2. Universidad Cardenal Herrera-CEU

Purpose: The aim of this study was to evaluate the chemomechanical properties, antibacterial activity, and cytotoxicity of an experimental adhesive resin containing halloysite nanotubes (HNT), doped with alkyl trimethyl ammonium bromide (ATAB). Materials and Methods: A filler of HNT doped with ATAB was obtained (ATAB:HNT) and incorporated (5 wt%) into a resin blend made of bisphenol A glycerolate dimethacrylate, 2-hydroxyethyl methacrylate and a photoinitiator/co-initiator system (GATAB:HNT). The same resin blend without ATAB:HNT was used as control (Ctrl). The ATAB:HNT filler was assessed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The two tested adhesives were evaluated for degree of conversion (DC) in vitro and in situ, softening in alcohol, dentin microtensile bond strength (μTBS), antibacterial activity, and cytotoxicity (n = 5). Results: SEM showed that the nanotubes had a characteristic tubular-needle morphology, while the TEM analysis confirmed the presence of ATAB inside the lumens of HNT. The incorporation of ATAB:HNT induced no reduction (p > 0.05) of the DC either in situ or in vitro. No difference was encountered after the softening challenge test (p > 0.05) and no difference was found in μTBS between the two adhesives, both at 24 h (p > 0.05) and after 6 months of storage in distilled water (p > 0.05). However, ATAB:HNT reduced Streptococcus mutans viability (p < 0.05) without a cytotoxic effect on pulp cells (p > 0.05). Conclusions: GATAB:HNT adhesive demonstrated appropriate polymerization without significant differences in softening after solvent immersion, while concomitantly maintaining reliable bond strength after 6 months of water aging. Moreover, the ATAB:HNT filler can provide antibacterial activity to the adhesive resin without affecting pulp cell viability.

This study aimed at evaluating the shear bond strength (SBS) of modern self-adhesive resin cements and resin-modified glass ionomer cements applied to di erent prosthetic substrates. Zirconia, lithium-disilicate glass-ceramic and a noble metal alloy were used as bonding substrates. They were all sand-blasted with alumina, while LD was further etched with 9.6% hydrofluoric acid (10 s). A light-curing resin-modified glass ionomer cement (3M-GIC: Ketac Cem Plus) and a self-curing resin-modified glass ionomer cement (GC-GIC: FujiCEM 2) were compared to self-adhesive resin cements (PAN: Panavia SA Universal) and (3M-RES: Rely X Unicem 2). Ten specimens for each substrate were produced and up to five cylinders of each cement were bonded to each substrate. The shear bond strength (SBS) was evaluated after 24 h or after thermocycling (TC) aging (5000 cycles). The data was statistically analysed by two-way ANOVA and Student–Newman–Keuls test ( = 0.05). Failure modes were analysed through stereoscopic microscopy. The greatest SBS was attained with PAN, whilst 3M-GIC showed the lowest SBS and failed prevalently in adhesive mode. No di erence in SBS was observed between GC-GIC and 3M-RES. After TC aging, all cements showed significant drop (p < 0.05) in SBS, but PAN showed the greatest SBS. Reliable bond strength to prosthetic substrates can be achieved with specific universal resin-luting cements and may be an alternative to glass ionomer cements when luting alloy substrates.

The aim of this study was to evaluate the infuence of boron-nitride nanotubes (BNNTs) on the properties of resin-based light-curing dental sealants (RBSs) when incorporated at diferent concentration. RBSs were formulated using methacrylate monomers (90 wt.% TEGDMA, 10 wt.% BisGMA). BNNTs were added to the resin blend at 0.1 wt.% and 0.2 wt.%. A Control group without fller was also designed. Degree of conversion, ultimate tensile strength, contact angle, surface free energy, surface roughness and color of the RBSs were evaluated for the tested materials. Their cytotoxicity and mineral deposition ability (Bioactivity) were also assessed. A suitable degree of conversion, no efect in mechanical properties and no cytotoxic efect was observed for the experimental materials. Moreover, the surface free energy and the surface roughness decreased with the addition of BNNTs. While the color analysis showed no diference between specimens containing BNNTs and the control group. Mineral deposition occurred in all specimens containing BNNTs after 7d. In conclusion, the incorporation of BNNTs may provide bioactivity to resin-based dental sealants and reduce their surface free energy.

This study is aimed at evaluating the effects of triclosan-encapsulated halloysite nanotubes (HNT/TCN) on the physicochemical and microbiological properties of an experimental dental composite. A resin composite doped with HNT/TCN (8% w/w), a control resin composite without nanotubes (HNT/TCN-0%) and a commercial nanofilled resin (CN) were assessed for degree of conversion (DC), flexural strength (FS), flexural modulus (FM), polymerization stress (PS), dynamic thermomechanical (DMA) and thermogravimetric analysis (TGA). The antibacterial properties (M) were also evaluated using a 5-day biofilm assay (CFU/mL). Data was submitted to one-way ANOVA and Tukey tests. There was no significant statistical difference in DC, FM and RU between the tested composites (p > 0.05). The FS and CN values attained with the HNT/TCN composite were higher (p < 0.05) than those obtained with the HNT/TCN-0%. The DMA analysis showed significant differences in the TAN (p = 0.006) and Tg (p = 0) between the groups. TGA curves showed significant differences between the groups in terms of degradation (p = 0.046) and weight loss (p = 0.317). The addition of HNT/TCN induced higher PS, although no significant antimicrobial effect was observed (p = 0.977) between the groups for CFUs and (p = 0.557) dry weight. The incorporation of HNT/TCN showed improvements in physicochemical and mechanical properties of resin composites. Such material may represent an alternative choice for therapeutic restorative treatments, although no significance was found in terms of antibacterial properties. However, it is possible that current antibacterial tests, as the one used in this laboratory study, may not be totally appropriate for the evaluation of resin composites, unless accompanied with aging protocols (e.g., thermocycling and load cycling) that allow the release of therapeutic agents incorporated in such materials.