Although there is evidence of antibacterial activity from in vitro studies, clinical and long-term studies are still necessary to confirm the effectiveness of antibacterial orthodontic bonding systems in preventing caries disease.

This study evaluated the shear bond strength (SBS) of self-adhesive resin cements (SARCs) to dentin and their physical-chemical properties. Five commercial SARCs were evaluated [SmartCem®2 -DENTSPLY (SC2); BisCem® -Bisco (BC); SeT PP® − SDI (SeT); Relyx U100® -3M ESPE (U100) and YCEM® SA -Yller (YCEM)]. The SARCs were evaluated for SBS to dentin (n = 10) after 24 h, 6 months, and 12 months. The dentin demineralization caused by acidic monomers was observed by SEM, and pH-neutralization of eluate was observed for 24 h. Degree of conversion (DC), rate of polymerization (Rp), flexural strength (FS), and elastic modulus (E) were evaluated. Immediate SBS of SC2, SET, U100, and YCEM were statistically higher than that of BC (p < 0.001). After 12 months, all SARCs showed reduced SBS values and U100 showed values similar to those of SET and YCEM, and higher than those of BC and SC2 (p = 0.001). Demineralization pattern of SARCs was similar. At 24h, all SARCs showed no differences in the pH-value, except BC and U100 (p < 0.001). YCEM showed the highest Rp. U100, YCEM, and SC2 showed statistically higher FS (p<0.001) and E (p < 0.001) when compared with SET and BC. U100 and YCEM showed the best long-term bonding irrespective of the storage period. A significant reduction in SBS was found for all groups after 12 months. SBS was not shown to be correlated with physical-chemical properties, and appeared to be material-dependent. The polymerization profile suggested that an increased time of light activation, longer than that recommended by manufacturers, would be necessary to optimize DC of SARCs.

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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 (σ), 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 (α = 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.

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