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    ABSTRACT: Objective: This study investigated the mechanism of action at the interface between a commercially available Y-TZP and its veneering ceramic after final firing. Particular attention was paid, from a microstructural point of view, to evaluating the effects of different surface treatments carried out on the zirconia. Methods: In total, 32 specimens of presintered zirconia Y-TZP (LavaFrame, 3M ESPE, Germany) were cut with a low-speed diamond blade. The specimens were divided in two major groups, for testing after fracture or after mirror finishing, and were sintered following the manufacturer's instructions. Each major group was then randomly divided into four subgroups, according to using or not using the dedicated framework modifier, with or without a preliminary silica coating (CoJet, 3 M ESPE). A suitable veneering ceramic was used for each group (Lava Ceram Overlay Porcelain, 3 M ESPE). A detailed microstructural study of the interfaces of the zirconia-veneering ceramic was performed using a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer to evaluate chemical variation at the interfaces. Results: When the framework modifier was not applied on the Y-TZP surface, microdetachments, porosities, and openings in the ceramic layer were observed at the interlayers. A degree of diffusion of different elements through the interfaces from both the zirconia and veneering layers was detected. Conclusions: Application of the framework modifier can increase the wettability of the zirconia surfaces, allowing a continuous contact with the veneering layer. The microanalysis performed showed the presence of a reaction area at the interface between the different materials. Clinical significance: the increase of the wettability of the zirconia surface could improve the adhesion at interface with the veneering ceramic and reduce the clinical failure as chipping or delamination.
    No preview · Article · Aug 2014 · Dental Materials
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    ABSTRACT: Intellectual disability in Down syndrome (DS) appears to be related to severe neurogenesis impairment during brain development. The molecular mechanisms underlying this defect are still largely unknown. Accumulating evidence has highlighted the importance of GSK3β signaling for neuronal precursor proliferation/differentiation. In neural precursor cells (NPCs) from Ts65Dn mice and human fetuses with DS, we found reduced GSK3β phosphorylation and, hence, increased GSK3β activity. In cultures of trisomic subventricular-zone-derived adult NPCs (aNPCs) we found that deregulation of GSK3β activity was due to higher levels of the AICD fragment of the trisomic gene APP that directly bound to GSK3β. We restored GSK3β phosphorylation in trisomic aNPCs using either lithium, a well-known GSK3β inhibitor, or using a 5-HT receptor agonist or fluoxetine, which activated the serotonin receptor 5-HT1A. Importantly, this effect was accompanied by restoration of proliferation, cell fate specification and neuronal maturation. In agreement with results obtained in vitro, we found that early treatment with fluoxetine, which was previously shown to rescue neurogenesis and behavior in Ts65Dn mice, restored GSK3β phosphorylation. These results provide a link between GSK3β activity alteration, APP triplication and the defective neuronal production that characterizes the DS brain. Knowledge of the molecular mechanisms underlying neurogenesis alterations in DS may help to devise therapeutic strategies, potentially usable in humans. Results suggest that drugs that increase GSK3β phosphorylation, such as lithium or fluoxetine, may represent useful tools for the improvement of neurogenesis in DS.
    Full-text · Article · Jul 2014 · Neurobiology of Disease
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    ABSTRACT: Objectives This literature review summarizes the main aspects involved in the process of adhesion to enamel and dentin and focuses the reader's attention on the evolution of self-etch systems, highlighting their chemical and bond properties and applications in the clinical practice. Materials and methods An online search of keywords on the PubMed database was performed to search for scientific articles (reviews, original articles) published in recent years regarding self-etch adhesives. Results Multiple laboratory and clinical studies described adhesion mechanisms of self-etch adhesives. The majority of these publications found a higher bond quality of self-etch adhesive to dentin, while the bond to enamel remained questionable, especially for single step adhesives. Conclusions The self-etch technique is considered a valid dental adhesion approach from a restorative standpoint.
    No preview · Article · Jun 2014 · Dental Cadmos
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