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PubMed1991

Activity of urokinase diluted in 0.9% sodium chloride injection or 5% dextrose injection and stored in glass or plastic syringes.

The effects of the diluent, the container, the i.v. set, and the drug concentration on the adsorption of urokinase to i.v. administration systems were studied, along with the compatibility of urokinase with plastic and glass syringes. Solutions of urokinase 1500 and 5000 IU/mL in 0.9% sodium chloride injection and 5% dextrose injection in glass and polyvinyl chloride (PVC) containers were sampled at 2 and 30 minutes. Administration sets were attached to PVC containers containing the urokinase-5% dextrose injection solutions, and samples were collected at 90 and 150 minutes. Glass and polypropylene syringes containing urokinase 5000 IU/mL in 0.9% sodium chloride injection or 5% dextrose injection were sampled at 0, 4, 8, and 24 hours. Urokinase activity was measured by an in vitro clot lysis assay. No urokinase diluted in 0.9% sodium chloride injection adsorbed to glass or PVC containers. For urokinase 1500 IU/mL in 5% dextrose injection, a loss of 15% to 20% occurred almost instantaneously in PVC containers; additional losses to the infusion sets were minimal. However, for urokinase 5000 IU/mL in 5% dextrose injection, no losses were observed in the PVC systems. No drug loss to glass bottles was seen for urokinase 1500 or 5000 IU/mL in 5% dextrose injection. Urokinase potency remained constant in polypropylene and glass syringes for 24 hours. To minimize urokinase sorption to PVC containers, higher concentrations of urokinase diluted in 5% dextrose injection should be used, provided that clinical safety and efficacy are not compromised. The use of 0.9% sodium chloride injection as a diluent also prevents sorption losses.

Adsorption↗

PubMedDate not supplied

Resin-modified glass-ionomer cements.

The recently developed dual-setting resin glass-ionomer cements are discussed, and the question of whether they are the true glass-ionomer cements is addressed. Their chemistry and properties are examined and compared with conventional glass-ionomer cements. Resin-modified glass-ionomer cements have the advantage of a long working time combined with a rapid set and higher early strength. They are also easily bonded to resins. They have the strength properties comparable to conventional glass-ionomer cements rather than composite resins, but they share with composite resins the disadvantage of containing free monomers and therefore may not be as biocompatible as conventional glass-ionomer cements.

Glass Ionomer Cements↗

PubMedDate not supplied

[Glass ionomer cementing in stomatological practice].

Glass ionomers cements represent a cement system which develops by a reaction between a polyalchenic acid, usually a homo- or a copolymer of acrylic acid and a ion donor, usually an aluminium fluorosilicate glass. Introduction of these ionomers in the stomatological practice was determined by their remarkable adherence to dentin, by pulpal and parodontal biocompatibility, and because of the fact that they deliver continuously fluorine over a long period of time. These cements provide a good marginal sealing of the obturation. In the last years a new generation of glass ionomers cements has been introduced, that "Cormat" cements, in which the glass powder is intimately linked to a pure silver metallic powder by a synthetization process, and this provides a greatly increased resistance to abrasion, as compared to conventional glass ionomer cements. Presently glass ionomer cements have become increasingly known in the stomatological practice and they are used preferentially for base obturations, under obturations with composites on lateral teeth, in the treatment of mylolysis and for coronary erosions determined by brushing, which do not need preparation of retention cavities. They are also used for coronary reconstruction, and the treatment of atopical microcavities of occluding decay processes on the lateral teeth that have induced limited enamel losses. The perspective of these cements in the stomatological practice depends however on an improved translucency, which, for the present at least, does not match that of silicates and composites, as well as on an improved resistance to bending, and even the "Cormat" cements are inferior to silver amalgam which is used in the obturation of classical class II cavities.

Dental Alloys↗

PubMed1990

Microleakage and marginal placement of a glass-ionomer liner.

Glass-ionomer cements, with their ability to bond to dentin, have been reported to produce less microleakage than several other restorative resin materials. This matched-pair study reports the effect on microleakage of placement of a light-curing glass-ionomer cement used as a liner when extended out to the dentinal cervical cavosurface margin or held short of that margin. Pairs of circular Class V cavities involving 50% enamel, with bevel, and 50% cementum were cut in 31 extracted third molars. After placement of the glass-ionomer cement, etching of the bevel, and placement of a resin bonding system, microfilled resin was placed over the bonding agent in one increment, light-cured, finished, and given 500 thermocycled 500 times between 5 and 55 degrees C. A silver nitrate staining technique was used to evaluate microleakage measured in graticular units (gu) along the dentinal interface under stereomicroscopy. The extension of the glass-ionomer liner out to the dentinal cavosurface margin did not significantly improve microleakage performance compared to performance of the liner when it was placed short of that margin and covered by a resin veneer. From other considerations, such as the potential for mechanical breakdown of the glass-ionomer cement when exposed to the oral environment and abrasion, and the possibility for improved esthetics, the clinician should consider holding the glass-ionomer liner short of the dentinal cavosurface margin and covering it with a composite resin veneer of a thickness consistent with structural integrity.

Dental Bonding↗

PubMed1989

[Marginal leakage of glass ionomer as filling material for proximal decay in endodontic treatment].

The primary purpose of sealing proximal tooth defects during endodontic treatment is to prevent fluid, organic or bacterial contamination of the root canal system. At times, glass ionomers are used to restore proximal tooth defects between appointments, and after the root canal therapy. The purpose of this study was to evaluate the sealing ability of glass ionomers in teeth having proximal defects during root canal therapy. Sixty lower molars were extracted and prepared with standard endodontic access procedures. The mesial wall was then removed to mimic a proximal defect, and the tooth was filled with a glass ionomer in various thicknesses--0.8, 1.2 and 1.5 mm, respectively. After thermocycline treatment, all of the teeth were partially immersed in a 1% methylene blue dye for two weeks. During this period, the glass ionomer was directly observed to determine if any marginal leakage occurred. The glass ionomer was unacceptable if the dye penetrated to the interior wall of the pulp chamber. If not, it was classified as acceptable. The results indicated that dye penetration or leakage was least likely to occur in a 1.5 mm glass ionomer group.

Dental Leakage↗

PubMed1977

[Studies of calcium phosphate glass-ceramics--development of dental materials. (Part 2) Acid resistance--(author's transl)].

It is well known that minerals of bone or tooth are essentially of CaO-P2O5 system. Glass and the crystallized product, i.e., so-called "glass-ceramics" of which chemical composition is 55 CaO . 45 P2O5 (in mole %) and have been developed for biomaterials were subjected to chemical durability test. Human enamel was also tested for the comparison of the data with them. All the specimens were ground to powders in size from 74 to 140 micrometer. A hundred milligram of the powders were immersed into 100 ml. of N/10 acetate buffer (1 mol acetic acid) solution (pH 4.1) at a constant temperature of 37 degrees C. Amount of Ca2+ and P5+ dissolved were determined by an atomic absorption method and Fiske-Subbarow method, respectively. The order of dissolution is human enamel greater than glass greater than glass-ceramics: the amount of Ca2+ (SCa) and P5+ (Sp) with soaking time (t) was expressed by the following equations, :formula: (see book). The glass and the glass-ceramics show good resistance against a weak acid.

Acids↗

PubMed1973

Effects of certain purified plasma proteins on the compatibility of glass with blood.

The effects of certain purified plasma proteins on the coagulation-activation and platelet-adhesion properties of glass surfaces have been investigated. Albumin, transferrin, gammaG globulin, gammaM globulin and fibrinogen were obtained in highly purified form; ceruloplasmin was a more crude preparation. Each of these proteins was found to adhere to glass surfaces and influence reactions of these surfaces with blood. gammaG globulin or albumin adsorbed to glass markedly inhibited activation of the intrinsic coagulation system, while the other proteins tested were much less effective in this respect. Fibrinogen, of all the proteins tested, greatly enhanced the adhesion of platelets to glass. Albumin, ceruloplasmin, transferrin, gammaG globulin and gammaM globulin each decreased the adhesion of platelets to glass by approximately 50%. Ultrastructural studies of the interface area where blood reacted with the layer of protein adsorbed to glass demonstrated the deposition of a moderately thick irregular protein layer upon the surface, with adhesion of cellular elements to this unilaminar adsorbed layer. Ultrastructural studies also demonstrated that platelets which adhere to protein-coated surfaces formed pseudopods and spread upon such surfaces.

Afibrinogenemia↗

PubMed1982

Surface adsorption of factor XI. II. Evidence that different mechanisms are involved in binding to glass and plastic materials.

Blood coagulation factors XI and XIa possess binding site(s) for glass and plastics, located in the heavy chain of the molecule. To elucidate the nature of binding, adsorption and desorption properties of factor XI and XIa to different surfaces have been studied. Desorption experiments with high salt (2.4 M NaC1) suggest participation of ionic forces in the binding to glass. This is consistent with the decreased adsorption of factor XI (pI-9.0) to glass with increasing pH. The non-ionic detergent Triton X-100, which splits hydrophobic bonds, desorbs factor XI very well from plastics and partially from glass. The anionic detergent SDS, which will split hydrophobic as well as ionic bonds, is the most effective agent tested for the elution of factor XI from glass. We, therefore infer, that the binding of factor XI to glass is the combined effect of ionic and hydrophobic binding, whereas the adsorption of factor XI to plastics is primarily hydrophobic.

Adsorption↗

PubMedDate not supplied

Fluoride exchange from glass ionomer preventive resin restorations.

The purposes of this in vivo study were to determine if placing a sealant over a glass ionomer restoration modifies its fluoride release, and to examine the effect on glass ionomer of a 4-min application of topical fluoride. Fluoride release from glass ionomer preventive resin restorations placed in 21 bovine teeth was measured before and after removing their sealants. Fuji II, Ketac Silver, and Fuji LC were evaluated, representing the three generations of glass ionomers. Fluoride was extracted from the restorations by incubating the specimens in 5 ml deionized water and was measured by specific ion electrodes at 1 and 2 days, then once weekly for 7 weeks. The results indicated that fluoride release was not significantly different in pattern or quantity in the three types of ionomer (P > 0.05). A significant reduction in fluoride release occurred when the restorations were covered with a sealant when compared with control restorations of the same materials (P < 0.001). After removing the sealant from the glass ionomer preventive resin restorations, a significant release of fluoride occurred when compared with sealed restorations (P < 0.001). After 63 days in water, the unsealed restorations were subjected to a 4-min topical APF treatment and reimmersed in water for an additional 27 days to examine the ability of the various materials to absorb fluoride. The fluoride-depleted restorations treated with fluoride released significantly more fluoride than fresh, untreated ionomer restorations (P < 0.001) or amalgam restorations. As a result of fluoride release, the glass ionomer preventive resin restoration may afford chemical protection to the tooth if sealant loss occurs.

Absorption↗

PubMed1993

Induction of new bone by allogeneic demineralized bone matrix combined to bioactive glass composite in the rat.

Allogeneic diaphyseal demineralized bone matrix (DBM) cylinders containing bioactive glass rods were implanted for 4 and 8 weeks in the abdominal muscle wall of rats. DBM without glass served as control. The results suggest that new bone induction by DBM was accelerated by the presence of bioactive glass implants. However, the bone formation induced by DBM on the glass surface was relatively small. The biocompatibility of the glass was verified by the absence of adverse cellular reactions in the interface region between glass and bone. The method used provides a simple and fast means of exploring the characteristics of potential bone substitutes.

Animals↗

PubMed1994

[Dosimetric studies using glass fibers].

PURPOSE: Ionizing radiation may cause discolouring of glasses by creation of colour centers. So radiation induced optical loss is a measure of absorbed dose. With a doped glass fiber a small volume optical dosimeter is developed for clinical purposes providing real time dosimetry with high spatial resolution. MATERIALS AND METHODS: Discolouring of glass by ionizing radiation is dose dependent and can be measured as light attenuation at a fixed wavelength. Light power of usual light emitting diodes (LED) is sufficient for this purpose. The readout light is conducted through a transmission fiber of arbitrary length. Concurrent measurements were performed at several wavelengths (660 to 850 nm) using a time multiplexing technique. We investigated the radiation induced light attenuation of a lead doped silica fiber with 60 Wt-% PbO2, diameter < 0.5 mm, and length < 0.1 m. The fiber was exposed to high energy photons of cesium-137, cobalt-60, 12-MV-photons, and 18-MV-photons generated by a linear accelerator, respectively. The influence of various temperatures, doses, and dose rates was tested. When sensor fiber is termed by a mirror reflected light can be detected with one transmission fiber and optical pathway is doubled. RESULTS: In a wide dose range (0 to 112 Gy) radiation induced loss represents absorbed dose in a linear manner without saturation effects. Optical loss is diminished by partial recovery of radiation damage depending on time and temperature. In order to compensate fading a phenomenological model was fitted to experimental data. Temperature dependence may be corrected by measurements with several readout wavelengths. Above 1 MeV there is merely a slight dependence on photon energy. At a size of the glass fiber reflection sensor of L = 2 cm doses of 0.04 Gy may be detected. The reproducibility at 1 Gy is about 4%. CONCLUSION: Lead doped silica fiber is suitable for radiation dosimetry in a dose range interesting for clinical practice. Fading may be compensated during irradiation using a phenomenological model. The size of a reflection sensor is comparable to thermoluminescence dosimeters. In contrast to TLD glass fiber provides real time dose measurements. By this means optical glass fiber dosimeter may be appropriate for in-vivo dosimetry in radiation therapy.

Glass↗

PubMedDate not supplied

The effect of pulpal fluid flow on tensile bond strength of a glass-ionomer cement: an in vivo and in vitro comparison.

Previous studies of the bonding capabilities of glass-ionomer cements have concentrated on the use of in vitro testing conditions. Since early moisture contamination appears to have adverse effects on the physical properties of glass-ionomer cements, and with the probability of pulpally derived dentinal fluid being present under in vivo conditions, the objective of this study was to compare in vivo tensile bond strength with in vitro tensile bond strength of a glass-ionomer cement to dentin utilizing the same teeth under similar test conditions. A glass-ionomer lining cement was placed on freshly exposed labial dentin of the maxillary incisor on 10 Rhesus monkeys. Immediately following placement, an orthodontic button was placed over the cement and left undisturbed for 1 hour. The teeth were then extracted and stored in 100% relative humidity for 23 hours. An Instron testing machine was used to register in kilograms the force required to cause tensile bond failure of the cement. Identical methodology was then used on the same teeth for in vitro testing. The concluding results indicate that a statistically significant difference (P < or = 0.05) exists between in vivo and in vitro tensile bond strengths of the glass-ionomer lining cement and that the bond failure was cohesive in character for all cases both in vivo and in vitro. These findings suggest that clinically, tensile bond strengths of glass-ionomer cements to cut dentin can be expected to be weaker in vital teeth than in devital teeth.

Animals↗

PubMedDate not supplied

Impact strength of a modified continuous glass fiber--poly(methyl methacrylate).

The effect of fiber reinforcement of autopolymerizing poly(methyl methacrylate) was investigated. The impact strength of continuous E-glass fiber-poly(methyl methacrylate) composite was determined. Rectangular test specimens (n = 10 per group) were modified by incorporating an additional fiber reinforcement of untreated E-glass fibers, silanized E-glass fibers, or aramid fibers in the test specimens. Controls were either unreinforced or reinforced from the middle of the test specimen only. The impact strength of the specimens was measured by using a charpy-type pendulum impact tester after the specimens had been stored in water at 37 degrees C for 4 weeks. After the impact strength test, the length of the delamination of poly(methyl methacrylate) from the fibers was measured and plotted to the impact strength of the test specimens by using a linear regression model. The impact strength of unreinforced autopolymerizing poly(methyl methacrylate) was 7.8 kl/m2, while incorporation of glass fiber reinforcement with a fiber concentration of 12.4 wt% increased the impact strength to 74.7 kl/m2 (P = .000). The additional fiber reinforcement of the test specimen did not affect the impact strength (P = .363). Delamination negatively correlated with the impact strength of the test specimens (r = -.72, P = .000). The results of this study suggest that glass fiber reinforcement enhanced the impact strength of autopolymerizing poly(methyl methacrylate), while the use of additional fiber reinforcement made of aramid or glass fibers in the test specimens did not have an effect on the impact strength.

Analysis of Variance↗

PubMed1997

Bond strength between resin composite and etched and non-etched glass ionomer.

The authors evaluated, in vitro, the effects of etching glass ionomer cements prior to the application of a bonding agent and a resin composite on the bond strength of the glass ionomer/resin composite interface. Six glass ionomer cements were tested using the same bonding agent/resin composite system (Scotchbond Multipurpose/Z 100). For each material, 16 specimens were prepared and divided into two groups. Eight of the specimens were not etched while eight were etched with 37% phosphoric acid for 15 seconds. All the materials were used according to the manufacturers' instructions. Glass ionomer cylinders were prepared and were mounted in an assembly apparatus and the bonding agent/resin composite transferred to a demarcated area on the cement surface. The specimens were stored for 24 hours in distilled water at 37 degrees C and thermocycled. After thermocycling, the specimens were placed in a testing machine and a shear load applied with a knife-edged rod at the glass ionomer/resin composite interface. The shear bond strength was calculated and expressed in MPa. Data were analyzed by ANOVA and the Tukey-Kramer test. There were no significant differences among the shear bond strengths of the resin composite to etched and non-etched glass ionomer cements.

Acid Etching, Dental↗

PubMed1998

[Failure conditions of glass filament yarns: a contribution to the valuation of carcinogenic potentials of fiber fragments].

Failure of glass filament yarns results in the formation of many fragments. Through inhalation, these particles can intrude into the human body. If the fragments are sufficiently bioresistant and have a fiber dust geometry, according to the MAK-values (6), i.e. if they are longer than 5 microns and thinner than 3 microns and show an aspect ratio greater than 3, they have a carcinogenic potential. Since the glass filaments show a diameter greater than 3 microns, no fiber dust particles will be formed if transversal fiber failure occurs without crack-branching. In the present study the geometric distribution of fragments after failure of glass filament yarns under combined stress was investigated in order to estimate the carcinogenic potential of the fragments. The knot tension test was shown to be a suitable method for this investigation. A defined fraction of the total amount of fragments were analysed with scanning electron microscopy (SEM) by measuring their length and diameter. To investigate whether the analysed particles are fragments of the glass filament yarns, chemical analysis was performed with energy dispersive X-ray analysis (EDX). Morphologically, two different fragment types were observed: a) Fragments with their entire filament cross-section which were formed by transversal fiber fraction. b) Smaller fragments which were formed through crack-branching. These smaller fragments were observed to adhere on the bigger fragments due to high surface forces. During each knot tension test, 5-60 fragments per filament were formed. However, the fraction of fiber dust particles was very low and showed a maximum of 1.5%. Only in one of the four tested yarn types (high temperature yarn HT 75) the formation of fiber dust particles was observed. The other yarns showed fragments with dimensions close to fiber dust geometry. Therefore, it cannot be excluded that some fragments with fiber dust geometry may have been formed during mechanical testing. Fragment distribution of the studied E-glass yarns was shown to be dependent on the modification method. To date, it cannot be excluded that there are types of glass filament yarns forming a major quantity of fiber dust particles during failure. The fragments of type b such as fiber dust particles were observed to adhere on bigger fragments which are themselves too big to reach the alveoli. In the present study the stability of these agglomerates under various environmental conditions was not investigated. Moreover, fragment agglomerates should not be considered on their own but in connection with the application. The presented tests were carried out with simple yarns and, therefore, represent isolated observations.

Air Pollutants↗

PubMed2000

A comparison of the microstructure and properties of the IPS Empress 2 and the IPS Empress glass-ceramics.

The aim of this report is to analyze the microstructures of glass-ceramics of the IPS Empress 2 and IPS Empress systems by scanning electron microscopy. The main properties of the glass-ceramics were determined and compared to each other. The flexural strength of the pressed glass-ceramic (core material) was improved by a factor of more than three for IPS Empress 2 (lithium disilicate glass-ceramic) in comparison with IPS Empress (leucite glass-ceramic). For the fracture toughness, the K(IC) value was measured as 3.3 +/- 0.3 MPa. m(0.5) for IPS Empress 2 and 1.3 +/- 0.1 MPa. m(0.5) for IPS Empress. Abrasion behavior, chemical durability, and optical properties such as translucency of all glass-ceramics fulfill the dental standards. The authors concluded that IPS Empress 2 can be used to fabricate 3-unit bridges up to the second premolar.

Ceramics↗

PubMed2001

Long-term in vivo bioactivity and degradability of bulk sol-gel bioactive glasses.

Melt-derived bioactive glasses have been used with success in various clinical applications for over 10 years. Recently, particles of sol-gel-derived bioactive glasses with an initial high specific surface area have been shown to exhibit excellent osteoconductive properties as well as significant degradability. In this work, we explored the long-term in vivo bioactivity and degradability of bulk sol-gel-derived glasses in a rabbit model. Two sol-gel compositions (58S and 77S Bioglass) were used. Bulk 45S5 Bioglass was used as a control. Both sol-gel-derived glasses demonstrated osteoconductive properties similar to 45S5 Bioglass. In addition, absorbability was observed for both sol-gel-derived glasses starting after 12 weeks of implantation. Total absorption reached 40% after 52 weeks. No degradation could be measured in the case of bulk 45S5 melt-derived Bioglass within 1 year of implantation. The degradation process was highly time dependent, as demonstrated by regression analysis. New bone formation was found to fill in areas that had been resorbed, similar to bone remodeling. This absorbability can be assumed to be at least partially related to an osteoclastic resorption as viable osteoclasts-like cells were found to be in direct contact with the glass surfaces.

Absorbable Implants↗

PubMed2002

Bioactivity of three CaO-P2O5-SiO2 sol-gel glasses.

Three gel glasses containing 25 mol % of CaO and SiO(2) + P(2)O(5) contents (in mol %): 75 + 0 (S75); 72.5 + 2.5 (S72.5P2.5); and 70 + 5 (S70P5), respectively, were obtained, characterized, and studied when soaked in a simulated body fluid (SBF). The influence of composition in both textural properties (surface area and porosity) and in vitro behavior of glasses was studied. In as prepared S72.5P2.5 and S70P5 glasses, crystalline phosphate nuclei were detected through XRD and FTIR. In addition, N(2) adsorption and Hg porosimetry measurements showed that the surface area increased, whereas the pore volume and the pore diameter decreased as P(2)O(5) in glasses increased. These variations were explained on the basis of the withdrawal of calcium from the glass silica network, due to the calcium-phosphorous bonding. In vitro studies showed that the three compositions were bioactive, because an apatite layer was formed after soaking in SBF. S75 presented the highest initial reactivity but the lowest crystallization rate of the apatite-like phase. For S72.5P2.5, and S70P5 the amorphous calcium phosphate formation was slower than for S75, but the crystallization of apatite was observed after shorter periods in SBF. Furthermore, after 7 days of soaking, the layer thickness decreased as P(2)O(5) in glasses increased.

Apatites↗