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PubMed2002

The glass ionomer cement: the sources of soluble fluoride.

This study aimed to investigate certain processes of fluoride production which enable glass ionomer cements to leach fluoride. Two fluoroaluminosilicate glasses, G338 and LG26 were used. The free and total fluoride which could be dissolved from the glasses was measured, before and after acetic acid washing. Both glasses contained appreciable amounts of soluble fluoride prior to any acid treatment. The latter process reduced the amount to some 75% of the original levels. Replacing the customary polymeric acid with propionic acid produced a cement which disintegrated in water allowing the amount of fluoride generated by the cement forming process to be measured. Cement production increased soluble fluoride by a further 3%. Both glasses behaved similarly when undergoing the various processes. G338 produced significantly greater quantities of fluoride, of the order of 10, compared with LG26 although containing only three times the amount of fluoride in the glass formula. A substantial proportion, over half, of the total fluoride was complexed especially after contact with cement and when G338 was used. During the period of the experiment, 21 days, total fluoride release did not seem to depend on the square root of time.

Acetic Acid↗

PubMed2003

Reactive fibre reinforced glass ionomer cements.

The mechanical properties of glass ionomer cements used in restorative dentistry reinforced by chopped glass fibres were investigated. Reactive glass fibres with a composition in the system SiO(2)-Al(2)O(3)-CaF(2)-Na(3)AlF(6) and a thickness of 26 microm were drawn by a bushing process. The manufacturing parameters were optimized with respect to maximum strength of the glass fibre reinforced ionomer cements. Powder to liquid ratio, pre-treatment of the glass, grain size distribution and fibre volume fraction were varied. Glass fibre and cement were characterized by X-ray diffraction, transmission electron microscopy and energy dispersive spectroscopy techniques, respectively. The highest flexural strength of the reinforced cement (15.6 MPa) was found by compounding 20 vol% reactive fibres and extending the initial dry gelation period up to 30 min. Microscopic examination of the fractured cements indicated a distinct reactive layer at the fibre surface. A pronounced fibre pull out mode gives rise to an additional work-of-fracture contributed by pulling the fibres out of the fracture surface.

Compressive Strength↗

PubMed2001

Survival of Dicor glass-ceramic dental restorations over 16 years. Part III: effect of luting agent and tooth or tooth-substitute core structure.

STATEMENT OF PROBLEM: The influence of different types of restorative design features on the long-term survival of Dicor glass-ceramic restorations is only partially understood. PURPOSE: This study examined the effect of different types of luting agents and preparation core structures on the survival of Dicor glass-ceramic restorations functioning in vivo. MATERIAL AND METHODS: A total of 1444 Dicor glass-ceramic restorations were placed on the teeth of 417 adults. Failure was defined as a restoration that required remake because of material fracture. The survival of restorations of different types, with different luting agents and preparation core structures, was described with Kaplan-Meier survival functions. The significance of differences in survival between different tooth or tooth-substitute preparation core structures and different luting agents was determined with the log-rank test. RESULTS: The probability of survival of a typical acid-etched Dicor restoration luted to gold preparation core structures was 91% at 16 years compared with 75% for dentin preparation core structures (P<.01). The survival of acid-etched Dicor restorations luted to dentin preparations was significantly better than nonacid-etched restorations luted to dentin. Acid-etched Dicor restorations luted with resin composite exhibited a more favorable survival function than those luted with glass ionomer (P<.01) and zinc phosphate (P<.05). Differences between restorations luted with glass ionomer or zinc phosphate agents were not significant. CONCLUSION: Acid-etched Dicor restorations luted to gold preparation core structures exhibited significantly better intraoral survival than restorations luted to dentin. Acid-etched Dicor restorations survived better than nonacid-etched restorations when luted to dentin preparations. Acid-etched Dicor restorations luted with resin composite exhibited more favorable survivor functions than restorations luted with glass ionomer or zinc phosphate agents.

Acid Etching, Dental↗

PubMed2002

Infrared spectrometric study of acid-degradable glasses.

The composition of glasses used in glass-ionomer cements affects their leaching behavior and hence the properties of the cement. The aim of this study was to correlate the composition and leaching behavior of these glasses with their infrared absorption characteristics. The wavenumber of the absorption band of the Si-O asymmetric stretching vibration shifts to a higher value with decreasing content of mono- and bivalent cations in the glass. This effect can be ascribed to the influence of these extraneous ions on the glass network order and connectivity. Preferential leaching of these ions induces an increase of asymmetric stretching vibration and a general modification of the band profile. The results can be correlated with the x-ray diffraction characteristics of the glass.

Acetates↗

PubMedDate not supplied

Clinical outcome of glass-fiber-reinforced crowns and fixed partial dentures: a three-year retrospective study.

OBJECTIVE: Glass-fiber-reinforced resin composites for the fabrication of esthetic single crowns and fixed partial dentures have been developed recently. However, little data on the clinical outcome of such restorations have been published. The purpose of this retrospective study was to evaluate the clinical outcome of crowns and fixed partial dentures made from the glass-fiber-reinforced resin composite material Targis/Vectris. METHOD AND MATERIALS: Between 1995 and 1997, 39 patients were treated with 67 single crowns and 83 fixed partial dentures. Twenty-five crowns and 28 fixed partial dentures were cemented with temporary cement, while 42 crowns and 55 fixed partial dentures were cemented with either zinc-phosphate cement or glass-ionomer cement. RESULTS: In September 2001, 57 restorations in 17 patients were still in function. The three-year survival rate calculated according to the Kaplan-Meier method was 58.8% for all restorations. However, after this time, it was 37.5% for crowns and 59.9% for fixed partial dentures cemented with temporary cement, and 55.1% for crowns and 67.9% for fixed partial dentures cemented with zinc phosphate or glass ionomer. The differences between the restoration groups were not statistically significant. CONCLUSION: Glass-fiber-reinforced crowns and fixed partial dentures made with the glass-fiber-reinforced resin composite material Targis/Vectris showed a lower survival rate than that published for metal-ceramic crowns and fixed partial dentures. Therefore, the use of this material for the fabrication of single crowns or fixed partial dentures as permanent restorations cannot be recommended.

Adult↗

PubMed1996

Effect of crystallization on apatite-layer formation of bioactive glass 45S5.

The bioactive glass 45S5 was crystallized to 8-100 vol % of crystals by thermal treatments from 550-680 degrees C. The micro-structure of the glass-ceramics had a very uniform crystal size, ranging from 8 to 20 microns. Fourier-transform infrared (FTIR) spectroscopy was used to determine the rate of hydroxycarbonate apatite (HCA) formation that occurs on bioactive glass and glass-ceramic implants when exposed to simulated body fluid (SBF) solutions. Crystallization did not inhibit development of a crystalline HCA layer, but the onset time of crystallization increased from 10 h for the parent glass to 22 h for 100% crystallized glass-ceramic. The rate of surface reactions was slower when the percentage of crystallization was > or = 60%.

Apatites↗

PubMed1998

Bioactive glass fiber/polymeric composites bond to bone tissue.

Bioactive glass fibers were investigated for use as a fixation vehicle between a low modulus, polymeric composite and bone tissue. In an initial pilot study, bioactive glass fiber/polysulfone composites and all-polysulfone control rods were implanted into the rabbit tibia; the study was subsequently expanded with implantation into the rabbit femur. Bone tissue exhibited direct contact with the glass fibers and adjacent polymer matrix and displayed a mechanical bond between the composite and bone tissue after six weeks implantation. Interfacial bond strengths after six weeks implantation averaged 12.4 MPa, significantly higher than those of the all-polymer controls. Failure sites for the composite at six weeks generally occurred in the bone tissue or composite, whereas the failure site for the polymer implants occurred exclusively at the implant/tissue interface. The bioactive glass fiber/polysulfone composite achieved fixation to bone tissue through a triple mechanism: a bond to the bioactive glass fiber, mechanical interlocking between the tissue and glass fibers, and close apposition and possible chemical bond between the portions of the polymer and bone tissue. This last mechanism resulted from an overspill of bioactivity reactions from the fibers onto the surface of the surrounding polymer which we call the "halo" effect.

Animals↗

PubMed1999

Interactions between the bioactive glass S53P4 and the atrophic rhinitis-associated microorganism klebsiella ozaenae.

In an aqueous environment, ions are released from a bioactive glass (BAG) and the pH rises in its vicinity. This may influence both growth and colonization of microorganisms. We studied the effects of the BAG S53P4 on the atrophic rhinitis-associated microorganism Klebsiella ozaenae. The glass was used in the form of granules or discs. Growth inhibition was studied using an agar plate test. Adhesion was studied by incubating bacterial suspension with the glass. The effect of the presence of the bacteria on the formation of the Si-rich layer on the bioactive glass was also analyzed. Furthermore, a follow up study of 19-74 months with ozena patients surgically treated with the BAG S53P4 was performed. The bioactive glass showed no clear growth inhibition of K. ozaenae in the agar plate test. K. ozaenae showed low adherence to the BAG S53P4. No growth of the microbe was seen on the glass during the 8 h incubations and the Si-rich layer was formed normally. The clinical follow-up study showed no infections of the implants and the symptoms of the patients were markedly reduced. Thus, the BAG S53P4 did not favor adhesion and colonization of K. ozaenae, in vitro, which is supported by the in vivo findings showing no BAG-associated infections or reinfections.

Adolescent↗

PubMed1999

Bioactive glasses induce chemiluminescence by human polymorphonuclear leukocytes.

The effect of bioactive glasses on human polymorphonuclear leukocytes (PMNLs) were studied in vitro by a chemiluminescence (CL) assay. Eight different glasses were chosen. All glasses induced a rapid CL response by human PMNLs, which proved to be dose dependent. The CL response also seemed to depend on the durability of the glasses. The least durable glass caused the highest CL response, and highly durable glasses caused only low CL responses by the cells.

Bone Substitutes↗

PubMed1999

In vitro calcium phosphate layer formation on sol-gel glasses of the CaO-SiO(2) system.

A glass with a composition of SiO(2) 80% and CaO 20% (in mol %) was prepared by the sol-gel method, and its in vitro bioactivity was studied by soaking it in simulated body fluid (SBF) at 37 degrees C. The formation of a calcium phosphate layer on the glass was analyzed by determining the ionic concentrations in solution and by studying the surface of the glass with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and electron diffraction (ED) after it had been in SBF for varying periods of time. The composition of this bioactive glass, formed of only two components, allowed us to monitor the formation process of the hydroxycarbonate apatite (HCA) layer. The bioactive behavior of this glass indicates that the presence of phosphorous in the glass composition is not an essential requirement for the development of a HCA layer. In this case, the layer is formed because of the phosphorous present in the in vitro assay solution.

Biocompatible Materials↗

PubMed2000

Influence of filler content on static properties of glass-reinforced bone cement.

A commercial acrylic bone cement was modified by the incorporation of different weight fractions of glass spheres. The influence of the filler proportion on the mechanical behavior was assessed. Composite cements were prepared by replacing part of the powder phase of the cement by an equivalent weight of glass particles, which resulted in an increase in the liquid-to-powder (L/P) ratio of the polymeric matrix. Dynamic mechanical analysis revealed an increase in residual monomer content with increasing filler proportion as a consequence of the increase in L/P. Flexural, compressive, and fracture properties of the cement with varying amounts of glass particles were measured. It was found that up to 50 wt% glass particles could be added with significant increases in flexural modulus and fracture toughness. The mechanical behavior was explained in terms of both the reinforcing effect of the filler and the plasticizing effect of the monomer. Glass-filled bone cements displayed superior workability compared with the standard cement, which was attributed to a decrease in the viscosity of the initial mix and the surface characteristics of the glass particles. The observed increase in fracture toughness could be rationalized through the application of proposed mechanisms for toughening of particle-reinforced polymers.

Acrylic Resins↗

PubMed2001

A new bioactive bone cement: effect of glass bead filler content on mechanical and biological properties.

A new bioactive bone cement (designated GBC), consisting of bioactive glass beads as an inorganic filler and polymethylmethacrylate (PMMA) as an organic matrix, has been developed. The purpose of the present study was to examine the effect of the amount of glass bead filler added to GBC on its mechanical and biological properties, and to decide the most suitable content of filler. Serial changes in GBC with time were also examined. The newly designed bioactive beads, consisting of MgO-CaO-SiO2-P2O5-CaF2 glass, were added to the cement in the proportions 30, 40, 50, 60, and 70 wt %. These cements were designated GBC30, GBC40, GBC50, GBC60, and GBC70, respectively. The compressive strength and the elastic modulus of bending of GBC increased as the glass bead content increased. The various types of GBC were packed into the intramedullar canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index calculated as the length of bone in direct contact with the cement expressed as a percentage of the total length of the cement surface. Rats were killed at 4 and 8 weeks after the operation and the affinity index was calculated for each type of GBC. Histologically, new bone had formed along the surface of all types of GBC within 4 weeks, even in GBC30 containing only 30 wt % of glass beads. At each time interval studied, there was a trend for the affinity index of GBC to increase as the glass bead filler content increased. There was no significant increase of affinity index between GBC60 and GBC70. The affinity indices for all types of GBC increased significantly with time up to 8 weeks. The handling properties of GBC were comparable to those of conventional PMMA bone cement. We conclude that when mechanical properties and osteoconductivity are both taken into consideration, GBC60 is the most suitable formulation; it shows excellent osteoconductivity and sufficient mechanical strength for clinical use.

Animals↗

PubMed2001

Sintering temperature effects on the in vitro bioactive response of tape cast and sintered bioactive glass-ceramic in Tris buffer.

Tape casting procedures were used to form thin polymeric sheets (100 microm thickness) loaded with bioactive glass particulate. Blanks were punched from the sheets, stacked, laminated, and heated in air to 500 degrees C to remove the organic phase. The resulting bioactive glass discs were sintered at 800 degrees C, 900 degrees C, or 1000 degrees C. Because the material is built up in layers and can be machined in the green state, such a processing technique can be used to form complex-shaped materials. The in vitro bioactivity of the tape cast sintered (TCS) bioactive glass-ceramic discs was then assessed in Tris buffer. The sample surface area to volume buffer (SA/V) ratio was approximately 0.1 cm(2)/mL. Tape cast bioactive glass-ceramic sintered at 900 degrees C and 1000 degrees C formed crystalline hydroxyapatite layers after 24 h in Tris buffer as indicated by FTIR, SEM, and EDS analysis. Decreasing the SA/V ratio to 0.013 cm(2)/mL allowed for the formation of crystalline hydroxyapatite layers on the surface of 800C TCS bioactive glass-ceramic. Given the dependence of the bioactive response as a function of the processing schedule and SA/V ratio, it may be possible to tailor the response to that desired in vivo or in vitro for tissue engineering studies. Biaxial flexural strength of TCS bioactive glass-ceramic increased with increasing sintering temperature. Strength of samples sintered at 1000 degrees C for 3 h increased from 87 to 120 MPa after 2 weeks' immersion in Tris buffer.

Biocompatible Materials↗

PubMed2001

Dose-dependent behavior of bioactive glass dissolution.

The effect of glass dosage (0.001 g ml(-1) to 0.015 g ml(-1)) on the in vitro dynamic dissolution behavior of melt-derived 45S5 and sol-gel-derived 58S bioactive glasses, in simulated body fluid (SBF) at 37 degrees C, was evaluated. These glasses differ significantly in texture, especially the specific surface area and porosity, as a result of differences in manufacturing route. The concentrations of elements (Si, Ca, P, and Na) leached from the glasses into the dissolution medium, from 1 to 22 h, were evaluated with the use of induced coupled plasma analysis (ICP). The reacted powders were analyzed with the use of FTIR to observe the formation of a hydroxycarbonate apatite layer on the surface. The results show that the rate of HCA formation on both gel- and melt-derived bioactive glass powders in vitro depends on the concentration of the powders in solution. This result must be taken into account when carrying out in vitro cell-culture studies to simulate conditions in vivo and in experiments using extracts of the bioactive glass powders.

Apatites↗

PubMed2002

In vitro dissolution of melt-derived 45S5 and sol-gel derived 58S bioactive glasses.

Effects of powder type, particle size (5-20 microm; 90-300 microm; 90-710 microm), and type of dissolution medium on the dissolution behavior of bioactive glasses were investigated in vitro using melt-derived 45S5 and sol-gel derived 58S bioactive glass powders. Dissolution studies were performed in simulated body fluid and in alpha-MEM based cell culture medium at 37 degrees C under dynamic conditions (1 Hz) for periods of 30 min, 1, 2, 4, 8, 17, and 22 h. The concentrations of elements dissolved from the glasses were evaluated using inductively coupled plasma analysis. The reacted powders were analyzed for bioactivity using Fourier transform infrared spectrometry to observe the formation of a calcium phosphate layer on the surface. The non-porous surfaces of melt-derived 45S5 glass powders exhibited lower dissolution rates and rate of surface layer formation than 58S gel-glass powders. The rates of dissolution for both types of powders were lower in culture medium, compared to simulated body fluid, and increased as the particle size decreased. Thus, particle size range, glass type, and powder volume fraction can be used as a means to control the release rate of active ions that stimulate the gene expression and cellular response for tissue proliferation and repair.

Biocompatible Materials↗

PubMed2002

Interaction of bioactive glasses with peritoneal macrophages and monocytes in vitro.

Macrophage activation was analyzed following exposure to pure, crystalline alpha-quartz powders, two bioactive gel-glass powders of different compositions, and a melt-derived glass, 45S5 Bioglass. The release of reactive oxygen metabolites (chemiluminescence test), modifications of cell morphology, the amount of tumor necrosis factor alpha (TNFalpha) secreted, and the amount of TNFalpha mRNA expression were evaluated. The 45S5 Bioglass powders elicited the highest chemiluminescence response while the two solgel glasses had a lower response with less of an oxidative burst difference between them. Particulate bioactive glasses are actively ingested by mouse peritoneal macrophages, and only the 58S solgel glass had a moderate toxic effect on the macrophages. Macrophage cell morphology showed increased size and cell spreading, consistent with the high level of cytokine secretion induced by 45S5 Bioglass. The 45S5 Bioglass powders led to an increased release of TNFalpha and expression of TNFalpha mRNA relative to unstimulated and control treated monocytes. Bioactive glasses (and particularly 45S5 Bioglass) that in vivo induce rapid bone growth appear to activate an autocrine-like process in which the response evoked by the material (for example monocyte and macrophage activation with cytokine production) enhances subsequent interactions with cells in contact with the material.

Animals↗

PubMed1989

Interfacial analysis of fiber-reinforced bioactive glass dental root implants.

Bioactive glass can form an effective bond with bone. Essential for this connection are the interfacial reactions which lead to the development of a Si-rich film covered by a CaP-rich film. The presence of these layers can be demonstrated clearly by EDX analysis of fiber-reinforced bioactive glass and bulk bioactive glass implants installed for 4 and 16 months in the partial edentulous jaws of beagle dogs. EDX analysis reveals three types of microchemical interface. The first type develops when the implant is bonded to bone. Here, a smooth transition of the CaP profile can be observed between bioactive glass and the bone, thus providing for a compositional gradient between the implant and the surrounding tissues. The second type is seen when the implant surface is surrounded by fibrous tissue. This causes a discontinuity in the CaP profile. The third type is characterized by a gradual decrease in the Ca and P concentrations across the interface, caused by the presence of Ca and P in the fibrous tissue near the implant surface. This suggests that the interface is dynamic in time and transforms to a functionally better optimized interface. EDX analysis does not reveal any metal fiber ion contamination of the outer glass rim of the implant. When stainless-steel or wrought Co-Cr alloy is exposed to the surrounding fluids, the interfacial osteogenesis is disturbed, possibly by a synergistic effect of glass ions and metal ions. Exposure of titanium does not interfere with this osteogenesis. The bone bonding can also be influenced by surgical trauma. However, with precise implantation techniques, an enhancement of bone growth by osteoconductivity can be measured.

Animals↗

PubMed1993

Chemical durability of Y2O3-Al2O3-SiO2 glasses for the in vivo delivery of beta radiation.

Microspheres made from Y2O3-Al2O3-SiO2 (YAS) glasses, which contain radioactive Y-90, are currently being used to treat liver cancer in humans, where their chemical durability is of prime importance. In deionized water or saline at 37 degrees C, the weight percent Yttrium (Y) dissolved from eight different YAS glasses ranged from only 0.02-0.13% of the total Y present and their dissolution rate was barely measurable, < or = 1.0 x 10(-9) g/cm2-min. The most chemically durable YAS glass was 17Y2O3-19Al2O3-64SiO2, mol%. The small amount of Y released from microspheres, 25-35 microns diameter, of this glass after corrosion in saline or deionized water at 37 degrees C was essentially the same as for bulk glass samples. Based on their excellent chemical durability, it is concluded that YAS glass microspheres are suitable for in vivo use.

Aluminum Oxide↗