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PubMed1994

Development of an in vitro culture system for the study of osteoclast activity and function.

Resorption is a difficult process to study in vivo because of the complex organization of mineralized tissue. The objective of this study was to develop an in vitro culture system for studying osteoclast attachment and activity. Transparent, microporous substrata were prepared using radio frequency-sputtering techniques to apply a thin layer of hydroxyapatite on polycarbonate filters previously coated with Type I collagen. Dentinoclasts isolated from the root surface of rat molar teeth undergoing inflammatory resorption and osteoclasts isolated from the endosteal surfaces of rat long bones were incubated on the experimental substrata. The culture system proved successful, supporting osteoclast viability and activity as demonstrated by cellular attachment and spreading seen by scanning electron microscopy. Activity was further demonstrated by monitoring acid production using a fluorescent probe, acridine orange. Isolated osteoclasts or dentinoclasts, when combined with synthetically prepared substrata, were observed to respond by mechanisms comparable to those that occur in vivo. Therefore, the system developed permits basic observations of osteoclasts in an in vitro system.

Animals↗
PubMed1986

Extensive subretinal pigment epithelial deposit in two brothers suffering from dominant retinitis pigmentosa. A histopathological study.

The eyes of two brothers with retinitis pigmentosa were removed after death and examined by a variety of techniques, including conventional histology, fluorescence microscopy and both scanning and transmission electron microscopy. Their condition was considered to be of an autosomal dominant type but with some atypical clinical features. The outstanding histological feature in both pairs of eyes was a predominantly acellular deposit of amorphous material situated between the retinal pigment epithelium and Bruch's membrane. This material extended from the disc to beyond the ora serrata. In some regions of the retinae of both brothers, there was a cellular infiltrate into the deposit and this included multinucleate cells. In one brother the deposit was lined externally by a fibrovascular membrane in some few locations. All retinae were degenerate, but all showed preservation of abnormally short and sparse photoreceptor cells in both the peripheral and macular areas. There was only patchy loss of the choriocapillaris, which could have been age-dependent rather than disease-dependent, and the remaining choroidal vessels were patent in all cases. The widespread distribution of the deposit is unusual and suggests that it arises from disordered metabolism of the retinal pigment epithelium. We could not determine whether it was a primary disease process or if it arose as a secondary phenomenon.

Electron Probe Microanalysis↗
PubMed1998

Microstructure and homogeneity of dental porcelain frits.

The microstructure and homogeneity of three commercial dentin and incisal unfired porcelain frits (one conventional and two ultra-low fusing types, fused-to metal were analyzed by X-ray diffractometry, scanning electron microspectroscopy, and wavelength- and energy dispersive X-ray microspectroscopy. The average contents of tetragonal and cubic leucite for the conventional and one of the ultra-low fusing type frits were 20.1-22.6 wt% and 0-2.6 wt%, respectively, whereas those of another of the ultra-low fusing type frits were about 11.5-11.6 wt% and 2.9-4.6 wt%, respectively. The conventional type frits seemed to be admixtures of three kinds of glass frits. One of the ultra-low fusing type frits seemed to be an admixture of four kinds of glass frits. Another ultra-low fusing frits seemed to be only one kind of glass frit dispersed with small size, less than 1 micron, leucite crystals. There were no remarkable differences in microstructure and homogeneity between dentin and incisal porcelain frits in each brand.

Aluminum Silicates↗
PubMed1996

Electrolytes in the cornea: a therapeutic challenge.

BACKGROUND: Reported here are the results of electrolyte measurements in different layers of 70 apparently normal human corneas. METHODS: Samples were examined by energy-dispersive X-ray analysis under calibrated conditions in a scanning electron microscope. The method allows the simultaneous quantitative analysis of, among others, sodium (Na), chloride (Cl), phosphorus (P) and potassium (K). The results are related to the dry weight of the analyzed samples. Four distinct layers, subepithelium, middle stroma, posterior stroma and Descemet's membrane, were analysed in each cornea. RESULTS: In the middle stroma we found concentrations of: sodium 0.609 +/- 0.13, chloride 0.557 +/- 0.115, potassium 0.058 +/- 0.02 and phosphorus 0.038 +/- 0.01 (mol/kg dry weight) [corrected]. CONCLUSION: The collation of normal electrolyte concentrations provides reference values for future studies on changes of the corneal electrolyte composition in diseased or injured eyes. The electrolyte composition of rinsing fluids or eye drops should be adjusted to that of the corneal stroma. Phosphate buffer, for example, is not a good vehicle for topical eye treatments and should be replaced by organic buffering systems.

Adult↗
PubMed1988

Bone formation in vitro by stromal cells obtained from bone marrow of young adult rats.

Cells from fetal or neonatal skeleton can synthesize bone-like tissue in vitro. In contrast, formation of bone-like tissue in vitro by cells derived from adult animals has rarely been reported and has not been achieved using cells from bone marrow. We have explored development of bone-like tissue in vitro by bone marrow stromal cells. Marrow stromal cells obtained from 40-43-day-old Wistar rats were grown in primary culture for 7 days and then subcultured for 20-30 days. Cells were cultured in either alpha-minimal essential medium containing 15% fetal bovine serum, antibiotics, and 50 micrograms/ml ascorbic acid, or the above medium supplemented with either 10 mM Na-beta-glycerophosphate, 10(-8) M dexamethasone, or a combination of both. Cultures were examined using phase-contrast microscopy, undemineralized and demineralized tissue histology, histochemistry (for alkaline phosphatase activity), immunohistochemistry (for collagen type, osteonectin, and bone Gla-protein), scanning and transmission electron microscopy, energy dispersive X-ray microanalysis, and X-ray diffraction. Collagenous, mineralized nodules exhibiting morphological and ultrastructural characteristics similar to bone were formed in the cultures, but only in the presence of both beta-glycerophosphate and dexamethasone. Cells associated with the nodules exhibited alkaline phosphatase activity. The matrix of the nodules was composed predominantly of type-I collagen and both osteonectin and Gla-protein were present. X-ray microanalysis showed the presence of Ca and P, and X-ray diffraction indicated the mineral to be hydroxyapatite. The nodules were also examined for bone morphogenetic protein-like activity. Paired diffusion chambers containing partly demineralized nodules and fetal muscle were implanted intraperitonealy in rats. Induction of cartilage in relation to muscle was observed histologically after 40 days in the chambers. This finding provided further support for the bone-like nature of the nodules. The observations show that bone-like tissue can be synthesized in vitro by cells cultured from young-adult bone marrow, provided that the medium contains both beta-glycerophosphate and, particularly, dexamethasone.

Aging↗
PubMed1999

Morphological changes of human teeth with Er:YAG laser irradiation.

OBJECTIVE: The purpose of this study was to investigate morphological changes in human enamel and dentin structures irradiated with the use of an Er:YAG laser. SUMMARY BACKGROUND DATA: Despite the high number of research projects concerned with digital applications of lasers, few studies have targeted the effects of Er:YAG laser irradiation on human enamel or dentin structures. METHODS: Enamel and dentin surfaces of 40 extracted human teeth were irradiated for 5 seconds with a 2.94 microns wavelength, at an output of 300 mJ. Histological and scanning electron microscope studies were then performed to determine the morphological changes in the enamel and dentin structures of those teeth. RESULTS: The Er:YAG laser beam produced defects without signs of serious thermal damage to enamel or dentin. Undesirable thermal effects such as surface cracking or carbonization were not observed. Histological examinations revealed the presence of a thin basophilic line at the bottom and along the walls of defects in the dentin. These morphological changes were evidence of minimal thermal damage to surrounding tissue. CONCLUSIONS: These findings suggest that it is possible to remove the enamel and dentin using Er:YAG laser irradiation with minimal thermal changes. However, the mechanism involved in the ablation of enamel and dentin by Er:YAG laser irradiation has not been clarified in this study. Therefore, more research is necessary before the Er:YAG laser can be used clinically in the future.

Dental Enamel↗
PubMed1994

In vivo wear pattern of experimental composite resins containing different filler components.

Using a scanning electron microscope (SEM) and an electron probe surface roughness analyzer (ERA), we conducted the in vivo study of the effect of various filler components on the wear of composite resins. Experimental light-cured composite resins were prepared employing three different filler components; -(1) Silica type, (2) Strontium type, and (3) Barium type. The filler content for all three types was 80 wt%, with the mean particlesize being 2.6 microns in diameter. The resin monomers consisted of 40 wt% Bis-GMA, 40 wt% TEGDMA and 20 wt% UTMA. These materials were placed in 2 mm diameter cylindrical cavities located in the OCA (occlusal contact area) or the CFA (contact free area) of cast crowns temporarily set in a volunteer patient's mouth. The crowns were removed at monthly intervals for longitudinal SEM observation. After two months, worn surfaces were also analyzed by ERA. The result showed that the wear patterns of the composites were characterized by the filler components, especially in the OCA.

Adult↗
PubMed2004

Evaluation of shear bond strength at the interface of two porcelains and pure titanium injected into the casting mold at three different temperatures.

STATEMENT OF PROBLEM: Titanium has physical and mechanical properties, which have led to its increased use in dental prostheses despite casting difficulties due to high melting point and formation of oxide layers which affect the metal-ceramic bond strength. PURPOSE: This in vitro study evaluated the shear bond strength of the interface of 2 dental porcelains and pure titanium injected into a mold at 3 different temperatures. MATERIAL AND METHODS: Using commercially pure (cp) titanium bars (Titanium, Grade I) melted at 1668 degrees C and cast at mold temperatures of 430 degrees C, 700 degrees C or 900 degrees C, 60 specimens were machined to 4 x 4 mm, with a base of 5 x 1 mm. The 4-mm surfaces were airborne-particle abraded with 100 microm aluminum oxide before applying and firing the bonding agent and evaluating the 2 porcelains (Triceram/Triline ti and Vita Titankeramik). Ten specimens were prepared for each temperature and porcelain combination Shear bond testing was performed in a universal testing machine, with a 500-kg load cell and crosshead speed of 0.5 mm/min. The specimens were loaded until failure. The interfaces of representative fractured specimens of each temperature were examined with a scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Data for shear bond strength (MPa) were statistically analyzed by 2-way ANOVA and the Tukey test (alpha=.05). RESULTS: The results showed significant differences for the metal/porcelain interaction effect (P=.0464). There were no significant differences for the 2 porcelains (P=.4250). The Tukey test showed a significant difference between the pair cp Ti 430 degrees C Triceram and cp Ti 900 degrees C Triceram, with respective mean values and SDs of 59.74 +/- 11.62 and 34.03 +/- 10.35 MPa. CONCLUSION: Triceram porcelain showed a bond strength decrease with an increase in the mold temperature for casting titanium. The highest bond strength for Vita porcelain and the best metal-ceramic interface observed with the SEM were found with the mold temperature of 700 degrees C.

Air Abrasion, Dental↗
PubMed1991

Protein adsorption to poly(ethylene oxide) surfaces.

Surfaces containing poly(ethylene oxide) (PEO) are interesting biomaterials because they exhibit low degrees of protein adsorption and cell adhesion. In this study different molecular weight PEO molecules were covalently attached to poly(ethylene terephthalate) (PET) films using cyanuric chloride chemistry. Prior to the PEO immobilization, amino groups were introduced onto the PET films by exposing them to an allylamine plasma glow discharge. The amino groups on the PET film were next activated with cyanuric chloride and then reacted with bis-amino PEO. The samples were characterized by scanning electron microscopy, water contact angle measurements, gravimetric analysis, and electron spectroscopy for chemical analysis (ESCA). The adsorption of 125I-labeled baboon fibrinogen and bovine serum albumin was studied from buffer solutions. Gravimetric analysis indicated that the films grafted with the low-molecular-weight PEO contained many more PEO molecules than the surfaces grafted with higher-molecular-weight PEO. The high-molecular-weight PEO surfaces, however, exhibited greater wettability (lower water contact angles) and less protein adsorption than the low-molecular-weight PEO surfaces. Adsorption of albumin and fibrinogen to the PEO surfaces decreased with increasing PEO molecular weight up to 3500. A further increase in molecular weight resulted in only slight decreases in protein adsorption. Protein adsorption studies as a function of buffer ionic strength suggest that there may be an ionic interaction between the protein and the allylamine surface. The trends in protein adsorption together with the water contact angle results and the gravimetric analysis suggest that a kind of "cooperative" water structuring around the larger PEO molecules may create an "excluded volume" of the hydrated polymer coils. This may be an important factor contributing to the observed low protein adsorption behavior.

Adsorption↗
PubMed2001

Graded microstructure and mechanical properties of human crown dentin.

The mineralized tissue of intertubular dentin is a collagen-mineral composite with considerable local variations of mechanical properties. Area scans of human coronal dentin were made by complementary methods to investigate correlations between local mechanical properties and the density, size, and crystallinity of the mineral particles. Scanning images from the same specimen were collected with Fourier-transform infrared microspectroscopy in reflectance mode (FTIR-RM), small angle X-ray scattering (SAXS), quantitative backscattered electron imaging (qBEI), and Nanoindentation in an atomic force microscope. The mineral content of dentin was found to decrease and the thickness of mineral crystals to increase towards the dentin-enamel junction (DEJ). Hardness and elastic modulus both decreased towards the DEJ. In a correlation analysis, the mineral content and, even more, the thickness of mineral crystals were found as the best predictors of hardness. The dentin layer close to the DEJ corresponds to a local minimum in hardness and elastic modulus, a configuration known to be an effective obstacle for crack propagation. Hence, the observed variations of mechanical and structural properties in an area between 0 and 1.5 mm below the DEJ define crown dentin as a gradient material optimized for its mechanical function.

Crystallization↗
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↗
PubMed2002

Nanoindentation mapping of the mechanical properties of human molar tooth enamel.

The mechanical behavior of dental enamel has been the subject of many investigations. Initial studies assumed that it was a more or less homogeneous material with uniform mechanical properties. Now it is generally recognized that the mechanical response of enamel depends upon location, chemical composition, and prism orientation. This study used nanoindentation to map out the properties of dental enamel over the axial cross-section of a maxillary second molar (M(2)). Local variations in mechanical characteristics were correlated with changes in chemical content and microstructure across the entire depth and span of a sample. Microprobe techniques were used to examine changes in chemical composition and scanning electron microscopy was used to examine the microstructure. The range of hardness (H) and Young's modulus (E) observed over an individual tooth was found to be far greater than previously reported. At the enamel surface H>6GPa and E>115GPa, while at the enamel-dentine junction H<3GPa and E<70GPa. These variations corresponded to the changes in chemistry, microstructure, and prism alignment but showed the strongest correlations with changes in the average chemistry of enamel. For example, the concentrations of the constituents of hydroxyapatite (P(2)O(5) and CaO) were highest at the hard occlusal surface and decreased on moving toward the softer enamel-dentine junction. Na(2)O and MgO showed the opposite trend. The mechanical properties of the enamel were also found to differ from the lingual to the buccal side of the molar. At the occlusal surface the enamel was harder and stiffer on the lingual side than on the buccal side. The interior enamel, however, was softer and more compliant on the lingual than on the buccal side, a variation that also correlated with differences in average chemistry and might be related to differences in function.

Anatomy, Cross-Sectional↗
PubMed1993

Calcospherites in rabbit incisor predentin.

Calcospherites from the lower incisor dentin of rabbits were investigated by scanning and transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and electron diffraction analyses. In the labial predentin, globular calcospherites of 8-31 microns were present at the root apex, decreasing in size toward the incisal region. The calcospherites at the intermediate region were of mulberry- as well as of spindle-shape of 1.5-4 microns diameter. The incisal pulp horn contained micro-calcospherites of 0.3-0.6 micron in diameter. In the lingual predentin, small granular calcospherites of 1.8-3 microns were present at the root apex, increasing in size toward the intermediate region. Ultrathin sections of globular calcospherites showed bundles of collagen fibrils at the root apex of the labial predentin. The diameters of individual bundles ranged from 1.2-3.4 microns. The width of the fibrils in the bundles was approximately 120-170 nm. Bundles of collagen fibrils were not found in the lingual predentin. Crystals of calcospherites were identified as apatite by electron diffraction. Those at the intermediate region showed preferred orientation of the c-axis. TEM-EDS analyses indicated that Ca and P were the major elements, with small amounts of Mg. The Mg/Ca molar ratios decreased from the root apex to the incisal pulp horn. Ca peak intensities increased from the root apex to the incisal region.

Animals↗
PubMed2001

Observations at the articular surface of hip prostheses: an analytical electron microscopy study on wear and corrosion.

We used scanning electron microscopy in combination with X-ray microanalysis to evaluate Co-, Cr-, and Mo-based human femoral hip prostheses. In total, 23 retrieved implants and four new implants were included in this study. Scanning electron microscopy of the polished surface of all arthroplasties showed, in addition to the polishing marks, small round and angular holes or pits. Other types of surface irregularities were interpreted as wear or corrosion of the metal compound. In all cases studied, corrosion propagated from holes at the surface of the polished prosthesis heads, in some cases also along phase boundaries. X-ray microanalysis of the intact prosthetic surface showed a relative composition of the elements Co, Cr, and Mo, which was in agreement with the manufacturer's information (63:33:4%). However, X-ray microanalysis spot analysis of the surface holes showed deviation in the relative composition of the elements Co, Cr, and Mo and also the presence of Si, Ti, and Al. Furthermore, Ti and Al could be traced back at an artificially made fracture plane of a new prosthesis. Therefore, Ti and Al have to be present during the manufacturing process. These impurities in the metal prosthesis alloy may create a galvanic element with the Co, Cr, Mo alloy of the implant. If this is the case, such a galvanic element in combination with the electrolyte environment formed by body fluids, can induce galvanic corrosion with release of metal particles.

Arthroplasty, Replacement, Hip↗
PubMed1994

The distribution of calcium salt precipitates in the core, periphery and shell of cholesterol, black pigment and brown pigment gallstones.

Calcium bilirubinate, palmitate, carbonate and phosphate have been identified in the cores of cholesterol and pigment gallstones, suggesting a role for precipitated calcium salts in the early events of gallstone formation. Previous studies that compared the calcium salt contents of cholesterol and pigment stones required destruction of gallstone structure. We have used scanning electron microscopy with windowless energy-dispersive x-ray microanalysis to determine the prevalence of calcium salts in a series of cholesterol (n = 105), black pigment (n = 35) and brown pigment (n = 6) gallstones obtained from 146 consecutive patients undergoing cholecystectomy. These techniques provide specific identification of cholesterol and individual calcium salts as they occur within the core, periphery and shell of gallstones without destroying stone structure. Calcium precipitates more than 0.5 micron in diameter can be detected in a cholesterol background at a detection limit of 0.01% by weight. Calcium salts were detected in the centers of 88% of cholesterol and 100% of black (p < 0.05 vs. cholesterol) and brown pigment stones. Calcium bilirubinate was identified in the cores of 54% of cholesterol and in all pigment stones (p < 0.001 black pigment vs. cholesterol). Calcium palmitate was detected in all brown pigment stones, in 39% of cholesterol stones (p < 0.001 vs. brown pigment) and in 31% of black stones (p < 0.01 vs. brown pigment). Peripheral calcium salts were detected less in cholesterol (19%) than in black or brown stones (100%, p < 0.05). Fourteen percent of cholesterol and black pigment stones were surrounded by shells containing mostly calcium carbonate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

Intracellular electrolyte concentrations in epithelial tissue during various functional states.

The scanning electron microscope together with an energy dispersive system was used to quantify intracellular elemental concentrations of transporting epithelial cells under a variety of experimental conditions. In the frog skin, the Na transport pool is comprised of the intracellular compartments of all vital cells in the different cell layers, except the mitochondria rich cells. The Na content of this transport pool exchanges easily with the epithelial (outer) bathing solution. Vasopressin increases the Na permeability of the corial cell barrier. Proximal and distal tubular cells of the rat kidney show differences in the pattern of intracellular element concentrations. The distal tubular cell is more resistant to 20 min of ischemia than the proximal cell. The changes in intracellular electrolyte concentrations following 60 min of ischemia are reversible after reperfusing the kidney with blood for 60 min. In the cells of the frog skin and rat kidney, Na and K were equally distributed between the cytoplasm and the nucleus. Differences exist for P, Cl and dry weight.

Amiloride↗
PubMed1992

Root surface characteristics associated with subgingival placement of monolithic tetracycline-impregnated fibers.

The purpose of this investigation was to inspect and characterize the subgingival root surface after a 10-day exposure in vivo to 25% tetracycline hydrochloride by weight in an ethylene vinyl acetate copolymer fiber matrix with and without root planing therapy. The root surfaces were examined by fluorescent-light microscopy (FLM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Thirty-two teeth were selected for study, 4 from each of 8 patients. The teeth of each patient were randomly assigned to one of four treatment groups: non-treated control (C), scaling and root planing only (RP), tetracycline-impregnated fiber only (F), and scaling and root planing with tetracycline-impregnated fiber application (RP/F). SEM revealed a visible reduction in the subgingival microbial flora in both the F and RP/F treatment groups in comparison with the C group specimens. Many of the residual bacteria observed in F and RP/F specimens appeared non-viable, exhibiting obvious loss of membrane integrity. In contrast, the RP specimens exhibited randomly distributed areas of residual subgingival plaque and calculus with newly developing plaque fronts; the plaque fronts undoubtedly having formed during the 10 days post-therapy. All RP/F specimens exhibited an incomplete removal of adsorbed root surface pellicle and demineralization of the subsequently exposed root surface. EDS analysis of large crystals adhering to root surfaces of F and RP/F specimens revealed high chloride peaks, suggesting the presence of residual tetracycline. FLM examination of F and RP/F treated specimens showed a superficial penetration of tetracycline into the root surface of about 10 microns. Areas of demineralized root showed slight tetracycline penetration into exposed dentinal tubules.

Adsorption↗
PubMed1995

A new scanning electron microscopy approach to the quantification of bone mineral distribution: backscattered electron image grey-levels correlated to calcium K alpha-line intensities.

The introduction of backscattered electron (BSE) imaging in scanning electron microscopy (SEM) has led to new possibilities for the evaluation of mineral distributions in bone on a microscopic level. The different grey-levels seen in the BSE-images can be used as a measure for the local mineral content of bone. In order to calibrate these BSE-grey-levels (BSE-GL) and correlate them to mineral contents, various attempts, using reference samples with known weighted mean atomic number and/or using simulated bone tissues with known hydroxyapatite concentrations, have been made. In contrast, a new approach is presented here based on measurements of the X-ray intensities of the calcium K alpha-line on selected areas of real bone samples; the measured intensities are then related to the corresponding BSE-GL. A linear positive correlation between weight percent (wt%) calcium and BSE-GL was found. When the BSE-mode is standardized using carbon and aluminum as references, the different mineral contents in bone samples can be recorded as BSE-GL, calibrated to wt% of calcium or hydroxyapatite (HA), respectively. The resulting mineral concentration histograms have a dynamic range from 0 to 89 wt% HA and have a binwidth resolution of 0.45 wt% HA. The presented modifications of the BSE method strongly enhance its feasibility in the field of bone research and its application as a special diagnostic tool for bone diseases.

Bone Density↗