Influence of pH, bleaching agents, and acid etching on surface wear of bovine enamel

ABSTRACT Development of new materials for tooth bleaching justifies the need for studies to evaluate the changes in the enamel surface caused by different bleaching protocols. Objective The aim of this study was to evaluate the bovine dental enamel wear in function of different bleaching gel protocols, acid etching and pH variation. Material and Methods Sixty fragments of bovine teeth were cut, obtaining a control and test areas. In the test area, one half received etching followed by a bleaching gel application, and the other half, only the bleaching gel. The fragments were randomly divided into six groups (n=10), each one received one bleaching session with five hydrogen peroxide gel applications of 8 min, activated with hybrid light, diode laser/blue LED (HL) or diode laser/violet LED (VHL) (experimental): Control (C); 35% Total Blanc Office (TBO35HL); 35% Lase Peroxide Sensy (LPS35HL); 25% Lase Peroxide Sensy II (LPS25HL); 15% Lase Peroxide Lite (LPL15HL); and 10% hydrogen peroxide (experimental) (EXP10VHL). pH values were determined by a pHmeter at the initial and final time periods. Specimens were stored, subjected to simulated brushing cycles, and the superficial wear was determined (μm). ANOVA and Tukey´s tests were applied (α=0.05). Results The pH showed a slight decrease, except for Group LPL15HL. Group LPS25HL showed the highest degree of wear, with and without etching. Conclusion There was a decrease from the initial to the final pH. Different bleaching gels were able to increase the surface wear values after simulated brushing. Acid etching before bleaching increased surface wear values in all groups

Usefulness of susceptibility-weighted imaging for voxel placement in MR spectroscopy

MR spectroscopy is used to provide in vivo biochemical information about cerebral metabolites. Magnetic field homogeneity secondary to anatomic interfaces, hemorrhage, or necrosis may lead to suboptimal MR spectroscopy. Susceptibility-weighted imaging (SWI) can identify field inhomogeneity and could be used to guide MR spectroscopy voxel placement, leading to higher-quality MR spectroscopy examinations

Assessing the Potential Roles of Silicon and Germanium Phthalocyanines in Planar Heterojunction Organic Photovoltaic Devices and How Pentafluoro Phenoxylation Can Enhance π–π Interactions and Device Performance

In this study, we have assessed the potential application of dichloro silicon phthalocyanine (Cl₂-SiPc) and dichloro germanium phthalocyanine (Cl₂-GePc) in modern planar heterojunction organic photovoltaic (PHJ OPV) devices. We have determined that Cl₂-SiPc can act as an electron donating material when paired with C₆₀ and that Cl₂-SiPc or Cl₂-GePc can also act as an electron acceptor material when paired with pentacene. These two materials enabled the harvesting of triplet energy resulting from the singlet fission process in pentacene. However, contributions to the generation of photocurrent were observed for Cl₂-SiPc with no evidence of photocurrent contribution from Cl₂-GePc. The result of our initial assessment established the potential for the application of SiPc and GePc in PHJ OPV devices. Thereafter, bis­(pentafluoro phenoxy) silicon phthalocyanine (F₁₀-SiPc) and bis­(pentafluoro phenoxy) germanium phthalocyanine (F₁₀-GePc) were synthesized and characterized. During thermal processing, it was discovered that F₁₀-SiPc and F₁₀-GePc underwent a reaction forming small amounts of difluoro SiPc (F₂-SiPc) and difluoro GePc (F₂-GePc). This undesirable reaction could be circumvented for F₁₀-SiPc but not for F₁₀-GePc. Using single crystal X-ray diffraction, it was determined that F₁₀-SiPc has significantly enhanced π–π interactions compared with that of Cl₂-SiPc, which had little to none. Unoptimized PHJ OPV devices based on F₁₀-SiPc were fabricated and directly compared to those constructed from Cl₂-SiPc, and in all cases, PHJ OPV devices based on F₁₀-SiPc had significantly improved device characteristics compared to Cl₂-SiPc