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PubMed2001

[Effect of fibrin on osseointegration of bioactive glass-ceramic materials--experimental study].

PURPOSE OF THE STUDY: The aim of the experimental study is to find out how fibrin influences the speed of osteiontegration of bioactive glass-ceramic materials BAS-O, BAS-HA, BAS-R (LASAK Prague, Czech Republic) and how it influences the response of live tissue at the implant-bone interface in the interval of 1-8 weeks. MATERIAL: Dense materials BAS-0 (glass-ceramics), BAS-HA (hydroxyapatite) and BAS-R (beta tricalcium phosphate) in the form of 0.6-1 mm granules were implanted in artificially created defects in tibia of an experimental animal with the addition of 0.1 ml of fibrin adhesive system Beriplast. Control implantation was performed with the addition of physiological solution. Materials BAS-HA and BAS-R were implanted in the same way in the ratio of 7:3, 8:2 and 9:1. Duration of exposure was 1-8 weeks. Radiographs of samples were taken by Mammograph and decalcified sections were coloured by toluidine blue and examined at 60 times and 120 times magnification. RESULTS: Surgical wounds were healed per primam. Radiographs of materials with the fibrin system showed clearly after one week defects and implants, after the third week part of the materials penetrated above the bone surface, after the fourth week there were evident signs of bone tissue formation between particles of BAS-HA, BAS-R and their mixtures. The most marked bone formation took place in the seventh and eighth weeks. With the use of glass-ceramics without fibrin the particles were after three weeks less clear, after the fourth week BAS-HA and BAS-R penetrated above the surface. A significant bone formation was obvious after the sixth and seventh weeks. There were no signs of resorption or fibrous encapsulating. Microscopic examination proved enveloping of particles of BAS-0 by fibrous tissue which was evident partially also after the eight week. With the use of fibrin the situation was analogical. In BAS-HA and BAS-R the finding in the first week was similar. With fibrin, there was after the third week a mature lamellar bone in the vicinity of granules and the fibrous interlayer disappeared. Neither positive nor negative impact of fibrin on the process of healing was found. With the application of BAS-R and fibrin system the bone tissue was after the third week more significant and trabeculae more bulky. The final result after eight weeks was the same: Ingrowth of the mixtures of the given materials proceeded in the same way. DISCUSSION: The applied glass-ceramic materials are used in the clinical practice. The speed of osteointegration depends on the quality of the bone bed, and on the tolerance of these materials by live tissue. Osteintegration can be accelerated by the use of growth factors or stem cells cultivated in the tissue culture. Fibrin which creates a network along which osteoblasts can migrate should have a similar quality. It seems that of decisive importance is the thickness of the fibrin layer around the implants. If this layer is thick glass-ceramics is enveloped more probably to fibrous tissue. In a thin layer the process is accelerated within the first three weeks. After a longer exposure the differences are not evident. Samples of BAS-HA and BAS-R, both applied separately and in a mixture, showed a marked bioactivity in the experiment. During eight weeks no signs were found of resorption which is typical of tricalcium phosphate in a longer time interval. CONCLUSION: In the experiment on an animal the fibrin adhesive system accelerated osteointegration of bioactive materials BAS-HA, BAS-R and their mixtures until the third week after the implantation. Small differences with the use of fibrin were adjusted within six weeks. Materials BAS-HA, BAS-R and their mixtures were completely osteointegrated. Glass-ceramics BAS-0 was partially enveloped by fibrous tissue, even with the use of fibrin adhesive system. During eight weeks no resorption of materials was found. The process of ingrowth can be seen on radiographs. X-ray picture of bone formation in BAS-HA, BAS-R correlates with the histological finding. The fibrin adhesive system facilitates manipulation with fine granules.

Animals↗
PubMed1998

Silicon Crystals in Water of Autoclaved Glass Bottles.

Crystals were detected in glass bottles containing autoclaved (standard cycle: 1218 C, 17 lb/in2, for 20 min) tap water. Bottles were fitted with a sipper tube and stopper. Crystals were observed twice at approximately a 6-month interval. Analysis of crystals and crystal-laden water by transmission electron microscopy and inductively coupled plasma and energy X-ray analysis revealed that the crystals were silicon. Subsequently, procedures and processes involved with preparation of water bottles were analyzed to determine the source or factors involved with silicon contamination. Analyses of silicon concentrations were performed on samples of tap water (0.88 to 1.20 ppm), tap water autoclaved in polycarbonate (0.89 to 1.20 ppm) and glass water bottles (0.84 to 11.0 ppm), glass and polycarbonate bottles after purposeful contamination of tap water with various amounts of alkaline detergent (1.10 to 1.70 ppm), and on steam condensate from the autoclave (0.23 and 0.47 ppm) to ascertain the source of silicon. Water from autoclaved glass bottles had greater concentrations of silicon, compared with unautoclaved tap water. Siliconized rubber stoppers and stainless-steel sipper tubes were excluded as sources of silicon contamination. Autoclaving glass bottles with stopper pieces did result in crystal formation, despite only modest increases in silicon concentration. Detergent contamination did not influence silicon concentrations. Analysis of the data indicated that autoclaving glass water bottles can lead to increases in silicon concentration and, under some circumstances, crystals may form.

Journal Article↗
PubMed2003

Glass-containing gunshot residue particles: a new type of highly characteristic particle?

In 0.22 caliber rimfire ammunition, the primer often contains lead or lead and barium compounds. As residues from these primers do not contain lead, barium, and antimony, they cannot be uniquely classified as gunshot residue (GSR) under ASTM designation E 1588-95. In many types of 0.22 caliber rimfire ammunition, the cartridge contains a primer sensitized with glass. In this paper we describe a previously unreported type of GSR particle consisting of glass fused with other primer components. As there appear to be few potential environmental or occupational sources of particles composed of lead and barium compounds fused to glass, particularly borosilicate glass, these particles may have high evidential value. Scanning electron microscopy with energy dispersive X-ray detection (SEM-EDX) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were evaluated for the characterization of glass-containing GSR particles. The occurrence of glass-containing GSR particles was established in the residue from various brands of 0.22 caliber ammunition, and several sub-types were identified.

Journal Article↗
PubMed2000

[Coordination and local structure of Si and Al in silicate glasses and melts: X-ray absorption spectroscopic study].

The coordination and local structure of Si and Al in silicate glasses and melts have been studied using Si and Al K-edge X-ray absorption spectroscopy for the first time. It has been verified that in SiO2-P2O5 and Na2O-SiO2-P2O5 join phosphate silicate glasses, Si atoms remains tetrahedrally coordinated with oxygen when the content of P2O5 is below 32 mol%, but partial Si atoms become octahedrally coordinated with oxygen when the content of P2O5 increases above 32 mol%, and the proportion of the octahedrally coordinated Si atoms increases with the increasing content of P2O5. It has also been demonstrated that Al remains four-fold coordinated with oxygen in ambient NaAlSi2O6-NaAlSi3O8 glasses, but in the same composition glasses quenched at 4.4 GPa and 1,575 degrees C, partial Al atoms becomes five- and six-fold coordinated with oxygen, and at the same pressure and temperature, the proportions of five- and six-fold coordinated Al atoms increases with the increasing content of NaAlSi2O6 in the glasses. Thus, the pressure-induced coordination change of Al in aluminosilicate glasses and melts has been observed for the first time by Al K-edge X-ray absorption spectroscopy.

English Abstract↗
PubMed2006

[Scintigraphic detection of osteoblast activity after implantation of BAS-0 bioactive glass-ceramic material into long bone defects].

PURPOSE OF THE STUDY: The aim of the study was to demonstrate, by three-phase bone scintigraphy, radionuclide uptake at the site of defects in long bones filled with the non-resorbable bioactive glass-ceramic material BAS-0 at a long follow-up. MATERIAL: Twenty patients, 14 men and 6 women, operated on between 1990 and 2000 for benign bone tumors or tumor-like lesions localized in the femur, tibia or humerus were comprised in the study. Their average age at the time of operation was 14 years (range, 8 to 24). The diagnoses based on histological examination included juvenile bone cysts in 11, aneurysmal bone cyst in five, non-ossifying fibroma in two, and fibrous dysplasia in two patients. The lesions were localized in the femur, humerus and tibia in 11, five and four patients, respectively. The metaphysis was affected in eight and the diaphysis in 12 patients. METHODS: Clinical, radiological and scintigraphic examinations were carried out at 2 to 12 years (7 years on average) after surgery. The clinical evaluation included subjective complaints and objective findings. Radiographs were made in standard projections and the osteo-integration of glass-ceramic material was investigated. Three-phase bone scans were made and the healthy and the affected limbs in each patient were compared by means of an index. Radionuclide uptake was considered normal when the index value was equal to 1.0, mildly increased at an index value of 1.2, moderately increased at 1.2-1.5 and markedly increased at an index value higher than 1.5. RESULTS: The clinical evaluation showed that, in the patients with glass-ceramic filling of metaphyses, six had no subjective complaints and two reported transient pain. In the patients with implants in diaphyses, subjective complaints were recorded in nine and no complaints in three patients. No inflammatory changes in soft tissues were found. No restriction in weightbearing of the limb treated was reported by any of the patients. On radiography, 18 patients were free from any disease residue or recurrence. Two patients had a residual defect. The bioactive glass-ceramic material BAS-0 was completely incorporated in all patients. On three-phase bone scans, radionuclide distribution on the flow phase and soft tissue phase was symmetrical in both limbs of all patients. For the metaphyseal location of implants, the delayed images demonstrated physiological radionuclide distribution in one patient, mildly increased distribution (index up to 1.2) in four, increased uptake (index up to 1.5) in two patients, and highly increased uptake (index above 1.5) in one patient. For the diaphyseal location of implants, the delayed scans demonstrated slightly increased radionuclide distribution in two, markedly increased in two and highly increased uptake in eight patients. DISCUSSION: The tissue during incorporation of a non-resorbable synthetic material is influenced by stress-shielding. This changes local mechanical signals, which has a negative effect on the adjacent bone tissue. Stress accumulating at the interface of a rigid implant and bone tissue may result in pain, and is detected by scintigraphy as an increased nucleotide uptake, particularly in diaphyseal grafts. CONCLUSIONS: This paper presents problems associated with implantation of the non-resorbable bioactive glass-ceramic material BAS-0 in the treatment of diaphyseal defects of long bones. The results show that, for filling of the defects described herein, non-resorbable glass-ceramic materials are not suitable.

Adolescent↗
PubMed1977

[Transmission of staphylococci from the nose to hands and eye-glasses as a nosocomial problem (author's transl)].

The isolation of Staphylococcus aureus from the pharynx, the nasal vestibule, as well as the eye-glasses and palms of both clinical personnel and of healthy subjects of the general population, resp., is reported. In either group, the findings were largely identical. About half of the subjects (46%) proved to be carriers of staphylococci, with the bacteria being mostly localized in the nasal vestibule (91%) rather than in the pharynx. The majority of those harbouring staphylococci in their nasal vesibule carried the same strains on their eye-glasses (67%) and on their hands (62%). The reason for the occurrence of pathogenic staphylococci, in most cases, in the nasal vestibule may be seen in the anatomical and physiological peculiarities of the pharynx and nasal vestibule, resp. While there is a highly efficient anti-bacterial defence system on the basis of both cellular and humoral mechanisms in the pharynx and oral cavity, the keratinizing stratified epithelium lining the nasal vestibule offers a milieu favourable for bacterial growth with regard to nutrients, temperature, and humidity, humoral and cellular defence mechanisms being virtually absent. With respect to nosocomial problems, the important conclusions to been drawn from the present data are the following: 1. surgical masks barring the penetration of bacteria should be used frequently, not only during surgical operations but also in emergency wards, infant care and premature baby wards, and in similar clinical areas requiring critical attention. 2. persons dependent on wearing eye-glasses should wear sterilized glasses when performing surgery, or subject their glasses to an efficient disinfection procedure. The latter also applies to all personnel wearing glasses in the clinical area. 3. The very frequent association between the occurrence of staphylococci in the nasal vestibule and the contamination of hands makes it imperative to observe a strict rountine of disinfection of hands in all critical areas (emergency ward, premature baby care etc.). In food hygiene, too, proper attention should be paid to the chain of staphylococcal contamination from nose to food. Therefore, to minimize the hazard in such high-risk situations as public canteens and in the manufacture of ice cream, a well-planned routine of hand disinfection should be adhered to.

Cross Infection↗
PubMed2005

Fluoride release from aged resin composites containing fluoridated glass filler.

OBJECTIVES: The aim of this study was to evaluate the fluoride release from aged resin composites containing different types of fluoridated glass filler into both deionized distilled water and lactic acid solution. METHODS: Three resin composites, UniFil S (containing fluoro-alumino-silicate glass filler), Reactmer (containing pre-reacted glass-ionomer filler) and Beautifil (containing both types of fillers) were used. A conventional glass-ionomer cement, Ketac-Fil, was used as a control. Five disk specimens of each material were prepared and aged in water for 10 weeks. After aging, specimens were immersed in deionized distilled water for a further 6 days and then in aqueous lactic acid (pH 4.0) for 2 days. This process was repeated twice more and the specimens were subsequently immersed in water for a further 12 days. Fluoride release was measured every 2 days throughout the post-aging period. RESULTS: The amount of fluoride release for aged UniFil S and Beautifil markedly increased in acid solution compared with water storage. The difference was not so great for aged Reactmer and Ketac-Fil. UniFil S and Beautifil gave significantly greater fluoride release in water following immersion in acid solution (p<0.05, two-way ANOVA and Scheffe's test), but Reactmer and Ketac-Fil showed no such increase in fluoride release after acid immersion. SIGNIFICANCE: These results suggested that the nature of the fluoridated glass filler within a resin composite and the way in which the material interacts with an acidic environment affected the amount of fluoride released.

Analysis of Variance↗
PubMed2000

Mechanical properties and microstructures of glass-ionomer cements.

OBJECTIVE: The objective of this study was to determine the flexural strength (FS), compressive strength (CS), diametral tensile strength (DTS), Knoop hardness (KHN) and wear resistance of ten commercial glass-ionomer cements (GICs). The fracture surfaces of these cements were examined using scanning electron microscopic (SEM) techniques to ascertain relationships between the mechanical properties and microstructures of these cements. METHODS: Specimens were fabricated according to the instructions from each manufacturer. The FS, CS, DTS, KHN and wear rate were measured after conditioning the specimens for 7 d in distilled water at 37 degrees C. One-way analysis of variance with the post hoc Tukey-Kramer multiple range test was used to determine which specimen groups were significantly different for each test. The fracture surface of one representative specimen of each GIC from the FS tests was examined using a scanning electron microscope. RESULTS: The resin-modified GICs (RM GICs) exhibited much higher FS and DTS, not generally higher CS, often lower Knoop hardness and generally lower wear resistance, compared to the conventional GICs (C GICs). Vitremer (3M) had the highest values of FS and DTS; Fuji II LC (GC International) and Ketac-Molar (ESPE) had the highest CS; Ketac-Fil (ESPE) had the highest KHN. Ketac-Bond (ESPE) had the lowest FS; alpha-Silver (DMG-Hamburg) had the lowest CS. Four GICs (alpha-Fil (DMG-Hamburg), alpha-Silver, Ketac-Bond and Fuji II) had the lowest values of DTS, which were not significantly different from each other; alpha-Silver and Ketac-Silver had the lowest values of KHN. The highest wear resistance was exhibited by alpha-Silver and Ketac-Fil; F2LC had the lowest wear resistance. The C GICs exhibited brittle behavior, whereas the RM GICs underwent substantial plastic deformation in compression. The more integrated the microstructure, the higher were the FS and DTS. Higher CS was correlated with smaller glass particles, and higher KHN was found where there was a combination of smaller glass particles and lower porosity. Larger glass particle sizes and a more integrated microstructure contributed to a higher wear resistance. SIGNIFICANCE: The mechanical properties of GICs were closely related to their microstructures. Factors such as the integrity of the interface between the glass particles and the polymer matrix, the particle size, and the number and size of voids have important roles in determining the mechanical properties.

Analysis of Variance↗
PubMed2001

Fluoride release from glass-ionomer cements, compomers and resin composites.

The short and long-term fluoride release of 16 products (seven conventional glass-ionomers, five light-activated glass-ionomers, two polyacid-modified resin composites and two resin composites) commercialized as fluoride-releasing materials were measured. A potential link between the material type and its level of fluoride release was researched. The fluoride release was evaluated after different time intervals. Initial fluoride release from all materials was highest during the first 24 h and decreased sharply over the first week. Some groups of materials appeared to be significantly different after, respectively, 7 and 91 days. However, it was impossible to correlate the fluoride release of the materials by their type (conventional or resin-modified glass-ionomers, polyacid-modified resin composite and resin composite) except if we compared the products from the same manufacturer. The link between fluoride release and an acid-base reaction seems to be confirmed. The glass-ionomer composition (glass particles and polyacid's type, powder/liquid ratio) should have more influence on fluoride release than material type.

Acids↗
PubMed2002

Long-term fluoride release from a glass ionomer cement, a compomer, and from experimental resin composites.

The aqueous phase of glass ionomer cements enables fluoride ions to diffuse and to be released from the material. The matrix of resin composites is much less hydrophilic, and fluoride incorporated in the material is only released in small amounts. It was the purpose of the present work to study the influence of resin matrix formulation on the fluoride release from experimental, fluoride-containing resin composites. The resin composites were based on methacrylate monomers and the adduct of maleic anhydride and HEMA (2-hydroxyethyl methacrylate). The resin composites contained 1 w% or 5 w% of AlF3*3H2O. A glass ionomer cement and a compomer were used as controls. Five disks of each material were stored in distilled water at room temperature. By means of a fluoride sensitive electrode, the fluoride release from disk-shaped specimens was determined periodically over 3 years. The glass ionomer cement released the most fluoride (1.54 +/- 4 microg/cm2 after 1 year and 248 +/- 7 microg/cm2 after 3 years). The compomer released relatively little fluoride during the 1st year (30 +/- 1 microg/cm2) but after this time the rate of fluoride release became equal to that of the glass ionomer cement, resulting in a release of 122 +/- 8 microg/cm2 after 3 years. Regarding the resin composites, the fluoride release increased with the hydrophilicity and the acid character of the polymer matrix. The release, however, was significantly lower than that from the glass ionomer cement and the compomer and ranged from 1.2 +/- 0.07 to 42 +/- 3.9 microg/cm2 at 1 year and from 2.3 +/- 0.16 to 79 +/- 6 microg/cm2 at 3 years.

Aluminum Compounds↗
PubMed2001

X-ray diffraction study of acid-degradable glasses.

The composition of the degradable glasses used in commercial dental glass-ionomer cements determines their leaching behavior and hence the properties of the cement. The objective of the present study was to assess if the composition and leaching in acetic acid solutions are reflected in the x-ray diffraction characteristics of these glasses. The position (2theta) of the maximum of the first sharp diffraction peak shifts to higher diffraction angles with increasing number and ionic radius of mono- and bivalent cations in the glass. Upon acid-leaching, these ions are preferentially leached out, so that (2theta) decreases. These results can be related to the decreasing Si-Si distance in the glass network with increasing modifier radius.

Acetates↗
PubMed1986

Glass-ionomer cements of improved flexural strength.

The effect of glass and polyacid composition on cement strength has been investigated with a view to improving the glass-ionomer cements. The flexural strength of glass-ionomer cements was found to be greatly dependent on the glass and polyelectrolyte used to prepare them. Opaque and opal glasses containing crystallites tended to yield cements with high flexural strength. Flexural strength was also found to be increased by increasing the molecular weight of the polyacid. In water-setting systems, cement strength was shown to be critically dependent on the glass/polyacid ratio.

Acrylates↗
PubMed1998

Obliteration of the frontal sinus cavity with bioactive glass.

BACKGROUND: Bioactive glass (BG) is a glass ceramic material. It has been used as surgical bone replacement material in ear and oral surgery, orthopedics, and dentistry. METHODS: Bioactive glass was used as obliteration material in a series of osteoplastic frontal sinus operations on 10 patients suffering from chronic frontal sinusitis, which other, more-conservative treatment modalities had failed to cure. RESULTS: Bioactive glass is easy to handle, and complete obliteration of all sinusal recesses and excavations is easily achieved. No adverse effects of the implant material have been seen over a mean follow-up period of 5.0 years. One patient with a local recurrent infection in the outer table of the sinus was reoperated on 5 months after primary surgery. Repeated postoperative computed tomographic scans analyzed by digital region-of-interest (ROI) selection showed no remarkable changes in the frontal sinus cavities but a slight, yearly decrease in the density of the occlusion material. Laboratory monitoring of patients and histopathologic examination of two postoperative biopsy specimens indicated that the material is well tolerated and stable. CONCLUSIONS: Bioactive glass is a promising and well-tolerated bone graft suitable for osteoplastic frontal sinus operations. Total accurate obliteration of the sinus is achieved with different sizes of granules and blocks. The results of the obliteration are maintained owing to the stability of the material.

Adult↗
PubMed1998

Preparation and properties of radioactive rhenium glass microspheres intended for in vivo radioembolization therapy.

Rhenium glass microspheres composed of metallic rhenium particles dispersed within a magnesium alumino borate glass matrix were produced by sintering ReO2 powder and glass frit at 1050 degrees C. The in vitro chemical durability of radioactive and nonradioactive microspheres was determined from chemical corrosion tests on microspheres immersed in phosphate-buffered saline (PBS) solution at 37 degrees C. The dosimetric properties of these microspheres also were calculated. The rhenium glass microspheres are chemically durable in body fluids and release < 1.2% of radioactive rhenium after being immersed in PBS solution for 32 days at 37 degrees C. Therapeutic radioactive rhenium activities can be obtained in < 10 h by neutron activation of these microspheres in a thermal neutron flux of 8 x 10(13) cm(-2)s(-1). A 50 mg injection of radioactive rhenium glass microspheres containing 3.7 GBq of 186Re and 8.5 GBq of 188Re could deliver a 100 Gy dose to a cancerous liver while limiting the total body dose from rhenium dissolution in vivo to approximately 1 mGy.

Biocompatible Materials↗
PubMed1999

Complement activation by PEO-grafted glass surfaces.

Activation of the complement system is one way in which the human body reacts to foreign materials that come in contact with blood. Poly(ethylene oxide) (PEO) has been used quite frequently to modify biomaterial surfaces to prevent protein adsorption and cell adhesion. Despite extensive use of PEO, however, PEO-induced complement activation has not been examined before. We examined the complement activation by PEO chains grafted to glass surfaces. PEO was grafted to trichlorovinylsilane-treated glass (TCVS-glass) by gamma-irradiation using PEO homopolymer, Pluronic F108 (PF108), and PEO-polybutadiene-PEO triblock copolymer (COP5000). Complement activation was assessed by measuring the plasma C3a level. Of the three polymers grafted (PEO, PF108, and COP5000), only PF108 showed significant increases in complement activation over controls. Complement C3a production on PF108-grafted glass was linearly dependent on surface concentration of grafted PF108. The C3a concentration increased from 46 ng/mL to 316 ng/mL as the surface PF108 concentration increased from 0-0.25 microg/cm(2). Kinetics of C3a generation by PF108-grafted surfaces show that 60% of the steady state C3a concentration was generated during the first hour of plasma exposure. When the same PF108-grafted glass surface was repeatedly exposed to fresh plasma, the amount of C3a generated decreased by 70% after the first exposure. This supports the "single-hit" mechanism in complement activation. PEO homopolymer did not activate complement in bulk solution, and, thus, it appears that C3a complement activation by PF108-grafted surfaces is due to the presence of poly(propylene oxide) units. Grafting of PEO using PEO-containing block copolymers requires examination of complement activating properties of the non-PEO segment.

Biocompatible Materials↗
PubMed1999

Acid-base complex reactions in resin-modified and conventional glass ionomer cements.

Resin-modified glass ionomer cements are a recent development in which the desirable properties of glass ionomer cements and resin-composites are combined. The presence of resin may, however, retard the acid-base reaction of the ionomer component. This has led to a debate regarding the classification of resin modified materials as true glass ionomer cements, and the actual duration of the acid-base reaction after initial setting via light polymerization has taken place. To investigate this issue, a novel method employing FT-IR spectrophotometry was used to monitor the acid-base complexation reaction in a resin-modified glass ionomer cement (Fuji II LC) and a conventional, chemically cured cement (Fuji II Cap). This method involved subtraction of the background "resin" spectrum from the Fuji II LC spectra and subsequent application of a baseline to obtain the plot of absorbance area ratio in the range of 1685 to 1510 cm(-1) (complexed carboxyls) to that in the range of 1750 to 1685 cm(-1) (free carboxyls). This study demonstrates evidence of a delayed acid-base reaction for the resin-modified cement, which levels off after 168 hours of cement mixing. In contrast, the complexation reaction of the conventional glass ionomer cement was essentially complete after 24 hours.

Glass↗
PubMed1999

Real-time dissolution measurement of sized and unsized calcium phosphate glass fibers.

The objective of this study was to develop an efficient "real time" measurement system able to directly measure, with microgram resolution, the dissolution rate of absorbable glass fibers, and utilize the system to evaluate the effectiveness of silane-based sizing as a means to delay the fiber dissolution process. The absorbable glass fiber used was calcium phosphate (CaP), with tetramethoxysilane selected as the sizing agent. E-glass fiber was used as a relatively nondegrading control. Both the unsized-CaP and sized-CaP degraded linearly at both the 37 degrees C and 60 degrees C test temperature levels used. No significant decrease in weight-loss rate was recorded when the CaP fiber tows were pretreated, using conventional application methods, with the tetramethoxysilane sizing for either temperature condition. The unsized-CaP and sized-CaP weight loss rates were each significantly higher at 60 than at 37 degrees C (both p < 0.02), as expected from dissolution kinetics. In terms of actual weight loss rate measured using our system for phosphate glass fiber, the unsized-CaP fiber we studied dissolved at a rate of 10.90 x 10(-09) and 41.20 x 10(-09) g/min-cm(2) at 37 degrees C and 60 degrees C, respectively. Considering performance validation of the developed system, the slope of the weight loss vs. time plot for the tested E-glass fiber was not significantly different compared to a slope equal to zero for both test temperatures.

Calcium Phosphates↗
PubMed1999

Influence of composition and surface characteristics on the in vitro bioactivity of SiO(2)-CaO-P(2)O(5)-MgO sol-gel glasses.

Glasses in the system SiO(2)-CaO-P(2)O(5)-MgO were prepared by the sol-gel method. These glasses featured SiO(2) contents in the range 60-80 mol %, 4 mol % of P(2)O(5), and a CaO/MgO molar ratio of 4. Because of their composition and surface properties, all the glasses showed in vitro bioactivity, as evidenced by the formation of an apatite-like layer on their surface when soaked in an acellular medium with ionic composition similar to human blood plasma. An increase in the CaO content of the glasses also caused an increase in their porosity. Higher porosity facilitated the apatite nucleation on the sample surface during the first days of the in vitro test. On the other hand, those glasses with higher SiO(2) content also showed higher surface area values, as well as higher calcium phosphate layer growth rates. For longer soaking periods, the grown layer was analyzed, revealing a two-phase composition: apatite and whitlockite.

Biocompatible Materials↗