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PubMed2005

Nanocrystallization of ferroelectric strontium bismuth vanadium niobate in lithium tetraborate glasses.

Transparent glass samples in (100-3x) (Li2O-2B2O3)-x(SrO-Bi2O3-0.7Nb2O5-0.3V2O5) (10 < or = x < or = 60, in molar ratio) system have been fabricated via conventional melt-quenching technique. The as-quenched samples, of all the compositions under study have been confirmed to be amorphous, by X-ray powder diffraction (XRD) studies. Differential thermal analysis (DTA) was employed to confirm the glassy nature of the as-quenched glasses. Glass composites comprising vanadium doped strontium bismuth niobate nanocrystallites were obtained by controlled heat-treatment of the as-quenched glasses at 783 K for 6 h. Perovskite SrBi2(Nb0.7VO3)2O9-delta phase formation was found to be preceded by an intermediate fluorite phase which was established via XRD and transmission electron microscopy (TEM). The dielectric constants (epsilonr) of the as-quenched glasses as well as the glass nanocrystal composites decreased with increase in frequency (100 Hz-10 kHz) at 300 K. Interestingly, the dielectric constant of the glass nanocrystal composite (heat-treated at 783 K/6 h) undergoes a maximum in the vicinity of the crystallization temperature of the host glass (Li2B4O7) reaching an anomalously high value (approximately 10(6)) at 800 K. Different dielectric mixture formulae were employed to rationalize the dielectric properties of the glass nanocrystal composite. The optical transmission properties of these glass nanocrystal composites were found to have strong compositional dependence.

Bismuth↗
PubMed1992

Adhesion of mutants streptococci to glass with and without a salivary coating as studied in a parallel-plate flow chamber.

Deposition and adhesion to glass with and without a salivary coating in a parallel-plate flow chamber were studied with four strains of mutans streptococci. Stationary-state adhesion of the strains to uncoated glass ranged from 0.3 x 10(6) cm-2 (Streptococcus rattus HG218) to 12.7 x 10(6) cm-2 (Streptococcus sobrinus HG1025) and generally decreased after saliva coating of the glass. The poor adhesion found for S. rattus HG218 to both uncoated and saliva-coated glass could be due to its relatively high negative surface-charge. Deposition efficiencies of all strains were greater than or equal to 1 for uncoated glass and decreased greatly after saliva coating of the glass. Possibly, adhesion to a saliva coating is less efficient and more time-consuming than that to uncoated glass, because stereochemical groups in the pellicle and on the cell surfaces may have to re-arrange before an effective interaction can occur. Desorption rates, measured 1000 s and 5000 s after the start of an experiment, decreased by a factor of ten upon a five-fold increase in contact time, indicative of a two-phase adhesion process. Of the four strains studied, only Streptococcus cricetus HG737 showed a minor positive cooperativity on saliva-coated glass, possibly mediated by surface appendages observed by transmission electron microscopy on negatively-stained cells. Retention of adhering bacteria was strain-dependent on uncoated glass, but was identical for all strains on saliva-coated glass, which suggests that the structure and composition of the pellicle may be more important with respect to the retention of adhering cells than the cell-surface properties themselves.

Bacterial Adhesion↗
PubMed1990

[Basic studies on glass ceramics. 3. Influence on calcification of osteogenic cells in vitro].

Two established osteogenic cell lines (NY, MC 3 T3-E 1) were used in vitro to determine the biocompatibility of glass ceramics and their effect on initial calcification of osteogenic cells. Morphological study of the cell under the phase-contrast microscopy and histochemical staining were applied as follows. First, glass ceramic granules were placed in 60 mm dishes, and cells were suspended in the dishes in alpha-MEM supplemented with 10% FBS (basic medium) or medium with 50 micrograms/ml of L-ascorbic acid added. After 8 or 14 day of culturing, calcium formation was tested by von-Kossa's staining. Also, alkaline phosphatase staining was performed by the azo-dye method. As controls, cultures in dishes without glass ceramic granules were stained at the same time. The results obtained in the experimental culture were as follows. 1. Phase contrast microscopy showed that contacts with glass ceramics did not cause cellular death or degeneration. 2. In both cell cultures with the glass ceramics the von-Kossa reaction was positive as early as the 8th day. 3. The alkaline phosphatase reaction on the 8th day occurred only in MC 3 T3-E 1. The reaction was localized on fibroblastic cells which proliferated three-dimensionally around glass ceramics, and on small polyhedral cells situated relatively for apart from the ceramics. 4. On the 14th day, the MC 3 T 3-E 1 formed large nodules around the glass ceramics, and they were stained uniformly positive by von-Kossa's method. The alkaline phosphatase-positive cells extended spoke-like forms. 5. In medium with L-ascorbic acid, growth of NY was inhibited, After being cultured for 14 days, abundant von-Kossa positive reaction was found around glass ceramics in both cells. In MC 3 T 3-E1 on the 8th days, the alkaline phosphatase reaction was stronger with glass ceramics than with basic medium only. On the contrary, in the control cultures of both cells there was negative von-Kossa reaction during the culture period. The above results showed that glass ceramic granules have the biocompatibility needed for bone grafts, and they facilitated calcification of MC 3 T 3-E 1 in culture.

Alkaline Phosphatase↗
PubMed1999

The marginal seal of Class II restorations: flowable composite resin compared to injectable glass ionomer.

The objective of this study was to investigate the effect of a flowable composite resin (Tetric Flow) versus an injectable glass ionomer (Fuji II LC) on microleakage at the cavosurface margin of the proximal box of Class II restorations in permanent teeth in-vitro. Thirty caries and restoration-free human bicuspids were prepared with mesial and distal slot preparations and were filled either with a bonding agent (Optibond) plus a flowable composite resin (Tetric Flow), Group I; bonding agent (Optibond) plus a flowable glass ionomer (Fuji II LC), Group II; or a flowable glass ionomer (Fuji II LC) with no bonding agent, Group III. All specimens were then immersed in a 2% solution of basic fuschin dye for 24 hours to allow for dye penetration into possible existing gaps. These teeth were then carefully sectioned mesially/distally into two pieces using an Isomet saw. The teeth were then studied under a binocular microscope to measure depths of dye penetrations as an indication of marginal microleakage at the gingival cavosurface margin and scored as follows: 0 = no dye penetration, 1 = dye penetration into enamel only, 2 = dye penetration into enamel and dentin, 3 = dye penetration into the pulp. The specimens were also evaluated using a SEM. The results showed that there were statistically significant differences between Groups I (Tetric Flow) and (Fuji II LC plus bonding agent), II in favor of Group I; between Groups I and (Fuji II LC with no bonding agent), III in favor of Group I; as well as Groups II and III in favor of Group II (Fuji II LC plus bonding agent). Group I (bonding agent plus flowable composite resin) showed significantly less microleakage. Group II (bonding agent plus flowable glass ionomer) demonstrated a bond that existed between the bonding agent and the glass ionomer but microleakage within microgaps of the glass ionomer itself Group III (flowable glass ionomer plus no bonding agent) demonstrated significant microleakage between the glass ionomer and tooth structure, microgaps within the glass ionomer, and lack of retention of the restoration. It appears that the use of a flowable composite resin (Tetric Flow) plus a bonding agent (Optibond) in the proximal box of a Class II restoration in permanent teeth will significantly reduce the microleakage at the cavosurface margin when compared with an injectable glass ionomer (Fuji II LC) with or without a bonding agent (Optibond).

Composite Resins↗
PubMed1999

Measurement of dose rate at the interface of cell culture medium and glass dishes by means of ESR dosimetry using thin films of alanine.

Previous studies on human cervical cancer cells (NHIK 3025) have indicated that the cells, when X-irradiated in suspension, appeared to be more radiosensitive than when they were irradiated attached to glass dishes. However, this result depends on dosimetry, which is difficult in the situation where cells are attached to glass dishes due to backscattering electrons at the glass-liquid interface. Recently developed dosimetry that is based on detection of radiation-induced stable radicals in alanine and uses ESR spectroscopy offers a possibility for more relevant dosimetry at the glass-liquid interface than the previous estimates of doses based on Fricke dosimetry. Thin alanine films (>/=10 microm) were used to measure dose at the interface by irradiating the films while they were placed tightly against the bottom of dishes and covered with 1 mm of wax simulating the medium above cells. Fricke dosimetry was also performed, with different depths of Fricke solution in the dishes, to elucidate the contribution to the dose delivered by backscattering electrons at the glass-liquid interface. A dose rate of 1.9 Gy/min was measured with a thin layer (0.2-0.3 mm) of Fricke solution in petri dishes made of glass. However, this estimate appears to be too high, due to a contribution to dose by short-ranged electrons generated when the X rays passed through a steel lid 4.5 cm above the dishes. Dosimetry using alanine films resulted in dose rates of 1.15 and 0.87 Gy/min at the interfaces of glass-liquid and plastic- liquid, respectively. Hence there is a significant contribution to dose from backscattering electrons on dishes made of glass. The reason for our previous observation of a difference in radiosensitivity between cells irradiated in suspension and cells irradiated attached to glass appears to be a lack of accurate dosimetry at the glass-liquid interface.

Alanine↗
PubMed1991

Plaque accumulation on glass ionomer filling materials.

It has been suggested that fluoride released by glass ionomers inhibits the growth of plaque. The aim of this study was to compare plaque accumulation on glass ionomers and composite. The materials tested were (1) freshly mixed glass ionomer (Ketac-Fil), (2) artificially aged glass ionomer (Ketac-Fil), (3) freshly mixed silver glass ionomer (Ketac-Silver) and (4) light-cured hybrid composite (Valux). Ten volunteers wore an acrylic appliance for three periods of 18 hours, one for each glass ionomer. A glass ionomer disk was inserted on one randomly chosen side of the appliance and the composite disk on the other. The volunteers rinsed once an hour with a 15% sucrose solution. The amount of pellicle and plaque on the disk was estimated by analysing its protein content. During each cycle, more plaque accumulated on the glass ionomers than on the composite (fresh Ketac-Fil/Valux p less than 0.05, aged Ketac-Fil/Valux p less than 0.01, Ketac-Silver/Valux NS). On examination using a scanning electron microscope the surfaces of the glass ionomers were found to be markedly more porous, and to contain more microbes, than the composite surface. The presence of silver in the silver glass ionomers may have affected the initial adherence of bacteria.

Adult↗
PubMed1995

Glass and antimony electrodes for long-term pH monitoring: a dynamic in vitro comparison.

OBJECTIVE: To compare the performance of combined glass microelectrodes with monocrystalline and polycrystalline antimony electrodes with external reference in a 24-h dynamic in vitro study. DESIGN AND METHODS: In an artificial stomach, the pH of the contents titrated from pH1-7 and back by NaOH and HCI was simultaneously measured at 37 degrees C with antimony and glass probes connected to three recording devices. The recorded data were compared with data monitored continuously by a laboratory pH measurement system. The sensitivity and drift of glass microelectrodes were also analysed in intensive-care unit patients during intragastric pH monitoring for up to 96 h. RESULTS: The sensitivities of antimony polycrystalline, monocrystalline and of glass electrodes were 54.6, 55.3, and 61.8 mV/pH, respectively. The hysteresis was 6.4, 7.2 and 2.75 mV for antimony polycrystalline, monocrystalline and for glass electrodes, respectively. The drift in 24 h was -0.1 pH for glass over the pH range 1-7, and +0.3 pH over pH 1-2.5, and +0.15 pH over pH 2.5-7 for both of the antimony electrodes. The response times of both antimony and glass electrodes were similar over the pH range 2.5-7. The difference in the percentages of time below pH 1.5 was significant: 28.2% for glass, 17.3% for antimony polycrystalline and 18.1% for monocrystalline electrodes, respectively (P < 0.05). However, the difference in the percentages of time below pH 4 was not significant. After 96 h intragastric pH monitoring in six intensive-care unit patients, the mean drift of glass electrodes was 0.15 pH (range, pH 0.1-0.2) and the mean change in sensitivity 1.2%. CONCLUSIONS: (1) Antimony electrodes may be acceptable for intra-oesophageal pH monitoring but are not suitable for intragastric use. (2) The use of glass microelectrodes is recommended for intragastric pH monitoring, particularly when extended monitoring over periods longer than 24 h is required.

Aged↗
PubMed2000

[Effect of glass ceramics on bone regeneration in calvarial defects. Experimental study].

INTRODUCTION: The purpose of this study was to investigate the influence of different compositions of resorbable porous glass ceramics on their performance in calvarial defects. MATERIAL AND METHODS: Full-thickness defects (8.1 mm diameter) were made in the calvaria of 75 adult Sprague-Dawley rats. Pellets of porous glass ceramics were inserted press-fit into 60 defects. Four different materials were implanted into each of 15 animals: (1) glass ceramic with a high relation of calcium to phosphate containing silicate; (2) glass ceramic with a high relation of calcium to phosphate without silicate; (3) glass ceramic with a low relation of calcium to phosphate without silicate; and (4) glass ceramic with a low relation of calcium to phosphate containing silicate. Five implants of each group were evaluated by fluorescence microscopy and light microscopy after 6, 13, and 26 weeks. RESULTS: Those glass ceramics with a high relation of calcium to phosphate showed formation of new bone entering the defect from the margins as soon as 6 weeks postoperatively. After 26 weeks, the formation of new bone reached the center of the defect. In the other glass ceramics, the formation of unmineralized osteoid was visible entering the defect from the margins. No mineralization was seen 26 weeks postoperatively. There was no significant difference between glass ceramics containing silicate and those free of silicate. CONCLUSIONS: Bioresorbable glass ceramics may be of benefit in the treatment of osseous defects without functional loading.

Animals↗
PubMed2002

Multifocal glasses impair edge-contrast sensitivity and depth perception and increase the risk of falls in older people.

OBJECTIVES: To determine the extent to which multifocal glasses impair contrast sensitivity and depth perception at critical distances required for detecting hazards in the environment and whether multifocal glasses use increases the risk of falls in older people. DESIGN: One-year prospective cohort study. SETTING: Falls Laboratory, Prince of Wales Medical Research Institute. PARTICIPANTS: One hundred fifty-six community-dwelling people aged 63-90. MEASUREMENTS: Contrast sensitivity, depth perception, accidental falls. RESULTS: Eighty-seven subjects (55.8%) were regular wearers of multifocal (bifocal, trifocal, or progressive lens) glasses. These subjects performed significantly worse in the distant depth perception and distant edge-contrast sensitivity tests in conditions that forced them to view test stimuli through the lower segments of their glasses. Multifocal glasses wearers were more than twice as likely to fall in the follow-up period than nonmultifocal glasses wearers (odds ratio (OR) = 2.29, 95% confidence interval (CI) = 1.06-4.92), when adjusting for age, poor vision, reduced lower limb sensation and strength, slow reaction time, and increased postural sway. Multifocal glasses wearers were also more likely to fall because of a trip (OR = 2.79, 95% CI = 1.08-7.22), when outside their homes (OR = 2.55, 95% CI = 1.14-5.70), and when walking up or down stairs (P <.01). The population attributable risks of regular multifocal glasses use were 35.2% for any falls, 40.9% for falls due to a trip, and 40.9% for falls outside the home. CONCLUSIONS: The study findings indicate that multifocal glasses impair depth perception and edge-contrast sensitivity at critical distances for detecting obstacles in the environment. Older people may benefit from wearing nonmultifocal glasses when negotiating stairs and in unfamiliar settings outside the home.

Accidental Falls↗
PubMed2005

Comparing mercury-in-glass, tympanic and disposable thermometers in measuring body temperature in healthy young people.

AIM AND OBJECTIVES: The aim of this study was to determine whether a disposable thermometer was at least as accurate as a tympanic thermometer when compared with a mercury-in-glass thermometer and to investigate the waiting periods of mercury-in-glass thermometers. BACKGROUND: Although different methods of temperature measurement have been widely studied and described during the last decade, comparison between readings obtained when measuring body temperature using disposable, mercury-in-glass and tympanic thermometers is little documented and there is confusion about the waiting periods of mercury-in-glass thermometers. METHODS: This research was descriptive and comparative. Temperature measurements included three sequential readings using first a tympanic thermometer in the left ear, then a disposable thermometer in the left axillary area and finally a mercury-in-glass thermometer in the right axillary area. All the temperatures were measured on the Celsius (degrees C) scale. To identify the stabilization periods of the mercury-in-glass thermometers, the temperature measurement was repeated until the reading stabilized. F-tests were used to compare readings of the mean temperatures. RESULTS: It was found that body temperature readings measured by tympanic thermometer were higher than axillary mercury-in-glass thermometer by 0.12 degrees C, body temperature readings measured by tympanic thermometer were higher than axillary disposable thermometer readings by 0.65 degrees C and body temperature readings measured by axillary mercury-in-glass thermometer were higher by 0.53 degrees C than readings measured by axillary disposable thermometer. It was found that readings measured by mercury-in-glass thermometer stabilized in the eighth minute. RELEVANCE TO CLINICAL PRACTICE: When assessing body temperature it is important to take the type of thermometer into consideration. In addition, axillary mercury-in-glass thermometers must be kept in place a minimum of eight minutes.

Adolescent↗
PubMed2005

Shape of glass and amount of alcohol poured: comparative study of effect of practice and concentration.

OBJECTIVE: To determine whether people pour different amounts into short, wide glasses than into tall, slender ones. DESIGN: College students practised pouring alcohol into a standard glass before pouring into larger glasses; bartenders poured alcohol for four mixed drinks either with no instructions or after being told to take their time. SETTING: University town and large city, United States. PARTICIPANTS: 198 college students and 86 bartenders. MAIN OUTCOME MEASURES: Volume of alcohol poured into short, wide and tall, slender glasses. RESULTS: Aiming to pour a "shot" of alcohol (1.5 ounces, 44.3 ml), both students and bartenders poured more into short, wide glasses than into tall slender glasses (46.1 ml v 44.7 ml and 54.6 ml v 46.4 ml, respectively). Practice reduced the tendency to overpour, but not for short, wide glasses. Despite an average of six years of experience, bartenders poured 20.5% more into short, wide glasses than tall, slender ones; paying careful attention reduced but did not eliminate the effect. CONCLUSIONS: To avoid overpouring, use tall, narrow glasses or ones on which the alcohol level is premarked. To avoid underestimating the amount of alcohol consumed, studies using self reports of standard drinks should ask about the shape of the glass.

Adult↗
PubMed2002

The efficacy of computer glasses in reduction of computer worker symptoms.

BACKGROUND: Computer workers with presbyopia are at greater risk for the development of symptoms with a conventional prescription vs. a computer prescription because general-wear multi-focal corrections often do not provide adequate correction for the viewing distances and angles needed at the computer workstation. "Computer glasses," as defined by the American Optometric Association, are specifically designed for the computer workplace and have a different lens design or prescription than general-wear glasses. The purpose of this study is to evaluate the effectiveness of computer glasses in reduction of symptoms of presbyopic computer users. METHODS: Subjects were 26 symptomatic presbyopic computer users who had had an eye examination within the past year and had 20/20 vision at distance and near with habitual glasses. Two interventions in planned alternating order were tested for 3 weeks each on all subjects. One intervention was computer glasses. The comparison intervention was an ergonomic self-assessment tool (ESAT) with their habitual Rx. Symptoms were assessed before and after each intervention. A post-comparative questionnaire asked subjects to reflect on the relative efficacy and ease of use of the two interventions. RESULTS: The computer glasses were significantly more effective at reducing the frequency and severity (p < 0.008) of the symptoms than the ESAT, and 24 of 26 subjects judged the computer glasses to bemore effective. Subjects attributed 80.7% of symptom reduction to the computer glasses and 19.3% to the ESAT. Although the ESAT was judged effective, it was not as effective as the computer glasses. CONCLUSION: Computer glasses have been shown to be effective in reduction of vision-related symptoms of computer users.

Computers↗
PubMed1996

Crystallization of experimental bioactive glass compositions.

Crystallization kinetics studies for six experimental glass formulations in the system Na2O-CaO-SiO2-P2O5 synthesized by wet chemistry were conducted by means of differential thermal analysis. These glasses had CaO/P2O5 and SiO2/ (CaO + Na2O) ratios ranging from 8.74-3.38 and 0.92-3.03, respectively. Samples of each glass (n = 30 were heated from 23 to 1250 degrees C under N2 atmosphere at heating rates ranging from 10 to 50 degrees C/min. Glass-ceramics were obtained after heat treating the initial glasses at temperatures determined from their DTA exotherms. The activation energy of crystallization for each glass composition was calculated from an expression-relating log-heating rate and the reciprocal of the exothermic peak temperature. The compositions of the six glasses were significantly different (p = 0.05). The activation energy of crystallization (Q) values ranged from 196 to 782 kJ/mole. A correlation was obtained between Q and CaO/P2O5 and between Q and the Young's modulus (P < 0.001). Two of the six glasses exhibited bulk crystallization. X-ray diffraction studies showed that four of the six glasses exhibited different proportions of crystalline phases following heat treatment. These phases were wollastonite (CaSiO3), Na2CaSi3O9, combeite [Na4Ca3SI6O16(OH)2], and some unidentifiable phases. Two of the six bioceramic materials had a mixture of unknown crystalline phases.

Biocompatible Materials↗
PubMed1997

Compositional dependence of bioactivity of glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2.

The bioactivity, i.e., bone-bonding ability, of 26 glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2 was studied in vivo. This investigation of bioactivity was performed to establish the compositional dependence of bioactivity, and enabled a model to be developed that describes the relation between reactions in vivo and glass composition. Reactions in vivo were investigated by inserting glass implants into rabbit tibia for 8 weeks. The glasses and the surrounding tissue were examined using scanning electron microscopy (SEM), light microscopy, and energy-dispersive X-ray analysis (EDXA). For most of the glasses containing < 59 mol % SiO2, SEM and EDXA showed two distinct layers at the glass surface after implantation, one silica-rich and another containing calcium phosphate. The build-up of these layers in vivo was taken as a sign of bioactivity. The in vivo experiments showed that glasses in the investigated system are bioactive when they contain 14-30 mol % alkali oxides, 14-30 mol % alkaline earth oxides, and < 59 mol % SiO2. Glasses containing potassium and magnesium bonded to bone in a similar way as bioactive glasses developed so far.

Animals↗
PubMed2000

Press-formable CaO-MgO-SiO(2)-TiO(2)-Ag(2)O glass as a biomaterial.

Glass-ceramics were investigated to obtain a glass with a composition of CaO. MgO. 2SiO(2). 0.375TiO(2). 0.007Ag(2)O. The glass melted at 1500 degrees C and could be cast. Crystallization of diopside of this glass is controlled by volume nucleation and growth processes. In a crystallization treatment at 850 degrees -870 degrees C, this glass presented a milky white, semitransparent color. The crystals formed were diopside, their crystal grain diameter was 1-2 micrometer, and crystallization was 15-25%. The bending strength of the glass produced by a crystallization treatment of 25 min at 850 degrees C was 400 MPa, which is suitable for artificial bones. This crystallized glass also was extremely stable, with no weight loss after stability testing in artificial saliva. The softening point, as determined from the viscosity curve, was 830 degrees C, and the crystallization temperature was 895 degrees C. Thus this glass can be press-formed at a temperature of 830 degrees -880 degrees C. Actual press-forming at a pressure of 0.64 MPa was carried out for 40 min at 850 degrees C and resulted in the formation of desired shapes. Given its ready formation into desired shapes and its great strength after crystallization, such glass is applicable for use as artificial bones and as dental roots and crowns.

Biocompatible Materials↗
PubMed2000

Use of glass slides coated with apatite-collagen complexes for measurement of osteoclastic resorption activity.

This study was designed to evaluate the use of apatite-collagen complexes (ACC) coated onto glass slides for measurement of osteoclastic resorption activity. ACC-coated glass slides were prepared by immersion in beta-glycerophosphate solution for 7-14 days after glass slides coated with type I collagen had been treated with alkaline phosphatase and phosvitin. Osteoclast-containing cell suspensions were prepared from the long bones of 1-day-old rabbits and were seeded in medium 199 (containing 10% FBS) onto ACC-coated glass slides. After allowing the cells to attach for 1.5 h, the glass slides were incubated for periods of up to 96 h. The cells were observed by scanning electron microscopy and cytochemically for tartarate resistant acid phosphatase (TRAP) activity. Some slides were treated with FITC-phalloidin and anti-type I collagen antibody. TRAP-positive multinucleated cells were located in transparent spaces on the glass slides. These spaces did not stain immunohistochemically with anti-type I collagen antibody. Podosome formation was observed in the multinucleated cells facing the edge of the transparent spaces. The scanning electron microscopy demonstrated well-spread large cells located on the flattened surface on apatite particles covering the glass surface. Our results suggest that osteoclasts could resorb the apatite particles and coated collagen on the glass slide. The resorption lacunae appeared as transparent spaces, and the cytoskeleton of resorbing osteoclasts was observed in these spaces. ACC-coated glass slides could be useful for investigating the function and metabolic activities of osteoclasts.

Animals↗
PubMed1991

A heat-generating bioactive glass-ceramic for hyperthermia.

Glass plates of the chemical composition: CaO (29.0), SiO 2 (31.0), Fe 2O 3 (40.0), B 2O 3 (3.0), P 2O 5 (3.0) in weight ratio were heated to 1050 degrees C at a rate of 5 degrees C/min and then cooled to laboratory temperature. The resulting glass-ceramic containing magnetite and wollastonite crystals showed high-saturation magnetization. The bonding ability of this new glass-ceramic to bone tissue was evaluated using rabbit tibiae, and compared with glass of the same composition. This glass-ceramic formed a Ca, P-rich layer on its surface and bonded tightly with bone within 8 weeks of implantation. However, the glass did not form this Ca, P-rich layer, nor had it bonded with bone at 25 weeks. The bone-heating ability of this glass-ceramic was investigated by applying a max. 300-Oe, 100-kHz magnetic field. The granules of the glass-ceramic filled in the rabbit tibiae heated the whole surrounding bone to more than 42 degrees C and maintained this temperature for 30 min. Bioactive ceramics reinforce the mechanical strength of bone tissue. Furthermore, this heat-generating bioactive glass-ceramic can be used for hyperthermic treatment of bone tumors.

Animals↗
PubMed2002

Characterization of microrough bioactive glass surface: surface reactions and osteoblast responses in vitro.

The current study characterized the in vitro surface reactions of microroughened bioactive glasses and compared osteoblast cell responses between smooth and microrough surfaces. Three different bioactive glass compositions were used and surface microroughening was obtained using a novel chemical etching method. Porous bioactive glass specimens made of sintered microspheres were immersed in simulated body fluid (SBF) or Tris solutions for 1, 6, 24, 48, or 72 h, and the formation of reaction layers was studied by means of a scanning electron microscope/energy dispersive X-ray analysis (SEM/EDXA). Cell culture studies were performed on bioactive glass disks to examine the influence of surface microroughness on the attachment and proliferation of human osteoblast-like cells (MG-63). Cell attachment was evaluated by means of microscopic counting of in situ stained cells. Cell proliferation was analyzed with a nonradioactive cell proliferation assay combined with in situ staining and laser confocal microscopy. The microroughening of the bioactive glass surface increased the rate of the silica gel layer formation during the first hours of the immersion. The formation of calcium phosphate layer was equal between control and microroughened glass surfaces. In cell cultures on bioactive glass, the microrough surface enhanced the attachment of osteoblast-like cells but did not have an effect on the proliferation rate or morphology of the cells as compared with smooth glass surface. In conclusion, microroughening significantly accelerated the early formation of surface reactions on three bioactive glasses and had a positive effect on initial cell attachment.

Biocompatible Materials↗