Method of Preparation for High-Purity Nanocrystalline Anhydrous Cesium Perrhenate
This paper is devoted to the preparation of high-purity anhydrous nanocrystalline cesium perrhenate, which is applied in catalyst preparation. It was found that anhydrous cesium perrhenate with a crystal size <45 nm can be obtained using cesium ion sorption and elution using aqueous solutions of perrhenic acid with subsequent crystallisation, purification, and drying. The following composition of the as-obtained product was reported: 34.7% Cs; 48.6% Re and <2 ppm Bi; <3 ppm Zn; <2 ppm As; <10 ppm Ni; < 3 ppm Mg; <5 ppm Cu; <5 ppm Mo; <5 ppm Pb; <10 ppm K; <2 ppm Na; <5 ppm Ca; <3 ppm Fe.
Crystal Structure of β‐CsReO4, the Room‐Temperature Modification of Cesium Perrhenate.
The crystal structure o f /?-CsRe04, the roomtemperature modification o f cesium perrhenate, was determined from single-crystal X-ray data as orthorhombic, space group Pnma, a = 5.7556(9), b = 5.9964(8), c = 14.310(2) Ä and Z = 4. The structure was refined to R = 0.027, /?w = 0.023 for 779 absorption-corrected reflections. It represents an orthorhombic distortion o f the te­ tragonal high-temperature phase a -C sR e04. The structure o f /?-CsRe04 comprises isolated R e0 4 tetrahedra, linked together by Cs ions. The aver­ age R e -O distance was found to be 1.714(4) Ä.
Efficacy of Biodentine as an Apical Plug in Nonvital Permanent Teeth with Open Apices: An In Vitro Study
The aim of this study was to evaluate the apical microleakage of Biodentine and MTA orthograde apical plugs and to compare the effect of thickness of these biomaterials on their sealing ability. A total of eighty maxillary anterior teeth were used. The apices were removed by cutting with a diamond disc (Jota, Germany) 2 mm from the apical root end in an attempt to standardize the working length of all specimens to 15 ± 1 mm. Both materials were placed in 1–4 mm thickness as apical plugs root canal. Root canal leakage was evaluated by the fluid filtration technique. One-way ANOVA was used in order to determine normality of dispersal distribution of parameters; thereafter, results were analyzed by Kolmogorov-Smirnov test. Overall, between microleakage values of MTA and Biodentine regardless of apical plug thickness, no difference was observed. In terms of plug thickness, a statistically significant difference was observed between the subgroups of MTA and Biodentine (p < 0.05). The apical sealing ability of Biodentine was comparable to MTA at any apical plug thickness.