Effect of Different Cements on the Biomechanical Behavior of Teeth Restored with Cast Dowel‐and‐Cores—In Vitro and FEA Analysis

Purpose: To test the hypothesis that the type of cement used for fixation of cast dowel‐and‐cores might influence fracture resistance, fracture mode, and stress distribution of single‐rooted teeth restored with this class of metallic dowels. Materials and Methods: The coronal portion was removed from 40 bovine incisors, leaving a 15 mm root. After endodontic treatment and standardized root canal relief at 10 mm, specimens were embedded in polystyrene resin, and the periodontal ligament was simulated with polyether impression material. The specimens were randomly divided into four groups (n = 10), and restored with Cu–Al cast dowel‐and‐cores cemented with one of four options: conventional glass ionomer cement (GI); resin‐modified glass ionomer cement (GR); dual‐cure resin cement (RC); or zinc‐phosphate cement (ZP). Sequentially, fracture resistance of the specimens was tested with a tangential load at a 135° angle with a 0.5 mm/min crosshead speed. Data were analyzed using one‐way analysis of variance (ANOVA) and the Fisher test. Two‐dimensional finite element analysis (2D‐FEA) was then performed with representative models of each group simulating a 100 μm cement layer. Results were analyzed based on von Mises stress distribution criteria. Results: The mean fracture resistance values were (in N): RC, 838.2 ± 135.9; GI, 772.4 ± 169.8; GR, 613.4 ± 157.5; ZP, 643.6 ± 106.7. FEA revealed that RC and GR presented lower stress values than ZP and GI. The higher stress concentration was coincident with more catastrophic failures, and consequently, with lower fracture resistance values. Conclusions: The type of cement influenced fracture resistance, failure mode, and stress distribution on teeth restored with cast dowel‐and‐cores.     

Differential sensitivities of the NCX1.1 and NCX1.3 isoforms of the Na+-Ca2+ exchanger to alpha-linolenic acid

OBJECTIVE: Dietary intake of omega-3 polyunsaturated fatty acids (PUFA) like alpha-linolenic acid (ALA) is antiarrhythmic and cardioprotective. PUFA may also be beneficial in hypertension. Altered Na(+)-Ca(2+) exchanger (NCX) activity has been implicated in arrhythmias, hypertension and heart failure and may be a target for PUFA. Thus, we tested the effects of ALA and other distinct fatty acids on the cardiac (NCX1.1) and vascular (NCX1.3) NCX isoforms. METHODS: HEK293 cells stably expressing NCX isoforms were ramped from +60 to -100 mV (over 1600 ms) in the absence and presence of 25 microM oleic acid (OA, omega-9), linoleic acid (LA, omega-6), ALA (omega-3), or eicosapentaenoic acid (EPA, omega-3). NiCl(2) (5 mM) was used to inhibit and therefore identify the NCX current. The effect of 25 microM ALA on NCX1.1 and NCX1.3 activity was also assessed in adult rat ventricular cardiomyocytes and rabbit aortic vascular smooth muscle cells (VSMC) by measuring [Ca(2+)](i) following substitution of [Na(+)](o) with Li(+). RESULTS: Application of Ni(2+) had no effect in non-transfected cells. ALA and EPA (25 microM) reduced the Ni(2+)-sensitive forward NCX1.1 current (at -100 mV) by 64% and reverse current (at +60 mV) by 57%, and inhibited the Ni(2+)-sensitive NCX1.3 forward and reverse currents by 79% and 76%, respectively. Neither OA nor LA (25 microM) affected the NCX1.1 currents, but both partially inhibited the forward and reverse mode NCX1.3 currents. Inhibition of NCX1.3 by ALA occurred at a much lower IC(50) ( approximately 19 nM) than for NCX1.1 ( approximately 120 nM). In cardiomyocytes and VSMC, ALA significantly reduced the Li(+)-induced rise in intracellular [Ca(2+)]. CONCLUSIONS: NCX1.3 is more sensitive to inhibition by ALA than NCX1.1. In addition, only omega-3 PUFA inhibits NCX1.1, but several classes of fatty acids inhibit NCX1.3. The differential sensitivity of NCX isoforms to fatty acids may have important implications as therapeutic approaches for hypertension, heart failure and arrhythmias.     

Colony-stimulating factors: clinical evidence for treatment and prophylaxis of chemotherapy-induced febrile neutropenia

The hematopoietic growth factors (HGFs) are a family of glycoproteins which plays a major role in the proliferation, differentiation, and survival of primitive hematopoietic stem and progenitor cells, and in the functions of some mature cells. More than 20 different molecules of HGF have been identified. Among them, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) have been demostrated to be effective in reducing the incidence of febrile neutropenia when administered inmediately after chemotherapy and as supportive therapy in patients undergoing bone marrow transplantation. Chemotherapy used for treatment of cancer often causes neutropenia, which may be profound, requiring hospitalization, and leading to potentially fatal infection. The uses of the recombinant human hematopoietic colony-stimulating factors G-CSF and GM-CSF for treatment and prophylaxis of chemotherapy-induced febrile neutropenia will be reviewed here.     

枳■子黄酮类成分研究

从北枳（ＨｏｖｅｎｉａｄｕｌｃｉｓＴｈｕｎｂ）种子中首次分离并鉴定了４个黄酮类化合物，即双氢山奈酚（ｄｉｈｙｄｒｏｋａｅｍｐｆｅｒｏｌＩ）、槲皮素（ｑｕｅｒｃｅｔｉｎＩＩ）、（＋）３，３′，５′，５，７五羟基双氢黄酮［（＋）３，３′，５′，５，７ｐｅｎｔａｈｙｄｒｏｆｌａｖａｎｏｎｅＩＩ］和（＋）双氢杨梅黄素［（＋）ｄｉｈｙｄｒｏｍｙｒｉｃｅｔｉｎＩＶ］。其中ＩＩ为新化合物，Ｉ和ＩＶ为首次从该属植物中分到。