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At least 991 records · Page 55Linked to original sources
PubMed2000

Use of Raman spectroscopy in the characterisation of the acid-base reaction in glass-ionomer cements.

Raman spectra of various combinations of glass-ionomer cement components have been compared with those of the reactants and the salts of polyacrylic and tartaric acids. The components consisted of a fast-setting acid-degradable dental glass (containing, inter alia, oxides of Si, Al, Ca, Ba and Na), polyacrylic acid (PAA) and/or tartaric acid (TA). On the addition of water to the glass and tartaric acid, Raman spectroscopy indicated loss of acid and production of tartrate salts within seconds of mixing. Mixtures containing the glass, PAA and water in mass ratios 2:1:(0.1-4) reacted to form polyacrylate salts. The maximum fraction of unreacted PAA was found to decrease linearly with initial water/PAA mass ratio to a minimum of approximately 20% when this ratio exceeds 1.5. The data are consistent with 5.6 moles of water being required when each mole of acidic groups is neutralised. In newly prepared cements containing glass, water, polyacrylic and tartaric acids, polyacrylic acid and its salts, in both ionised and solid state form, can be detected. After about 1 h, however, Raman peaks associated with ionised species disappear.

Acrylic Resins↗
PubMed2001

Investigation of thermal parameters and crytallisation in a ternary CaO-Na2O-P2O5-based glass system.

This paper presents the results of a study of the thermal properties of a range of phosphate-based glasses in the system CaO-Na2O-P2O5. The glasses had a fixed P2O5 content of 45 mol% and the CaO:Na2O ratio was varied. The glasses were produced and ground and their thermal properties measured using a Setaram differential thermal analyser (DTA). Initial data showed that for the high Na2O containing glass, NaPO3 forms and a second unidentified phase that is probably calcium rich. In the middle compositional region, multiple phases precipitated out and were identified as NaPO3 and Na4Ca(PO3)6. For the high CaO content glasses, Na4Ca(PO3)6 was the only phase formed. Further studies were carried out to examine whether the phases were bulk or surface nucleating, by grinding the samples to different particle sizes. From this data, it is evident that the NaPO3 forms via a bulk nucleation mechanism and that Na4Ca(PO3)6 forms via surface nucleation. The factors controlling this precipitation process are discussed and ionic radius as a controlling factor is hypothesised.

Calcium Compounds↗
PubMed2001

Fluoride release from glass ionomer restorative materials and the effects of surface coating.

OBJECTIVES: This in vitro study on fluoride (F) release from conventional and metal-reinforced glass ionomer investigated the following: (1) the release of F in deionized water compared to artificial saliva, (2) the effect of various surface coatings on F release, (3) the uptake of released F by hydroxyapatite, (4) the expression of the release data in a mathematical model, (5) F content in the powders and set materials, and (6) surface morphology of varnished and resin-coated specimens. METHODS: Glass ionomer Ketac-Fil (KF), Fuji II (FJ), and Ketac-Silver (KS) were mixed according to the manufacturers' instructions, and prepared into specimens of 137.8 mm2 surface area. All three specimens were suspended in 50 ml of deionized water, artificial saliva, or aqueous solution of hydroxyapatite and submitted to constant agitation at 37 degrees C. In a separate experiment, the specimens were coated with varnish or light-cured bonding resin and tested for F release in solutions similar to those for uncoated specimens. The release of F occurred for 28 days. The concentration of F was measured with F-ion-specific electrode. RESULTS: All tested products showed a strong initial rate of F release which decreased with time until it reached a relatively steady rate after two weeks. The F released from KF and FJ was comparable in both pattern and magnitude. They released approximately four times more F than KS. In all cases, the release of F in artificial saliva was significantly (p < 0.001) less than in deionized water. Surface coating the specimens significantly reduced the F release ( p < 0.05 top < 0.001, depending on the product and type of coating). The inhibitory effect of coating markedly decreased with time. Resin coating reduced F release more than varnish in KF and KS, but not for FJ. Essentially, all F released in aqueous solution was taken up by the hydroxyapatite, with FJ ranking the highest in increasing hydroxyapatite F concentration. Over the 28 days, the quantities of F released from FJ, KF, and KS were, respectively, 3.8, 2.3, and 1.0% of the total F content in the specimens. The F concentration in the set KS was 53.9 and 72.5% of that found in KF and FJ, respectively. The release data as a function of time were best described by the power curve. Micromorphological examinations revealed remnants of surface coatings on specimens after 14 days storage in artificial saliva. CONCLUSIONS: Glass ionomer cements released significantly less F in artificial saliva than in deionized water. Surface coating the specimens substantially reduced F release. These clinically relevant factors were not considered by many in vitro release studies which overestimate the F availability from glass ionomers. A recall appointment 24 h after the placement of glass ionomer restoration should be given for surface finishing.

Cermet Cements↗
PubMed2001

In vitro characterisation of zirconia coated by bioactive glass.

An in vitro evaluation of a biomedical device, which combines the mechanical properties of zirconia substrates with the bioactivity of two different glass layers (AP40 and RKKP), was performed. In this work, data on different kinds of analysis were reported both on as-sintered zirconia samples and on RKKP- and AP40-coated zirconia substrates. Structure, composition and morphology of the apatite layer growth on the coated samples after 30 days of soaking in an acellular simulated body fluid, serum protein adsorption, fibroblasts and human osteoblast-like cells adhesion, growth, morphology and biochemical aspects were studied. Results of soaking test in SBF, revealed the growth of an apatite layer on the surface of the glass-coated samples. Proteins adsorbed to the materials were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and results evidenced that the two glass-coated materials bound a higher amount of total protein than did the zirconia substrate. Fibroblasts and osteoblast-like cells cultured on RKKP- and AP40-coated zirconia showed a higher proliferation rate, leading to confluent cultures with higher cell density and a generally better expression of osteoblast alkaline phosphatase activity in comparison with zirconia substrate. In conclusion, our results indicate that the surface chemical characteristics of the two glass coatings AP40 and RKKP, with no great differences between them, substantially enhance zirconia integration with bone cells at least in vitro. This effect may be of significance in the stability of glass-coated zirconia orthopaedic and dental implants.

Adsorption↗
PubMed2001

Effect of water storage of E-glass fiber-reinforced composite on adhesion of Streptococcus mutans.

This study investigated the effect of water storage of fiber-reinforced composite on the adhesion of Streptococcus mutans (S. mutans) and its ability to stay adhered and multiply on the FRC. The materials (E-glass fibers and denture base polymer) were stored in water for 14 or 30 days or left dry. Water contact angles of the materials before and after water storage were determined. Test specimens, with or without parotid saliva or serum pellicle, were incubated in a suspension of S. mutans allowing initial adhesion to occur. Bacterial adhesion and multiplication was studied using scanning electron microscopy. Contact angles of both materials were significantly reduced after water storage indicating an increase in surface free energy. When studied without a surface pellicle, water storage significantly increased adhesion of S. mutans to both glass and polymer. Saliva coating of the materials resulted in higher degree of adhesion to glass fibers in comparison with polymer and after 14 days water storage glass bound over twice as much S. mutans cells than the polymer matrix. Bacterial growth and biofilm formation occurred equally on both materials. The results of this in vitro study suggest that in order to avoid the possible increase in S. mutans adhesion, the reinforcing glass fibers should be covered with the matrix polymer of the composite.

Bacterial Adhesion↗
PubMed2002

Preparation and in vitro bioactivity of hydroxyapatite/solgel glass biphasic material.

Hydroxyapatite/solgel glass biphasic material has been obtained in order to improve the bioactivity of the hydroxyapatite (OHAp). A mixture of stoichiometric OHAp and the precursor gel of a solgel glass, with nominal composition in mol% CaO-26, SiO2-70, P205-4, has been prepared. The amounts of components used have been selected to obtain a final relationship for OHAp/solgel glass of 60/40 on heating. Two different thermal treatments have been used: (i) 700 degrees C, temperature of solgel glass stabilisation and (ii) 1000 degrees C, lower temperature of hydroxyapatite sintering. The bioactivity of the resulting materials has been examined in vitro by immersion in simulated body fluid at 37 degrees C. The results obtained show that both materials are bioactive. The apatite-like layer grown is greater for the new materials than for the OHAp and the solgel glass themselves.

Calcium Compounds↗
PubMed2002

Fluoroapatite glass-ceramic coatings on alumina: structural, mechanical and biological characterisation.

The aim of this work was to realise bioactive coatings on full density alpha-alumina substrates. An SiO2-CaO-based glass (SC) and an SiO2-Al2O3-P2O5-K2O-CaO-F--based glass-ceramic (SAF) were used for this purpose. Specifically, SAF is a fluoroapatite containing glass-ceramic and previous studies have shown that it is a highly bioactive biomaterial. Furthermore, these fluoroapatite crystals possess a needle-shaped morphology which mimics that of hydroxylapatite found in human hard tissues, particularly in teeth. SAF is a very viscous glass-ceramic and for this reason an intermediate, less viscous, SC layer was interposed in direct contact with alumina aiming to obtain a good coating adhesion. Moreover, this intermediate layer strongly lowers the Al3+ diffusion and thus minimises both compositional changes in the SAF outer layer and the risk of detrimental modifications of the nature of the crystalline phases. A complete characterisation of the coated samples was performed by means of X-ray diffraction, optical and scanning microscopy. Coating adhesion on alumina was tested by comparative shear tests while biocompatibility was investigated on alumina. bulk SAF and on the realised coatings. For this purpose, cytotoxicity, adhesion and proliferation of human osteoblast-like cells were cultured onto the three materials. Results showed that the interposition of the SC layer was successful in allowing a good softening and spreading of the SAF outer layer and in avoiding the crystallisation of undesired crystalline phases maintaining the good bioactive properties of the bulk one. In vitro results on the coatings showed osteoblast-like cell behaviour similar to bulk fluoroapatite glass-ceramic and better respect to alumina substrates, being a promising index of bone material integration and of its in vivo possible applications.

Aluminum Oxide↗
PubMed2003

The use of hyaluronan and its sulphated derivative patterned with micrometric scale on glass substrate in melanocyte cell behaviour.

Surface microfabrication techniques were widely utilised for the spatial control of in vitro cell behaviour. A photo-immobilisation procedure was utilised to create micropatterned surfaces: four different stripe patterns (100, 50, 25 and 10 microm) of hyaluronan (Hyal) and its sulphated derivative (HyalS) on silanised glass substrate were obtained.The morphological analysis showed that the surface topography showed regular stripes of 100, 50, 25 and 10 microm wide and ranging from 300 nm up to 1 microm in thickness. They reproduced the exact photo-mask pattern: glass stripes alternating with polysaccharide ones. On the contrary, Hyal microstructures showed just a topographic pattern as the glass stripes appeared to be covered by a thin layer of the macromolecule by TOF-SIMS. Cell adhesion studies demonstrated that melanocytes adhered and oriented within the first 2h of culture on HyalS microdomains and not on Hyal microstructures where they spread on glass substrate around the patterned area. Double photo-immobilised samples characterised by a 100 microm stripe pattern of Hyal or HyalS on the top of a continuous layer of the two polysaccharides were also created in order to investigate the effect of the topography on cell behaviour. The obtained results demonstrated that melanocytes adhered on HyalS stripes while on the Hyal micropatterned surfaces they spread on silanised glass substrate around the structured area, resulting in the exclusion of the topographic pattern.

Animals↗
PubMed2003

The effects of adding fluoride compounds to a fluoride-free glass ionomer cement on subsequent fluoride and sodium release.

Studies have shown that ions in a glass ionomer matrix are 1-10% of the amounts present in the original glass. To measure more precisely the release from a cement matrix, known amounts of ions were added to LG30 glass which was fluoride and sodium-free. Cement without additions acted as the control. 1.4-1.6% of each of sodium, calcium and aluminum fluorides were added to three portions of control blend. The sodium and fluoride release into deionised water from five discs of each cements blend was measured for 8 months. This represented complete release for sodium but not for fluoride. Traces of fluoride and sodium in the glass produced low but measurable amounts indicating about a third of the fluoride and substantially all sodium present in LG30 was released. The addition of calcium fluoride had no significant effect on sodium or fluoride release and aluminium fluoride minimal effects. Adding sodium fluoride significantly enhanced release of both ions although fluoride release was less than from a glass containing 5% fluoride. Only small proportions of the additions, 2-5% of the fluoride and 13% of sodium, were released. Sodium and fluoride appeared to be released independently. For LG30 cements additives were poor at supplying extra ions.

Acrylic Resins↗
PubMed2003

A comparative study between in vivo bone ingrowth and in vitro apatite formation on Na2O-CaO-SiO2 glasses.

This study compared in vivo bioactivity with the in vitro apatite-forming ability of biomaterials. Granules of five kinds of P(2)O(5)-free Na(2)O-CaO-SiO(2) glasses, showing different apatite-forming ability in simulated body fluid (SBF), were implanted into a defect on the femoral condyle of rabbits. Bone ingrowth was evaluated using scanning electron microscopy among five kinds of glasses at 1, 2, 3, 6, and 12 weeks. Quantitative analysis was performed measuring the depth of new bone ingrowth from the periphery. In addition, the total areas of newly formed bone among glass particles were examined at 3 and 6 weeks using confocal laser scanning microscopy (CLSM) after weekly administration of fluorescent calcein. The depth of bone ingrowth among glass particles increased in proportion to their apatite-forming ability in vitro. The CLSM study showed a correlation between the quantities of labeled newly formed bone and in vitro apatite-forming ability. In the P(2)O(5)-free Na(2)O-CaO-SiO(2) glasses, the periods within 3-6 days for inducing apatite in SBF considered a necessary condition to convey bioactivity in vivo, and in vivo evaluations at 2-3 weeks is important to determine this. The in vivo bioactivity was precisely reproduced by apatite-forming ability in SBF. Therefore, evaluating apatite formation in SBF is a good screening test for the in vivo bioactivity of materials, resulting in reduction of the need for animal sacrifices and savings in experimental time.

Animal Testing Alternatives↗
PubMed2004

Bioactive glass as a drug delivery system of tetracycline and tetracycline associated with beta-cyclodextrin.

The aim of this study was to evaluate the physical-chemical properties, in vivo biocompatibility and antimicrobial activity of bioactive glasses (BG) used as a controlled release device for tetracycline hydrochloride and an inclusion complex formed by tetracycline and beta-cyclodextrin at 1:1 molar ratio. The BG as well as their compounds loaded with tetracycline (BT) and tetracycline:beta-cyclodextrin (BTC) were characterized by FTIR spectroscopy, X-ray powder diffraction, differential scanning calorimetry and by scanning electron microscopy and energy dispersive spectroscopy. The in vivo test was carried out with female mice split into three groups treated with bioactive glass either without drugs, or associated with tetracycline, or with tetracycline:beta-cyclodextrin by subcutaneous implantation. The histological examination of tissue at the site of implantation showed moderate inflammatory reactions in all groups after 72 h. The bacterial effect was tested on A. actinomycetemcomitans suspended in BHI broth, with or without bioactive particles. A considerable bacteriostatic activity was found with BT and BTC glasses, as compared to plain glass. The presence of cyclodextrin was important to slow down the release of tetracycline for a long period of time and it was verified that the presence of tetracycline or its inclusion complex, tetracycline:beta-cyclodextrin, did not affect the bioactivity of the glass.

Animals↗
PubMed1998

Confocal microscopic observation of structural changes in glass-ionomer cements and tooth interfaces.

This study aimed to develop techniques to allow dynamic imaging of a cavity before, during and after placement of glass-ionomer restorative materials. Cavities were cut in recently extracted third molars and the teeth longitudinally sectioned. Each hemisected tooth surface was placed in green modelling compound at 90 to the optical axis of the microscope. The cavity surface was imaged using a video rate confocal microscope in conjunction with an internally focusable microscope objective. The sample on the stage was pushed up to the objective lens which 'clamped' the cover glass onto it. Water, glycerine or oil was placed below the coverglass, with oil above. Internal tooth structures were imaged by changing the internal focus of the objective. The restorative material was then placed into the cavity. Video images were stored either onto video tape or digitally, using a frame grabber, computer and mass memory storage. Software controls produced time-lapse recordings of the interface over time. Preliminary experiments have examined the placement and early maturation of conventional glass-ionomer cements and a syringeable resin-modified glass-ionomer cement. Initial contact of the cement matrix and glass particles was visible as the plastic material rolled past the enamel and dentine, before making a bond. Evidence for water movement from the dentine into the cement has also been seen. After curing, the early dimensional changes in the cements due to water flux were apparent using the time-lapse facility. This new technique enables examination of developing tooth/restoration interfaces and the tracking of movement in materials.

Dental Caries↗
PubMed2000

Antibacterial silver-containing silica glass prepared by sol-gel method.

Recently, various inorganic antibacterial materials containing silver have been developed and some of them are in commercial use. Colorless and more chemically durable materials which slowly release the silver ion for a long period are, however, desirable to be developed for medical applications such as composite resin for dental restoration. In the present study, Si(OC2H5)4, Al(NO3)3 x 9H2O, AgNO3, HNO3, C2H5OH and H2O solutions with various Al/Ag atomic ratios under a constant Si/Ag atomic ratio of 1/0.023 were kept at 40 degrees C for gelation and drying. Thus obtained gels were pulverized into fine powders with average particle size of approximately 10 microm and then heat-treated at 900-1000 degrees C for 2 h. For the composition Al/Ag = 0, a yellow-colored glass was formed, since the silver existed in the form of metallic colloids in the glass. However, for the compositions Al/Ag > or = 1, colorless glasses were successfully obtained, since the silver existed in the form of Ag+ ions in the glasses. For the composition Al/Ag = 0, the silver ions got released rapidly into the water, whereas, for the compositions Al/Ag > or = 1, they gradually got released into the water at a controlled rate. A composite of the obtained powders with Al/Ag atomic ratio of 1 with Bis-GMA/TEGDMA in 70:30 weight ratio showed excellent antibacterial property. The sol-gel derived silica glass powders containing silver with compositions Al/Ag > or = 1 are believed to be useful as an antibacterial material for medical applications such as filler of composite resin for dental restoration.

Aluminum Compounds↗
PubMed1999

Analysis of bacterial communities on historical glass by denaturing gradient gel electrophoresis of PCR-amplified gene fragments coding for 16S rRNA.

The present study describes the analysis of bacterial communities on historical window glass by denaturing gradient gel electrophoresis of PCR-amplified 16S rDNA fragments. So far, only a few studies have been published in which the microflora and the corrosion mechanisms of glass surfaces have been investigated. Some microorganisms, especially fungi, have been isolated from different glass samples in the past. However, our results demonstrate that bacterial communities on biodeteriorated glass surfaces are much more complex than previously believed. In addition, bacteria were identified, which have never been isolated from glass samples before.

Bacteria↗
PubMed1984

Enzyme-linked immunosorbent assay (ELISA) with covalently bound protein on glass tubes: 1. Stable antigenicity and binding of IgG as a model antigen after repeated use.

A modification of the ELISA procedure is described. The system is based on the covalent binding of protein to glass tubes. Human IgG was used as model antigen. Optimal conditions were tested for the removal of alkaline phosphatase-labeled antibodies from their antigen. Under such optimal conditions, a regenerable system could be created which exhibited many advantages, as compared with conventional ELISAs with antigens absorbed unspecifically to plastic surfaces. The advantages are: 1. A higher density of IgG as model antigen on the solid phase, i.e., 1 molecule IgG per 94 nm2 with glass tubes as compared with 110 nm2 with polystyrene (PS) or 143 nm2 with polyvinylchloride (PVC) microtiter plates. 2. A much smaller unspecific absorption of less than 1% as compared with 39% with PS-plates or 16% with PVC-plates treated under identical conditions. 3. A higher stability of the binding of the model antigen to the solid phase, i.e., a drastically reduced protein loss of less than 6% during the first ELISA procedure (including the regeneration) and of less than 1% during the subsequent ELISA and regeneration cycles with glass tubes as compared with 46% (PS plates) or 55% (PVC plates). 4. A smaller intraday variation coefficient of the ELISAs of 4.8% with glass tubes as opposed to 9.7% or 7.5% with PS or PVC plates respectively. The system with covalently bound antigens on glass tubes could be used in at least 20 consecutive measuring cycles. In five consecutive cycles, a protein loss of less than 5% was observed and the interday variation coefficient of the ELISA reaction was smaller than 5% using the same tubes repeatedly. Our results indicate that covalent linkage of protein can improve ELISA and lead to repeatedly usable systems as long as the antigen is stable against the regeneration procedure. Such an ELISA system may be helpful with highly purified proteins.

Adsorption↗
PubMed2000

Effect of finishing technique on the microleakage and surface texture of resin-modified glass ionomer restorative materials.

PURPOSE: The purpose of this study was to evaluate the effects of wet and dry finishing/polishing procedures on the microleakage and surface texture of resin-modified glass ionomer (RMGI) restorative materials. MATERIALS AND METHODS: Class V cavity preparations were made at the cemento-enamel junction (CEJ) on the buccal and lingual surface of 30 extracted human molars. The teeth were restored in three groups of 10 (20 preparations in each group) using Fuji II LC and Vitremer, both RMGIs, and Fuji II, a capsulated conventional glass ionomer cement (control). One restoration per tooth was finished/polished with copious applications of water and the other was finished/polished without water. All restorations were finished/polished using a sequence of four abrasive disks. Finishing/polishing was initiated according to manufacturers' instructions-immediately after light-curing Fuji II LC and Vitremer, and 15min after placement for Fuji II. The specimens were thermocycled and subjected to a silver nitrate leakage test. Each tooth was sectioned buccolingually and examined with an optical microscope at 40x to determine the extent of microleakage at enamel and dentin margins. The data were subjected to a non-parametric statistical analysis. To evaluate surface roughness after polishing, three disks each of Vitremer and Fuji II LC were fabricated in Teflon molds. One disk of each material was not finished/polished (control). The others were finished/polished using Sof-Lex abrasive disks. One specimen of each material was kept wet during all finishing/polishing procedures, while the other was kept dry. Atomic force microscopy was used to determine the average roughness (R(a)) of the specimens. RESULTS: For each material, microleakage at the enamel margin was very slight. Leakage of the conventional glass ionomer Fuji II was severe at dentin margins. Statistical analysis indicated that both Vitremer and Fuji II LC had significantly less leakage than Fuji II, and that Vitremer had significantly less leakage than Fuji II LC (p<0.05). Leakage at enamel margins was significantly less than at dentin margins. Differences related to wet and dry polishing were not statistically significant. Profilometry data indicated that polished specimens were rougher than those cured against a Mylar strip. Wet polishing created greater surface roughness than dry polishing. CONCLUSIONS: RMGIs rather than conventional glass ionomers should be used in Class V cavity sites to allow immediate finishing and to reduce the incidence of microleakage. Dry finishing of RMGIs with abrasive disks is recommended because it produces a smoother surface and does not contribute to microleakage. However, wet finishing of conventional glass ionomers is still recommended to avoid desiccation.

Composite Resins↗
PubMed2001

A biomechanical reconstruction of a wound caused by a glass shard--a case report.

During the course of a criminal trial, an investigating pathologist is commonly asked how much force was required to produce an injury. This subjective opinion is based on the pathologist's previous experience of dealing with wounds inflicted with similar weapons. However, in the case of stab wounds inflicted by broken glass, it is unlikely that two glass fragments would be physically similar. In the case studied, two theories were examined: that a wound resulted from a thrown glass fragment or that it had been caused as a stab injury by the glass held in the bare hand. The investigation involved quantifying the energy required for human tissue penetration, comparison of sharpness, a biomechanical analysis of throwing actions and testing of the hypothesis that if the glass shard were used as a stabbing implement it would result in a cut to the hand.The investigation utilised a scientific methodology that reduced the need for speculative (though informed) opinion from the pathologist by producing quantitative results.

Biomechanical Phenomena↗
PubMed2001

Puncture wounds caused by glass mistaken for with stab wounds with a knife.

Three cases are presented where fatal puncture wounds caused by broken glass were very similar to stab wounds inflicted by a knife with a single-edged blade. Thus, all three cases caused a murder investigation to be initiated. It could only be determined that these wounds had been caused by glass after a detailed forensic autopsy. In two of the three cases, the only evidence for this was the identification of glass fragments in the wounds. The importance of X-ray examinations is underlined because modern glass in common use is radiopaque. Glass fragments lodged in the wounds can reduce the loss of blood and thus, prolong the capacity to act despite severe injuries.

Accidental Falls↗