Study of the effects of unsupervised over‐the counter whitening products on dental enamel using μ‐Raman and μ‐EDXRF spectroscopies

The purpose of this in vitro study was to assess whether the mineralization degree and elemental content in tooth enamel are altered when bleaching the teeth with two different over‐the‐counter bleaching gels, exceeding the recommendations of the manufacturer. In order to perform this evaluation, 12 healthy teeth were used, six samples were treated with Teeth Whitening Home Kit, and the other six samples were treated with WHITE! (Bingo‐UK) bought in online shopping sites, for the period of 39 days. The pH of each product and the elemental content of each sample, before and after, were obtained by energy dispersive X‐ray spectrometry and phosphate (PO₄^3‐) profile was evaluated with Raman spectroscopy. Data was analyzed accordingly to a pre‐established plan with a mixed‐model ANOVA for repeated measures, significance was set at 5%. Both products were markedly acidic and below enamel critical level of 5.5. Moreover, seven days after treatment, demineralization was significant, wherein at the end of the study the degree of demineralization seems to be permanent. Copyright © 2015 John Wiley & Sons, Ltd.     

Assessment of teeth elemental content using μ‐EDXRF: effects by in‐office and at‐home bleaching products

The purpose of this in vitro study is to assess whether the elemental content of tooth enamel is altered when bleaching the teeth with bleaching gel. Because of tooth bleaching growing popularity and to match the public demands, manufacturers increased the range of bleaching products available, changing its presentation, techniques and concentration of active principles. This way, two different bleaching products were compared, one for in‐office and another for domestic use. In order to perform this evaluation, sound vestibular surfaces of anterior healthy teeth, extracted for periodontal or orthodontic reasons, were treated with the bleaching products accordingly to manufacturer instructions. Spectra were acquired using the M4 Tornado μ‐XRF setup, and quantitative calculations were performed using fundamental parameter method to determine the elemental composition of the analyzed samples before and after treatment. No significant statistical differences in the mineral content of the analyzed teeth were obtained. Copyright © 2014 John Wiley & Sons, Ltd.     

Microdistribution of lead in human teeth using microbeam synchrotron radiation X‐ray fluorescence (μ‐SRXRF)

Lead (Pb) exposure is known to be associated with adverse effects on human health, especially during the prenatal period and early childhood. The Pb content in teeth has been suggested as a useful biomarker for the evaluation of cumulative Pb exposure. This study was designed to employ the microbeam synchrotron radiation X‐ray fluorescence technique to determine the microdistribution of Pb within the tooth to evaluate the reliability of the technique and the effectiveness of tooth Pb as a biomarker of Pb exposure. The results showed that in the incisor sample, Pb primarily deposited in secondary dentine region close to the pulp and secondarily at enamel exterior. In addition, Pb colocalised with Zn, indicating a positive correlation between Pb and Zn. By contrast, in the two molar samples, Pb accumulated principally in the pulp, and secondarily in the enamel. At the same time, Pb in these two molar samples colocalised with Ca instead of Zn as was observed in the incisor sample. Several batches of line scans further confirmed the conclusions. The feasibility of using microbeam synchrotron radiation X‐ray fluorescence to determine the microdistribution of Pb in teeth and of using the tooth Pb, especially in dentine, as a biomarker was discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Spatial and temporal distribution of γH2AX fluorescence in human cell cultures following synchrotron‐generated X‐ray microbeams: lack of correlation between persistent γH2AX foci and apoptosis

Formation of γH2AX foci (a marker of DNA double‐strand breaks), rates of foci clearance and apoptosis were investigated in cultured normal human fibroblasts and p53 wild‐type malignant glioma cells after exposure to high‐dose synchrotron‐generated microbeams. Doses up to 283 Gy were delivered using beam geometries that included a microbeam array (50 µm wide, 400 µm spacing), single microbeams (60–570 µm wide) and a broad beam (32 mm wide). The two cell types exhibited similar trends with respect to the initial formation and time‐dependent clearance of γH2AX foci after irradiation. High levels of γH2AX foci persisted as late as 72 h post‐irradiation in the majority of cells within cultures of both cell types. Levels of persistent foci after irradiation via the 570 µm microbeam or broad beam were higher when compared with those observed after exposure to the 60 µm microbeam or microbeam array. Despite persistence of γH2AX foci, these irradiation conditions triggered apoptosis in only a small proportion (<5%) of cells within cultures of both cell types. These results contribute to the understanding of the fundamental biological consequences of high‐dose microbeam irradiations, and implicate the importance of non‐apoptotic responses such as p53‐mediated growth arrest (premature senescence).     

In situ energy dispersive X‐ray fluorescence analysis of rock art pigments from the ‘Abrigo dos Gaivões’ and ‘Igreja dos Mouros’ caves (Portugal)

A portable energy dispersive X‐ray fluorescence spectrometer was used to obtain the elemental composition of Neolithic rock art paintings of the ‘Abrigo dos Gaivões’ and ‘Igreja dos Mouros’ caves. These caves, located in the Esperança parish, Arronches' county, in the San Mamede's mountains (Portugal), belong to a group of spread shelters just next to the western Spanish border. Results show the strong presence of iron in bare rock, and this element can be clearly detected as the main component of the red paintings. No evidence of manganese was detected in either the brownish or the black paintings, contrary to other Neolithic paintings in the Mediterranean area. Copyright © 2011 John Wiley & Sons, Ltd.     

The β‐silicon effect. 4: substituent effects on the solvolysis of 1‐alkyl‐2‐(aryldimethylsilyl)ethyl trifluoroacetates

Solvolysis rates of 2‐(aryldimethylsilyl)‐1‐methylethyl and 2‐(aryldimethylsilyl)‐1‐tert‐butylethyl trifluoroacetates were determined conductimetrically in 60% (v/v) aqueous ethanol. The effects of aryl substituents at the silicon atom on the solvolysis rates at 50 °C were correlated with parameters of r⁺ = 0.15 with the Yukawa–Tsuno equation, giving ρ values of ?1.5 for both secondary α‐Me and α‐tert‐Bu systems. The ρ values for those secondary systems are less negative than ?1.75 for the 2‐(aryldimethylsilyl)ethyl system that proceeds by the Eaborn (non‐vertical) mechanism, while they are distinctly more negative than ?0.99 for 2‐(aryldimethylsilyl)‐1‐phenylethyl system that should proceed by the Lambert (vertical) mechanism. There was a fairly linear relationship between the reaction constants (ρ) for the β‐silyl substituent effects and the solvolysis reactivities for a series of β‐silyl substrates. The solvolyses of the α‐Me and tert‐Bu substrates proceed through the transition state (TS) with an appreciable degree of the β‐silyl participation, close to the Eaborn (non‐vertical) TS rather than to the Lambert (vertical) TS. Copyright © 2010 John Wiley & Sons, Ltd.     

Loose‐powder technique for X‐ray fluorescence analysis of ancient pottery using a small (100 mg) powdered sample

A molded‐loose‐powder technique using a small powdered sample (100 mg) was developed for the X‐ray fluorescence analysis of 22 components (Na₂O, MgO, Al₂O₃, SiO₂, P₂O₅, K₂O, CaO, TiO₂, MnO, Fe₂O₃, V, Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, and Pb) in ancient pottery. This loose powder specimen was prepared by pressing the small powdered sample into a sample holder, formed from a stainless steel disk (48‐mm diameter × 0.8‐mm height) with a hole (11‐mm diameter), by hand. Calibration standards were prepared by homogenizing chemical reagents containing these 22 analytes using the concentration ranges of 166 ancient potteries and three clay materials from Japan. The calibration curves of these benchmark mixtures exhibited a good linearity (correlation coefficient, r = 0.990–1.000), accuracy, and reproducibility compared with those of other synthesized specimens and three reference standards. The lower limits of detection were less than tens of mg kg^?1 (e.g., 94 mg kg^?1 for Na₂O, 11 mg kg^?1 for P₂O₅, 1.1 mg kg^?1 for Rb, and 0.9 mg kg^?1 for Y). Using the present method, we determined 22 components in two prehistoric potteries from Japan. The advantage of this method is that only a small amount of sample is required, which can be prepared easily and rapidly and reused for other analyses. Copyright © 2012 John Wiley & Sons, Ltd.     

Surface‐enhanced Raman scattering of 4‐mercaptopyridine on sub‐monolayers of α‐Fe2O3 nanocrystals (sphere,spindle, cube)

We report surface‐enhanced Raman scattering (SERS) spectra from 4‐mercaptopyridine (4‐Mpy) adsorbed on sub‐monolayers of α‐Fe₂O₃ nanocrystals (sphere, spindle, cube). The maximum enhancement factor has been estimated to be about 10⁴ compared to that of 4‐Mpy in solution. A possible mechanism has been proposed that the charge transfer between the α‐Fe₂O₃ nanocrystals and the 4‐Mpy molecules is most likely responsible for the observed enhancement of Raman intensity of adsorbed 4‐Mpy molecules as surface plasmon resonances have not occurred. Copyright © 2009 John Wiley & Sons, Ltd.     

Solid phase synthesis of novel α/β‐tetrapeptides,electrospray ionization mass spectrometric evaluation of their metal cation complexation behavior,and conformational analysis using density functional theory (DFT)

Thirty‐four novel α/β‐tetrapeptides ( 1–34 ) have been prepared employing solid‐phase and in‐parallel synthetic protocols. α/β ‐Tetrapeptides 1 – 34 were prepared by a combination of three α‐amino acid residues (alanine (Ala), phenylalanine (Phe), and isoleucine (Ile)) with one β‐amino acid residue (β³‐homophenylglycine). The corresponding complexes of several selected α/β‐tetrapeptides with alkali, alkaline earth, and transition metals, [tP + M⁺], were evaluated using ion electrospray‐ionization mass spectrometry (ESI‐MS). According to the results from analysis of mixtures, we can conclude that the position of the β‐amino acid is determinant in the affinity toward different metal cations. Computational modeling (DFT, B3LYP 6‐311++G) provided useful information regarding the most likely coordination sites of the metal ions on the receptor α/β‐tetrapeptide 12 , HO₂C‐α‐Phe‐α‐Phe‐α‐Ile‐β³‐hPhg‐NH₂, as well as the conformational changes induced by the metal upon [tP + M⁺] complex formation. Copyright © 2008 John Wiley & Sons, Ltd.     

Measurement of the third‐order nonlinear optical susceptibility χ(3) for the 1002‐cm–1 mode of benzenethiol using coherent anti‐Stokes Raman scattering with continuous‐wave diode lasers

The components of the third‐order nonlinear optical susceptibility χ⁽³⁾ for the 1002‐cm^–1 mode of neat benzenethiol have been measured using coherent anti‐Stokes Raman scattering with continuous‐wave diode pump and Stokes lasers at 785.0 and 852.0 nm, respectively. Values of 2.8 ± 0.3 × 10^–12, 2.0 ± 0.2 × 10^–12, and 0.8 ± 0.1 × 10^–12 cm·g^–1·s² were measured for the xxxx, xxyy, and xyyx components of |3χ⁽³⁾|, respectively. We have calculated these quantities using a microscopic model, reproducing the same qualitative trend. The Raman cross‐section σ_RS for the 1002‐cm^–1 mode of neat benzenethiol has been determined to be 3.1 ± 0.6 × 10^–29 cm² per molecule. The polarization of the anti‐Stokes Raman scattering was found to be parallel to that of the pump laser, which implies negligible depolarization. The Raman linewidth (full‐width at half‐maximum) Γ was determined to be 2.4 ± 0.3 cm^–1 using normal Stokes Raman scattering. The measured values of σ_RS and Γ yield a value of 2.1 ± 0.4 × 10^–12 cm·g^–1·s² for the resonant component of 3χ⁽³⁾. A value of 1.9 ± 0.9 × 10^–12 cm·g^–1·s² has been deduced for the nonresonant component of 3χ⁽³⁾. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrostatic interactions effect in the aminolysis of some β‐lactams in the presence of poly(ethyleneimine):structure‐reactivity

The aminolysis reaction of a series of β‐lactams in the presence of poly(ethyleneimine) (PEI) at 30°C and pH = 8.40 has been studied. The substrates investigated follow a pseudo first order rate, except two β‐lactams which show a two step consecutive reaction. Increasing the polyelectrolyte concentration, Michaelis–Menten type kinetics are been observed and for four substrates a more complex rate behaviour was verified owing to the polyelectrolyte inhibition effect. Both the binding constant K₁ between polyelelectrolyte and β‐lactam and the first order rate constant of the reactive complex decomposition k_cat were calculated. The substituent effect at C‐6′ or C‐7′ position of β‐lactam on the aminolysis rate does not correlate with the σ_I value (Taft plot). Most probably, steric and electronic effects are important, but the electrostatic ones are determining factors for the relevant acceleration attributable to both the binding phenomena and the increased reactivity of the substrate–polyelectrolyte complex. The comparison between poly(ethyleneimine) and Human Serum Albumin (HSA) is also discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Comparative studies on reaction of bis(p‐nitrophenyl) phosphate and α‐nucleophiles in cationic micellar media

We studied the cleave of bis(p‐nitrophenyl) phosphate (BNPP) over a pH range of 7.0–12.0 in the presence of cationic micelles of cetyldiethylethanolammonium bromide, cetyldimethylethanolammonium bromide, cetylpyridinium bromide, cetyltrimethylammonium bromide, and cetylpyridinium chloride by using different α‐nucleophiles, viz acetohydroxamate, benzohydroxamate, salicylhydroxamate, butane‐2,3‐dione monooximate, and α‐benzoin oximate ions. With the use of α‐nucleophiles in cationic micellar media, the hydrolytic cleavage of BNPP was found to be approximately 10⁵‐fold faster than its spontaneous hydrolysis. All reactions followed pseudo‐first‐order kinetics. The effect of various concentrations of cationic micelles for the reaction of BNPP and α‐nucleophiles has been studied. The variation of k_obs values of the reactions depends on the micellar structure, that is, head groups, hydrophobic tail length, and counter ion. Copyright © 2012 John Wiley & Sons, Ltd.     

Detection of a new SRS‐promoting phonon mode and cross‐cascaded χ(3)‐nonlinear lasing in single crystals of calcite (trigonal CaCO3)

For calcite (CaCO₃), one of the pioneer crystals in nonlinear optics, new results of stimulated Raman scattering (SRS) spectroscopy are presented. Among them are the discovery of a new SRS‐promoting vibration mode with ω_SRS2 ≈︁ 282 cm^‐1 and its participation, together with the main SRS mode ω_SRS1 ≈︁ 1086.5 cm^‐1, in cross‐cascaded (χ⁽³⁾ ↔ χ⁽³⁾) nonlinear‐lasing generation, as well as the observation of efficient self‐upconversion via cascaded parametric four‐wave processes of one‐micron Stokes and anti‐Stokes χ⁽³⁾‐lasing into the UV‐region of third harmonic generation. The investigations show that calcite is able to generate a χ⁽³⁾‐lasing comb of more than two octaves bandwidth. The article also gives a brief review on the discovery and study of the SRS‐effect in natural crystals (minerals), which have expanded our ability to study the photon‐phonon nonlinear‐laser interactions in crystalline materials. A short summary of information about χ⁽³⁾‐lasing properties of the triangular planar structure units in SRS‐active crystals is included.     

Calculated polar substituent effects on the stability of 4‐substituted(X) ‐ cub‐1‐yl and ‐bicyclo[2.2.2]oct‐1‐yl cations: a DFT study

The effects of substituents on the stability of 4‐substituted(X) cub‐1‐yl cations ( 2 ), as well as the benchmark 4‐substituted(X) bicyclo[2.2.2]oct‐1‐yl cation systems ( 7 ), for a set of substituents (X = H, NO₂, CN, NC, CF₃, COOH , F, Cl, HO, NH₂, CH₃, SiH₃, Si(CH₃)₃, Li, O^?, and NH) covering a wide range of electronic substituent effects were calculated using the DFT theoretical model at the B3LYP/6‐311 + G(2d,p) level of theory. Linear regression analysis was employed to explore the relationship between the calculated relative hydride affinities (ΔE, kcal/mol) of the appropriate isodesmic reactions for 2 / 7 and polar field/group electronegativity substituent constants (σ_F and σ_χ, respectively). The analysis reveals that the ΔE values of both systems are best described by a combination of both substituent constants. This highlights the distinction between through‐space and through‐bond electronic influences characterized by σ_F and σ_χ, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

Calculated polar substituent effects on the stability of 3‐substituted(X) bicyclo[1.1.1]pent‐1‐yl cations and 4‐substituted(X) bicyclo[2.2.1]hept‐1‐yl cations: a DFT study

The effects of substituents on the stability of 3‐substituted(X) bicyclo[1.1.1]pent‐1‐yl cations (3) and 4‐substituted(X) bicyclo[2.2.1]hept‐1‐yl cations (4), for a set of substituents (X = H, NO₂, CN, NC, CF₃, CHO, COOH , F, Cl, HO, NH₂, CH₃, SiH₃, Si(CH₃)₃, Li, O^?, and NH₃⁺) covering a wide range of electronic substituent effects were calculated using the DFT theoretical model at the B3LYP/6‐311 + G(2d,p) and B3LYP/6‐31 + G (d) levels of theory, respectively. Linear regression analysis was employed to explore the relationship between the calculated relative hydride affinities (ΔE, kcal/mol) of the appropriate isodesmic reactions for 3/4 and polar field/group electronegativity substituent constants (σ_F and σ_χ, respectively). The analysis reveals that the ΔE values for both systems are best described by a combination of both substituent constants. The result highlights the importance of the σ_χ dependency of charge delocalization in these systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of novel bis(β‐cyclodextrin)s linked with aromatic diamine and their molecular recognition with model substrates

Novel β‐cyclodextrin (β‐CD) dimers with aromatic diamine linkers, 1,3‐(aminomethyl)‐benzylamine‐bridged bis(6‐amino‐6‐deoxy‐β‐CD) (2) , 4,4′‐diaminodiphenylmethano‐bridged bis(6‐amino‐6‐deoxy‐β‐CD) (3) , and 4,4′‐ ethylenedianiline‐bridged bis(6‐amino‐6‐deoxy‐β‐CD) (4) , were synthesized. The inclusion complexation behaviors of these compounds, together with 4,4′‐aminophenyl ethyl‐bridged bis(6‐amino‐6‐deoxy‐β‐CD) (5) , with substrates such as acridine red (AR), neutral red (NR), ammonium 8‐anilino‐1‐naphthalenesulfonate (ANS), sodium 2‐(p‐toluidinyl) naphthalenesulfonate (TNS), rhodamine B (RhB), and brilliant green (BG), were investigated by ultraviolet, fluorescence, circular dichroism, and 2D NMR spectroscopy. The results indicated that the two linked CD units cooperatively bound to a guest, and the molecular binding affinity toward substrates, especially curved guest ANS and linear guests such as NR and AR, was increased. The linker length between two CD units played a crucial role in the molecular recognition of the hosts with guest dyes. The binding constants of the hosts for AR, TNS, ANS, and RhB decreased with increasing linker length in hosts 2‐4 . Moreover, structurally similar hosts 3 and 5 exhibited very different binding behavior for the guests. Host 5 showed much higher Ks values toward positively charged guests and lower Ks toward negatively charged guests than host 3 . The 2D NMR spectra of hosts 3 and 5 with RhB were acquired to understand the binding difference between 3 and 5 . The molecular binding ability and selectivity of model substrates by these hosts were sufficiently investigated to reveal not only the cooperative contributions of the linker group and CD cavities upon inclusion complexation with dye guest molecules, but also the controlling factors for the molecular selective binding. Copyright © 2008 John Wiley & Sons, Ltd.