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PubMed2004

Comparison of the mechanical properties of 2 prosthetic mini-implants.

Two prosthetic mini-implants (MTI and MDI), which have very similar shapes, are widely used. In this investigation, the mechanical and physical properties of 2 prosthetic mini-implants were investigated. The flexural properties were measured with a universal testing machine. The surface image was observed by SEM with EDX. X-ray analyses were performed. The maximum strength and proportion limit for the different implants differed significantly (P <0.01); however, elastic modulus did not differ significantly (P >0.01). Although the surface of the MTI was smooth, the MDI had a rough surface. The elemental analysis detected titanium (Ti) in the MTI, and Ti, aluminum, and vanadium in the MDI. From the x-ray diffraction pattern, the MTI, which is composed of pure titanium, had a narrow, sharp Ti (syn) peak, whereas the corresponding peak for the MDI was small and broad. Although the 2 devices have similar shapes and dimensions, their surfaces and mechanical properties differ greatly. MTI is easy to remove and wrought in clinical use, and MDI is excellent in flexural properties compared with MTI. (Implant Dent 2004;13:251-256)

Aluminum↗
PubMed1992

Characterization of inorganic fillers in visible-light-cured dental composite resins.

Inorganic fillers in seven visible-light (VL)-cured dental composite resins were examined for their size, composition, phase and content, employing the following analytical instruments. SEM observations indicated that five samples could be classified into the hybrid type while the remaining two belonged to micro-filled and sub-micron types. EDX analyses revealed that five samples contained BaO while others lacked BaO. XRD analyses showed that three were in vitreous phase, two were in the crystalline phase and two were mixtures of both. DTG thermal analyses indicated that the hybrid type composites had the higher inorganic filler content (wt%) than the composites of two other types. In conclusion, wide varieties exist in the inorganic fillers in VL-cured dental composite resins currently utilized.

Aluminum Oxide↗
PubMed1995

X-ray microprobe analysis of corpora amylacea.

Since corpora amylacea is concentrated in the high density fraction in the subcellular fractionation of autopsy brain. It is suspected that inorganic materials accumulate in corpora amylacea. Therefore, elemental analyses of partially purified corpora amylacea from autopsy brain from a patient with Alzheimer's disease and those from brain of a non-demented patient were performed by the X-ray microprobe method. Prominent peaks of sodium, phosphorus, sulphur and chloride were observed, and mapping analyses confirmed that these elements were actually contained within the corpora amylacea. A similar result was obtained using cryostat sections. Corpora amylacea are characteristically distributed along the margin of blood vessels, beneath the pial border of the hippocampus and in the subependymal zones of ventricles of aged brains, namely in the vicinity of blood and cerebrospinal fluid. From this distribution and from the results of the present paper, we suggest that corpora amylacea play a role in the absorption and accumulation of inorganic materials which have been extravasated from blood and cerebrospinal fluid (CSF) and taken up by astrocytes. This may reflect alteration of the blood-brain and blood-CSF barriers in the ageing brain.

Alzheimer Disease↗
PubMed1990

Effects of axotomy on distribution and concentration of elements in rat sciatic nerve.

X-ray microprobe analysis was used to determine the effects of axotomy on distribution and concentration (millimoles of element per kilogram dry weight) of Na, P, Cl, K, and Ca in frozen, unfixed sections of rat sciatic nerve. Elemental concentrations were measured in axoplasm, mitochondria, and myelin at 8, 16, and 48 h after transection in small-, medium-, and large-diameter fibers. In addition, elemental composition was determined in extraaxonal space (EAS) and Schwann cell cytoplasm. During the initial 16 h following transection, axoplasm of small fibers exhibited a decrease in dry weight concentrations of K and Cl, whereas Na and P increased compared to control values. Similar changes were observed in mitochondria of small axons, except for an early, large increase in Ca content. In contrast, intraaxonal compartments of larger fibers showed increased dry weight levels of K and P, with no changes in Na or Ca concentrations. Both Schwann cell cytoplasm and EAS at 8 and 16 h after injury had significant increases in Na, K, and Cl dry weight concentrations, whereas no changes, other than an increase in Ca, were observed in myelin. Regardless of fiber size, 48 h after transection, axoplasm and mitochondria displayed marked increases in Na, Cl, and Ca concentrations associated with decreased K. Also at 48 h, both Schwann cell cytoplasm and EAS had increased dry weight concentrations of Na, Cl, and K. The results of this study indicate that, in response to nerve transection, elemental content and distribution are altered according to a specific temporal pattern. This sequence of change, which occurs first in small axons, precedes the onset of Wallerian degeneration in transected nerves.

Animals↗
PubMed2003

Eradication of Propionibacterium acnes by its endogenic porphyrins after illumination with high intensity blue light.

Propionibacterium acnes is a Gram-positive, microaerophilic bacterium that causes skin wounds. It is known to naturally produce high amounts of intracellular porphyrins. The results of the present study confirm that the investigated strain of P. acnes is capable of producing endogenic porphyrins with no need for any trigger molecules. Extracts from growing cultures have demonstrated emission peaks around 612 nm when excited at 405 nm, which are characteristic for porphyrins. Endogenic porphyrins were determined and quantified after their extraction from the bacterial cells by fluorescence intensity and by elution retention time on high-performance liquid chromatography (HPLC). The porphyrins produced by P. acnes are mostly coproporphyrin, as shown by the HPLC elution patterns. Addition of delta-aminolevulinic acid (ALA) enhanced intracellular porphyrin synthesis and higher amounts of coproporphyrin have been found. Eradication of P. acnes by its endogenic porphyrins was examined after illumination with intense blue light at 407-420 nm. The viability of 24 h cultures grown anaerobically in liquid medium was reduced by less than two orders of magnitude when illuminated once with a light dose of 75 J cm(-2). Better photodynamic effects were obtained when cultures were illuminated twice or three times consecutively with a light dose of 75 J cm(-2) and an interval of 24 h between illuminations. The viability of the culture under these conditions decreased by four orders of magnitude after two illuminations and by five orders of magnitude after three illuminations. When ALA-triggered cultures were illuminated with intense blue light at a light dose of 75 J cm(-2) the viability of the treated cultures decreased by seven orders of magnitude. This decrease in viability can occur even after a single exposure of illumination for the indicated light intensity. X-ray microanalysis and transmission electron microscopy revealed structural damages to membranes in the illuminated P. acnes. Illumination of the endogenous coproporphyrin with blue light (407-420 nm) apparently plays a major role in P. acnes photoinactivation. A treatment protocol with a series of several illuminations or illumination after application of ALA may be suitable for curing acne. Treatment by both pathways may overcome the resistance of P. acnes to antibiotic treatment.

Acne Vulgaris↗
PubMed1995

Age-related differences in the structure of human pineal calcium deposits: results of transmission electron microscopy and mineralographic microanalysis.

Pineal tissue calcifications (male, ages 14, 47, 62, 82), which were metallographically embedded and polished at controlled levels and studied by transmission electron microscopy and microanalytic spectroscopy, showed age-related differences. Results show that concentrically arranged crescent-shaped lamellae increase in number and decrease in width with age. Calcium (Ca) and phosphorus (P) per point measurements in dark and light lamellae at various distances from the core show Ca/P molar ratios between 1.49-1.62 in the 82-year-old specimen as compared to 1.26 to 1.41 in the younger specimens. The 62-year-old specimens show a decrease in P and an increase in Ca from periphery to center. These data and other descriptive details suggest that the sum of these changes represent remodelling of the mineralogical structure within the same calcification throughout the life span.

Adolescent↗
PubMed1993

Bio-microscopical observation of dystrophic calcification induced by calcium hydroxide.

Calcium hydroxide paste was introduced into a rabbit ear chamber, and the effect of calcium hydroxide on the vascular tissue was observed under a bio-microscope continuously up to 14 weeks. Many precipitates were observed at the border of living tissue, after the dissolution of microvessels around the paste. They increased both in size and number to combine like a river bank in the first 48 h. After 1 week, microcirculation recovered, and newly-formed capillaries approached the precipitate-bank, the edge of which became smoother as weeks went by. The bank was stable and compatible to microvessels during the observation period. By SEM observation, the width of the bank was from 200 to 400 microns, and the tissue-side of the bank appeared like amorphous lamellae, while the inner-side showed particle-like appearance. EDX examination revealed high peaks of Ca and P similar to calcium phosphate at the tissue-side of the bank, but only Ca peak at the inner-side. The precipitates seemed to have the potential to induce dystrophic calcification by absorbing Ca and P from the tissue.

Animals↗
PubMed1984

Single bovine enamel particles examined by electron optics.

Whole enamel scrapings from teeth of embryonic calves have been separated by density gradient centrifugation in organic solvents into fractions (1.6 less than p less than 2.4 g/cm3) representing progressive stages of mineral phase maturation. Single enamel particles or their small aggregates from such fractions were examined by transmission electron microscopy, electron diffraction, and high-spatial-resolution electron probe micro-analysis. The electron optical methods demonstrated the presence of poorly crystalline hydroxyapatite as the only detectable solid phase in all fractions. Octacalcium phosphate and brushite were not identified in the fractions. Changes in electron diffraction patterns were indicative of a progressive increase in apatite crystallinity with enamel maturation. Molar Ca/P ratios were found to range from 1.48 to 1.70, with a higher mean value obtained for lower-density fractions (p less than 2.0 g/cm3). Lower-density fractions contained some particles with high ratios (approximately equal to 2.0-4.0) and a non-uniform distribution of Ca and P, as revealed by electron probe mapping. These characteristics are suggested as possibly being related to carbonate phases in early enamel.

Animals↗
PubMed1986

The relationship between hardness and structure of Pd-Cu-Ga alloys.

Most Pd-Cu-Ga alloys on the market have a yield strength of the order of 1000 MPa, which is too high for an adequate adjustment of the margins of a crown and may promote wear of an opposing natural tooth. In the present work, the structure of a commercial Pd-10 wt% Cu-9 wt% Ga alloy has been shown by means of TEM to consist of thin (5-25 nm) laths with two ordered fct phases with the composition Pd3GaxCu1-x. The c/a ratios in these fct phases are, alternatingly, greater than 1 and less than 1. The transformation of an fcc structure by short atomic movements into the fct structures occurs rapidly below 500 degrees C, as judged by thermal expansion measurements. Such fct structures are likely to provide substantial resistance to dislocation movement and thus a high yield stress and hardness. By adding 6 wt% Ag to the Pd-Cu-Ga alloy and reducing the Ga and Cu content correspondingly, a predominantly fcc structure occurred with nearly no fct laths. At the same time, the hardness was reduced to approximately half the value for the initial Pd-Cu-Ga alloy.

Chemical Phenomena↗
PubMed2005

Rotary culture enhances pre-osteoblast aggregation and mineralization.

Three-dimensional environments have been shown to enhance cell aggregation and osteoblast differentiation. Thus, we hypothesized that three-dimensional (3D) growth environments would enhance the mineralization rate of human embryonic palatal mesenchymal (HEPM) pre-osteoblasts. The objective of this study was to investigate the potential use of rotary cell culture systems (RCCS) as a means to enhance the osteogenic potential of pre-osteoblast cells. HEPM cells were cultured in a RCCS to create 3D enviroments. Tissue culture plastic (2D) cultures served as our control. 3D environments promoted three-dimensional aggregate formations. Increased calcium and phosphorus deposition was significantly enhanced three- to 18-fold (P < 0.001) in 3D cultures as compared with 2D environments. 3D cultures mineralized in 1 wk as compared with the 2D cultures, which took 4 wks, a decrease in time of nearly 75%. In conclusion, our studies demonstrated that 3D environments enhanced osteoblast cell aggregation and mineralization.

Calcification, Physiologic↗
PubMed1998

The development of apical embryonic pattern in Arabidopsis.

The apical portion of the Arabidopsis globular stage embryo gives rise to the cotyledons and the shoot apical meristem (SAM). The SHOOT MERISTEMLESS (STM) gene is required for SAM formation during embryogenesis and for SAM function throughout the lifetime of the plant. To more precisely define the development of molecular pattern in the apical portion of the embryo, and the role of the STM gene in the development of this pattern, we have examined AINTEGUMENTA (ANT), UNUSUAL FLORAL ORGANS (UFO) and CLAVATA1 (CLV1) expression in wild-type and stm mutant embryos. The transcripts of these genes mark subdomains within the apical portion of the embryo. Our results indicate that: (1) the molecular organization characteristic of the vegetative SAM is not present in the globular embryo but instead develops gradually during embryogenesis; (2) radial pattern exists in the apical portion of the embryo prior to and independent of STM with STM expression itself responding to radial information; (3) the embryonic SAM consists of central and peripheral subdomains that express different combinations of molecular markers and differ in their ultimate fates; and (4) STM activity is required for UFO expression, STM is required for maintenance but not onset of CLV1 expression and the pattern of ANT expression is independent of STM.

Arabidopsis↗