silicon and hexamethyldisiloxane

The purpose of this study was twofold: 1) to characterize the zirconia (Y-TZP) surfaces through scanning electronic microscopy associated with energy-dispersive spectroscopy and atomic force microscopy after the deposition of a thin organosilicon film by nonthermal plasma (NTP) treatment, and 2) to determine the zirconia surface hydrophilicity, before and after aging, through surface energy analysis.. Surfaces of 16 zirconia disks (10 x 3 mm) were treated for 30 min each with hexamethyldisiloxane and argon plasmas, followed by oxygen plasma. Disks were analyzed before NTP treatment, immediately after NTP treatment, and after aging for 7, 15, and 30 days. The surface energy of the Y-TZP disks was measured with a goniometer. Quantitative data were submitted to statistical analysis using ANOVA and Tukey's test (p < 0.05).. Immediately after NTP treatment, the surface energy of the zirconia disks was significantly higher than at any other tested period (p < 0.001), and the water contact angle on the zirconia disks was reduced to 0 degrees. Similar surface energy results were obtained before NTP treatment and after 15 or 30 days of aging (p > 0.05; Tukey's test). Energy-dispersive spectroscopy results revealed the presence of carbon, oxygen, and silicon on the surface after NTP treatment.. NTP treatment was useful for treating the zirconia surface for cementation procedures, as it produced a high level of hydrophilicity on the zirconia surface. However, this high level of hydrophilicity did not persist after aging.

Topics: Air; Argon; Carbon; Coated Materials, Biocompatible; Humans; Hydrophobic and Hydrophilic Interactions; Materials Testing; Microscopy, Atomic Force; Microscopy, Electron, Scanning; Oxygen; Plasma Gases; Silicon; Siloxanes; Spectrometry, X-Ray Emission; Surface Properties; Surface Tension; Time Factors; Wettability; Yttrium; Zirconium

Surface transformation with nonthermal plasma may be a suitable treatment for dental ceramics, because it does not affect the physical properties of the ceramic material.. The purpose of this study was to characterize the chemical composition of lithium disilicate ceramic and evaluate the surface of this material after nonthermal plasma treatment.. A total of 21 specimens of lithium disilicate (10 mm in diameter and 3 mm thick) were fabricated and randomly divided into 3 groups (n=7) according to surface treatment. The control group was not subjected to any treatment except surface polishing with abrasive paper. In the hydrofluoric acid group, the specimens were subjected to hydrofluoric acid gel before silane application. Specimens in the nonthermal plasma group were subjected to the nonthermal plasma treatment. The contact angle was measured to calculate surface energy. In addition, superficial roughness was measured and was examined with scanning electron microscopy, and the chemical composition was characterized with energy-dispersive spectroscopy analysis. The results were analyzed with ANOVA and the Tukey honestly significant difference test (α=.05).. The water contact angle was decreased to 0 degrees after nonthermal plasma treatment. No significant difference in surface roughness was observed between the control and nonthermal plasma groups. Scanning electron microscopy and energy-dispersive spectroscopy images indicated higher amounts of oxygen (O) and silicon (Si) and a considerable reduction in carbon (C) in the specimens after nonthermal plasma treatment.. Nonthermal plasma treatment can transform the characteristics of a ceramic surface without affecting its surface roughness. A reduction in C levels and an increase in O and Si levels were observed with the energy-dispersive spectroscopy analysis, indicating that the deposition of the thin silica film was efficient.

Topics: Acid Etching, Dental; Argon; Carbon; Ceramics; Dental Polishing; Dental Porcelain; Hot Temperature; Humans; Hydrofluoric Acid; Materials Testing; Microscopy, Electron, Scanning; Oxygen; Plasma Gases; Random Allocation; Silanes; Silicon; Silicon Dioxide; Siloxanes; Spectrometry, X-Ray Emission; Surface Properties; Surface Tension; Time Factors; Wettability

Biotransformations make use of biological systems to catalyze or promote specific chemical reactions. Transformations that utilize enzymes as "greener" and milder catalysts compared to traditional reaction conditions are of particular interest. Recently, organosilicon compounds have begun to be explored as non-natural enzymatic substrates for biotransformations. The aims of this study were to screen readily available (approximately eighty) enzymes for their ability to catalyze in vitro siloxane bond formation under mild reaction conditions using a model monoalkoxysilane as the substrate and to make a preliminary evaluation of potential factors that might lead to activity or inactivity of a particular enzyme. Several new hydrolase enzymes were observed to catalyze the formation of the condensation product when compared to peptide controls, or buffer solutions at the same pH, as judged from quantitative analyses by gas chromatography. Aspergillus ficuum phytase, Aspergillus niger phytase, chicken egg white lysozyme, porcine gastric mucosa pepsin, and Rhizopus oryzae lipase all catalyzed the condensation of silanols in aqueous media. Factors involved in determining the activity of an enzyme towards silanol condensation appear to include: the presence of imidazole and hydroxyl functions in the active site; solvent; the presence of water; the surface properties of the enzyme; possible covalent inhibition; and steric factors in the substrate.

Topics: Animals; Aspergillus; Chickens; Humans; Hydrogen-Ion Concentration; Hydrolases; Hydrolysis; Oxygen; Rhizopus; Silicon; Siloxanes; Solvents; Swine