In Vitro Evaluation of marginal adaptation of polyether ether ketone and zirconia copings

Background

Polyether ether ketone (PEEK) has emerged as a new thermoplastic material with potential applications as a restorative material. Aim: This study aimed to evaluate the marginal adaptation of PEEK copings compared to zirconia copings using field emission scanning electron microscopy.

Materials and Methods

A freshly extracted maxillary central incisor was prepared for a full-coverage restoration following standard principles of tooth preparation. The tooth was sent to a laboratory for fabrication of samples using computer-aided design and manufacturing (CAD/CAM). Twenty samples of polyether ether ketone (PEEK) copings (group A) and 20 of zirconia copings were fabricated (group B). The copings were scanned under a field emission scanning electron microscope and measurements were taken at four distinct points. The marginal adaptation over the buccal, lingual, mesial, and distal margins for both groups was evaluated. One-way analysis of variance (ANOVA) and independent t test were applied.

Results

Our findings indicate that PEEK showed better marginal adaptation than zirconia at all measurement points. The mean marginal gap value of the PEEK group was 33.99 ± 8.81 μm and of the zirconia group was 56.21 ± 15.07 μm. On comparing marginal adaptation among the mesial, distal, buccal, and lingual aspects, PEEK showed better adaptation on all four margins, with the best adaptation on the buccal margin that had the lowest mean gap value of 29.27 ± 6.07 μm. The zirconia group adapted best at the distal margin, with a lowest mean gap value of 53.58 ± 15.25 μm (P ≤ 0.05).

Conclusion

PEEK copings had better marginal adaptation and fit compared to zirconia copings. It may have applications as a restorative material in fixed prostheses.

Microstructural and heavy metal analysis of gallstones prevalent in Jharkhand and its implications in the treatment

OBJECTIVES

In the present study the structural and compositional analysis of gallstones was carried out by various characterization techniques. Also, the utility of the study was evaluated on how the findings can enhance the treatment and dissolution therapies of gallstones?

METHODS

Gallstones from the Jharkhand region were analyzed both structurally as well as chemically using Field emission scanning electron microscope (FESEM) and Energy-dispersive X-ray spectroscopy, inductively coupled optical emission spectrometry (ICP-OES), Carbon hydrogen and nitrogen analyzer (CHNS), Nuclear magnetic resonance (NMR), Thermal gravimetric analysis (TGA) and Differential Thermal Analysis (DTA) and other instruments. The content of heavy metal was represented statistically as a mean with standard deviation.

RESULTS

FESEM analysis unveiled the crystal and globular structure of cholesterol and pigment gallstones respectively. Through ICP-OES analysis metals such as Fe, Mn, Cu, Pb, Cr, Zn etc. were detected in gallstones. FTIR and XRD analysis confirmed the presence of cholesterol and calcium carbonate and other compounds in mixed stones and calcium bilirubinate and bilirubin in pigment gallstones. NMR analysis revealed the presence of monohydrate cholesterol (Crystalline) in Cholesterol and mixed gallstones. Mixed gallstones were found to be predominant in this region in contrast to pigmented stones that were prevalent earlier.

CONCLUSION

The present study uncovered the current composition and content of different heavy metals in gallstones of Jharkhand region which can be instrumental in enhancing the dissolution therapies for gallstone treatment. This can serve as a major tool for practitioners for gallstone treatment and change the way they are looked at.

Investigation of High-Sensitivity NO2 Gas Sensors with Ga2O3 Nanorod Sensing Membrane Grown by Hydrothermal Synthesis Method

In this work, Ga₂O₃ nanorods were converted from GaOOH nanorods grown using the hydrothermal synthesis method as the sensing membranes of NO₂ gas sensors. Since a sensing membrane with a high surface-to-volume ratio is a very important issue for gas sensors, the thickness of the seed layer and the concentrations of the hydrothermal precursor gallium nitrate nonahydrate (Ga(NO₃)₃·9H₂O) and hexamethylenetetramine (HMT) were optimized to achieve a high surface-to-volume ratio in the GaOOH nanorods. The results showed that the largest surface-to-volume ratio of the GaOOH nanorods could be obtained using the 50-nm-thick SnO₂ seed layer and the Ga(NO₃)₃·9H₂O/HMT concentration of 12 mM/10 mM. In addition, the GaOOH nanorods were converted to Ga₂O₃ nanorods by thermal annealing in a pure N₂ ambient atmosphere for 2 h at various temperatures of 300 °C, 400 °C, and 500 °C, respectively. Compared with the Ga₂O₃ nanorod sensing membranes annealed at 300 °C and 500 °C, the NO₂ gas sensors using the 400 °C-annealed Ga₂O₃ nanorod sensing membrane exhibited optimal responsivity of 1184.6%, a response time of 63.6 s, and a recovery time of 135.7 s at a NO₂ concentration of 10 ppm. The low NO₂ concentration of 100 ppb could be detected by the Ga₂O₃ nanorod-structured NO₂ gas sensors and the achieved responsivity was 34.2%.

Biosynthesis of zinc oxide nanoparticles using anjbar (root of Persicaria bistorta) extract and their cytotoxic effects on human breast cancer cell line (MCF-7)

Biosynthesis of nanoparticles (NPs) using biomass is now one of the best methods for synthesising NPs due to their nontoxic and biocompatibility. Plants are the best choice among all biomass to synthesise large-scale NPs. The objectives of this study were to synthesise zinc oxide nanoparticles (ZnO-NPs) using Anjbar (root of Persicaria bistorta) [An/ZnO-NPs] and investigate the cytotoxic and anti-oxidant effects. For this purpose, the An/ZnO-NPs were synthesised by using Bistort extract and characterised using UV-Visible spectroscopy, transmission electron microscope, field emission scanning electron microscope, x-ray diffraction and Fourier-transform infrared spectroscopy. The cytotoxic effects of the An/ZnO-NPs on MCF-7 cells were followed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays at 24, 48, and 72 h. Nuclear morphology changed and apoptosis in cells was investigated using acridine orange/propodium iodide (AO/PI) staining and flow cytometry analysis. The pure biosynthesised ZnO-NPs were spherical in shape and particles sizes ranged from 1 to 50 nm. Treated MCF-7 cells with different concentrations of ZnO-NPs inhibited cell viability in a time- and dose-dependent manner with IC50 about 32 μg/ml after 48 h of incubation. In flow cytometry analysis the sub-G1 population, which indicated apoptotic cells, increased from 12.6% at 0 μg/ml (control) to 92.8% at 60 μg/ml, 48 h after exposure. AO/PI staining showed that the treated cells displayed morphologic evidence of apoptosis, compared to untreated groups.

Bio‐green synthesis ZnO‐NPs in Brassica napus pollen extract: biosynthesis, antioxidant, cytotoxicity and pro‐apoptotic properties

The bio‐green methods of synthesis nanoparticles (NPs) have advantages over chemo‐physical procedures due to cost‐effective and ecofriendly products. The goal of current investigation is biosynthesis of zinc oxide NPs (ZnO‐NPs) and evaluation of their biological assessment. Water extract of Brassica napus pollen [rapeseed (RP)] prepared and used for the synthesis of ZnO‐NPs and synthesised ZnO‐NP characterised using ultraviolet–visible, X‐ray diffraction, Fourier‐transform infrared spectroscopy, field emission scanning electron microscope and transmission electron microscope. Antioxidant properties of ZnO‐NPs, cytotoxic and pro‐apoptotic potentials of NPs were also evaluated. The results showed that ZnO‐NPs have a hexagonal shape with 26 nm size. ZnO‐NPs synthesised in RP (RP/ZnO‐NPs) exhibited the good antioxidant potential compared with the butylated hydroxyanisole as a positive control. These NPs showed the cytotoxic effects against breast cancer cells (M.D. Anderson‐Metastasis Breast cancer (MDA‐MB)) with IC₅₀ about 1, 6 and 6 μg/ml after 24, 48 and 72 h of exposure, respectively. RP/ZnO‐NPs were found effective in increasing the expression of catalase enzyme, the enzyme involved in antioxidants properties of the cells. Bio‐green synthesised RP/ZnO‐NPs showed antioxidant and cytotoxic properties. The results of the present study support the advantages of using the bio‐green procedure for the synthesis of NPs as an antioxidant and as anti‐cancer agents.

One-pot green synthesis and structural characterisation of silver nanoparticles using aqueous leaves extract of Carissa carandas: antioxidant, anticancer and antibacterial activities

Facile green synthesis of silver nanoparticles (AgNPs) using an aqueous extract of Carissa carandas (C. carandas) leaves was studied. Fabrication of AgNPs was confirmed by the UV-visible spectroscopy which gives absorption maxima at 420 nm. C. carandas leaves are the rich source of the bioactive molecules, acts as a reducing and stabilising agent in AgNPs, confirmed by Fourier transforms infrared spectroscopy. The field emission scanning electron microscope revealed the spherical shape of biosynthesised AgNPs. A distinctive peak of silver at 3 keV was determined by energy dispersive X-ray spectroscopy. X-ray diffraction showed the facecentred cubic structure of biosynthesised AgNPs and thermal stability was confirmed by the thermogravimetric analysis. Total flavonoid and total phenolic contents were evaluated in biosynthesised AgNPs. Biosynthesised AgNPs showed free radical scavenging activities against 2, 2-diphenyl-1-picrylhydrazyl test and ferric reducing antioxidant power assay. In vitro cytotoxicity against hepatic cell lines (HUH-7) and renal cell lines (HEK-293) were also assessed. Finally, biosynthesised AgNPs were scrutinised for their antibacterial activity against methicillin-resistant Staphylococcus aureus, Shigella sonnei, Shigella boydii and Salmonella typhimurium. This study demonstrated the biofabrication of AgNPs by using C. carandas leaves extract and a potential in vitro biological application as antioxidant, anticancer and antibacterial agents.

Use of an Annular Silicon Drift Detector (SDD) Versus a Conventional SDD Makes Phase Mapping a Practical Solution for Rare Earth Mineral Characterization

A number of techniques for the characterization of rare earth minerals (REM) have been developed and are widely applied in the mining industry. However, most of them are limited to a global analysis due to their low spatial resolution. In this work, phase map analyses were performed on REM with an annular silicon drift detector (aSDD) attached to a field emission scanning electron microscope. The optimal conditions for the aSDD were explored, and the high-resolution phase maps generated at a low accelerating voltage identify phases at the micron scale. In comparisons between an annular and a conventional SDD, the aSDD performed at optimized conditions, making the phase map a practical solution for choosing an appropriate grinding size, judging the efficiency of different separation processes, and optimizing a REM beneficiation flowsheet.

Biofabrication of gold nanoparticles using marine endophytic fungus - Penicillium citrinum

Nanotechnology is one of the promising fields of research and generating new avenues and applications in medicine. Recently, marine floras such as, marine endophytes are gaining the attention of many researchers due to the myriad of bioactive molecules that they possess. In addition, they find applications in many pharmaceutical and cosmetic industries. In this study, they have studied the green synthesis of gold nanoparticles (AuNPs) from Penicillium citrinum (P. citrinum) and its antioxidant activity. P. citrinum was isolated from brown algae. The identity of the fungus was established by comparing its 18S rDNA sequence. AuNPs were synthesised using P. citrinum and were characterised by UV-visible spectrophotometer (UV-vis), field emission scanning electron microscope (FESEM), X-ray diffraction, Fourier transform infrared spectroscopy and dynamic light scattering (DLS). AuNPs were tested for free radical scavenging activity by 1,1-diphenyl-2-picrylhydrazyl method. The particle sizes of AuNps were determined by FESEM and DLS. The reduction of gold metal ion was confirmed from the UV-vis spectrum. AuNPs showed significant antioxidant potential and the activity was comparable to the standard ascorbic acid. Further, in vitro and in vivo studies on these AuNPs will help in developing an alternative, cost-effective and acceptable drug for various ailments.

A Comparative Evaluation of Intraradicular Smear Removal Efficacy of 2% Chitosan (Low Molecular Weight), 4% Chitosan Citrate, and 10% Citric Acid when Used as Final Rinse in Irrigation Protocols: A Field Emission Scanning Electron Microscopic Study

Aim:

This study aims to compare the smear layer removal efficacy of 2% chitosan (low molecular weight) (C-LMV), 4% chitosan citrate (CC), and 10% citric acid (CA) when used in specific irrigant protocols.

Materials and Methods:

A total of 60 single-rooted maxillary incisors and canines were decoronated, standardized to a root length of 15 mm, and prepared with rotary files up to protaper F3 size. Sodium hypochlorite was used as initial rinse [8 ml]. The samples were divided into experimental (Group III, IV, V, and VI) (n = 10) and control groups (I – 17% EDTA, II – normal saline) (n = 5) based on the type of final rinse solution (5 ml) used, that is, 2% C-LMV, 4% C-citrate, 10% CA, and 1% acetic acid. Samples were dehydrated, split buccolingually, gold sputter coated, and examined in field emission scanning electron microscope.

Results:

Overall, the Group IV, V, and III presented the least amounts of smear, debris, and erosion among the experimental groups at the apical, middle, and coronal one-thirds of the root canal with a mean value of 1.53 ± 0.42, 1.33 ± 0.42, and 1.60 ± 0.46, respectively, and there was no statistically significant difference (P > 0.05).

Conclusion:

The use of CC as final rinse solution during biomechanical preparation seems promising.

A 'NanoSuit' surface shield successfully protects organisms in high vacuum: observations on living organisms in an FE-SEM

Although extremely useful for a wide range of investigations, the field emission scanning electron microscope (FE-SEM) has not allowed researchers to observe living organisms. However, we have recently reported that a simple surface modification consisting of a thin extra layer, termed 'NanoSuit', can keep organisms alive in the high vacuum (10(-5) to 10(-7) Pa) of the SEM. This paper further explores the protective properties of the NanoSuit surface-shield. We found that a NanoSuit formed with the optimum concentration of Tween 20 faithfully preserves the integrity of an organism's surface without interfering with SEM imaging. We also found that electrostatic charging was absent as long as the organisms were alive, even if they had not been coated with electrically conducting materials. This result suggests that living organisms possess their own electrical conductors and/or rely on certain properties of the surface to inhibit charging. The NanoSuit seems to prolong the charge-free condition and increase survival time under vacuum. These findings should encourage the development of more sophisticated observation methods for studying living organisms in an FE-SEM.

Dressing living organisms in a thin polymer membrane, the NanoSuit, for high-vacuum FE-SEM observation

Scanning electron microscopy (SEM) has made remarkable progress and has become an essential tool for observing biological materials at microscopic level. However, various complex procedures have precluded observation of living organisms to date. Here, a new method is presented by which living organisms can be observed by field emission (FE)-SEM. Using this method, active movements of living animals were observed in vacuo (10(-5)-10(-7) Pa) by protecting them with a coating of thin polymer membrane, a NanoSuit, and it was found that the surface fine structure of living organisms is very different from that of traditionally fixed samples. After observation of mosquito larvae in the high vacuum of the FE-SEM, it was possible to rear them subsequently in normal culture conditions. This method will be useful for numerous applications, particularly for electron microscopic observations in the life sciences.