Physico-mechanical characterization and fracture reliability of dental resin composites for enamel restoration

This study evaluated the physico-mechanical behavior and the fracture reliability of different dental resin composites indicated for the restoration of the highly mineralized enamel. The following resin composites were tested: Concept Advanced (Vigodent), Fill Magic (Vigodent), Llis (FGM), and Natural Look (DFL); Filtek Z250 (3M ESPE) was used as a universal control. All composites were fully characterized with the following tests: degree of conversion (DC), flexural strength (sigma), flexural modulus (E), water sorption (WS) and solubility (SL), hardness (KMN). Scanning electron microscopy was used for morphological evaluation, whereas the topographical evaluation was carried out by profilometry (Ra) and atomic force microscopy. The color stability of the resin composites was also assessed using a digital spectrophotometer and the CIEL*a*b* system. Data were analyzed with ANOVA as well as the Weibull analysis (alpha = 5%). DC was similar among all composites (51.0-62.3%, p = 0.104). Llis and the control showed overall greater mechanical performance and hardness than the others. Llis and Natural Look presented lower WS and SL than the others. The control acquired smoother surface than the enamel composites. Concept Advanced and Natural Look demonstrated the greatest and lowest reliability of the study, respectively, whereas Llis showed the greatest characteristic strength (p < 0.05). Llis showed the greatest color stability of the study after 28 days of water storage (p < 0.05). In conclusion, our findings confirmed the performance of four different resin composites indicated to restore dental enamel, showing that two of them (Llis and Natural Look) can be sufficiently strong for the restoration of stress-receiving areas, such as the posterior dentition. Most of the enamel composites were as reliable as the universal control resin composite.