Silicates

It has been documented that total removal of carious dentin, assessed according to clinical criteria, does not mean complete eradication of bacteria. For that reason in prevention of caries and pulp inflammations, application of the materials having high antibacterial properties seems to be indispensable. Determination of antibacterial activities of two white Mineral Trioxide Aggregate (MTA) preparations against bacteria of the genus Streptococcus. Antibacterial activities of the materials were determined by diffusion method on a solid tryptic-soy medium (Tryptic Soy Agar, Oxoid). Wells were prepared on the medium with a puncher of 7 mm diameter and 5 mm depth (four for each material). The bottom was poured with 10 microlitres of liquid TSA for sealing. Bacterial suspension was inoculated with cotton swabs onto the medium surface and then the wells were filled with the materials prepared ex tempore. The plates were left in room temperature for 30 minutes and incubated at 37 degrees ...

The purpose of this study was to report the success rate of using mineral trioxide aggregate (MTA) and zinc oxide eugenol (ZOE) as vital pulp therapy agents in immature permanent teeth with carious or traumatic pulp exposure. Subjects were children with permanent teeth requiring pulpotomy (apexogenesis) and without systemic diseases. Both ZOE and MTA treatments as pulpotomy agents showed clinical and radiographic success in immature permanent teeth. Although MTA was more successful, it is more expensive, and dentin bridges may develop over canal orifices, complicating future root canal therapy.

Objective: NovaMin is technically described as amorphous sodium calcium phosphosilicate, and has been shown in laboratory studies to rapidly occlude dentin tubules through the deposition of particles that react to form a protective layer, similar to bone mineral, on the dentin surface. NovaMin was originally developed as a bone regenerative material and is highly biocompatible. The objective of this pilot study was to compare the safety and effectiveness of two prototype formulations containing 2.5% and 7.5% w/w NovaMin to a placebo dentifrice for the treatment of dentin hypersensitivity. Methods: This was a randomized, double-blind, placebo-controlled pilot study. Sixty-six subjects with a confirmed diagnosis of dentin hypersensitivity were randomized to one of three treatments: 2.5% NovaMin, 7.5% NovaMin, or placebo. Two standard test stimuli, tactile and thermal air, were applied to sensitive cervical dentin surfaces. Subjects recorded the intensity of sensitivity in response to each stimulus on a visual analog scale at baseline, and after two, four, and eight weeks of twice-daily product use. Oral soft tissues were examined and spontaneous reports of adverse experiences were also monitored. Results: Comparison of the mean change from baseline among the three treatment groups indicated a meaningful reduction in sensitivity scores in the 7.5% group that was significant compared to reductions observed in the placebo control group at all time points. Conclusion: The results of this study are supportive of the incorporation of NovaMin into products intended for the reduction of dentin hypersensitivity.

Influence of polishing methods on water sorption and solubility of denture base acrylic resins was studied. Eighty samples were divided into groups: Clássico (CL), and QC 20 (QC) - hot water bath cured; Acron MC (AC), and Onda Cryl (ON) - microwave cured; and submitted to mechanical polishing (MP) - pumice slurry, chalk powder, soft brush and felt cone in a bench vise; or chemical polishing (CP) - heated monomer fluid in a chemical polisher. The first desiccation process was followed by storage in distilled water at 37 ± 1ºC for 1 h, 1 day, 1, 2, 3 and 4 weeks. Concluding each period, water sorption was measured. After the fourth week, a second desiccation process was done to calculate solubility. Data were submitted to analysis of variance, followed by Tukey test (p<0.05). Means of water sorption (%) and solubility (%), respectively, were: CL-MP: 1.92 and 0.02; CL-CP: 1.98 and 0.52; QC-MP: 2.31 and -0.05; QC-CP: 2.32 and 0.25; AC-MP: 2.45 and -0.07; AC-CP: 2.43 and 0.41; ON-MP: ...

Apical surgery should be considered as the last treatment option and employed when conventional endodontic treatment does not provide the expected result. In teeth undergoing apical surgery, the type of retrograde filling material is one of the factors interfering with the repair of periapical tissues. The material in intimate contact with the periapical tissues plays a fundamental role in the repair process. Several materials have been studied and indicated for use in apical surgery procedures, but the mineral trioxide aggregate (MTA) is still the most frequently used one. Guided tissue regeneration (GTR) techniques have been proposed as an adjunct to apical surgery to enhance bone healing. Here is reported a clinical case in which apical surgery was performed in conjunction with MTA-based root reconstruction of the maxillary right second incisor. After the apical surgery, a root-end cavity was prepared at the vestibular face of the involved tooth and filled with MTA. A bovine bone...

Photon detectors are indispensable in many areas of fundamental physics research, particularly in the emerging fields of particle astrophysics, nuclear and particle physics, as well as in medical equipment (i.e. PET), in physical check-ups and diagnosis as in-vitro inspection (Radioimmunoassay and Enzyme immunoassay as luminescent, fluorescent,

Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine–rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagene...

Zr‐based bulk metallic glasses (BMGs) possess attractive properties for prospective biomedical applications. The present study designs Ni‐free Zr–Cu–Al–Nb–Pd BMGs and investigates their in vitro biocompatibility by studying mechanical properties, bio‐corrosion resistance, and cellular responses. The Ti–6Al–4V alloy is used as a reference material. It is found that the Zr‐based BMGs exhibit good mechanical properties, including high strengths above 1600 MPa, high hardness over 4700 MPa, and low elastic moduli of 85–90 GPa. The Zr‐based BMGs are corrosion resistant in a simulated body environment, as revealed by wide passive regions, low passive current densities, and high pitting overpotentials. The formation of ZrO2‐rich surface passive films of the Zr‐based BMGs contributes to their high corrosion resistance, whereas their pitting corrosion in the phosphate buffered saline solution can be attributed to the sensitivity of the ZrO2 films to the chloride ion. The general biosafety of ...

Among diatoms, Phaeodactylum tricornutum is a peculiar species that exists in three morphotypes with distinct cell wall structures and low silica content. X‐ray photoelectron spectroscopy (XPS) analysis was performed on P. tricornutum and compared with diatom Thalassiosira pseudonana; the results provide new information on the chemical composition (elements, chemical functions, classes of biochemical compounds) of the cell surface. Two types of silicon were found: condensed silica (SiO2) and weakly polymerised silicate. Cells of T. pseudonana showed the highest concentration of silicon, with a majority in the form of condensed silica. For the fusiform and triradiate morphotypes of P. tricornutum, the majority of the small concentration of silica found was in the form of weakly polymerised silicate. For all morphotypes of P. tricornutum, higher polysaccharide concentrations replaced silica as a structural part of the cell wall. In both diatoms, a high concentration of lipids was meas...

Despite the excellence properties of mineral trioxide aggregate sealer (MTAS), it may have some influence in its sealing ability. The purpose of this study was to analyze and compare sealing ability of MTAS and resin epoxy sealer (RES). Thirty-two extracted human lower premolar teeth had their canals prepared with ProTaper Universal. This group divided into two groups, group 1, the root canals were filled using guttaperca with MTAS and Group 2 root canals were filled using guttaperca with RES. All samples were incubated at the temperature of 370C for 24 hours with 100% humidity. Then the whole sample were immersed in India ink for 7 days. Samples were washed and decalcified until became transparent. The penetration of India ink was evaluated by using a stereo microscope, and the scores are were given by criteria: score 1: 0-0.5 mm ink penetration; a score 2: ink penetration 0.511mm; and a score 3: ink penetration > 1 mm. Score 1 in the group RES 37.5%, and 21.9% MTAS group, score...

Victor A. Rassulov All-Russian Scientific-Research Institute of Mineral Resources, Moscow, vimS@df.ru The revised crystallochemical formula of calcurmolite, (Ca,Na),(U02hMo,(O,OH)11 nH,O, is given on the basis of electron microprobe analyses of the samples from Kazakhstan (Kyzyl-Sai) and Armenia (Kadjaran). Parameters of the monoclinic unit cell: a = 16.30 0.03 A, b = 25.490.05 A, c = 19.50 0.06 A, ~ = 90°07', are estimated by X-ray diffraction method. The IR spectra and spectra of laser luminescence of two mentioned findings of the mineral have been obtained for the first time; they show the identity, stability, and diagnostic value of both methods. Micro-textural and structural peculiarities of calcurmolite prevent from the research of a crystal structure of the mineral. Calcurmolite was formed as a pseudomorph after uranophane. 2 tables, 8 figures, 14 references.

The aim of this study was to assess the current status of mineral trioxide aggregate (MTA) as an educational material in dental schools in Turkey. A survey was sent to senior members of the endodontic departments of seventeen dental schools; fourteen responded. All respondents reported that they used MTA in their clinical practice, with apexification, perforations, retrograde fillings, and root resorptions being the most frequently occurring treatment procedures. All reported that information was given to students regarding MTA mainly as part of the curriculum. The third and fourth years were the periods when MTA was introduced to students in most of the schools. Twelve schools reported that students had the opportunity to observe procedures in which MTA was used, but students had the chance to use the material in a very minor proportion of the schools, mainly under the supervision of clinical instructors. Ten schools agreed that MTA should be included in the regular endodontic curr...

This study evaluated the radiopacity of 3 repair materials, Biodentine, MM-MTA, and MTA Angelus. Standardized cylindrical rings were prepared. Samples of Biodentine MM-MTA and MTA Angelus were prepared ( in each group), filled into the rings, and preserved at 37°C until setting. A 1 mm thick dentin slice was used as control. All set specimens were removed and radiographed along with the dentine slice and a graduated aluminium step wedge. Digital images were transferred to the computer using a software. The radiographic densities of the specimens were determined, and the values were converted into millimetres of aluminium (mm Al). One-way ANOVA was used for intergroup comparison, whereas Tukey HSD test was used for detecting the group with the difference. The mean radiopacities of Biodentine, MTA Angelus, and MM-MTA were 2.8 ± 0.48, 4.72 ± 0.45, and 5.18 ± 0.51 mm Al, respectively. The radiopacity of Biodentine was significantly lower compared to other materials (), whereas no signif...

Crystalline and amorphous orthosilicates of magnesium, zinc, cadmium and copper were prepared by non-traditional sol-gel schemes connected with the use of high-boiling chemically active (HBCA) additives to prevent the polycondensation of silicate anions at early synthesis stages. Metal acetates and nitrates were used as the metal oxide precursors, tetraethoxysilane and γ-aminopropyltriethoxysilane - as the SiO 2 precursors, resorcinol and triethanolamine - as the HBCA additives, water and dimethyl formamide- as the solvents. Gelation and drying of the precursor solutions were carried out at 20° or 120°C, the further thermal treatment of samples were performed in three stages up to 900°C. Chemical evolution of the systems during the thermal treatment, was controlled using TGA-DTA and XRD techniques, the kinetic molybdate method, FTIR and UV-VIS spectrophotometry. The use of high-boiling chemically active additives was shown to reduce the content of free metal oxides in the synthesis ...

We have studied the mineral poldervaartite CaCa[SiO3(OH)(OH)] which forms a series with its manganese analogue olmiite CaMn[SiO3(OH)](OH) using a range of techniques including scanning electron microscopy, thermogravimetric analysis, Raman and infrared spectroscopy. Chemical analysis shows the mineral is reasonably pure and contains only calcium and manganese with low amounts of Al and F. Thermogravimetric analysis proves the mineral decomposes at 485°C with a mass loss of 7.6% compared with the theoretical mass loss of 7.7%. A strong Raman band at 852 cm(-1) is assigned to the SiO stretching vibration of the SiO3(OH) units. Two Raman bands at 914 and 953 cm(-1) are attributed to the antisymmetric vibrations. Intense prominent peaks observed at 3487, 3502, 3509, 3521 and 3547 cm(-1) are assigned to the OH stretching vibration of the SiO3(OH) units. The observation of multiple OH bands supports the concept of the non-equivalence of the OH units. Vibrational spectroscopy enables a det...

The mineral meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)] is a crystalline sodium calcium beryllium silicate which has the potential to be used as piezoelectric material and for other ferroelectric applications. The mineral has been characterized by a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and vibrational spectroscopy. EDS analysis shows a material with high concentrations of Si and Ca and low amounts of Na, Al and F. Beryllium was not detected. Raman bands at 1016 and 1050 cm(-1) are assigned to the SiO and AlOH stretching vibrations of three dimensional siloxane units. The infrared spectrum of meliphanite is very broad in comparison with the Raman spectrum. Raman bands at 472 and 510 cm(-1) are assigned to OSiO bending modes. Raman spectroscopy identifies bands in the OH stretching region. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral meliphanite.

Incipient sympatric speciation in blind mole rat, Spalax galili, in Israel, caused by sharp ecological divergence of abutting chalk-basalt ecologies, has been proposed previously based on mitochondrial and whole-genome nuclear DNA. Here, we present new evidence, including transcriptome, DNA editing, microRNA, and codon usage, substantiating earlier evidence for adaptive divergence in the abutting chalk and basalt populations. Genetic divergence, based on the previous and new evidence, is ongoing despite restricted gene flow between the two populations. The principal component analysis, neighbor-joining tree, and genetic structure analysis of the transcriptome clearly show the clustered divergent two mole rat populations. Gene-expression level analysis indicates that the population transcriptome divergence is displayed not only by soil divergence but also by sex. Gene ontology enrichment of the differentially expressed genes from the two abutting soil populations highlights reproduct...