Hans Odelius

Multi-technique surface charaterization of oxide films on electropolished and anodically oxidized titanium

The widespread use of pure Ti in biomedical applications and in basic biomaterials research has led to an increasing interest in the properties of its surface oxides, and how they can be modified. In this work, which was part of a broad surface characterization of oxide films on pure Ti and Ti-6A1-4V, the chemical composition of anodic oxide films formed on pure Ti during electropolishing and anodic oxidation was investigated using multi-technique surface analysis (XPS, AES/SAM, SIMS, RBS and NRA). XPS and AES Ti line shapes show that the oxide formed is mainly TiO2, but the chemical composition can be modified by anion adsorption and/or incorporation when H2SO4 or H3PO4 electrolytes are used. Modification of the anodic oxide film composition also occurs during sterilization; increased Ca and H levels are observed by SIMS and NRA after autoclaving. AES and XPS depth profiles, together with RBS measurements, show that the oxide thickness depends linearly on the anodizing potential in the range 5–80 V, with a growth constant αm≈ 1.1 × 1016 oxygen atoms/V⋯ cm2. The present results are compared with parallel studies of the composition and microstructure of thermal and anodic oxides on pure Ti and Ti-6A1-4V. The demonstrated systematic variation of oxide properties opens up the possibility to study the influence of specific surface properties on the biological response to Ti materials.

Secondary ion mass spectrometry and X-ray microanalysis of hypomineralized enamel in human permanent first molars

A common finding in Swedish children is hypomineralization in first molars of unknown cause. Little is known about the chemical composition of the disturbed enamel. The aim here was to analyse the concentration gradients for F, Cl, Na, Mg, K and Sr in hypomineralized enamel from 17 permanent molars by means of secondary ion mass spectrometry, to complete this analysis with an examination of the main matrix elements O, P and Ca by means of X-ray microanalysis, and to compare them with normal enamel. Hypomineralized enamel had a higher content of carbon and the calcium as well as the phosphorus concentration was lower than in normal enamel. The mean Ca/P ratio in hypomineralized areas was significantly lower (1.4) than in the adjacent normal enamel (1.8). The F content was highly variable in impaired enamel and higher than in normal, but close to the surface there was most often no difference between the two. Contents of Mg and K were slightly higher in hypomineralized areas, especially towards the surface. Also Na had a somewhat higher content toward the surface in defective enamel. Cl and Sr contents had negligible or no diversity in relation to the degree of mineralization.

Secondary Ion Mass Spectrometry of Human Deciduous Enamel

Secondary ion mass spectrometry was used for determining the distribution of Na, K, Mg, Sr, F and Cl in the buccal enamel of human deciduous incisors. 16 teeth were analyzed. The samples were coated, by vapour deposition, with an aluminium grid, thus making it possible to produce two-dimensional contour maps of the elements. These contour maps were used to establish the distribution of elements throughout the enamel. The metallic elements except for Sr showed increasing concentrations towards the interior of the enamel. The halogens, in contrast, had higher concentrations at the surface and decreased towards the enamel-dentin junction. Sr showed a fairly even distribution throughout the enamel. No clean-cut differences in elemental distribution were seen between post- and prenatal enamel, although the postnatal enamel exhibited relatively wide variations for some elements

Applications of SIMS in Interdisciplinary Materials Characterization

Although pioneering work on secondary ion mass spectrometry was performed already in the 1930-s, one may say that SIMS as a microstructural-microanalytical technique for materials research saw the light of day about 21 years ago1, 2. As a commercially available tool, SIMS is only some 14 years old3–6. Since about half that time, its typical assets, mechanisms and artifacts have been illuminated by extensive and thorough international discussion7, 8, and today SIMS is widely accepted as an off-age technique for very sensitive three-dimensional characterization of materials. Current trends9–11 are directed mainly towards perfected quantitation, towards efficient routines in daily applications, and towards apparative development for further improved detection sensitivity and spacial resolution.

Calibration methods for the ion probe determination of fluorine in mineralized tissue

SummaryAn ion micro-analyzer (Cameca IMS 300 with a TD 1000 computer unit) has been calibrated for quantitative point determination of fluorine in apatites, including tooth and bone material. Samples with macroscopically measured F concentrations were used as external standards. The samples were bombarded with O− primary ions. Secondary positive ion currents were registered as mass spectra containing mass numbers 19, 20, 31, 44, 59, 60 and 61. The latter mass numbers were used in isotopic correction to subtract oxide and hydroxide contributions from the fluoride 59 peak. For each bombarded spot, the ratios19F+/40Ca2+, respectively59CaF+/44Ca+, were plotted in a log-log graph against40Ca2+/44Ca+, the abscissa providing a measure of ionization efficiency. The plots yielded two sets of parallel straight lines, with ordinate values proportional to the respective F/Ca concentration ratios, in agreement with earlier theory. Each set of lines constitutes a calibration graph, where the fluorine concentration at an investigated spot is obtained when substituting the measured ion current ratios. With biological apatites, account must also be taken of effects due to, among other things, adsorbed humidity, other contaminations, and non-stoichiometry. When all precautions are taken, the accuracy of the determined F contents in the point analysis of an area some 100 μm in diameter can be expected to be better than 6% at 1500 ppm F, and better than 25% at 100 ppm F. The calibration is effective down to about 20 ppm F. Applications have been carried out on samples of human tooth enamel.

Ion Probe Study of Fluorine Gradients in Outermost Layers of Human Enamel

F concentrations in the outermost layers of human tooth enamel were studied with the aid of a secondary ion microanalyzer. Concentration profiles were recorded in continuous sputtering analysis from the surface down to a depth of about 0.3 micrometer. Samples previously subjected to topical fluoride treatment were compared with reference specimens. In some samples, the results were compared with those obtained at greater depths by macrascopic etching analysis.

A computerized induction analysis of possible co-variations among different elements in human tooth enamel

In recent decades software tools in the area of artificial intelligence have rapidly developed for use in personal computers. Interactive rule induction utilizing mathematical algorithms has become a powerful tool in data analysis and in making rules and patterns explicit. Data from a Secondary Ion Mass Spectrometry (SIMS) elemental analysis of human dental enamel were used to elucidate co-variations between certain elements. A co-variation analysis was performed employing a computerized induction analysis program, as well as a neural network program. Both analyses, confirming each other, revealed co-variations between certain elements in dental enamel in addition to exclusion of data of no importance for chosen outcomes. The results are presented in hierarchic diagrams, in which the importance for every specific element is given by its position and level in the diagram (decision tree). From the results it became evident that elements such as chlorine and sodium expressed a high co-variation level. Similarly fluorine and potassium co-varied, as well as magnesium and the trace element strontium. It was demonstrated that data from an elemental analysis could be processed by an induction analysis to reveal co-variations between certain elements in tooth enamel. The biological significance of these data is not fully understood, and further analyses in the field are needed.

SIMS yields from glasses; secondary ion energy dependence and mass fractionation

SIMS studies of glasses indicate that calibration of positive monatomic ion yields via relative sensitivity factors (RSF) is significantly dependent both on the kinetic energyEk and on the massMt of the analyzed ions. Due to elemental differences in the energy distributions of the sputtered ions, relative emissivities at highEk are radically different from those at the tops of the distributions. While the RSF values of cations from glasses range within ca. 3 powers of ten, atEk above ca. 40 eV the range remains within a factor of ten or less, and further change of relative elemental sensitivities withEk is slow. At low exit energy the LTE formalism is reasonably well obeyed. At highEk, a trend is noted towards a relative suppression of the ion yields of lowvalent elements.Measurements of isotope fractionation in secondary ion yield were performed on 17 elements sputtered from glasses. The mass factorα (defined by the proportionality of the yield toMi−α) is found to range from near-zero toα≅2.5, dependent on the element and onEk. For most elements a drops steeply at lowEk, but generally a slow rise is noted at higher energies. The behaviour ofα appears to be to some extent connected with the shape of the energy distribution curve. The dependence ofα onEk and on elemental parameters can qualitatively be described in terms of a simple phenomenological model.

SIMS Analysis of Deciduous Enamel from Normal Full-Term Infants, Low Birth Weight Infants and from Infants with Congenital Hypothyroidism

Secondary ion mass spectrometry (SIMS) was used for determining the concentrations of Na, K, Mg, Sr, F and Cl in human deciduous enamel from three groups of children. From infants with a birth weight

Differences in Co-variation of Inorganic Elements in the Bulk and Surface of Human Deciduous Enamel: An Induction Analysis Study

This paper demonstrates a method for determination of co-variation between some inorganic elements in the bulk and surface areas of human tooth enamel. The technique is based on a computerised induction analysis of data obtained by secondary ion mass spectrometry (SIMS). When comparing the present data with an earlier study from our laboratory, it became evident that with only a moderate increase in the amount of data for the induction analysis, the results increased very considerably in reliability and precision. The patterns of co-variation between different elements differed between the bulk- and surface enamel. Only Mg expressed a similar pattern. In the bulk enamel the elements Na and P expressed a high degree of co-variation. Similarly, Mg and C expressed a high degree of co-variation. Mg was an element often found to co-vary with bulk enamel elements. In the enamel surface, F and Cl co-varied. In addition, Cl was an element often found to co-vary with other enamel surface elements.