Miriam Grenón

Microscopic X-ray fluorescence analysis of human dental calculus using synchrotron radiation

In this work, new results of one- and two-dimensional spatial distributions of major, minor and trace elements of human dental calculus are presented. X-ray fluorescence induced by a synchrotron radiation source was used. The measurements were carried out in the X-ray microprobe station mounted at the X-ray fluorescence beamline of the Brazilian National Synchrotron Light Laboratory (LNLS). Two-dimensional distributions show that calcium, the major element in this type of sample, has a uniform pattern over the mapped area, while trace elements are non-homogeneously distributed. By means of different linear scans along the growing axis of the dental calculus, a markedly spatial correlation between Cu and Zn was found. A semi-quantitative analysis for Cu and Zn was performed by means of calibration curves using appropriate fabricated standards. The concentration values found for these metals were higher than those obtained in conventional bulk analysis. It was observed that these metals accumulated preferentially in the subgingival part of the calculus, near the tooth surface. These results indicate that the mineralization processes, which take place for both type of calculus, are essentially different.

SRXRF analysis with spatial resolution of dental calculus

This work presents elemental-composition studies of dental calculus by X-ray fluorescence analysis using synchrotron radiation. The intrinsic characteristics of synchrotron light allow for a semi-quantitative analysis with spatial resolution. The experiments were carried out in the high-vacuum station of the XRF beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). All the measurements were performed in conventional geometryO45∞a 45∞U and the micro-collimation was attained via a pair of orthogonal slits mounted in the beamline. In this way, pixels of 50 lm 50 lm were obtained keeping a high flux of photons on the sample. Samples of human dental calculus were measured in diAerent positions along their growing axis, in order to determine variations of the compositions in the pattern of deposit. Intensity ratios of minor elements and traces were obtained, and linear profiles and surface distributions were determined. As a general summary, we can conclude that lXRF experiments with spatial resolution on dental calculus are feasible with simple collimation and adequate positioning systems, keeping a high flux of photon. These results open interesting perspectives for the future station of the line, devoted to lXRF, which will reach resolutions of the order of 10 lm. ” 2000 Elsevier Science B.V. All rights reserved.

Qualitative microanalysis of calcium local structure in tooth layers by means of micro-RRS

The Resonant inelastic X‐ray scattering or resonant Raman scattering is an inelastic process of second order that becomes important when the energy of the excitation radiation is below but close to an absorption edge. In this process, the emitted photons have a continuous energy distribution with a high energy cut‐off limit. In the last few years, experiments of resonant Raman scattering has become a very powerful technique to investigate excitations of electrons in solids. A qualitative study of the calcium local structure in the different layers of teeth was carried out. In order to perform the analysis, several measurements of tooth samples were achieved using monochromatic synchrotron radiation at the XRF station of the D09B‐XRF beamline at the Brazilian synchrotron facility (LNLS, Campinas), below and close to the K absorption edge of Ca to inspect the resonant Raman scattering spectra. First of all, the spectra were analyzed with specific software to fit the experimental data. After that, the residuals were determined and a  fast Fourier transform smoothing procedure was applied, taking into account the instrument functions of the detecting system. These oscillations present patterns that depend of the tooth layer, i.e. of the calcium state.

A crystallinity study of dental tissues and tartar by infrared spectroscopy

In this paper we report a study of an important property of biomineralized phases, crystallinity, on the basis of previous results for synthetic apatite. Crystallinity is not only important for understanding biomineralization, it is also related to the maturation and mechanisms of growth of calcium phosphates in biological surroundings. We studied two kinds of sample, teeth as an example of biomineralized tissues and dental calculi (adhering) as an example of mineralization without participation of biological agents, except possibly bacteria. The investigation focused on study of ν1–ν3 infrared absorption bands of PO43– phosphates. We used ATR (attenuated total reflection) analysis to examine human dental tissues and tartar on several samples. The results confirm for the first time previous assumptions about the growth and maturation of dental calculi, i.e., crystallinity progresses from regions of high crystallinity to regions of lower crystallinity, and, in addition, its quantification with spatial resolution in the sample. A gradual pattern was observed in dental calculus. Another result from this study was that cementum and dentine had similar crystallinity, despite their different biological and mechanical functions.

Titanium diffusion in shinbone of rats with osseointegrated implants.

Dental implants are composed of commercially pure Ti (which is actually an alloy of titanium, and minor or trace components such as aluminium and vanadium). When the implant is inserted, its surface undergoes a number of chemical and mechanical processes, releasing particles of titanium to the medium. The metabolism of free ions of titanium is uncertain; the uptaking processes in the body are not well known, nor their toxic dose. In addition, physical properties of newly formed bone, such as diffusivity and activation energy, are scarce and rarely studied. In this study, we analysed the diffusion of titanium in the titanium‐implanted shinbones of six adult male Wistar rats by spatially resolved micro x‐ray fluorescence. The measurements were carried out at the microfluorescence station of the x‐ray fluorescence (XRF) beamline of the Brazilian synchrotron facility LNLS (from Portuguese ‘Laboratorio Nacional de Luz Sincrotron’). For each sample, XRF spectra were taken by linear scanning in area near the new bone formed around the Ti implant. The scanning line shows a clear effect of titanium diffusion whereas calcium intensity presents a different behaviour. Moreover, a clear correlation among the different structures of bones is observed in the Ti and Ca intensities. The results obtained in these measurements may allow determining quantitatively the parameters of diffusion rates and other physical properties of new bone like diffusion coefficients.