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PubMedDate not supplied

Bone bonding behavior of three kinds of apatite containing glass ceramics.

We have produced three kinds of apatite-containing glass ceramics of the same chemical composition: MgO (4.6), CaO (44.9), SiO2 (34.2), P2O5 (16.3), CaF2 (0.5) (in weight ratio). They contain different crystal combinations and have different mechanical properties. The first glass ceramic (A-GC) was prepared by heating a glass plate to 870 degrees C. It contains only oxy- and fluoroapatite (35 wt%). The second glass ceramic (A-W-GC), and the third (A-W-CP-GC), were prepared by heating glass powder compacts to 1050 degrees C and 1200 degrees C, respectively. A-W-GC contains oxyapatite and fluoroapatite (Ca10(PO4)6(O,F2] (35 wt%) and beta-wollastonite (40 wt%). A-W-CP-GC contains oxyapatite and fluoroapatite (20 wt%), beta-wollastonite (CaO X SiO2) (55 wt%), and beta-whitlockite (3CaO X P2O5) (15 wt%). The bending strengths of A-GC, A-W-GC, and A-W-CP-GC were 88MPa, 178MPa, and 213MPa, respectively, in air. Rectangular ceramic plates (15mm X 10mm X 2mm) were implanted into a rabbit tibia. Ten and 25 weeks after implantation, the segment of tibia with implant was excised for examination. The segment was held by a special jig and the traction breaking load (failure load) was measured by an autograph. A-GC showed a lower load than A-W-GC and A-W-CP-GC. The loads for A-W-GC and A-W-CP-GC were almost equal. The failure loads did not change significantly between 10 and 25 weeks for any of the materials. The interface was examined by Giemsa surface staining, contact micro-radiography, and SEM-EPMA. Giemsa surface staining and CMR revealed direct bonding between the materials and the bone for all the three materials. SEM-EPMA showed that Si and Mg content decreased, Ca content did not change, and P content increased at the reaction zone between all three glass ceramics and bone. This was observed at 10 weeks, as well as at 25 weeks, after implantation. The reaction zone was narrowest with A-GC, wider with A-W-GC, and widest with A-W-CP-GC.

Animals↗
PubMed2003

Effect of processing variables on texture development in a mica-based glass-ceramic.

The purpose of this study was primarily to determine the feasibility of heat-pressing a mica-based glass-ceramic with the use of commercially available dental equipment, and secondly to evaluate the effect of various processing variables on the degree of crystal alignment in the pressed glass-ceramic. The hypotheses were that the mica-based glass-ceramic could be successfully heat-pressed and that some degree of crystal orientation would be obtained, depending on the processing variables. The glass composition was melted at 1400 degrees C for 2 h and cast into 12 x 60-mm rods. Ingots (10 x 12 mm) were cut from the glass rods, heat treated, and heat-pressed under various conditions. The microstructure of the pressed specimens was investigated by SEM and compared to that of heat-treated controls. The length of Vickers-induced cracks was measured on heat-pressed specimens and heat-treated controls. The results showed that mica-based glass-ceramics could be successfully pressed with the use of commercially available dental equipment. The resulting degree of crystal alignment (texture) along the direction of pressing varied between 35 +/- 6 and 79 +/- 6. There was a linear relationship between the degree of texture and the apparent aspect ratio of the mica platelets. A significant decrease in the length of the Vickers-induced cracks in the direction perpendicular to pressing was observed, associated with an increase in length in the direction of pressing.

Aluminum Silicates↗
PubMed2001

Mutation of the zebrafish glass onion locus causes early cell-nonautonomous loss of neuroepithelial integrity followed by severe neuronal patterning defects in the retina.

Mutation of the glass onion locus causes drastic neuronal patterning defects in the zebrafish retina and brain. The precise stratified appearance of the wild-type retina is absent in the mutants. The glass onion phenotype is first visible shortly after the formation of optic primordia and is characterized by the rounding of cells and disruption of the ventricular surface in the eye and brain neuroepithelia. With exception of the dorsal- and ventral-most regions of the brain, neuroepithelial cells lose their integrity and begin to distribute ectopically. At later stages, the laminar patterning of retinal neurons is severely disrupted. Despite the lack of lamination, individual retinal cell classes differentiate in the glass onion retina. Mosaic analysis reveals that the glass onion mutation acts cell nonautonomously within the retina and brain, as neuroepithelial cell morphology and polarity in these tissues are normal when mutant cells develop in wild-type hosts. We conclude that the glass onion mutation affects cell-cell signaling event(s) involved in the maintenance of the neuroepithelial cell layer shortly after its formation. The disruption of neuroepithelial integrity may be the cause of the neuronal patterning defects following neurogenesis. In addition, the expression of the glass onion phenotype in a subset of neuroepithelial cells as well as its onset following the initial formation of the neuroepithelial sheets indicate the presence of genetically distinct temporal and spatial subdivisions in the development of this histologically uniform tissue.

Animals↗
PubMed1985

[Death by peroral ingestion of soluble glass (sodium silicate)].

The intake of 0.51 of water glass (sodium metasilicate; colloid pH 12.5) led to death within 1-1.5 h. Autopsy revealed alkali burns of the stomach mucosa. The stomach contained a small amount of liquid with a pH of 11.5. Histologically, numerous bronchioles and alveoles were filled with amorphous material. This material was chemically proved to be condensed water glass. The obstruction of large parts of the lungs by water glass led to an inhibition of alveolar gas diffusion, which may have been the cause of death. The transformation of the water glass from liquid to solid occurred in the lungs by means of the carbonic acid of expiration air. This was made possible because the pH of water glass had been changed by gastric secretions from 12.5 to 11.5. Water glass starts to solidify around pH 11.4-11.3.

Aged↗
PubMed1995

Scanning electron microscopy-electron probe microanalysis study of the interface between apatite and wollastonite-containing glass-ceramic and rabbit tibia under load-bearing conditions after long-term implantation.

Glass-ceramic implants containing oxy- and fluoroapatite [Ca10(PO4)6(O, F2)] and beta-wollastonite (CaSiO3) were studied under load-bearing conditions in a segmental replacement model in the tibia of the rabbit. A 16-mm segment of the middle of the tibial shaft was resected at a point distal to the junction of the tibia and the fibula. The defect was replaced by a 15 mm-long hollow, cylindrical implant that was fixed by intramedullary nailing using Kirschner wire. The implants were 9 mm in diameter and 15 mm long bearing a central hole 3.05 mm in dianeter. The rabbits used were killed 6 months, 1 year, 18 months, and 2 years after implantation. The interface between the bone and the glass-ceramic was investigated by scanning electron microscopy-electron-probe microanalysis (SEM-EPMA). None of the glass-ceramic implants broke, and the glass-ceramic had bonded directly to the bone tissue without any intervening soft tissue. A calcium-phosphorus layer (Ca-P layer) was observed at the glass-ceramic/bone interface. This layer was 30-100 microns thick at 6 months after implantation, 60-110 microns thick at 1 year after implantation, 80-200 microns thick at 18 months, and 120-350 microns thick at 2 years. At the lateral surface of the glass-ceramic uncovered by the bone, the calcium-phosphorus layer was 50-80 microns thick at 6 months after implantation, 250-450 microns thick at 1 year, 300 approximately 400 microns thick at 18 months, and 300 microns thick at 2 years. The thickness of the calcium-phosphorus layer increased moderately after long-term implantation. However, it was difficult to estimate the rate of increase in the thickness of calcium-phosphorus layer.

Animals↗
PubMed2001

Studies of LA-ICP-MS on quartz glasses at different wavelengths of a Nd:YAG laser.

The capability of LA-ICP-MS for determination of trace impurities in transparent quartz glasses was investigated. Due to low or completely lacking absorption of laser radiation, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) proves difficult on transparent solids, and in particular the quantification of measurement results is problematic in these circumstances. Quartz glass reference materials of various compositions were studied by using a Nd:YAG laser system with focused laser radiation of wavelengths of 1064 nm, 532 nm and 266 nm, and an ICP-QMS (Elan 6000, Perkin Elmer). The influence of ICP and laser ablation conditions in the analysis of quartz glasses of different compositions was investigated, with the laser power density in the region of interaction between laser radiation and solid surface determining the ablation process. The trace element concentration was determined via calibration curves recorded with the aid of quartz glass reference materials. Under optimized measuring conditions the correlation coefficients of the calibration curves are in the range of 0.9-1. The relative sensitivity factors of the trace elements determined in the quartz glass matrix are 0.1-10 for most of the trace elements studied by LA-ICP-MS. The detection limits of the trace elements in quartz glass are in the low ng/g to pg/g range.

Journal Article↗
PubMed1995

Atomic force microscopy of coated glasses.

Atomic force microscopy has been used to investigate the topology of alkoxide gel dip coatings on different substrates. Results of SiO(2) - TiO(2) - ZrO(2) (STZ) coatings are presented on float glass, on polished fused silica, on commercially coated insulating flat glass, and on PtRh. Consolidated STZ coatings display the so-called glass pattern with ripples equal or less than 2 nm high. The same pattern is seen on partially dense STZ coatings, as soon as the surface is stiff enough for scanning, and also on the bottom of a 50 nm deep sputtering crater in the consolidated coating. The vitreous STZ coating on the fire side of the float glass is as flat as the float glass itself. It has the same tendency to contamination. 100 nm wide and 50 nm deep polishing grooves on fused silica have been filled up with the 80 nm thick coating, only dips of a few nm remain. The trenches between the SnO(2) crystallites on the insulating flat glass were filled up and the roughness of the substrate was partially reduced. PtRh sheet remained rough even after the coating. On the partially densified STZ coating, sputtering generates a grained surface.

Journal Article↗
PubMed2006

Mirror glasses for minimally invasive surgery.

INTRODUCTION: The operator performing minimally invasive surgery is prevented from seeing the whole field with both eyes by the restricted small thoracotomy incision. To overcome this problem, we developed mirror glasses. METHODS: Use of these glasses was evaluated in terms of the time required for threading of sutures with endoscopic forceps. Three surgeon ligated thread a suture five times with and without use of the glasses in the box, and the mean time was calculated for each surgeon. RESULTS: The time required for ligation (mean +/- SD) was 24.2 +/- 2.9 s with mirror glasses and 27.0 +/- 2.5 s without the glasses (p = 0.01). CONCLUSION: The mirror glasses may be found useful for fine manipulation for minimally invasive surgery.

Equipment Design↗
PubMed1989

A method of removing gels from narrow-diameter glass tubes as part of a mini-two-dimensional electrophoresis procedure.

A glass chamber that facilitates the removal of polyacrylamide gels from narrow glass tubes after the completion of isoelectric focusing is described. The tube is firmly held at one end of the glass chamber and a syringe is connected to the other end. By slowly forcing water from the syringe into the glass chamber, sufficient pressure can be generated to cause the rod gel to move slowly out of the glass tube. The rod gel is then used for the second stage of a mini-two-dimensional electrophoresis technique. Rod gels of 1.7-mm diameter have been used most extensively and can be removed from the glass tubes with almost 100% success.

Electrophoresis, Gel, Two-Dimensional↗
PubMed2004

Effect of additional materials on the properties of glass-ceramic produced from incinerator fly ashes.

There are 21 Metro-waste incinerators in Taiwan under construction and are expected to be finished at year 2003. It is estimated that these incinerators will produce about two million tons of incinerator ash. In order to reduce the volume and eliminate contamination problems, high temperature molten technology studies have been conducted. The purpose of this research was that of trying to control the chemical composition of the glass-ceramic produced from incinerator fly ash, in order to improve the characteristics of the glass-ceramic. The experimental results showed that the additional materials, Mg(OH)2 and waste glass cullet, can change glass-ceramic phases from gehlenite to augite, pigeonite, and diopside. The physical, mechanical and chemical resistance properties of the glass-ceramic also showed much better characteristics than prepared glass-ceramic using incinerator fly ash alone.

Carbon↗
PubMed2004

Bacterial adhesion to glass and metal-oxide surfaces.

Metal oxides can increase the adhesion of negatively-charged bacteria to surfaces primarily due to their positive charge. However, the hydrophobicity of a metal-oxide surface can also increase adhesion of bacteria. In order to understand the relative contribution of charge and hydrophobicity to bacterial adhesion, we measured the adhesion of 8 strains of bacteria, under conditions of low and high-ionic strength (1 and 100 mM, respectively) to 11 different surfaces and examined adhesion as a function of charge, hydrophobicity (water contact angle) and surface energy. Inorganic surfaces included three uncoated glass surfaces and eight metal-oxide thin films prepared on the upper (non-tin-exposed) side of float glass by chemical vapor deposition. The Gram-negative bacteria differed in lengths of lipopolysaccharides on their outer surface (three Escherichia coli strains), the amounts of exopolysaccharides (two Pseudomonas aeruginosa strains), and their known relative adhesion to sand grains (two Burkholderia cepacia strains). One Gram positive bacterium was also used that had a lower adhesion to glass than these other bacteria (Bacillus subtilis). For all eight bacteria, there was a consistent increase in adhesion between with the type of inorganic surface in the order: float glass exposed to tin (coded here as Si-Sn), glass microscope slide (Si-m), uncoated air-side float glass surface (Si-a), followed by thin films of (Co(1-y-z)Fe(y)Cr(z))3O4, Ti/Fe/O, TiO2, SnO2, SnO2:F, SnO2:Sb, A1(2)O3, and Fe2O3 (the colon indicates metal doping, a slash indicates that the metal is a major component, while the dash is used to distinguish surfaces). Increasing the ionic strength from 1 to 100 mM increased adhesion by a factor of 2.0 +/- 0.6 (73% of the sample results were within the 95% CI) showing electrostatic charge was important in adhesion. However, adhesion was not significantly correlated with bacterial charge and contact angle. Adhesion (A) of the eight strains was significantly (P < 10(-25)) correlated with total adhesion free energy (U) between the bacteria and surface (A = 2162e(-1.8U)). Although the correlation was significant, agreement between the model and data was poor for the low energy surfaces (R2 = 0.68), indicating that better models or additional methods to characterize bacteria and surfaces are still needed to more accurately describe initial bacterial adhesion to inorganic surfaces.

Bacillus subtilis↗
PubMed2005

Influence of shear on microbial adhesion to PEO-brushes and glass by convective-diffusion and sedimentation in a parallel plate flow chamber.

Microbial adhesion to surfaces often occurs despite high wall shear rates acting on the adhering microorganisms. In this paper, we compare the wall shear rates needed to prevent microbial adhesion to bare glass and poly(ethylene oxide) (PEO)-brush coated glass in a parallel plate flow chamber. Initial microbial deposition rates were determined for different wall shear rates between 4 and 1600 s(-1) on the top and bottom plates of the flow chamber. Deposition efficiencies alpha(SL), based on the Smoluchowski-Levich approach, for Pseudomonas aeruginosa D1, Escherichia coli O2K2 and Candida tropicalis GB 9/9 decreased with increasing wall shear rates and were lower for PEO-brush coated glass than for bare glass. Characteristic shear rates preventing adhesion to the bottom plate were around 10 and 1.0 s(-1) for the bacteria on glass and the PEO-brush and 36 and 3.4s(-1) for the yeast strain on glass and the PEO-brush, respectively. This demonstrates that the adhesive forces between microorganisms and a PEO-brush are comparatively weak, although some strains may have the ability to adhere to a PEO-brush under low shear conditions. Microbial deposition efficiencies alpha(SL) were much larger, however, than unity for bottom plate deposition, but could be reduced to realistic values by averaging the deposition rates found for the top (negative contribution of sedimentation) and bottom (positive contribution of sedimentation) plates.

Bacterial Adhesion↗
PubMed2001

Alpha particle emission from reference glass surfaces implanted with 210Po.

Implanted long-lived radon decay products in glass surfaces have been used as a measure of past radon exposure in homes. Special track-etch devices (so-called 'retro-detectors') attached to the glass surface, have the ability to specifically measure the implanted activity of 210Po in situ. Calibrating these devices for 210Po is fairly straightforward, but the retro-detectors are also sensitive to the background activity of the glass substrate. Thus, for the successful calibration of retro-detectors, it is necessary to determine the complete alpha emission energy spectrum of the reference glass sheet utilised as a calibration pad. In order to achieve accurate knowledge of the alpha surface emission rate, we have combined several different approaches, i.e. alpha spectrometry of the pad surface with both surface-barrier and pulse-ionisation detectors, and activity determination of the glass matrix by means of radiochemical methods. The part of the alpha emission spectrum originating from the glass volume is then calculated theoretically and compared with experimental results.

Journal Article↗
PubMed2000

Diagnosing and treating chronic prostatitis: do urologists use the four-glass test?

OBJECTIVES: To examine the diagnosis and treatment of chronic prostatitis, we conducted a national mail survey of practicing urologists in 1998. METHODS: Probability samples were drawn from the American Medical Association Registry of Physicians. RESULTS: Five hundred four urologists responded (response rate 64%). Urologists reported seeing a median of 30 patients (interquartile range 11 to 60) newly diagnosed with chronic prostatitis in the previous 12 months. Eighty percent of urologists responded that they "rarely" (47%) or "never" (33%) performed the Meares-Stamey four-glass diagnostic test. Only 4% answered "almost always." Forty percent of urologists responded that they treat "all" their patients with antibiotics and 42% more responded that they treat "more than half" with antibiotics. Physicians who routinely performed the four-glass test did not differ in antibiotic use from those who used the test less often; however, they were more likely to use treatment other than antibiotics. For example, alpha-blockers were used in one half or more of the patients by only 35% of physicians who never do the four-glass test compared with 42% who rarely do the test and 57% who do the test more often (P = 0.002). Results were similar for treatment with natural remedies. CONCLUSIONS: Urologists frequently diagnose chronic prostatitis but rarely perform the four-glass diagnostic test. Use of the four-glass test does not appear to affect urologists' antibiotic treatment patterns. Although bacterial prostatitis is thought to be rare, antibiotic use in the population of men with prostatitis is not. The four-glass test and empiric antibiotics are practices in the diagnosis and treatment of prostatitis that deserve scrutiny.

Adult↗
PubMed1995

Effects of vacuuming on dye penetration patterns in root canals and glass tubes.

This study compared the dye leakage pattern of prepared root canals with that of glass tubes, with and without vacuuming. The apical 12 mm of 40 calcified root canals were prepared to tubes with a diameter of 0.5 mm. The coronal end of these canals and 40 glass tubes with similar diameters (12 mm x 0.5 mm) were closed with 2 mm of Cavit. Twenty samples from each group were left empty, and the rest (20) were filled with gutta-percha without sealer. Half of the samples of filled (10) and unfilled (10) specimens were then placed horizontally in 2% methylene blue dye. The other half (10) of the samples from each group were placed in a vacuum (25 mm Hg) and submerged in the dye. Leakage was then measured in millimeters and statistically analyzed using analysis of variance. The 20 empty glass tubes with or without vacuum leaked 17% or less of their lengths. The 20 glass tubes filled with gutta-percha averaged 70.5% leakage. Of those, the 10 glass tubes that were vacuumed had 100% leakage. Empty root canals exhibited mean leakage of 74% without vacuum and 91% of their length with vacuum. Canals filled with gutta-percha leaked a mean of 95.5% of their entire lengths without vacuum and 100% with vacuum (no significant difference). The results showed that filled and unfilled, prepared root canals leaked significantly more than their glass tube counterparts (p < 0.001), and vacuuming may not be necessary for dye leakage studies in filled root canals.

Air↗
PubMed1997

Bioactivity of ferrimagnetic glass-ceramics in the system FeO-Fe2O3-CaO-SiO2.

Bioactive and ferrimagnetic glass-ceramics are useful as thermoseeds for hyperthermia treatment of cancer. A heat treatment of a 40(FeO, Fe2O3)-60CaO x SiO2 wt% glass gives a ferrimagnetic glass-ceramic containing 36 wt% magnetite in a CaO x SiO2 matrix. However, it does not show bioactivity since a small amount of iron ion remains in the matrix. In the present study, bioactivities of ferrimagnetic glass-ceramics which were prepared by heat treatment of glasses of the composition 40(FeO, Fe2O3)-60CaO x SiO2 (wt%) with various components added at 100:3 weight ratio were evaluated in vitro by examining bone-like apatite formation on their surfaces in a simulated body fluid. It was found that glass-ceramics with Na2O or B2O3 added in combination with P2O5 show bioactivity.

Apatites↗
PubMed2001

Inulin glasses for the stabilization of therapeutic proteins.

Sugar glasses are widely used to stabilize proteins during drying and subsequent storage. To act successfully as a protectant, the sugars should have a high glass transition temperature (Tg), a poor hygroscopicity, a low crystallization rate, and contain no reducing groups. When freeze drying is envisaged as method of drying, a relatively high Tg of the freeze concentrated fraction (Tg') is preferrable. In this study, whether inulins meet these requirements was investigated. Inulins of various degrees of polymerisation (DP) were evaluated. Trehalose glass was used as a positive control. It was found that the Tg and the Tg' of inulins with a number/weight average DP (DP(n)/DP(w)) higher than 5.5/6.0 were higher than those of trehalose glass. Furthermore, inulin glasses showed a similar hygroscopicity to that of trehalose glass but crystallized less rapidly. Less than 6% of the sugar units of inulins with a DP(n)/DP(w) higher than 5.5/6.0 contained reducing groups. Trehalose contained no reducing groups. Freeze drying of an alkaline phosphatase solution without protectant induced an almost complete loss of the activity of the protein. In contrast, when inulins with a DP(n)/DP(w) higher than 5.5/6.0 or trehalose were used as stabilizer, the activity was fully maintained, also after subsequent storage for 4 weeks at 20 degrees C and 0, 45, or 60% RH, respectively. The stabilizing capacities of inulin with a lower DP and glucose were substantially less pronounced. After storage at 60 degrees C for 6 days, the activity of freeze dried samples containing inulins with a DP(n)/DP(w) higher than 5.5/6.0 was still about 50% whereas the activity of samples containing inulin with a lower DP, glucose, or trehalose was completely lost. It is concluded that inulins with a DP(n)/DP(w) higher than 5.5/6.0 meet the physico-chemical characteristics to successfully act as protectants for proteins. The stabilizing potential of these inulins was clearly shown using alkaline phosphatase as a model protein.

Alkaline Phosphatase↗
PubMed2002

Investigations into the stabilisation of drugs by sugar glasses: I. Tablets prepared from stabilised alkaline phosphatase.

The aim of this study was to investigate the formulation of sugar glass stabilised alkaline phosphatase from bovine intestine (BIAP) into tablets. Two major subjects of tablet formulation were investigated. First, the compaction behaviour of the inulin sugar glass was investigated. Secondly, the effect of the compaction process on the physical stability of sugar glass stabilised BIAP was investigated, comparing inulin and trehalose glass. The tabletting properties of freeze-dried inulin without BIAP were studied first. Freeze-dried inulin conditioned at either 20 degrees C/0% relative humidity (RH) or 20 degrees C/45% RH was compacted at various pressures. As expected, the yield pressure of the material conditioned at 0% RH was higher (68 MPa) than after conditioning at 45% RH (39 MPa). Tablets made of the material stored at 0% RH showed severe capping tendency, especially at high compaction pressures. In contrast, material conditioned at 45% RH gave tablets without any capping tendency and a friability of less than 1%. Sugar glasses of BIAP and either inulin or trehalose were prepared by freeze-drying (BIAP/sugar 1/19 (w/w)). The material was subsequently compacted. Tablets and powders were stored at 60 degrees C/0% RH. The activity of the incorporated BIAP was measured at various time intervals. It was found that inulin was by far superior to trehalose as stabiliser of BIAP in tablets. The poor stabilising capacities of trehalose after compaction are explained by crystallisation of trehalose induced by the compaction process and moisture in the material. The results clearly show that inulin is an excellent stabiliser for BIAP. The tabletting properties are adequate, showing sufficient tablet strengths and low friability. Furthermore, the good (physical) stability of inulin glass with respect to exposure to high relative humidities makes it practical to work with.

Alkaline Phosphatase↗