Bisacryl Resins: Mechanical Properties, Sorption, Solubility and Filler Particles Characterization

Objectives: This study evaluated the flexural modulus (FM) and flexural strength (FS) after artificial aging, sorption (SP) and solubility (SB). Additionally, the filler particles of bisacryl resins were characterized.
Methods: An acrylic resin (Alike/GC) was used as a control and six bisacryl resins (Luxatemp/DMG, Protemp/3M, Systemp/Ivoclar, Tempsmart/GC [self- and dual-cure modes], Structur/Voco, Yprov/Yller) were evaluated. Samples (25x2x2mm) were prepared for three-point bending test, and were tested after 24-h, 1-month, or 1-year of immersion in distilled water at 37^oC, in order to obtain FM and FS data (n=10). Samples (15-mm diameter, 1-mm thickness) were prepared for SP and SB evaluation following ISO:4049 (n=5). To characterize filler particles under SEM and EDS analyses, base and catalyst pastes of all resins were dissolved with organic solvents. Data were analyzed by two- (FS and FM) and one-way (SP and SB) ANOVA, followed by Bonferroni’s (FS and FM), Games-Howell’s (SP) and Tukey’s (SB) tests (α=0.05).
Results: After one year of water storage, no material presented reduction in FM and FS. On the other hand, FM and FS of few of them increased. All bisacryl resins obtained higher values of FM and FS than the control after one year, except for the FM of Yprov, which did not differ from the control. Materials with lower SP tended to present the highest values of FM and FS after one year of water storage. Not very relevant differences were noticed for SB results. All bisacryl resins presented micrometric clusters composed of nanometric fillers, having different shapes and compositions.
Conclusions: Despite the differences in fillers compositions and microstructures, the bisacryl resins tested after one year of water storage presented stable FM and FS. Materials with lower SP showed higher mechanical properties.