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1.
Braz Oral Res ; 34: e018, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32187304

RESUMEN

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.


Asunto(s)
Silicatos de Aluminio/química , Recubrimiento Dental Adhesivo/métodos , Ácido Fluorhídrico/química , Ácidos Fosfóricos/química , Compuestos de Potasio/química , Análisis de Varianza , Porcelana Dental/química , Ensayo de Materiales , Metacrilatos/química , Microscopía Electrónica de Rastreo , Valores de Referencia , Reproducibilidad de los Resultados , Cementos de Resina/química , Resistencia al Corte/efectos de los fármacos , Silanos/química , Propiedades de Superficie , Factores de Tiempo
2.
Braz Oral Res ; 33: e041, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31508723

RESUMEN

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.


Asunto(s)
Grabado Ácido Dental , Cerámica/química , Recubrimiento Dental Adhesivo/métodos , Ácido Fluorhídrico/administración & dosificación , Porcelana Dental/química , Análisis del Estrés Dental , Ácido Fluorhídrico/química , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Cementos de Resina/química , Resistencia al Corte , Propiedades de Superficie , Factores de Tiempo
3.
PLoS One ; 14(3): e0214192, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30917172

RESUMEN

Adherence of the microorganism to submerged solid surfaces leads to biofilm formation. Biofilm formation modifies the surfaces in favor of bacteria facilitating the survival of the bacteria under different stressed conditions. On the other hand, the formation of biofilm has a direct adverse economic impact in various industries and more importantly in medical practices. This adherence is the reason for the failure of many indwelling medical devices. Surface biofilm adhesion is the key to biofilm growth and stability. Hence this adhesion needs to be substantially lowered to inhibit biofilm stability. Both chemical and physical properties of the surface influence biofilm formation and modulating these properties can control this formation. In this study, we have investigated the effect of Hydrofluoric acid (HF), at a specific concentration as an etchant, on the surface morphology of substrates and the growth of biofilms of Pseudomonas aeruginosa. and Staphylococcus aureus. We find that the bacterial counts on the etched surfaces undergo a periodic increase and decrease. This, on one hand, shows the close correlation between the biofilm growth and the particular roughness scale, and on the other hand, explains the existing contradictory results regarding the effects of etching on substrate roughness and biofilm growth. We propose a simple model of a sequence of hole formation, hole expansion and etching away of the hole walls to form a new, comparatively smooth surface, coupled with the preferential accumulation of bacteria at the hole edges, to explain these periodicities.


Asunto(s)
Biopelículas/crecimiento & desarrollo , Vidrio/química , Ácido Fluorhídrico/química , Pseudomonas aeruginosa/fisiología , Staphylococcus aureus/fisiología , Propiedades de Superficie
4.
Methods Mol Biol ; 1954: 47-57, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30864123

RESUMEN

The envelope of gram-positive bacteria encompasses the cell wall, a rigid exoskeleton comprised of peptidoglycan that provides protection against lysis and governs bacterial cell shapes. Peptidoglycan also serves as the site of attachment for proteins and nonproteinaceous polymers that interact with the bacterial environment. Nonproteinaceous molecules include teichoic acids, capsular polysaccharides, and secondary cell wall polysaccharides (SCWP). Treatment of gram-positive bacterial cells with proteases, nucleases, and detergents results in the isolation of "murein sacculi" (i.e., peptidoglycan with bound carbohydrate polymers). Incubation of sacculi with acid or base releases carbohydrate polymers that can be purified for further biochemical characterization. This protocol describes the hydrofluoric acid extraction and purification of the secondary cell wall polymer of Bacillus anthracis that is also found in the envelope of the other members of the Bacillus cereus sensu lato group of bacteria.


Asunto(s)
Pared Celular/química , Cromatografía en Gel/métodos , Cromatografía de Fase Inversa/métodos , Bacterias Grampositivas/química , Ácido Fluorhídrico/química , Peptidoglicano/aislamiento & purificación , Polisacáridos Bacterianos/aislamiento & purificación , Bacillus anthracis/química , Fraccionamiento Químico/métodos , Cromatografía Líquida de Alta Presión/métodos , Infecciones por Bacterias Grampositivas/microbiología , Humanos , Peptidoglicano/química , Polisacáridos Bacterianos/química , Ácidos Teicoicos/química , Ácidos Teicoicos/aislamiento & purificación
5.
Bioresour Technol ; 278: 116-123, 2019 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-30684724

RESUMEN

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.


Asunto(s)
Celulosa/química , Ácido Fluorhídrico/química , Níquel/química , Catálisis , Calor , Pirólisis
6.
Braz Dent J ; 29(5): 492-499, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-30517449

RESUMEN

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%.


Asunto(s)
Grabado Ácido Dental/métodos , Cerámica/química , Recubrimiento Dental Adhesivo/métodos , Porcelana Dental/química , Ácido Fluorhídrico/química , Cementos de Resina/química , Ensayo de Materiales , Microscopía de Fuerza Atómica , Resistencia al Corte , Estrés Mecánico , Propiedades de Superficie
7.
Mater Sci Eng C Mater Biol Appl ; 92: 121-131, 2018 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-30184735

RESUMEN

In this work, Ti-Ag sintered alloys (Ti-Ag) with different Ag contents were prepared by a spark plasma sintering (SPS) technique, which is a new, efficient and convenient method of powder metallurgy. The Ti-Ag samples were then treated with a mixture of 40 wt% hydrofluoric acid (HF) and nitric acid (HNO3). The surface features, ion release, antibacterial activities and biocompatibilities of the acid-etched Ti-Ag (Ti-Ag(AE)) samples were systematically characterized. The surface characterization results revealed the formation of micropits and particles with high Ag contents. Antibacterial experiments demonstrated that the antibacterial ratios of the Ti-Ag samples increased significantly after the acid etching treatment, and the particles with high Ag contents are thought to play a key role in the antibacterial mechanism. Biocompatibility experiments indicated that the cell proliferation, cell morphology, and osteoblastic differentiation did not significantly differ between the pure titanium (cp-Ti) and Ti-Ag(AE) samples. The Ti-Ag(AE) samples with 3 wt% and 5 wt% Ag not only possessed sustained antibacterial activities for at least 30 days but also did not have impaired biocompatibility.


Asunto(s)
Aleaciones/química , Antibacterianos/química , Materiales Biocompatibles/química , Animales , Antibacterianos/farmacología , Materiales Biocompatibles/farmacología , Línea Celular , Supervivencia Celular/efectos de los fármacos , Ácido Fluorhídrico/química , Ensayo de Materiales , Ratones , Ácido Nítrico/química , Gases em Plasma , Plata/química , Staphylococcus aureus/efectos de los fármacos , Propiedades de Superficie , Titanio/química
8.
Photomed Laser Surg ; 36(11): 614-620, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30227090

RESUMEN

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).


Asunto(s)
Cerámica/química , Grabado Dental/métodos , Láseres de Estado Sólido , Grabado Ácido Dental/métodos , Silicatos de Aluminio , Diseño Asistido por Computadora , Porcelana Dental , Ácido Fluorhídrico/química , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Resistencia al Corte , Propiedades de Superficie
9.
J Mech Behav Biomed Mater ; 87: 306-311, 2018 11.
Artículo en Inglés | MEDLINE | ID: mdl-30103112

RESUMEN

This study investigated the effect of etching with distinct hydrofluoric (HF) acid concentrations on the cyclic load-to-failure (CLf) of simplified lithium disilicate glass-ceramic restorations adhesively cemented to a dentin analogue (n = 20): non-etched/control (CTRL), or etched for 20 s with HF acid at 3% (HF3), 5% (HF5), or 10% (HF10). A silane coating was then applied onto the ceramic surfaces. Fatigue tests followed the staircase approach (initial load= 720 N; step-size= 70 N; 500,000 cycles per sample; 20 Hz) using a hemispheric stainless-steel piston (Ø= 40 mm) under water. The CLf data were analyzed using Dixon and Mood method. Topographic and fractographic analyses were conducted. CLf (in N) of HF3 (1355 ±â€¯32.0) and HF5 (1335 ±â€¯58.8) groups were the highest and statistically similar; HF10 presented intermediate CLf (1175 ±â€¯132.9), while the non-etched group had the lowest one (965 ±â€¯145.0). Topographical analysis showed that the higher the HF acid concentration, the more pronounced the topographical changes. All failures (radial cracks) started from the inner surface of the ceramic discs. Topographical changes promoted by intermediate HF acid concentrations (3% and 5%) may improve fatigue performance for adhesively-cemented lithium disilicate restorations.


Asunto(s)
Porcelana Dental/química , Fracaso de la Restauración Dental , Ácido Fluorhídrico/química , Animales , Ensayo de Materiales , Soporte de Peso
10.
Dent Mater ; 34(9): e255-e263, 2018 09.
Artículo en Inglés | MEDLINE | ID: mdl-30031547

RESUMEN

OBJECTIVES: To evaluate the effects of the etching with different hydrofluoric acid (HF) concentrations on the cyclic load-to-failure (CLf) of machined lithium disilicate crowns cemented to dentin analogue material. METHODS: Pairs of dentin analogue prosthetic preparations and lithium disilicate ceramic crowns with simplified and standardized designs were machined (n=18). The preparations were etched with 10% HF (60s), followed by primer application. The intaglio surface of the ceramic crowns was treated as follows: non-etched (control, CTRL); or etched for 20s with different HF concentrations - 3% (HF3), or 5% (HF5), or 10% (HF10). A silane coating was then applied onto the treated ceramic surfaces, and they were adhesively cemented to the preparations. To perform the fatigue tests (staircase approach), a hemispheric stainless-steel piston (Ø=40mm) applied cyclic loads in the center of the crowns under water (initial load: 720N; step-size: 70N; cycles: 500,000; frequency: 20Hz). Additionally, topographic, fractographic, and fractal analyses were carried out. The fatigue data were analyzed using the Dixon and Mood method. RESULTS: Although the topographic and fractal analyses depicted the action of HF etching altering the superficial complexity and topography, the preponderant topography pattern was established by machining on CAD/CAM. All groups showed similar CLf (in N) (CTRL=805.00±91.23; HF3=781.25±29.87; HF5=755.00±154.49; HF10=833.75±100.74). SIGNIFICANCE: Etching with different HF acid concentrations did not promote a deleterious effect on the cyclic load-to-failure of machined lithium disilicate crowns.


Asunto(s)
Grabado Ácido Dental/métodos , Coronas , Porcelana Dental/química , Fracaso de la Restauración Dental , Ácido Fluorhídrico/química , Diseño Asistido por Computadora , Análisis del Estrés Dental , Ensayo de Materiales , Silanos/química , Estrés Mecánico , Propiedades de Superficie
11.
Int J Mol Sci ; 19(6)2018 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-29849015

RESUMEN

The use of laser 3D printers is very perspective in the fabrication of solid and porous implants made of various polymers, metals, and its alloys. The Selective Laser Melting (SLM) process, in which consolidated powders are fully melted on each layer, gives the possibility of fabrication personalized implants based on the Computer Aid Design (CAD) model. During SLM fabrication on a 3D printer, depending on the system applied, there is a possibility for setting the amount of energy density (J/mm³) transferred to the consolidated powders, thus controlling its porosity, contact angle and roughness. In this study, we have controlled energy density in a range 8⁻45 J/mm³ delivered to titanium powder by setting various levels of laser power (25⁻45 W), exposure time (20⁻80 µs) and distance between exposure points (20⁻60 µm). The growing energy density within studied range increased from 63 to 90% and decreased from 31 to 13 µm samples density and Ra parameter, respectively. The surface energy 55⁻466 mN/m was achieved with contact angles in range 72⁻128° and 53⁻105° for water and formamide, respectively. The human mesenchymal stem cells (hMSCs) adhesion after 4 h decreased with increasing energy density delivered during processing within each parameter group. The differences in cells proliferation were clearly seen after a 7-day incubation. We have observed that proliferation was decreasing with increasing density of energy delivered to the samples. This phenomenon was explained by chemical composition of oxide layers affecting surface energy and internal stresses. We have noticed that TiO2, which is the main oxide of raw titanium powder, disintegrated during selective laser melting process and oxygen was transferred into metallic titanium. The typical for 3D printed parts post-processing methods such as chemical polishing in hydrofluoric (HF) or hydrofluoric/nitric (HF/HNO3) acid solutions and thermal treatments were used to restore surface chemistry of raw powders and improve surface.


Asunto(s)
Titanio/química , Calor , Humanos , Ácido Fluorhídrico/química , Porosidad , Propiedades de Superficie
12.
Braz Oral Res ; 32: e43, 2018 May 24.
Artículo en Inglés | MEDLINE | ID: mdl-29846386

RESUMEN

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.


Asunto(s)
Cerámica/química , Recubrimiento Dental Adhesivo/métodos , Porcelana Dental/química , Ácido Fluorhídrico/química , Cementos de Resina/química , Análisis del Estrés Dental , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Propiedades de Superficie , Resistencia a la Tracción
13.
J Proteome Res ; 17(7): 2542-2551, 2018 07 06.
Artículo en Inglés | MEDLINE | ID: mdl-29812941

RESUMEN

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.


Asunto(s)
ADP-Ribosilación , Ácido Fluorhídrico/química , Poli(ADP-Ribosa) Polimerasa-1/química , Adenosina Difosfato Ribosa/metabolismo , Cromatografía Liquida , Espectrometría de Masas en Tándem
14.
J Xray Sci Technol ; 26(3): 499-508, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29562583

RESUMEN

BACKGROUND: There is abundant quartz deposit in Nigeria which has been used for export and building purposes. However, its electrical and piezoelectric properties have not been studied. Thus, whether it can be used as raw material for the indigenous electric industries is unknown to date. OBJECTIVE: This study aims to characterize the piezoelectric properties of smoky quartz for ultrasonic transducer and determine its sonic properties. METHOD: In the research approach, the raw quartz was cut into six crystals of rectangular shape using a universal cutter. The crystals were purified with a 100 ml hydrofluoric and hydrochloric acid solution under a temperature of 250°C in a furnace. The sizes, weights, and capacitance of crystals were determined using the standard measuring instruments. The resonance method was used for the determination of the frequency of minimum and maximum impedance of the crystals. The piezoelectric constants of the crystals were derived using the standard formula for determination of piezoelectric constants. RESULTS: The results show that the sonic properties represented by the piezoelectric charge constant (d31) and the piezoelectric voltage constant (g31) values are 2.52 (±1.075) ×10-8c/m2 and 1030.6114 ± 250.89v/m2 respectively. CONCLUSION: The present study has characterized Nigerian quartz for its piezoelectric properties and found that it was suitable for use in the construction of ultrasonic transducers.


Asunto(s)
Cuarzo/química , Transductores , Ultrasonografía/instrumentación , Capacidad Eléctrica , Impedancia Eléctrica , Análisis de Falla de Equipo , Ácido Clorhídrico/química , Ácido Fluorhídrico/química , Ensayo de Materiales , Nigeria , Temperatura
15.
Oper Dent ; 43(2): E81-E91, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29504886

RESUMEN

The aim of this study was to evaluate the effect of etching, with different hydrofluoric acid concentrations at the intaglio surface of feldspathic ceramic inlays, on the fatigue failure load of restored premolars. A total of 60 upper premolars were embedded in plastic cylinders with acrylic resin (up to 3 mm below the cement-enamel junction) and prepared using a device specially designed for that purpose. Teeth were randomly assigned to three groups (n=20): HF1, HF5, and HF10 (etching with hydrofluoric acid for 60 seconds at concentrations of 1%, 5%, and 10%, respectively). Preparations were scanned and restorations were milled by a computer-aided design / computer-aided manufacturing system. The inner surfaces of the inlays were etched and received an application of a silane coupling agent; the dentin and enamel were treated appropriately for the luting system (RelyX ARC, 3M-ESPE). The restorations were cemented and the fatigue failure load (in N) was determined using the staircase method (10 Hz; 105 cycles in each step). The initial load (585.5 N) was applied on the slopes of the cusps (labial and palatal/lingual, simultaneously) through a cylinder attached to the test machine (Instron ElectroPuls E3000). The tested samples were analyzed under a stereomicroscope for failure analysis. Fatigue data were analyzed by one-way analysis of variance. There was no statistical difference among the fatigue failure loads (in N): HF1 (448.5±79.1), HF5 (360.7±55.4), and HF10 (409.5±121.1). Regarding the fracture mode, there was a predominance of interfacial fracture (50%), followed by cusp fracture (34.6%). It may be concluded that the etching with hydrofluoric acid at the tested concentrations (1%, 5%, and 10%) does not influence the fatigue failure load of feldspathic ceramic inlays cemented on premolars.


Asunto(s)
Grabado Ácido Dental/métodos , Cerámica/química , Fracaso de la Restauración Dental , Ácido Fluorhídrico/química , Silicatos de Aluminio/química , Diente Premolar , Bisfenol A Glicidil Metacrilato , Diseño Asistido por Computadora , Preparación de la Cavidad Dental/métodos , Diseño de Prótesis Dental , Análisis del Estrés Dental , Humanos , Técnicas In Vitro , Ensayo de Materiales , Polietilenglicoles , Ácidos Polimetacrílicos , Compuestos de Potasio/química , Distribución Aleatoria , Cementos de Resina/química , Propiedades de Superficie
16.
J Microencapsul ; 35(2): 192-203, 2018 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-29537334

RESUMEN

Hollow glass bubbles (HGBs) with through-holes at micron level were fabricated by etching them using diluted 1% hydrofluoric acid (HF) solution in a specially designed reaction system. In this study, the function of each component in the system was carefully investigated and improved to realise the controllable etching process. Various parameters were investigated to explore the optimal etching condition. Highest gross yield of about 85% and effective yield of about 50% were obtained at the optimised etching condition. A separating method was proposed to separate the etched HGBs with different hole sizes with the help of reduced pressure. After separation, HGBs with hole size at sub-micron level, less than 10 µm, and bigger than 10 µm, were achieved. The well-etched HGBs can be used as universal containers to store both reactive and inactive chemicals for applications in self-healing materials, biochemical engineering, and energy industry.


Asunto(s)
Vidrio/química , Ácido Fluorhídrico/química , Ensayo de Materiales , Porosidad , Propiedades de Superficie
17.
Dent Mater ; 34(4): 667-675, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-29397196

RESUMEN

OBJECTIVE: This study investigated the influence of hydrofluoric acid (HF) etching at different concentrations on the fatigue failure load of adhesively cemented feldspathic ceramic discs (Vita Mark II). Besides, their effect on the micromorphology of ceramic surface was investigated. METHODS: Eighty ceramic discs (ϕ=10 mm; thickness=1.5 mm) were cemented to epoxy supporting discs (ϕ=10 mm; thickness=2.0mm) using different surface conditioning methods (n=20): nonetched control (CTRL), or etched for 60s with different HF concentrations: 1% (HF1), 5% (HF5), or 10% (HF10). All the ceramic discs received a silane application (Monobond Plus). The epoxy discs were etched with 10% HF for 60s and received a primer coating (Multilink Primer A+B). Adhesively cementation was performed (Multilink Automix), and the assemblies (ceramic discs/epoxy discs) were subjected to cyclic loads in water by a staircase approach (500,000 cycles; 20Hz; initial load=290N; step size=30N). Fatigue failure load data were analyzed using 1-way ANOVA and post-hoc Tukey's tests (α=.05). RESULTS: Mean failure load of the HF5 group (255.0±23.0N) was significantly lower; HF1 group (301.7±71.0N) presented intermediate values, and the highest values were achieved in CTRL (351.7±13.4N) and HF10 (341.7±20.6N) groups. All the failures were radial cracks starting from the bonding surface. SIGNIFICANCE: In terms of fatigue failure load, etching with 1% and 5% HF had a deleterious effect on the fatigue behavior of an adhesively cemented feldspathic ceramic, while 10% HF had no negative influence.


Asunto(s)
Grabado Ácido Dental , Silicatos de Aluminio/química , Cementos Dentales/química , Fracaso de la Restauración Dental , Ácido Fluorhídrico/química , Compuestos de Potasio/química , Cementos de Resina/química , Cerámica/química , Análisis del Estrés Dental , Técnicas In Vitro , Ensayo de Materiales , Propiedades de Superficie
18.
J Toxicol Environ Health B Crit Rev ; 21(6-8): 370-381, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-30977440

RESUMEN

Use of lithium-ion batteries has raised safety issues owing to chemical leakages, overcharging, external heating, or explosions. A risk assessment was conducted for hydrofluoric acid (HF) and lithium hydroxide (LiOH) which potential might leak from lithium-ion batteries. The inhalation no-observed-adverse-effect-level (NOAEL) for HF was 0.75 mg/kg/d. When a lithium-ion battery explodes in a limited space, HF emissions amount to 10-100 ppm. Assuming the worst-case scenario, the conversion rate was calculated to be 81.8 mg/m3, and the average daily dose (ADD) was 19.5 mg/kg/d. Consequently, the margin of exposure (MOE = NOAEL/ADD) was 0.034, a value which constitutes an unsafe inhalation exposure for HF. Conversely, skin toxicity NOAEL for LiOH was 41.35 mg/kg/d-. This LiOH value reflects the amount of lithium in the lithium-ion battery, which is generated upon contact between water and the electrolyte. The quantity of lithium in a mobile phone is approximately 295 mg, and systemic exposure dose (SED) was 4.92 mg/kg/d. Accordingly, the MOE (NOAEL/SED) value was 8.41, and skin exposure of LiOH was deemed as safe for humans. However, it is important that Energy Storage System batteries still require safety measures and technologies for next-generation batteries, to prevent any potential explosions of lithium-ion batteries.


Asunto(s)
Suministros de Energía Eléctrica/efectos adversos , Explosiones , Ácido Fluorhídrico/química , Compuestos de Litio/química , Litio/química , Explosiones/clasificación , Humanos , Iones , Medición de Riesgo
19.
J Mech Behav Biomed Mater ; 77: 375-382, 2018 01.
Artículo en Inglés | MEDLINE | ID: mdl-28988143

RESUMEN

This study aimed to evaluate the effect of etching time and hydrofluoric acid (HF) concentration on the fatigue failure load and surface characteristics of zirconia-reinforced lithium silicate glass (ZLS) ceramic cemented to a dentin-like, fiber reinforced epoxy resin. Ceramic (Suprinity, VITA) (1.0mm thick) and epoxy resin (2.5mm thick) discs (10mm diameter) were produced. The bonding surface of the ceramic samples was nonetched (control group), or etched for 30, 60 or 90s by 5% or 10% HF. The epoxy resin discs were etched by 10% HF for 30s followed by the application of an adhesive material (Single Bond Universal, 3M ESPE). Pairs of ceramic/epoxy resin discs were cemented with a dual cure resin cement. The fatigue failure load was determined by the staircase method (500,000 cycles at 20Hz; initial load = 925N; step size = 45N). In 10% HF the etching time was shown to influence the fatigue failure load, which increased as the etching time increased (30s < 60s < 90s), and in 5% HF the fatigue failure load was not shown to be affected by the etching time; the lowest fatigue failure loads were produced in the control group without ceramic etching followed by 10% HF acid etching for 30s. Topography analysis showed variations based on the etching protocols. All fractures (radial cracks) were shown to originate from defects at the ceramic surface on the cementing interface. For fatigue loading improvements of ZLS ceramic, 10% HF acid etching for 90s and silanization of the ceramic surface is recommended.


Asunto(s)
Cerámica/química , Recubrimiento Dental Adhesivo , Grabado Dental/métodos , Porcelana Dental/química , Ácido Fluorhídrico/química , Litio/química , Circonio/química , Bisfenol A Glicidil Metacrilato/química , Resinas Compuestas/química , Grabado Dental/instrumentación , Análisis del Estrés Dental , Ensayo de Materiales , Resistencia al Corte , Silicatos , Propiedades de Superficie
20.
Environ Geochem Health ; 40(3): 1093-1109, 2018 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-28600727

RESUMEN

The junction area of Yunnan, Guizhou, and Sichuan provinces is the heaviest coal-burning endemic fluorosis zones in China. To better understand the pathogenicity of endemic fluorosis in this area, 87 coal samples from the late Permian outcrop or semi-outcrop coal seams were collected in eight counties of the junction area of Yunnan, Guizhou, and Sichuan provinces. The total fluorine and sulfate content, etc. in the coal was determined using combustion-hydrolysis/fluoride-ion-selective electrode method and ion chromatography, respectively. The results show that the total fluorine concentrations in the samples ranged from 44 to 382 µg g-1, with an average of 127 µg g-1. The average pH of the coals is 5.03 (1.86-8.62), and the sulfate content varied from 249 to 64,706 µg g-1 (average 7127 µg g-1). In addition, the coals were medium- and high-sulfur coals, with sulfur mass fraction ranging from 0.08 to 13.41%. By heating the outcrop coals, HF release from the coal was verified quantitatively without exception, while simulated combustion directly confirmed the release of sulfuric acid (H2SO4). The acid in coal may be in the form of acidic sulfate ([Formula: see text]/H2SO4) because of a positive relationship between pH and [Formula: see text] in the acidic coal. The possible reaction mechanism would be that a chemical reaction between the acid (H2SO4 or [Formula: see text]) and fluorine in the coal occurred, thereby producing hydrogen fluoride (HF), which would be the chemical form of fluorine released from coal under relatively mild conditions. The unique chemical and physical property of HF may bring new insight into the pathogenic mechanism of coal-burning endemic fluorosis. The phenomenon of coal-burning fluorosis is not limited to the study area, but is common in southwest China and elsewhere. Further investigation is needed to determine whether other endemic fluorosis areas are affected by this phenomenon.


Asunto(s)
Contaminación del Aire Interior/análisis , Carbón Mineral , Intoxicación por Flúor/epidemiología , Ácidos Sulfúricos/química , China/epidemiología , Carbón Mineral/análisis , Electrodos , Enfermedades Endémicas , Humanos , Ácido Fluorhídrico/análisis , Ácido Fluorhídrico/química , Concentración de Iones de Hidrógeno , Microscopía Electrónica de Rastreo , Solubilidad , Sulfatos/química
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