Effect of Silyl Ether Bulk on Excited-State Intramolecular Proton Transfer-Based Sensing of Extant Hydrogen Fluoride for G-Series Nerve Agent Detection.

Luminescence-based sensing provides a method for the rapid detection of nerve agents. Previous approaches have generally focused on sensing materials containing a nucleophilic group that can react with the electrophilic phosphorus atom found in nerve agents. Herein we report an alternative approach for the detection of phosphonofluoridate-based G-series nerve agents that utilizes the fact they contain hydrogen fluoride. We have developed silylated sensing materials based on an excited-state intramolecular proton transfer (ESIPT) reporter compound, 2-[benzo[d]thiazol-2-yl]phenol. Thin films of differently silylated 2-[benzo[d]thiazol-2-yl]phenol were found to react with the hydrogen fluoride found in di-iso-propyl fluorophosphate (DFP), a simulant of sarin (G-series nerve agent), and turn on the ESIPT emission of the reporter compound. The use of the ESIPT emission reduced the impact of background fluorescence and improved the sensitivity of the detection. The effectiveness of the approach was dependent on the stability of the silyl protecting group used, with the least sterically hindered (trimethylsilyl) found to be too unstable to the ambient environment while the most sterically hindered, e.g., tri-iso-propylsilyl and tert-butyldiphenylsilyl were found to be insufficiently reactive to be useful in a real detection scenario. The sensing material composed of the tert-butyl dimethylsilyl protected 2-[benzo[d]thiazol-2-yl]phenol was found to have the best balance between stability under ambient conditions, and reactivity and selectivity to hydrogen fluoride. In a 3 s exposure, it could detect hydrogen fluoride down to a concentration of around 23 ppm in DFP with 99% purity.

Biocompatibility Analyses of HF-Passivated Magnesium Screws for Guided Bone Regeneration (GBR).

Background: Magnesium (Mg) is one of the most promising materials for human use in surgery due to material characteristics such as its elastic modulus as well as its resorbable and regenerative properties. In this study, HF-coated and uncoated novel bioresorbable magnesium fixation screws for maxillofacial and dental surgical applications were investigated in vitro and in vivo to evaluate the biocompatibility of the HF coating. Methods: Mg alloy screws that had either undergone a surface treatment with hydrofluoric-acid (HF) or left untreated were investigated. In vitro investigation included XTT, BrdU and LDH in accordance with the DIN ISO 10993-5/-12. In vivo, the screws were implanted into the tibia of rabbits. After 3 and 6 weeks, degradation, local tissue reactions and bony integration were analyzed histopathologically and histomorphometrically. Additionally, SEM/EDX analysis and synchrotron phase-contrast microtomography (µCT) measurements were conducted. The in vitro analyses revealed that the Mg screws are cytocompatible, with improved results when the surface had been passivated with HF. In vivo, the HF-treated Mg screws implanted showed a reduction in gas formation, slower biodegradation and a better bony integration in comparison to the untreated Mg screws. Histopathologically, the HF-passivated screws induced a layer of macrophages as part of its biodegradation process, whereas the untreated screws caused a slight fibrous tissue reaction. SEM/EDX analysis showed that both screws formed a similar layer of calcium phosphates on their surfaces and were surrounded by bone. Furthermore, the µCT revealed the presence of a metallic core of the screws, a faster absorbing corrosion front and a slow absorbing region of corroded magnesium. Conclusions: Overall, the HF-passivated Mg fixation screws showed significantly better biocompatibility in vitro and in vivo compared to the untreated screws.

Synthesis of Densely Immobilized Gold-Assembled Silica Nanostructures.

In this study, dense gold-assembled SiO2 nanostructure (SiO2@Au) was successfully developed using the Au seed-mediated growth. First, SiO2 (150 nm) was prepared, modified by amino groups, and incubated by gold nanoparticles (ca. 3 nm Au metal nanoparticles (NPs)) to immobilize Au NPs to SiO2 surface. Then, Au NPs were grown on the prepared SiO2@Au seed by reducing chloroauric acid (HAuCl4) by ascorbic acid (AA) in the presence of polyvinylpyrrolidone (PVP). The presence of bigger (ca. 20 nm) Au NPs on the SiO2 surface was confirmed by transmittance electronic microscopy (TEM) images, color changes to dark blue, and UV-vis spectra broadening in the range of 450 to 750 nm. The SiO2@Au nanostructure showed several advantages compared to the hydrofluoric acid (HF)-treated SiO2@Au, such as easy separation, surface modification stability by 11-mercaptopundecanoic acid (R-COOH), 11-mercapto-1-undecanol (R-OH), and 1-undecanethiol (R-CH3), and a better peroxidase-like catalysis activity for 5,5'-Tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) reaction. The catalytic activity of SiO2@Au was two times better than that of HF-treated SiO2@Au. When SiO2@Au nanostructure was used as a surface enhanced Raman scattering (SERS) substrate, the signal of 4-aminophenol (4-ATP) on the surface of SiO2@Au was also stronger than that of HF-treated SiO2@Au. This study provides a potential method for nanoparticle preparation which can be replaced for Au NPs in further research and development.

A Shortcut to the Synthesis of Peptide Thioesters.

Peptide thioesters serve as fundamental building blocks for the synthesis of proteins and cyclic peptides. Classically, methods to synthesize thioesters have been based on acid-labile amino-protecting groups for which final side-chain deprotection required the use of hazardous hydrogen fluoride (HF). Alternative protection schemes based on base-labile amino-protecting groups have become preferred methods but are not suitable due to the lability of thioester bonds toward bases. In this method, we employ a trifluoracetic acid/trimethylsilyl bromide (TFA/TMSBr) protocol using a hydroxymethyl resin obviating the need for HF. TFA/TMSBr is volatile enough to be easily removed yet less hazardous than HF, making it more practical for general peptide chemists. We describe optimized cleavage procedures and appropriate protecting group schemes and discuss in situ neutralization protocols. The method is relatively simple, straightforward, and easily scalable, allowing the facile preparation of alkyl and aryl thioesters.

Hydrofluoric acid and nitric acid cotreatment for biofunctionalization of polyetheretherketone in M2 macrophage polarization and osteogenesis.

Due to its excellent mechanical and low-friction properties, polyetheretherketone (PEEK) has been widely investigated for use in orthopedic applications over the past decade. However, the bioinertness and poor osteogenic properties of PEEK have hampered its clinical application. In this study, the surface of PEEK was modified by co-treatment with hydrofluoric acid and nitric acid (AFN). The microstructures of the modified PEEK surfaces were investigated using scanning electron microscopy. The water contact angles of the surfaces were also measured. To evaluate their cytocompatibility, PEEK samples were used as substrates to culture rat bone mesenchymal stem cells, and cell adhesion, viability, and expression of specific marker genes were measured. Treatment of PEEK with AFN (PEEK-AFN) was found to enable better osteoblast adhesion, spreading, and proliferation; the activity of alkaline phosphatase (an early osteogenic differentiation marker) was also found to be enhanced post-treatment. Furthermore, PEEK-AFN was able to modulate macrophage polarization and down regulated the expression of proinflammatory factors via inhibiting the NF-κB pathway. Thus, treatment of PEEK with AFN could promote M2 polarization of the macrophages and stimulate the differentiation of osteoblasts. These results provide valuable information that could facilitate the use of PEEK-based composites as bone implant materials.

Anhydrous Hydrogen Fluoride Cleavage in Boc Solid Phase Peptide Synthesis.

Solid phase peptide synthesis using tert-butyloxycarbonyl/benzyl chemistry (Boc-SPPS) is important for producing peptides for fundamental research as well as for clinical use. During Boc-SPPS, liquid anhydrous hydrogen fluoride (HF) is used to remove the side chain protecting groups of the assembled peptide and to release it from the resin. Here, we provide a detailed protocol for "HF cleavage," aiming to improve accessibility and the use of this valuable and well-validated technique.

Hydrofluoric acid concentration, time and use of phosphoric acid on the bond strength of feldspathic ceramics

Abstract The objective of this study was to evaluate the influence of hydrofluoric acid (HF) concentration, etching time, and application of phosphoric acid (PA) followed by neutralization with sodium bicarbonate on the bond strength between a feldspar ceramic and resin cement. Thus, 80 blocks (10 x 12 x 2 mm) of glass ceramic (VM - Vita Mark II - Vita Zahnfabrik) were made and randomly assigned to eight groups (n = 10) according to the factors: HF concentration (5 and 10%), etching time (60 and 120 s), and use of phosphoric acid (PA) (with and without). According to the experimental group, 37% PA (Condac, FGM) was applied after HF etching for 60s. Afterwards, samples were immersed in sodium bicarbonate for 1 min then in an ultrasonic bath in distilled water (5 min) for cleaning. After surface bonding treatment, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block. The samples were then stored in water (37ºC) for 90 days and submitted to the shear bond test (50 KgF, 1 mm/min). Failure analysis was performed by stereomicroscope and scanning electron microscopy. Data (MPa) were analyzed with 3-way ANOVA and Tukey's test. Only the factor "HF concentration" was significant (p = 0.02). Most failures were of cohesive in ceramic (40%) and mixed types (42.5%). The 10% HF resulted in higher shear bond strength value than the 5% HF. Surface cleaning with phosphoric acid followed by sodium bicarbonate and HF time (60 or 120 seconds) did not influence the resin bond strength to feldspar ceramic.

Enhancement of light aromatics from catalytic fast pyrolysis of cellulose over bifunctional hierarchical HZSM-5 modified by hydrogen fluoride and nickel/hydrogen fluoride.

Pore structure and accessible active sites of HZSM-5 (Z5) are the key factors for its catalysis. The bifunctional hierarchical Z5 were prepared with leaching agent HF and loading Ni, and their performance for catalytic fast pyrolysis (CFP) of cellulose was investigated in a drop tube quartz reactor. Z5 modified with 0.5 mol/L HF (0.5F-Z5) showed excellent light aromatics (LAs) yield, which can be attributed to the enhancement in the small mesopores (2-10 nm) and the decrease of Brønsted acid sites during dealumination. Simultaneously, the loading of a 1 wt% Ni produced more LAs than 0.5F-Z5, due to the improvement in deoxidation/hydrogenation reactions. The highest LAs yield (31.3%) was obtained over 1%Ni-0.5 mol/LHF-Z5, which increased by 44.9% compared to the parent Z5. In addition, the reaction routes over different active centers and acid-catalyzed reactions were analyzed, based upon the composition of bio-oils and catalyst characterization.

Effect of hydrofluoric acid concentration and etching time on resin-bond strength to different glass ceramics

Abstract: The objective of this study was to evaluate the effect of the hydrofluoridric acid (HF) concentration and time of acid conditioning on bond strength of three glass ceramics to a resin cement. Thus, fifty blocks (10 mm x 5 mm x 2 mm) of each ceramic (LDCAD: IPS e.max CAD; LCAD: IPS Empress CAD and LDHP: IPS e.max Press) were made and embedded in acrylic resin. The surfaces were polished with sandpaper (#600, 800, 1000, and 1200 grits) and blocks were randomly divided into 15 groups (n = 10) according to the following factors: Concentration of HF (10% and 5%), conditioning time (20 s and 60 s) and ceramic (LDCAD, LDHP, and L). After conditioning, silane (Prosil / FGM) was applied and after 2 min, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block using a Teflon strip as matrix and light cured for 40 s (1,200 mW/cm2). Then, the samples were thermocycled (10,000 cycles, 5/55°C, 30s) and submitted to the shear bond test (50 KgF, 0.5 mm/min). The data (MPa) were analyzed with 3-way ANOVA and Tukey's test (5%). Failure analysis was performed using a stereomicroscope (20x) and a scanning electron microscope (SEM). ANOVA revealed that the "concentration" factor (p = 0.01) and the interaction "acid concentration X ceramic" (p = 0.009) had a significant effect, however, the "ceramic" (p = 0.897) and "conditioning time" (p = 0.260) factors did not influence the results. The LDHP10%60s (10.98 MPa)aA* group presented significantly higher bond strength than LDHP10%20s (6.57 MPa)bA, LCAD5%20s (6,90 ±3,5)aB and LDHP5%60s (5.66 ± 2,9MPa)aA* groups (Tukey). Failure analysis revealed that 100% of specimens had mixed failure. In conclusion, etching with 5% HF for 20 seconds is recommended for lithium disilicate and leucite-reinforced CAD/CAM ceramics. However, for pressed lithium disilicate ceramic, 10% HF for 60 s showed significantly higher bond strength to resin cement.

Shear Bond Strength of Different CAD/CAM Ceramics: Acid vs Er:YAG Laser Etching.

OBJECTIVE: To evaluate whether Er:YAG laser etching could be an alternative surface treatment to hydrofluoric (HF) acid etching. BACKGROUND: Surface treatment is important to bonding properties and utility times of computer aided design/computer aided manufacture (CAD/CAM) dental ceramics. The traditional method of HF acid etching is harmful to humans if not handled properly. MATERIALS AND METHODS: Four different CAD/CAM ceramics (Vita Mark II, IPS Empress CAD, IPS e.max CAD, and Vita Enamic) were cut into 72 blocks and divided into 6 groups according to different surface treatments (n = 12): Group A: no treatment; Group B: HF acid; and Group C to F: different Er:YAG laser power settings (300, 400, 500, and 600 mJ). Ten blocks of each group were measured for shear bond strength (SBS) and the failure modes were evaluated; the rest blocks were observed by scanning electronic microscopy (SEM). RESULTS: HF acid etching resulted in the highest SBS for Vita Mark II, IPS Empress CAD, and Vita Enamic; however, the difference was not statistically significant (p > 0.05) compared to the second highest group of laser with 600 mJ in IPS Empress CAD. For IPS e.max CAD, the highest SBS was obtained from laser group with 400 mJ. The SBS results were consistent with failure modes and surface characterizations in SEM images. CONCLUSIONS: Our results showed that Er:YAG laser had little impact on Vita Mark II and Vita Enamic; but proper power settings could be an alternative surface treatment to HF acid etching (600 mJ for IPS Empress CAD and 400 mJ for IPS e.max CAD).

Adhesion to a lithium disilicate glass ceramic etched with hydrofluoric acid at distinct concentrations

Abstract This study evaluated the effect of different hydrofluoric acid (HF) concentrations on the bond strength between a lithium disilicate-based glass ceramic and a resin cement. Eighty ceramic-blocks (12×7×2 mm) of IPS e.Max CAD (Ivoclar Vivadent) were produced and randomly assigned to 8 groups, considering 2 study factors: HF concentration in 4 levels, i.e., 1% (HF1), 3% (HF3), 5% (HF5), and 10% (HF10), and storage in 2 levels, i.e., baseline (tests were performed 24 h after cementation), and aged (storage for 150 days + 12,000 thermal-cycles at 5°C and 55°C). Acid etching (20 s) was performed, followed by washing, drying, and silanization. Four resin cement cylinders (ϕ= 0.96 mm) were built-up from starch matrices on each ceramic sample (n= 40). Additional ceramic samples were etched and analyzed for contact angle, micro-morphology, and roughness. In baseline condition (without aging), the HF3, HF5, and HF10 groups showed similar bond strength values (13.9 - 15.9 MPa), and HF1 (11.2 MPa) presented lower values than HF5, being that statistically different (p= 0.012). After aging, all the mean bond strengths statistically decreased, being that HF3, HF5, and HF10 (7.8 - 11 MPa) were similar and higher than HF1 (1.8 MPa) (p= 0.0001). For contact angle, HF3, HF5, and HF10 presented similar values (7.8 - 10.4°), lower than HF1 and CTRL groups. HF5 and HF10 presented rougher surfaces than other conditions. For better bond strength results, the tested ceramic may be etched by HF acid in concentrations of 3%, 5%, and 10%.

Resumo Este estudo avaliou o efeito de diferentes concentrações de ácido fluorídrico (HF) na resistência de união entre uma cerâmica vítrea à base de dissilicato de lítio e um cimento resinoso. Oitenta blocos cerâmicos (12×7×2 mm) de IPS e.Max CAD (Ivoclar Vivadent) foram produzidos e distribuídos aleatoriamente em 8 grupos, considerando 2 fatores de estudo: concentração de HF em 4 níveis, isto é, 1% (HF1), 3% (HF3), 5% (HF5), e 10% (HF10), e armazenamento em 2 níveis, isto é, condição inicial (testes foram realizados 24 h após a cimentação), e envelhecidos (150 dias de armazenamento + 12.000 ciclos térmicos a 5°C e 55°C). Condicionamento ácido (20 s) foi realizado, seguido por lavagem, secagem e silanização. Quatro cilindros de cimento resinoso (ϕ= 0.96 mm) foram construídos a partir de matrizes de amido em cada amostra cerâmica (n= 40). Amostras cerâmicas adicionais foram condicionadas e analisadas quanto ao ângulo de contato, micro-morfologia e rugosidade. Na condição inicial (sem envelhecimento), os grupos HF3, HF5, e HF10 mostraram valores de resistência de união similares (13.9 - 15.9 MPa), e HF1 apresentou valores menores que HF5, sendo estatisticamente diferente (p= 0.012). Após o envelhecimento, todas as médias de resistência de união diminuíram estatisticamente, sendo que HF3, HF5 e HF10 foram similares e maiores que HF1 (p= 0.0001). Para o ângulo de contato, HF3, HF5 e HF10 apresentaram valores similares (7.8 - 10.4°), menores que os grupos HF1 e CTRL. HF5 e HF10 apresentaram superfícies mais rugosas que as outras condições. Para melhores resultados de resistência de união, a cerâmica testada pode ser condicionada com ácido fluorídrico nas concentrações de 3%, 5% e 10%.

Hydrofluoric Acid-Based Derivatization Strategy To Profile PARP-1 ADP-Ribosylation by LC-MS/MS.

Despite significant advances in the development of mass spectrometry-based methods for the identification of protein ADP-ribosylation, current protocols suffer from several drawbacks that preclude their widespread applicability. Given the intrinsic heterogeneous nature of poly(ADP-ribose), a number of strategies have been developed to generate simple derivatives for effective interrogation of protein databases and site-specific localization of the modified residues. Currently, the generation of spectral signatures indicative of ADP-ribosylation rely on chemical or enzymatic conversion of the modification to a single mass increment. Still, limitations arise from the lability of the poly(ADP-ribose) remnant during tandem mass spectrometry, the varying susceptibilities of different ADP-ribose-protein bonds to chemical hydrolysis, or the context dependence of enzyme-catalyzed reactions. Here, we present a chemical-based derivatization method applicable to the confident identification of site-specific ADP-ribosylation by conventional mass spectrometry on any targeted amino acid residue. Using PARP-1 as a model protein, we report that treatment of ADP-ribosylated peptides with hydrofluoric acid generates a specific +132 Da mass signature that corresponds to the decomposition of mono- and poly(ADP-ribosylated) peptides into ribose adducts as a consequence of the cleavage of the phosphorus-oxygen bonds.

The effect of hydrofluoric acid and resin cement formulation on the bond strength to lithium disilicate ceramic

Abstract To investigate how the hydrofluoric acid (HF) concentrations applied to a lithium disilicate glass-ceramic (EMX) affects the surface morphology and microtensile bond strength (μTBS) of ceramics to dentin, using light-cured resin cements with or without UDMA. Sixty-three EMX square ceramic blocks were etched for 20 seconds using different HF concentrations (1%, 5% and 10%) and luted to dentin using two types of resin cement combinations: BisGMA/TEGDMA and BisGMA/TEGDMA/UDMA (n = 10). Each bonded EMX-dentin block was sectioned to obtain 1 mm2 sticks for μTBS evaluation. Half of the sticks were tested after 24 hours and the other half was assessed after 6 months of water storage. Data were statistically assessed using split-plot three-way ANOVA and multiple comparisons were performed using the Tukey's post hoc test (α = 0.05). One EMX sample from each HF concentration was analyzed using field-emission scanning electron microscope (FE-SEM) to characterize the etching pattern. According to the FE-SEM images, increasing the concentration of HF from 1 to 5 and then to 10% led to increased removal of glassy matrix and greater exposure of lithium disilicate crystals. The 10% HF concentration yielded higher μTBS when compared to 1% for BisGMA/TEGDMA formulation (p < 0.05); whereas HF 1% and 5% showed similar μTBS values when compared to 10% HF for BisGMA/TEGDMA/UDMA resin matrix (p > 0.05) at both storage times. Water aging decreased the μTBS values (p < 0.05), except when 10% HF was associated with BisGMA/TEGDMA resin cement. Resin cement formulation and hydrofluoric acid concentrations can interfere with the immediate and long-term glass-ceramic bond strength to dentin.

The Effect of Hydrofluoric Acid Concentration and Heat on the Bonding to Lithium Disilicate Glass Ceramic

Abstract The aim of this study was to evaluate the effects of hydrofluoric acid (HF) concentration and previous heat treatment (PHT) on the surface morphology and micro-shear bond strength (mSBS) of a lithium disilicate glass ceramic (EMX) to resin cement. One hundred four EMX specimens were randomly assigned to two groups (n=52) according to the HF concentration: 5% and 10%. A new random distribution was made according to the PHTs (n=13): control (no PHT); previously heated HF (70 °C); previously heated EMX surface (85 °C); the combination of heated HF + heated EMX surface. The etching time was set at 20 s. All EMX blocks were silanated and received a thin layer of an unfilled resin. Five resin cement cylinders were made on each EMX surface using Tygon tubes as matrices, and then stored for 24 h at 37 °C. One random etched EMX sample from each group was analyzed using field-emission scanning electron microscopy (FE-SEM). The data were subjected to two-way ANOVA and multiple comparisons were performed using the Tukey post hoc test (a=0.05). For the control groups, 5% HF showed statistically lower mSBS values when compared to 10% HF (p<0.05). PHT increased the mSBS values for 5% HF, yielding statistically similar results to non-PHT 10% HF (p<0.05). FE-SEM images showed increased glassy matrix removal when PHT was applied to HF 5%, but not to the same degree as for 10% HF. PHT has the potential to improve the bond strength of 5% HF concentration on lithium disilicate glass ceramic.

Resumo O objetivo deste estudo foi avaliar os efeitos das concentrações de ácido fluorídrico (AF) e do prévio tratamento térmico (PTT) na morfologia da superfície e resistência de união ao microcisalhamento (mRUM) de uma cerâmica vítrea de dissilicato de lítio (EMX) ao cimento resinoso. Cento e quatro espécimes de EMX foram aleatoriamente distribuídos em dois grupos (n=52) de acordo com a concentração do AF: 5% e 10%. Os espécimes foram novamente distribuídos de forma aleatória de acordo com o PTT (n=13): controle (sem PTT); AF previamente aquecido (70 °C); superfície do EMX previamente aquecida (85 °C); combinação entre AF e EMX aquecidos. O tempo de condicionamento foi fixado em 20 s. Todos os espécimes de EMX foram silanizados e receberam a aplicação de uma fina camada de um adesivo sem carga. Cinco cilindros de cimento resinoso foram confeccionados usando tubos Tygon como matrizes e então armazenados por 24 h a 37 °C. Uma amostra condicionada de cada grupo foi aleatoriamente selecionada e analisada em um microscópio eletrônico de varredura em emissão de campo (MEVEC). Os dados foram submetidos ao teste ANOVA de dois fatores e múltiplas comparações foram feitas pelo teste de Tukey (a=0.05). Para os grupos controle, AF 5% mostrou valor de mRUM estatisticamente menor do que AF 10% (p<0.05). PTT aumentou os valores de mRUM para o AF 5%, proporcionando resultados estatisticamente similares ao grupo AF 10% controle (p<0.05). MEVEC mostrou um aumento na remoção da matriz vítrea quando o PTT foi aplicado ao grupo AF 5%, no entanto esse efeito não foi visto no grupo AF 10%. O PTT tem o potencial de melhorar a resistência de união do AF 5% na cerâmica vítrea reforçada por disilicato de lítio.

Obviation of hydrogen fluoride in Boc chemistry solid phase peptide synthesis of peptide-αthioesters.

Under suitable conditions, trifluoromethanesulfonic acid performs comparably to hydrogen fluoride for the on-resin global deprotection of peptides prepared by Boc chemistry solid phase peptide synthesis (SPPS). Obviation of hydrogen fluoride in Boc chemistry SPPS enables the straightforward synthesis of peptide-αthioesters for use in native chemical ligation.

Roughness gradients on zirconia for rapid screening of cell-surface interactions: Fabrication, characterization and application.

Roughness is one of the key parameters for successful osseointegration of dental implants. The understanding of how roughness affects cell response is thus crucial to improve implant performance. Surface gradients, which allow rapid and systematic investigations of cell-surface interactions, have the potential to facilitate this task. In this study, a novel method aiming to produce roughness gradients at the surface of zirconia using hydrofluoric acid etching was implemented. The topography was exhaustively characterized at the microscale and nanoscale by white light interferometry and atomic force microscopy, including the analysis of amplitude, spatial, hybrid, functional, and fractal parameters. A rapid screening of the influence of roughness on human mesenchymal stem cell morphology was conducted and potential correlations between roughness parameters and cell morphology were investigated. The roughness gradient induced significant changes in cell area (p < 0.001), aspect ratio (p = 0.01), and solidity (p = 0.026). Nanoroughness parameters were linearly correlated to cell solidity (p < 0.005), while microroughness parameters appeared nonlinearly correlated to cell area, highlighting the importance of multiscale optimization of implant topography to induce the desired cell response. The gradient method proposed here drastically reduces the efforts and resources necessary to study cell-surface interactions and provides results directly transferable to industry. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2502-2514, 2016.

Micromorfología superficial de 2 cerámicas grabables tratadas con diferentes ácidos / Superficial micromorphology of 2 etchable ceramics treated with different acids

Para lograr una unión fuerte entre las restauraciones de cerámica sin metal y las resinas de cementación se indican acondicionamientos de superficie previos a la cementación. Nuestro objetivo es describir y comparar al MEB las superficies de cerámicas feldespáticas y reforzadas con disilicato de litio antes y después de ser tratadas con 2 procedimientos ácidos. Se utilizaron 8 bloques de cerámica feldespática (A) y 8 de cerámica reforzada con disilicato de litio (B). Se subdividieron en 2 grupos de 4 bloques (A1 y A2) y (B1 y B2). Los grupos A1 y B1 fueron tratados con ácido fluorhídrico 9% (HF) y los grupos A2 y B2 con ácido fluorhídrico, seguido de ácido fosfórico al 35%. Posteriormente, se observaron al MEB (1.000 ×) y se procesaron las imágenes con el programa Matlab R2012a, que mide el contraste. Los estadísticos utilizados fueron el test ANOVA y el test «t¼ no pareado Resultados El ácido fluorhídrico 9% crea irregularidades en ambos tipos de cerámicas. Al aplicar HF, seguido de ácido fosfórico sobre la cerámica feldespática no se aprecian diferencias en el contraste, con respecto a utilizar solo HF. Al usar ambos ácidos, en la cerámica reforzada con disilicato de litio se aprecian menos irregularidades respecto a las tratadas con un solo ácido. Conclusiones El ácido fluorhídrico 9% crea microrretenciones en ambas cerámicas. El HF al 9%, seguido del ácido fosfórico 35% parece modificar los valores de contraste de la cerámica colada, en cambio en las feldespáticas no hay diferencias significativas con ambos tratamientos.

Surface conditioning prior to cementing is indicated to achieve a strong bond between metal-free ceramic restorations and resin cements. The aim of this study is to describe and compare the scanning electron microscopy (SEM) images of the surfaces of Feldspathic ceramic and Lithium disilicate glass ceramic before and after being treated with two acid procedures. For this, 8 blocks of Feldspathic ceramic (A) and 8 of Ceramic lithium disilicate (B) were used. They were subdivided into two groups of 4 blocks (A1 and A2) and (B1 and B2). Groups A1 and B1 were treated with 9% Hydrofluoric Acid (HF) and the A2 and B2 groups, with 9% Hydrofluoric Acid followed by 35% Phosphoric Acid. Subsequently, they were observed using SEM (1,000 ×) and the images processed with the program Matlab R2012a, which measures the contrast. The statistics used were ANOVA test and the unpaired t test. Results 9% Hydrofluoric Acid creates irregularities in both types of ceramics. When applying HF followed by Phosphoric Acid on Feldspathic ceramics, no differences in contrast were found, compared to using only HF. With ceramic lithium disilicate using both acids, there are fewer irregularities with respect to those treated with a single acid. Conclusion 9% Hydrofluoric Acid creates micro-retentions in both ceramics. 9% HF followed by 35% Phosphoric Acid appears to significantly modify the Lithium disilicate glass ceramic contrast values. On the other hand, the Feldspathic ceramic showed no significant differences with both treatments.

Influência do tempo de condicionamento ácido na alteração superficial, resistência de união e compressão da cerâmica de dissilicato de lítio / Influence of etching time on the superficial alterations, bond strength and compression resistence of lithium disilicate ceramic

Este estudo in vitro propôs analisar os padrões de condicionamento da superfície da cerâmica a base de dissilicato de lítio após três tempos de condicionamento com ácido fluorídrico a 10%, a influência desses tempos na resistência ao cisalhamento de cilindros cerâmicos e à compressão de placas cerâmicas cimentadas em esmalte de dentes bovinos. Para análise de superfície foram utilizadas 36 placas de cerâmica (IPS e.max Press), sem tratamento e condicionadas por 10s, 20s e 60s (E0,E10,E20,E60; n=3), observadas em MEV, energia dispersiva espectroscópica (EDS) e perfilômetro. Para o teste de resistência de união, 180 cilindros cerâmicos (2mm diâmetro x 2mm comprimento; n=20) foram condicionados e cimentados (80 m de espessura) com RelyX ARC em esmalte variando os sistemas adesivos {Silano+Single Bond (S); RelyX Ceramic Primer Silano +Single Bond (R); Single Bond Universal (U)}, obtendo-se os grupos: E10S, E20S, E60S, E10R, E20R, E60R, E10U, E20U e E60U. Após 24h realizou-se o teste de cisalhamento (EMIC, 0,5mm/min, 50Kgf). O teste de compressão ao esmalte (Kratos, 0,5mm/min 50Kgf) foi realizado após 24h da cimentação de 60 placas cerâmicas quadradas (5x5mm com 1mm de espessura; n=10), condicionadas e cimentadas (RelyX ARC, 80m) variando os sistemas adesivos R e U (10R, 20R, 60R, 10U, 20U e 60U). Os resultados da análise em MEV mostraram que foi mantido o mesmo padrão de condicionamento, porém, mais evidenciado com o aumento do tempo de tratamento. A quantidade de sílicio observada em EDS foi: E0:24,73% < E10:61,10% < E20:67,50% = E60:67,54% e a rugosidade: E0: 6,25 m < E10: 10,6m < E20: 12,0m < E60: 18,0m. Para os resultados dos ensaios de cisalhamento foi usado um modelo linear generalizado, com distribuição normal para a variável resposta e função de ligação do tipo raiz quadrada. Para compressão, usamos um modelo linear normal. Em ambos os casos, a hipótese de normalidade dos desvios foi verificada a partir do Q-Q Plot e do Teste de Kolmogorov-Smirnov. Para os testes de cisalhamento (MPa), independente do tempo de condicionamento, o grupo S apresentou os menores valores, enquanto os grupos R e U apresentaram valores semelhantes (E10S:84,2±7,2A/a, E10R:124,4±7,9A/b, E10U:117,2±7,8A/b, E20S:102,3±7,6B/a, E20R:146,2±8,2B/b, E20U:138,4±7,9B/b, E60S:107,2±7,8B/a, E60R:152,1±8,1B/b, E60U:144,1±8,1B/b). Para o teste de compressão (N), os valores Médios foram: 10R:869,8±122a, 10U:879,3±159a, 20R:795,0±219ab, 20U:852,3±227ab, 60R:772,7±162b, 60U:704,0±235b. O aumento do tempo de condicionamento da superfície da cerâmica a base de dissilicato de lítio aumentou a rugosidade superficial, não demonstrou diferença significativa da resistência de união de 20s par 60s, e apresentou leve diminuição para resistência de compressão.(AU)

The present in vitro study aimed to analyze the etching patterns of lithium disilicate based ceramic after three etching times with 10% hydrofluoric acid, and the influence of these times on the shear bond strength of ceramic cylinders and compression resistance of ceramic plates cemented to bovine enamel teeth. For the surface analysis, 36 ceramic plates (IPS e.max Press) were used untreated and etched for 10s, 20s and 60s (E0, E10, E20, E60; n = 3), as observed in SEM, energy dispersive spectroscopy (EDS) and profilometry. For the bond strength test, 180 ceramic cylinders (2x2mm; n = 20) were etched and cemented with RelyX ARC (80 m thick) on the enamel varying adhesive systems {Silane + Single Bond (S); RelyX Ceramic Primer Silane + Single Bond (R); Single Bond Universal (U)}, yielding the groups: E10S, E20S, E60S, E10R, E20R, E60R, E10U, E20U and E60U. After 24h, the shear bond strength test was performed (EMIC, 0.5 mm/min, 50Kgf). The ceramic compression test (Kratos, 0.5 mm/min, 50Kgf) was performed 24h after etching and cementing (RelyX ARC, 80m) 60 square ceramic plates (5x5mm, 1mm thick; n = 10), varying R and U adhesive systems (10R, 20R, 60R, 10U, 20U and 60U). The same pattern of damage was maintained as seen in the SEM analysis, however, it worsened with increasing the etching time. The amounts of silicium seen on EDS were: E0: 24.73%

Unusual hydrogen bonding in L-cysteine hydrogen fluoride.

L-Cysteine hydrogen fluoride, or bis(L-cysteinium) difluoride-L-cysteine-hydrogen fluoride (1/1/1), 2C3H8NO2S(+)·2F(-)·C3H7NO2S·HF or L-Cys(+)(L-Cys···L-Cys(+))F(-)(F(-)...H-F), provides the first example of a structure with cations of the 'triglycine sulfate' type, i.e. A(+)(A···A(+)) (where A and A(+) are the zwitterionic and cationic states of an amino acid, respectively), without a doubly charged counter-ion. The salt crystallizes in the monoclinic system with the space group P2(1). The dimeric (L-Cys···L-Cys(+)) cation and the dimeric (F(-)···H-F) anion are formed via strong O-H···O or F-H···F hydrogen bonds, respectively, with very short O···O [2.4438 (19) Å] and F···F distances [2.2676 (17) Å]. The F···F distance is significantly shorter than in solid hydrogen fluoride. Additionally, there is another very short hydrogen bond, of O-H···F type, formed by a L-cysteinium cation and a fluoride ion. The corresponding O···F distance of 2.3412 (19) Šseems to be the shortest among O-H···F and F-H···O hydrogen bonds known to date. The single-crystal X-ray diffraction study was complemented by IR spectroscopy. Of special interest was the spectral region of vibrations related to the above-mentioned hydrogen bonds.

Four chemical methods of porcelain conditioning and their influence over bond strength and surface integrity

OBJECTIVE: To assess four different chemical surface conditioning methods for ceramic material before bracket bonding, and their impact on shear bond strength and surface integrity at debonding.METHODS: Four experimental groups (n = 13) were set up according to the ceramic conditioning method: G1 = 37% phosphoric acid etching followed by silane application; G2 = 37% liquid phosphoric acid etching, no rinsing, followed by silane application; G3 = 10% hydrofluoric acid etching alone; and G4 = 10% hydrofluoric acid etching followed by silane application. After surface conditioning, metal brackets were bonded to porcelain by means of the Transbond XP system (3M Unitek). Samples were submitted to shear bond strength tests in a universal testing machine and the surfaces were later assessed with a microscope under 8 X magnification. ANOVA/Tukey tests were performed to establish the difference between groups (α= 5%).RESULTS: The highest shear bond strength values were found in groups G3 and G4 (22.01 ± 2.15 MPa and 22.83 ± 3.32 Mpa, respectively), followed by G1 (16.42 ± 3.61 MPa) and G2 (9.29 ± 1.95 MPa). As regards surface evaluation after bracket debonding, the use of liquid phosphoric acid followed by silane application (G2) produced the least damage to porcelain. When hydrofluoric acid and silane were applied, the risk of ceramic fracture increased.CONCLUSIONS: Acceptable levels of bond strength for clinical use were reached by all methods tested; however, liquid phosphoric acid etching followed by silane application (G2) resulted in the least damage to the ceramic surface.

OBJETIVO: avaliar quatro métodos de condicionamento químico da superfície cerâmica, previamente à colagem de braquetes, e seu impacto sobre a resistência ao cisalhamento e a integridade da superfície ao descolamento.MÉTODOS: quatro grupos experimentais (n = 13) foram delineados de acordo com o método de condicionamento da superfície cerâmica empregado: G1 = ácido fosfórico a 37%, seguido da aplicação de silano; G2 = ácido fosfórico líquido a 37%, seguido da aplicação de silano sem lavagem prévia do ácido; G3 = ácido fluorídrico a 10%; e G4 = ácido fluorídrico a 10%, seguido da aplicação de silano. Após o condicionamento da superfície, braquetes metálicos foram colados à porcelana utilizando-se o sistema Transbond XP (3M Unitek). As amostras foram submetidas a ensaios de resistência ao cisalhamento, em máquina de ensaio universal, e as superfícies cerâmicas foram posteriormente avaliadas em microscópio, com magnitude de 8X. Testes ANOVA/Tukey foram realizados para verificar-se a diferença entre os grupos (α = 5%).RESULTADOS: os maiores valores de resistência ao cisalhamento foram encontrados nos grupos G3 e G4 (22,01 ± 2,15MPa e 22,83 ± 3,32Mpa, respectivamente), seguidos por G1 (16,42 ± 3,61MPa) e G2 (9,29 ± 1,95MPa). Quanto à avaliação da superfície após a descolagem do braquete, a utilização de ácido fosfórico líquido seguido da aplicação de silano, sem lavagem do ácido (G2), produziu menores danos à porcelana. Quando ácido fluorídrico e silano foram aplicados, o risco de fraturar a cerâmica aumentou.CONCLUSÕES: níveis aceitáveis de resistência de união para uso clínico foram alcançados por todos os métodos testados. No entanto, o condicionamento com ácido fosfórico líquido, seguido da aplicação de silano (G2), resultou em menor dano à superfície cerâmica.