Silicates

Hyperkalemia is a common electrolyte abnormality that may be difficult to manage because of a lack of effective therapies. Sodium zirconium cyclosilicate is a nonabsorbed cation exchanger that selectively binds potassium in the intestine. To evaluate the efficacy and safety of zirconium cyclosilicate for 28 days in patients with hyperkalemia. HARMONIZE was a phase 3, multicenter, randomized, double-blind, placebo-controlled trial evaluating zirconium cyclosilicate in outpatients with hyperkalemia (serum potassium ≥5.1 mEq/L) recruited from 44 sites in the United States, Australia, and South Africa (March-August 2014). Patients (n = 258) received 10 g of zirconium cyclosilicate 3 times daily in the initial 48-hour open-label phase. Patients (n = 237) achieving normokalemia (3.5-5.0 mEq/L) were then randomized to receive zirconium cyclosilicate, 5 g (n = 45 patients), 10 g (n = 51), or 15 g (n = 56), or placebo (n = 85) daily for 28 days. The primary end point was mean serum potassium...

This study was conducted to observe the rat subcutaneous connective tissue reaction to implanted dentin tubes that were filled with mineral trioxide aggregate, Sealapex, Calciobiotic Root Canal Sealer (CRCS), Sealer 26, and the experimental material, Sealer Plus. The animals were sacrificed after 7 and 30 days, and the specimens were prepared for histological analysis after serial sections with a hard-tissue microtome. The undecalcified sections were examined with polarized light after staining according to the Von Kossa technique for calcium. At the tube openings, there were Von Kossa-positive granules that were birefringent to polarized light. Next to these granulations, there was irregular tissue, like a bridge, that was Von Kossa-positive. The dentin walls of the tubes exhibited a structure highly birefringent to polarized light, usually like a layer, in the tubules. These results were observed with all the studied materials, except the CRCS, which didn't exhibit any kind of...

To evaluate the radiopacity, ultimate tensile strength (UTS), microhardness (KHN), degree of conversion (DC), water sorption (WS) and solubility (SL) of experimental adhesives. Five experimental adhesives with different concentrations of barium-borosilicate oxide microfillers [0% (R0), 30% (R30), 40% (R40), 50% (R50), 60% (R60)] were formulated based on the adhesive system Ambar (FGM). The adhesive Adper Single Bond 2 (SB, 3M ESPE) was used as commercial reference. For the radiopacity (n = 5), KHN (n = 5), WS (n = 10), and SL (n = 10) tests, adhesive disks were constructed (5.0 mm in diameter and 1.0 mm thick), while for UTS (n = 5), hourglass-shaped specimens with a cross-sectional area of 0.8 mm2 were used. The FTIR spectra of unpolymerized and polymerized adhesives were used to determine the DC. Data were submitted to a one-way ANOVA and Tukey's test (α = 0.05). All experimental adhesives showed radiopacity similar to enamel, except those of R0 and SB. Filler addition did not...

SUMMARY Objective This in vitro study evaluated the influence of different cleansing techniques on the bond strength of self-adhesive cement to dentin. Methods and Materials A total of 33 noncarious human molars were sectioned mesiodistally and embedded in chemically cured resin with the buccal or lingual surfaces facing upward. Superficial dentin was exposed and resin disk provisional restorations were cemented to the dentin surfaces with noneugenol provisional cement and were stored in distilled water at 37°C. After seven days, the provisional restorations were removed and 13 specimens were randomly assigned to each of the five groups (n=13), according to the following cleansing treatments: G1—excavator (control); G2—0.12% chlorhexidine digluconate; G3—40% polyacrylic acid; G4—mixture of flour pumice and water; and G5—sandblasting with 50 μm aluminum oxide particles at a pressure of 87 psi. Resin composite disks (Filtek Supreme Plus, 3M ESPE Dental Products, St Paul, MN, USA) 4.7 ...

A method is presented to prepare nanocrystalline α-Zn2SiO4 with the smallest crystal size reported so far for this system. Our approach combines the advantages of organometallic single-source precursor routes with aerosol processing techniques. The chemical design of the precursor enables the preferential formation of pure zinc silicates. Since gas-phase synthesis reduces intermolecular processes, and keeps the particles small, zinc silicate was synthesized from the volatile organometallic precursor [{MeZnOSiMe3}4], possessing a Zn-methyl- and O-silyl-substituted Zn4O4-heterocubane framework (cubane), under oxidizing conditions, using the chemical vapor synthesis (CVS) method. The products obtained under different process conditions and their structural evolution after sintering were investigated by using various analytical techniques (powder X-ray diffraction, transmission electron microscopy, EDX analysis, solid-state NMR, IR, Raman, and UV/Vis spectroscopy). The deposited aerosol obtained first (processing temperature 750 °C) was amorphous, and contained agglomerates with primary particles of 12 nm in size. These primary particles can be described by a [Zn-O-Si] phase without long-range order. The deposit obtained at 900 °C contained particles with embedded nanocrystallites (3–5 nm) of β-Zn2SiO4, Zn1.7SiO4, and ZnO in an amorphous matrix. On further ageing, the as-deposited particles obtained at 900 °C form α-Zn2SiO4 imbedded in amorphous SiO2. The crystallite sizes and primary particle sizes in the formed α-Zn2SiO4 were found to be below ∼50 nm and mainly spherical in morphology. A gas-phase mechanism for the particle formation is proposed. In addition, the solid-state reactions of the same precursor were studied in detail to investigate the fundamental differences between a gas-phase and a solid-state synthesis route.

Odontogenic ameloblast-associated protein (ODAM) has been shown to be specifically expressed in ameloblasts and odontoblasts and has been suggested to play a role in the mineralization of the enamel, possibly through the regulation of matrix metalloproteinase 20. However, its function in dentin is not clear. The purpose of this study was to evaluate the effect of ODAM on tertiary dentin formation. MDPC-23 odontoblastic cells were cultured, and the effect of recombinant ODAM (rODAM) on mineralized nodule formation was evaluated. Pinpoint pulp exposures were made in rat teeth and then capped with rODAM mixed with a carrier (rODAM group), carrier only (Carrier group), or white mineral trioxide aggregate (WMTA group). After 1, 2, and 4 weeks, odontoblasts and tertiary dentin were investigated histologically and immunohistochemically. Nodule formation in MDPC-23 cells was enhanced by rODAM treatment. Odontoblasts were polarized and showed a palisade arrangement in the remaining pulp from...

This study evaluated the effect of pumice prophylaxis on the level of microleakage around and between the sealant and enamel. A total of 32 freshly extracted sound upper first premolars, assigned as suitable for sealant application, were chosen and divided randomly into two groups: (1) a test group, without prophylaxis; and (2) a control group, with prophylaxis. Sealant was applied to all teeth using the same conventional technique, with prophylaxis being omitted in the test group. The sealed teeth were thermocycled (120 x 30 s, 5 and 55 degrees C cycles) and then immersed in 2% Basic Fuchsin solution for 72 h. Each tooth was sectioned and examined for dye penetration under a stereomicroscope (x 60 magnification). No dye penetration was seen in 19 (29.6%) of the teeth in the test group and 36 (56.2%) of the teeth in the control group. Dye had penetrated to the base of the fissure in 31 (48.4%) of the teeth in the test group and 23 (35.9%) of the teeth in the control group. Using a c...

To evaluate, using conventional in vitro procedures, the abrasivity, enamel polishing properties, and stain removal effectiveness of various commercial dentifrices that have a variety of compositions and are marketed for cleaning, whitening, and/or polishing capabilities, and to examine their relationships between stain removal and abrasivity. The Relative Dentin Abrasivity (RDA) method was used to measure abrasivity, and the Pellicle Cleaning Ratio (PCR) procedure was used to evaluate stain removal performance. A Cleaning Efficiency Index (CEI) was calculated using the RDA and PCR values. Enamel polish was determined on bovine enamel specimens using a reflectometer. All treatments were performed on a V-8 cross-brushing machine using aqueous dentifrice slurries and standard nylon-bristle toothbrushes. A total of 26 dentifrices, purchased at retail, were tested against the American Dental Association (ADA) calcium pyrophosphate reference standard. All dentifrices removed extrinsic st...

Aim  To compare the major constituents present in ProRoot mineral trioxide aggregate (MTA), ProRoot MTA (tooth coloured formula), ordinary Portland cement and white Portland cement using powder X-ray diffractometery.Methodology  X-ray diffractometery of the four materials was carried out with the divergence and scatter slits set at 1° and the receiving slit at 0.10 mm. The scan range was set at 5–70° and continuous scans for the θ–2θ range were run with a scan speed of 2° min−1. The patterns obtained were then compared with the Powder Diffraction Files (PDF) found in the International Centre for Diffraction Data database. The three strongest peaks were used for the identification of the constituents. The relative intensities were plotted against the angle 2θ and compared with the plots in the PDF.Results  The main constituents were found to be tricalcium silicate, tricalcium aluminate, calcium silicate, and tetracalcium aluminoferrite in all the four cements with the additional presence of Bi2O3 in ProRoot MTA and ProRoot MTA (tooth coloured formula).Conclusions  The four cements had similar major constituents. Data on Portland cement may be used for the further development or modification of ProRoot MTA in order to improve its physical characteristics and expand its scope of clinical applications.

The aim of this research was to evaluate the fatigue behavior and reliability of monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate and hand-layer-veneered zirconia all-ceramic crowns. A CAD-based mandibular molar crown preparation, fabricated using rapid prototyping, served as the master die. Fully anatomically shaped monolithic lithium disilicate crowns (IPS e.max CAD, n = 19) and hand-layer-veneered zirconia-based crowns (IPS e.max ZirCAD/Ceram, n = 21) were designed and milled using a CAD/CAM system. Crowns were cemented on aged dentinlike composite dies with resin cement. Crowns were exposed to mouth-motion fatigue by sliding a WC-indenter (r = 3.18 mm) 0.7 mm lingually down the distobuccal cusp using three different step-stress profiles until failure occurred. Failure was designated as a large chip or fracture through the crown. If no failures occurred at high loads (> 900 N), the test method was changed to staircase r ratio fatigue....