Dentine Remineralisation Induced by "Bioactive" Materials through Mineral Deposition: An In Vitro Study.

This study aimed to assess the ability of modern resin-based "bioactive" materials (RBMs) to induce dentine remineralisation via mineral deposition and compare the results to those obtained with calcium silicate cements (CSMs). The following materials were employed for restoration of dentine cavities: CSMs: ProRoot MTA (Dentsply Sirona), MTA Angelus (Angelus), Biodentine (Septodont), and TheraCal LC (Bisco); RBMs: ACTIVA BioACTIVE Base/Liner (Pulpdent), ACTIVA Presto (Pulpdent), and Predicta Bioactive Bulk (Parkell). The evaluation of the mineral deposition was performed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) on the material and dentine surfaces, as well as at the dentine-material interface after immersion in simulated body fluid. Additionally, the Ca/P ratios were also calculated in all the tested groups. The specimens were analysed after setting (baseline) and at 24 h, 7, 14, and 28 days. ProRoot MTA, MTA Angelus, Biodentine, and TheraCal LC showed significant surface precipitation, which filled the gap between the material and the dentine. Conversely, the three RBMs showed only a slight ability to induce mineral precipitation, although none of them was able to remineralise the dentine-material interface. In conclusion, in terms of mineral precipitation, modern "bioactive" RBMs are not as effective as CSMs in inducing dentine remineralisation; these latter represent the only option to induce a possible reparative process at the dentin-material interface.

The Influence of Indirect Bonding Technique on Adhesion of Orthodontic Brackets and Post-Debonding Enamel Integrity-An In Vitro Study.

The increasing demand for orthodontic treatments due to the high prevalence of malocclusion has inspired clinicians and material scientists to investigate innovative, more effective, and precise bonding methods with reduced chairside time. This study aimed at comparing the shear bond strength (SBS) of metal and ceramic brackets bonded to enamel using the indirect bonding technique (IDB). Victory Series metal brackets (Metal-OPC, Metal-APC) and Clarity™ Advanced ceramic brackets (Ceramic-OPC) (3M Unitek, Monrovia, CA, USA) were bonded indirectly to extracted human premolars through the etch-and-rinse technique. A qualitative assessment of the enamel surface using microscopic methods was performed, and the amount of residual adhesive was reported as per the adhesive remnant index (ARI). Moreover, the bracket surface was evaluated with SEM-EDS. The highest SBS mean values were observed in the Ceramic-OPC group (16.33 ± 2.01 MPa), while the lowest ones were obtained with the Metal-OPC group (11.51 ± 1.40 MPa). The differences between the Metal-AOPC vs. Metal-APC groups (p = 0.0002) and the Metal-OPC vs. Ceramic-OPC groups (p = 0.0000) were statistically significant. Although the Ceramic-OPC brackets bonded indirectly to the enamel surface achieved the highest SBS, the enamel damage was significantly higher compared to that of the other groups. Thus, considering the relatively high bond SBS and favourable debonding pattern, Metal-APC brackets bonded indirectly may represent the best choice.

Polystyrene nanoparticles: the mechanism of their genotoxicity in human peripheral blood mononuclear cells.

Plastic nanoparticles are widely spread in the biosphere, but health risk associated with their effect on the human organism has not yet been assessed. The purpose of this study was to determine the genotoxic potential of non-functionalized polystyrene nanoparticles (PS-NPs) of different diameters of 29, 44, and 72 nm in human peripheral blood mononuclear cells (PBMCs) (in vitro). To select non-cytotoxic concentrations of tested PS-NPs, we analyzed metabolic activity of PBMCs incubated with these particles in concentrations ranging from 0.001 to 1000 µg/mL. Then, PS-NPs were used in concentrations from 0.0001 to 100 µg/mL and incubated with tested cells for 24 h. Physico-chemical properties of PS-NPs in media and suspension were analyzed using dynamic light scattering (DLS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and zeta potential. For the first time, we investigated the mechanism of genotoxic action of PS-NPs based on detection of single/double DNA strand-breaks and 8-oxo-2'-deoxyguanosine (8-oxodG) formation, as well as determination of oxidative modification of purines and pyrimidines and repair efficiency of DNA damage. Obtained results have shown that PS-NPs caused a decrease in PBMCs metabolic activity, increased single/double-strand break formation, oxidized purines and pyrimidines and increased 8oxodG levels. The resulting damage was completely repaired in the case of the largest PS-NPs. It was also found that extent of genotoxic changes in PBMCs depended on the size of tested particles and their ζ-potential value.

Detection of siloxane thin films on glass substrate using IR ratio-reflectance spectrum.

In case of thin films of siloxane obtained from different organo-silane derivatives (alkoxy and chloro) on soda lime silica glass substrates, IR-ATR and IR-SR could not detect the organic functional groups of the coating. This becomes even more problematic for the case of tetraethoxysilane (when fully hydrolyzed), the coating of which possesses the same functional groups as the glass substrate. In this work we propose to employ the so-called ratio-reflectance spectra in the v(Si-O) wavenumber region, where both glass and the siloxane coating give most prominent bands, important for the evaluation of the quality of coating formation and qualitative knowledge on its structure. We show that the reflectance-absorbance spectra obtained from the ratio-reflectance spectra are in direct connection to the structure of the siloxane network which depends not only on the chemical nature of the parent silane, but also on the dipping time and the solvent composition. Some characteristics of the reflectance-absorbance spectra, like the appearance of a two well defined bands at 1110 and 975 cm-1, can be correlated to the film morphology and bridging oxygen number. We support our conclusions using principal component analysis of reflectance spectra, contact angle, AFM and SEM measurements.

Traditional Microscopic Techniques Employed in Dental Adhesion Research-Applications and Protocols of Specimen Preparation.

Microscopy is a traditional method to perform ex vivo/in vitro dental research. Contemporary microscopic techniques offer the opportunity to observe dental tissues and materials up to nanoscale level. The aim of this paper was to perform a literature review on four microscopic methods, which are widely employed in dental studies concerning the evaluation of resin-dental adhesive interfaces-confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The literature search was performed using digital databases: PubMed, Web of Science and Scopus. On the basis of key words relevant to the topic and established eligibility criteria, finally 84 papers were included in the review. Presented microscopic techniques differ in their principle of operation and require specific protocols for specimen preparation. With regard to adhesion studies, microscopy assists in the description of several elements involved in adhesive bonding, as well as in the assessment of the condition of enamel surface and the most appropriate etching procedures. There are several factors determining the quality of the interaction between the substrates which could be recognized and a potential for further implementation of microscopic techniques in dental research could be recognized, especially when these techniques are used simultaneously or combined with spectroscopic methods. Through such microscopy techniques it is possible to provide clinically relevant conclusions and recommendations, which can be easily introduced for enamel-safe bonding and bonding protocols, as well as optimal pretreatments in dentine preparation.

Antimicrobial activity and toxicological risk assessment of silver nanoparticles synthesized using an eco-friendly method with Gloeophyllum striatum.

Recently, nanomaterials synthesized ecologically using microorganisms have attracted much interest. In the present study, the ability of Gloeophyllum striatum to synthesize silver nanoparticles is described for the first time. Nanoparticles were formed in an eco-friendly extracellular manner and characterized by UV-Vis, FT-IR, MADLS and SEM techniques. The obtained nanoparticles showed excellent activity against gram-positive and gram-negative bacteria. The MIC values for gram-negative bacteria were 15 µM, while for gram-positive strains they reached 30 µM. The haemolytic and cytotoxic activities of the synthesized nanoparticles towards mammalian cells were also determined. The addition of AgNPs at the concentrations above 30 µM caused 50% haemolysis of red blood cells after they 24-hour incubation. A decrease in the viability of fibroblasts by over 50% was also found in the samples treated with nanoparticles at the concentrations above 30 µM. The ecotoxicological risk of silver nanoparticles was assessed using A. franciscana and D. magna crustaceans as well as L. sativum plants. The EC50 values for A. franciscana and D. magna were 61.97 and 0.275 µM, respectively. An about 20% reduction in the length of L. sativum shoots and roots was noted after the treatment with AgNPs at the concentration of 100 µM.

Understanding the Role of Silver Nanostructures and Graphene Oxide Applied as Surface Modification of TiO2 in Photocatalytic Transformations of Rhodamine B under UV and Vis Irradiation.

This work is focused on photocatalytic properties of titanium dioxide thin coatings modified with silver nanostructures (AgNSs) and graphene oxide (GO) sheets which were analyzed in processes of chemical transformations of rhodamine B (RhB) under ultraviolet (UV) or visible light (Vis) irradiation, respectively. UV-Vis spectroscopy was applied to analyze the changes in the RhB spectrum during photocatalytic processes, revealing decolorization of RhB solution under UV irradiation while the same process coexisting with the transformation of RhB to rhodamine 110 was observed under Vis irradiation. The novelty of this study is the elaboration of a methodology for determining the parameters characterizing the processes occurring under the Vis irradiation, which enables the comparison of photocatalysts' activity. For the first time, the method for quantification of rhodamine B transformation into rhodamine 110 in the presence of a semiconductor under visible light irradiation was proposed. Photocatalysts with various surface architectures were designed. TiO2 thin coatings were obtained by the sol-gel method. GO sheets were deposited on their surface using the dip-coating method. AgNSs were photogenerated on TiO2 or grown spontaneously on GO flakes. For characterization of obtained photocatalysts, scanning electron microscopy (SEM), X-ray diffraction (XRD) and diffuse-reflectance spectroscopy (DRS) techniques were applied. The results indicate that the surface architecture of prepared coatings does not affect the main reaction path but have an influence on the reaction rates and yields of observed processes.

A Multiparametric Study of Internalization of Fullerenol C60(OH)36 Nanoparticles into Peripheral Blood Mononuclear Cells: Cytotoxicity in Oxidative Stress Induced by Ionizing Radiation.

The aim of this study was to investigate the uptake and accumulation of fullerenol C60(OH)36 into peripheral blood mononuclear cells (PBMCs). Some additional studies were also performed: measurement of fullerenol nanoparticle size, zeta potential, and the influence of fullerenol on the ionizing radiation-induced damage to PMBCs. Fullerenol C60(OH)36 demonstrated an ability to accumulate in PBMCs. The accumulation of fullerenol in those cells did not have a significant effect on cell survival, nor on the distribution of phosphatidylserine in the plasma membrane. However, fullerenol-induced depolarization of the mitochondrial membrane proportional to the compound level in the medium was observed. Results also indicated that increased fullerenol level in the medium was associated with its enhanced transport into cells, corresponding to its influence on the mitochondrial membrane. The obtained results clearly showed the ability of C60(OH)36 to enter cells and its effect on PBMC mitochondrial membrane potential. However, we did not observe radioprotective properties of fullerenol under the conditions used in our study.

Chitosan-Functionalized Graphene Nanocomposite Films: Interfacial Interplay and Biological Activity.

Graphene oxide (GO) has recently captured tremendous attention, but only few functionalized graphene derivatives were used as fillers, and insightful studies dealing with the thermal, mechanical, and biological effects of graphene surface functionalization are currently missing in the literature. Herein, reduced graphene oxide (rGO), phosphorylated graphene oxide (PGO), and trimethylsilylated graphene oxide (SiMe3GO) were prepared by the post-modification of GO. The electrostatic interactions of these fillers with chitosan afforded colloidal solutions that provide, after water evaporation, transparent and flexible chitosan-modified graphene films. All reinforced chitosan-graphene films displayed improved mechanical, thermal, and antibacterial (S. aureus, E. coli) properties compared to native chitosan films. Hemolysis, intracellular catalase activity, and hemoglobin oxidation were also observed for these materials. This study shows that graphene functionalization provides a handle for tuning the properties of graphene-reinforced nanocomposite films and customizing their functionalities.

The Synergy of Ciprofloxacin and Carvedilol against Staphylococcus aureus-Prospects of a New Treatment Strategy?

Staphylococcus aureus infections are common and difficult to treat. The increasing number of drug-resistant staphylococcal infections has created the need to develop new strategies for the treatment of these infections. The synergistic antimicrobial activity of different pharmaceuticals seems to be an interesting alternative. The aim of this study was to assess the synergistic activity of ciprofloxacin and carvedilol against S. aureus strains. The antibacterial potential of ciprofloxacin and carvedilol was evaluated according to the CLSI guidelines. The calcium content in S. aureus cells was measured using flow cytometry and atomic absorption spectroscopy. Moreover, confocal and scanning electron microscopy were used to determine the mechanism of antibacterial synergy of ciprofloxacin and carvedilol. The antibacterial effect of ciprofloxacin was higher in the presence of carvedilol than in S. aureus cultures containing the antibiotic only. A significant increase in S. aureus membrane permeability was also observed. The simultaneous administration of the tested compounds caused damage to S. aureus cells visualized by SEM. Enhancement of the antimicrobial action of ciprofloxacin by carvedilol was correlated with an increase in free calcium content in S. aureus cells, morphological changes to the cells, and a reduction in the ability to form bacterial aggregates.

Impact of Perfluoro and Alkylphosphonic Self-Assembled Monolayers on Tribological and Antimicrobial Properties of Ti-DLC Coatings.

The diamond-like carbon (DLC) coatings containing 1.6%, 5.3% and 9.4 at.% of Ti deposited by the radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on the silicon substrate were modified by n-decylphosphonic acid (DP) and 1H, 1H, 2H and 2H-perfluorodecylphosphonic acid (PFDP). The presence of perfluoro and alkylphosphonic self-assembled monolayers prepared by the liquid phase deposition (LPD) technique was confirmed by Fourier transform infrared spectroscopy (FTIR). It was shown that DP and PFDP monolayers on the surface of titanium incorporated diamond-like carbon (Ti-DLC) coatings had a huge influence on their wettability, friction properties, stability under phosphate- and tris-buffered saline solutions and on antimicrobial activity. It was also found that the dispersive component of surface free energy (SFE) had a significant influence on the value of the friction coefficient and the percentage value of the growth inhibition of bacteria. The dispersive component of SFE caused a reduction in the growth of bacteria and the friction coefficient in mili- and nano-newton load range. Additionally, both self-assembled monolayers prepared on Ti-DLC coatings strongly reduced bacterial activity by up to 95% compared to the control sample.

Multi-Layer Application of Self-Etch and Universal Adhesives and the Effect on Dentin Bond Strength.

Contemporary self-etch and multi-mode adhesives were introduced to ensure a fast and reliable bonding procedure. Yet, in terms of bond strength and stability they failed to perform as well as two-bottle, etch-and-rinse adhesives, which remain the gold standard in terms of durability. The purpose of this study was to assess the shear bond strength (SBS) of dental adhesives to dentin with different application protocols. Two self-etch (Adper Easy One and Xeno V) and two multi-mode adhesives (Single Bond Universal and Prime&Bond One Select) were used in the study. The highest SBS was obtained for Single Bond Universal applied in three layers, while the lowest, for Xeno V applied in one layer. Other tested adhesives obtained the highest SBS when applied in three layers. For all tested adhesives, multi-layer application resulted in an increase in adhesive layer thickness, as observed in SEM. The increased thickness of the adhesive layer produced by triple application of unfilled adhesives corresponded with higher SBS values. The present study showed that using triple adhesive layers with simplified adhesive systems can be recommended to improve their performance. Due to differences in the composition of self-etch and universal adhesives, the exact application protocol is product dependent.