusal load is subject to caution. Further, the swelling behaviour of some of the bulk-fill materials may be a reason for concern, which highlights the critical requirement for a veneering material, not only to improve aesthetic quality of the translucent material, but to reduce the impact of degradation.