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1.
J Adhes Dent ; 23(5): 461-467, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34549929

RESUMO

PURPOSE: To evaluate the microtensile bond strength (µTBS) of a one-step self-etch adhesive (1-SEA) to dentin and its interfacial nanomechanical properties after 8 years of water storage. MATERIALS AND METHODS: Flat coronal dentin surfaces of extracted human third molars were bonded with a 1-SEA (Clearfil S3 Bond Plus, CS3+) and built up with a hybrid resin composite (Clearfil AP-X). After storage in water for 24 h or 8 years, non-trimmed stick-shaped specimens were fabricated from the central part of each bonded tooth and subjected to the µTBS test at a crosshead speed of 1.0 mm/min. Failure modes and the morphology of debonded interfaces were analyzed using a scanning electron microscope (SEM). In addition, the elastic modulus (E) and hardness (H) of the adhesive layer and the resin composite were determined by an instrumented nanoindentation test. The acquired µTBS, E, and H data were statistically analyzed using t-tests to examine the effect of storage time (α = 0.05). RESULTS: The 8-year µTBS was slightly lower than that after 24 h, but the difference was not significant (p = 0.123). The SEM observation of debonded surfaces after 8 years revealed extrusions and lacunas. E and H of the adhesive layer and the resin composite significantly decreased over the 8-year water storage (p < 0.001). CONCLUSIONS: Although 8 years of water storage did not decrease the µTBS of CS3+ significantly, the observed failure mode patterns and significantly decreased nanomechanical properties indicated resin degradation of the adhesive and the resin composite.


Assuntos
Colagem Dentária , Dentina , Resinas Compostas , Cimentos Dentários , Análise do Estresse Dentário , Adesivos Dentinários , Humanos , Teste de Materiais , Cimentos de Resina , Estresse Mecânico , Propriedades de Superfície , Resistência à Tração
2.
Anal Sci ; 35(7): 751-757, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-30853694

RESUMO

For the rapid, easy, and safe purification of alkali and alkaline-earth elements from rock samples for stable isotope analysis, we developed a semi-automated, high-throughput procedure using borate fusion and an ion chromatography system equipped with a fraction collector. This HF-free procedure for the decomposition of silicate rock samples can be performed in a short time without isotope fractionation; the purification procedure enables the collection of baseline-separated peaks of multiple target elements and the complete removal of interference matrices from reagents and samples. The accuracy of this procedure was verified by confirming the correspondence of stable isotopic values of Li, Mg, Sr (δ7Li, δ26Mg, δ88Sr) and radiogenic isotopic values of Sr (87Sr/86Sr) to previously reported values in various geochemical reference materials in which the concentration range of Li was 7.78 - 86.6 ng g-1, that of Mg was 0.02 - 26.9%, and that of Sr was 178 - 7240 ng g-1. These results demonstrate that this procedure, which allows for the concurrent multi-isotope analysis of alkali and alkaline-earth elements in the same sample, is applicable to a wide variety of sample types.

3.
Food Chem ; 283: 656-664, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30722924

RESUMO

The aim of this study was to prove the usefulness of multielements as provenance markers of olive oils by evaluating their link with soil composition and their discriminatory power. Eleven elements in twenty-one olive oils and their paired soils from four Tunisian regions were characterized. Chemometrics have been implemented for ICP-MS data processing. Principal component analysis identified the predominant geochemical source of the elements in the oils based on their associations according to Goldschmidt's rule. Although a clear correlation was not proven, correspondence was identified between the discriminating elements for both the soils and olive oils, which included Fe, Rb, Mg, and Pb. Linear discriminant analysis achieved classification and prediction rates of 92.1% and 87.3%, respectively. Our study substantiates the validity of multielements as markers of the olive oils' provenance, and that an elemental fingerprinting approach can be successfully applied in the construction of a database of Tunisian olive oils.


Assuntos
Azeite de Oliva/química , Solo/química , Análise Discriminante , Frutas/química , Frutas/metabolismo , Espectrometria de Massas/métodos , Metais/análise , Micro-Ondas , Olea/química , Olea/metabolismo , Azeite de Oliva/metabolismo , Análise de Componente Principal
4.
Dent Mater J ; 37(3): 506-514, 2018 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-29491200

RESUMO

We evaluated the effect of different curing strategies for universal adhesives on micro-tensile bond strength (µTBS) between resin cement and dentin and/or between resin cement and indirect resin composite. Flat coronal dentin surfaces and composite resin disks were pretreated with silane-containing universal adhesives, with or without light-curing on the dentin-side and/or composite resin disk-side. Resin disks were luted onto the pretreated dentin surfaces with the corresponding dual-cure adhesive resin cements and light-cured, and cut into beams after 24-h water storage. After 0 or 10,000 thermocycles (5ºC/55ºC) in a water bath, the µTBS of the composite resin disk-dentin beam was tested. The µTBS was highest when universal adhesives were applied to both the dentin- and the indirect composite resin disk-side, followed by light-curing. Thermocycling decreased µTBS in all but the Scotchbond Universaltreated group, with light-curing on both sides. The effect of curing strategies is dependent upon the materials.


Assuntos
Resinas Acrílicas/química , Resinas Compostas/química , Colagem Dentária/métodos , Adesivos Dentinários/química , Poliuretanos/química , Restauração Dentária Permanente , Análise do Estresse Dentário , Humanos , Técnicas In Vitro , Cura Luminosa de Adesivos Dentários , Teste de Materiais , Cimentos de Resina , Resistência à Tração
5.
J Chromatogr A ; 1531: 157-162, 2018 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-29198448

RESUMO

We describe the mass descrimination and validation of an offline method for purification of Li, Mg and S with an ion chromatograph coupled to an automated fraction collector for use prior to stable isotope measurements. Significant sub-fraction mass fractionation was observed for both the Li and the Mg stable isotope ratios. The lighter Li and heavier Mg isotopes were preferentially retained by the column, resulting in 7Li/6Li and 26Mg/24Mg biases up to 85.8‰ and 0.95‰, respectively. The isotopic compositions of Li, Mg, and S separated from seawater were δ7LiL-SVEC = +30.9‰, δ26MgDSM3 = -0.83 ± 0.10‰, and δ34SVCDT = +19.4 ± 0.6‰; each chromatographic peak was completely recovered, and the results were in good agreement with the published values regardless of whether or not chemical suppressor was used. The purification method enables multi-isotope analysis of a sample using various mass spectrometry techniques, such as multiple-collector inductively coupled plasma and thermal ionization mass spectrometry.


Assuntos
Cromatografia por Troca Iônica , Lítio/isolamento & purificação , Magnésio/isolamento & purificação , Água do Mar/química , Enxofre/isolamento & purificação , Marcação por Isótopo
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