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PubMed1989

Abrasives in snuff?

The purpose of this study was to determine and calculate the inorganic contents of four brands of snuff. Visual inspection of wet snuff showed fairly large, yellow crystal-like particles. Scanning electron microscopy and X-ray dispersive (EDX) analyses were used to study both wet snuff and ashes of snuff, whereas light emission spectrography was used to determine elements in the ashes. The crystal-like particles did not dissolve in distilled water or in ethanol heated to 60 degrees C. EDX analyses showed that most elements remained in the particles after washing. The total weight percentage of inorganic material in snuff was calculated after burning dried snuff until constant weight was obtained. The ashes of snuff did not contain any crystal-like particles but consisted of a small-grained amorphous mass. The following elements were detected: Ag, Al, Ba, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, P, Pb, Si, Sr, Ti, Va, and Zr. Other elements such as rare earths were not searched for. The weight percentage of inorganic elements ranged between 12.35 +/- 0.69 and 20.95 +/- 0.81. Provided snuff is used in the same manner as chewing tobacco, and some people admit to doing so, there is a risk that its relatively high contents of inorganic material and heavily soluble salts may be conducive to excessive abrasion of teeth and restorations.

Calcium↗
PubMed1997

Effect of particle morphology on emitted dose of fatty acid-treated disodium cromoglycate powder aerosols.

These studies assess the quantity and morphology of the emitted aerosolized dose of irregularly shaped disodium cromoglycate particles in the fine particle fraction using in vitro methods. Disodium cromoglycate was treated with a homologous series of saturated fatty acids, between C8 and C18, in a range of concentrations. The products of these treatments were powders with a variety of particle size, shape, and aggregation characteristics. Samples of these powders were loaded in gelatin capsules, generated as aerosols from a Rotahaler and collected in a two-stage liquid impinger or eight-stage inertial impactor. Particles were examined directly by scanning electron microscopy and subsequently the images were analyzed to define morphology. The aerodynamic fine-particle fraction determined by the two-stage impinger increased approximately twofold with lauric acid treatment (0.0317 g/g, 6.7%) and threefold with stearic acid treatment (0.58 g/g; 9.7%) compared with disodium cromoglycate alone (0 g/g, 3.56%). The lauric acid formulation appeared to alter deposition primarily by changing particle morphology. Stearic acid altered particle shape to some extent and the increase in the fine-particle fraction appeared to be attributable to improved particle dispersion properties. The uncontrolled presence of irregular-shaped particles can introduce dosing errors due to effects on dispersion and aerodynamic behavior. Conversely, controlled particle morphology and size may be employed to optimize the dose delivered to the lungs particularly if particle-particle and particle-surface interactions can be minimized.

Aerosols↗
PubMed2000

[Ultrastructure and elemental composition of frog bladder granular epithelial cells in normal state and upon stimulation of water transport].

Changes in the frog urinary bladder granular cell ultrastructure were analysed in parallel with those in element composition of these cells after induction of water transport across the urinary bladder wall. Two ultrastructural (ultrathin section and freeze-fracture) methods were used in addition to two methods of object preparation for electron microprobe analysis--freeze-drying and freeze-substitution. It has been shown that arginin-vasotocin stimulation of osmotic water flow across the urinary bladder wall causes certain morphological changes in the granular cells: decrease in electron density of the cytoplasm, depolymerization of the apical submembrane layer of actin microfilaments, increase in the number of sites of specific granules and apical membrane fusion, emergency of intramembrane particle aggregates in the apical membrane P-face. The quantitative electron microprobe analysis made it possible to reveal a statistically significant increase in sodium and calcium concentration and fall in that of potassium and chlorine in granular cells after water transport stimulation. A concentration gradient of sodium and potassium ions was seen to appear along the apical-basal axis in the cytoplasm of granular cells. Possible association between the obvious morphological transformations in granular cells and changes in their elemental composition has been discussed, in addition to some regulatory significance of calcium concentration increase in granular cells after arginin-vasotocin-induced osmotic water transport.

Animals↗
PubMed2000

Bonding of a self-etching primer to non-carious cervical sclerotic dentin: interfacial ultrastructure and microtensile bond strength evaluation.

PURPOSE: The objectives of this study were 1) to examine the ultrastructural features of the resin-sclerotic dentin interface following the application of Clearfil Liner Bond II sigma to natural cervical wedge-shaped lesions, and 2) to evaluate the regional tensile bond strength of this self-etching primer at different locations on natural and artificially-created cervical lesions. MATERIALS AND METHODS: Deep cervical natural lesions were bonded using the self-etching primer. Micromorphology of the bonded interface at different locations within the lesions were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy/energy dispersive x-ray analysis (STEM/EDX). Ultrastructural features were further compared with the use of the same self-etching primer on artificial lesions created in sound cervical dentin. A nontrimming technique was used to evaluate the regional tensile bond strength from the occlusal, gingival, and the deepest central part of both natural and artificial cervical lesions. Beams with a mean area of 0.46 +/- 0.03 mm2 were prepared and were pulled to failure using a Bencor Multi-T testing device attached to an Instron universal tester. Bond strength results were evaluated using a two-way ANOVA design. RESULTS: A hypermineralized layer devoid of intact, banded collagen was invariably present on the surface of the natural lesions. Depending upon its thickness at different locations of the lesion, the action of a self-etching primer may be limited to this surface layer alone, producing a hybridized hypermineralized surface layer. Penetration of the self-etching primer into the underlying sclerotic dentin produced a hybridized complex containing a hybridized hypermineralized surface layer as well as a subsurface layer of hybridized intertubular dentin. Bacterial colonization of the lesion surface resulted in the formation of an additional zone of hybridized intermicrobial matrix over the surface of the lesions. Dentinal tubules remained blocked with sclerotic casts, and resin tags were rarely observed. Regional tensile bond strength results showed that the overall bond strength to natural sclerotic dentin was about 20% lower than sound cervical dentin, but was independent of the different locations within the lesions from which bond strength was evaluated. CONCLUSION: There were four factors that may have influenced the overall decrease in bond strength in natural cervical sclerotic lesions: a) the presence of a hybridized intermicrobial matrix together with entrapped bacteria may have weakened the bonds, b) inability of a self-etching primer to etch through a thick, hypermineralized surface layer, c) presence of a layer of possibly remineralized, denatured collagen at the base of the hypermineralized surface layer, and d) retention of acid-resistant sclerotic casts that obliterate the tubular lumina and prevent effective resin tag formation.

Acid Etching, Dental↗
PubMedDate not supplied

Effects of Nd: YAG laser, air-abrasion and acid-etching on human enamel and dentin.

The effects of the Nd:YAG laser, air-abrasion and acid-etching systems on mineral content and surface morphology of cut dentin and enamel were examined in 10 extracted human teeth. Enamel specimens were lased for two seconds at a fluence of 0.75 J and a frequency of 15 Hz, air-abraded for two seconds with 50 micron Al-oxide and etched for 60 seconds with 37% ortho-phosphoric acid. Dentinal specimens were subjected to the same procedure for half the time. Untreated areas of the same specimens served as the control. Morphologically, the lased dentin showed an apparently melted surface with partial obstruction of the dentin tubules, as well as cracks along the lased surface. Air-abrasion created very irregular surfaces on enamel and dentin. Dentin tubules were observed on the acid-etched dentin samples but not the air-abraded surfaces. The Nd:YAG laser created the most surface irregularity on both enamel and dentin. Laser treatment appeared to alter the chemical structure and surface morphology of the dentin and enamel.

Acid Etching, Dental↗
PubMed2002

Characteristics of porous nickel-titanium alloys for medical applications.

We investigate the behavior of NiTi porous alloys, possessing the property of shape memory, by using different characterization methods XPS, Auger, DSC and SEM. The study mainly focuses on the determination of porosity, surface characteristics and the phase transformation. In the case of porous material the biomechanical compatibility is closely related to the internal structure and porosity distribution. To describe appropriately the influence of the properties of NiTi on the memory shape, two types of materials provided by different sources has been analyzed. Despite the fact that both materials present different pores size, they exhibit an open and interconnected porosity. Our measurements show that the temperature of the inception of the martensite-austenite phase transition occurs at 60 degrees C, which is by 20 degrees C greater than the body temperature. Moreover, we show that the surface characteristics can be greatly influenced by heat treatment. Furthermore, we observe that the R-phase occurs only for one of the used materials after its heat treatment. The correlation between the composition and the other characteristics measured has been found.

Alloys↗
PubMedDate not supplied

Surface chemistry effects of topographic modification of titanium dental implant surfaces: 2. In vitro experiments.

PURPOSE: To determine, in vitro, cytotoxicity and cell adhesion on 3 different implant surfaces. MATERIALS AND METHODS: All samples had machined surfaces, but they were subjected to different cleaning procedures, which produced 3 different surface chemistries. One of the samples was "as-produced" from the machining tools. The other samples were subjected to partial and total cleaning routines. Cytotoxicity was evaluated using mouse fibroblast cultures, and cell adhesion was evaluated with osteoblast-like SaOS-2 cells. RESULTS: The "as-produced" sample showed a pronounced surface contamination by lubricating oils. For partially and totally cleaned samples, an increasing amount of titanium and a decreasing carbon/titanium ratio was observed as cleaning became more complete. DISCUSSION: Differences in surface chemistry such as those normally found on titanium implant surfaces (see part 1 of this series) can lead to those same effects which, in in vitro experiments, are normally accounted for in terms of surface topography alone. CONCLUSION: Effects related to surface chemistry can operate over and above surface topography, making it impossible, without proper characterization, to make definite statements about the role of topography alone.

Animals↗
PubMedDate not supplied

Cell analysis with the new Leipzig high-energy ion nanoprobe.

The high-energy ion nanoprobe LIPSION at the University of Leipzig has been in operation since 1998. The ultrastable, 3.5 MV SINLETRON accelerator supplies the H+ or He+ ion beam. A magnetic scanning system moves the focused beam across the sample. At present, a resolution of 41 +/- 4 nm in the low current mode and 300 nm at 5 pA can be achieved. The experimental chamber is equipped with electron-, energy dispersive X-ray-, and particle detectors. They can be used simultaneously to analyse the sample by means of PIXE (particle induced X-ray emission), RBS (Rutherford backscattering), and in the case of thin sections or monolayer samples STIM (scanning transmission ion microscopy). A goniometer allows the application of channeling measurements in single crystals in combination with these methods. In contrast to previous publication describing microbeam facility at LIPSION, the current biomedical research has concentrated on microscopy and tomography on chondrocytes in pig cartilages and fixed single endothelial cells (HUVEC). For the irradiation of single living cells, an external beam facility with irradiation platform, fast beamgate and mini-Petri dishes is under construction.

Animals↗
PubMed2003

The otoliths of the antarctic teleost Trematomus bernacchii: scanning electron microscopy and X-ray diffraction studies.

The authors studied the otoliths of the Nototheniid Trematomus bernacchii with scanning electron microscopy and X-ray diffraction analysis. Results obtained reveal that three otoliths are present: a large sagitta, a lapillus and a fragile asteriscus. Their sensorial faces appear finely decorated as shown by scanning electron microscopy (SEM). The sagitta and the lapillus are aragonitic while the asteriscus is vateritic, as demonstrated by X-ray diffraction.

Animals↗
PubMedDate not supplied

Early tissue reaction at the interface of immediately loaded dental implants.

PURPOSE: The treatment of patients with early or immediately loaded dental implants has renewed interest in the behavior of osteoblasts at the implant surface under load. A newly designed dental implant indicated for immediate loading was tested in vivo for early stages of osteoblast behavior at the implant surface. MATERIALS AND METHODS: Thirty-two implants were placed in the mandibles of 8 minipigs. Half of the implants (n = 16) were immediately loaded under occlusal contacts, and implants placed in non-occlusal relations served as a control. RESULTS: All implants, except 1 that showed signs of tissue infection, healed uneventfully and were stable throughout the experimental period. Ultrastructural analysis of mandibular specimens revealed an intimate attachment of osteoblasts to the material surface beginning as early as day 1. Application of either occlusal or non-occlusal load did not alter the phenotypic morphology of the attached osteoblasts. Transmission electron microscopy and x-ray diffraction analysis demonstrated a direct contact of bone-like minerals over the whole implant surface with no signs of crestal hard tissue alteration. Electron diffraction analysis showed a slight release of titanium from the implant side. DISCUSSION: These results indicate that immediate loading of specially designed dental implants can be performed without disruption of the titanium/bone interface or disturbance of osteoblast physiology in the early loading phase. CONCLUSION: Immediate loading protocols can be performed without disturbance of normal bone biology.

Animals↗
PubMed1991

Detection of bone and bone-plus-bullet particles in backspatter from close-range shots to heads.

A victim was shot in the head with a 9-mm Smith & Wesson pistol using Winchester Silvertip hollow-point ammunition. Of interest in this case was the distance from the muzzle of the weapon to the victim's head, since the wound characteristics were equivocal for firing distance. Two other handguns (revolvers) were involved in this shooting, in addition to a revolver owned by the victim. The handguns were sampled using tape lifts, and the casings were sampled by washing them in distilled water, followed by vacuum filtration of the washing water through 0.2-microns-pore Nuclepore filters. These materials were examined by scanning electron microscopy/energy-dispersive X-ray analysis. Calcium-phosphorous (bone) particles were detected on the 9-mm Smith & Wesson pistol, on two casings found at the scene, and on one of the revolvers. Two of the calcium-phosphorous particles on the casings had associated bullet fragments. Test shots on live pigs destined for slaughter showed that bone particles are a feature of backspatter from close-range shots to heads. Contamination of nearby surfaces by bone fragments and bone-plus-bullet fragments, as well as other organic debris, appears to be quite heavy.

Animals↗
PubMed1991

Heterogeneity of crystals attached to the human enamel and cementum surfaces after calculus removal in vitro.

Twenty one extracted human teeth with dental calculi on the enamel and cementum surfaces, fixed in 10% neutral formaldehyde, were selected for this study. After ethanol dehydration and air drying, these calculi were removed by tweezers to observe the teeth surfaces under them. The inspection of these surfaces using SEM and EDX revealed hexahedrally based crystals including pseudocuboidal, rhombohedral and variable rugged rocky shapes. These crystals were identified as Mg-containing whitlockite. The pseudocuboidal crystals, measuring about 4.5 microns in maximum length, were widely distributed on the cervical enamel surface previously covered by calculus. On the root surface, however, these areas decreased remarkably; the shapes changed from pseudocubes into rhombohedrons and rugged rocky structures, while their sizes were smaller and the Mg content decreased. The difference in frequency and morphological variation of the hexahedrally based crystals might be caused by the different characteristics of enamel and cementum surfaces and the Mg present on these surfaces.

Calcium Phosphates↗
PubMed1991

[Texture formation of the dental ceramic core material In-Ceram and thermal expansion of its individual components].

Electron microscopic investigations of the core material In-Ceram show how its texture is formed. While these are processed the Al2O3 crystallites turn idiomorphic. Etching the material with sulphuric acid selectively dissolves the glassy phase and reveals the crystallites. The chemical composition of the two components of the core material is determined by microprobe analysis. While the crystallites are pure Al2O3, the glass consists of La2O3, SiO2, Al2O3 and CaO. Measurements of the thermal expansions of the glass and the Al2O3 frame show the value for the glass to be 5.1% lower than that of the Al2O3 frame. This results in internal pressure and contributes to the high strength of the material.

Aluminum Oxide↗
PubMed1991

SEM and energy dispersive X-ray surface analysis of the interfacial region of selected porcelain-metal systems.

Comparative bond strength data of Ceramco and Vita opaque and body porcelains when fired to high noble, medium noble, and base metal porcelain-fused-to-metal alloys were recently published. In the present study SEM and energy dispersive X-ray (EDX) microanalyses were undertaken--using the same specimens after debonding--to relate the bond strengths reported for 12 different porcelain-metal composites to morphology and chemistry at fracture sites. SEM examination revealed intimate contact between the different porcelains and the metal oxide substrates. On Olympia, a medium noble alloy, bubbles trapped in porcelain at or near fracture sites appeared to decrease the potential interaction. Area scan semiquantitative EDX analysis of the interfacial fracture sites detected high concentrations of metal oxides thought to be essential for a successful chemical bond. Multi-spot surface spectroscopy on similar traces of porcelain residuals revealed significant differences in the amount of particular back scattering activity. Further examination with cross sectional quantitative EDX analysis is suggested for a more precise characterization of element concentration within all components of the porcelain-metal interface.

Dental Alloys↗