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At least 19 recordsLinked to original sources

PubMed1992

Comparison of the shear bond strength of a light-cured glass ionomer and a chemically cured glass ionomer for use as an orthodontic bonding agent.

Light-cured glass ionomers with an initial set of 20 seconds may produce higher initial bond strengths, as well as decreased sensitivity to moisture contamination and desiccation, than chemically cured glass ionomers making them attractive for use as orthodontic bonding agents. The purpose of this study was to determine and compare the shear bond strength of stainless steel orthodontic attachments to enamel with a light-cured glass ionomer (Zionomer) tested at 60 minutes and 24 hours, and a rapidly setting chemically cured glass ionomer (Ketac-Bond) tested at 60 minutes and 24 hours. Fifty-two recently extracted human premolars were randomly divided into four groups--1-hour and 24-hour light-cured glass ionomer groups and 1-hour and 24-hour chemically cured glass ionomer groups. Stainless steel lingual buttons were bonded to prepared enamel surfaces, and the samples were placed in a water bath at 37 degrees C until ready for testing. The shear bond strength of each sample was determined with a universal testing instrument. Results from the study conclude: (1) The mean shear bond strength of the light-cured glass ionomer is greater than that of the chemically cured glass ionomer at 1 and 24 hours. (2) The mean shear bond strength of both glass ionomers increases from 1 to 24 hours. (3) The mean shear bond strength of the light-cured glass ionomer is not significantly different from 1 to 24 hours, but the shear bond strength of the chemically cured glass ionomer cement is different.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Etching, Dental↗

PubMed1991

Glass ceramic approach to controlling the properties of a glass-ionomer bone cement.

Glass-ionomer dental cements have potential as bone cements in joint replacement surgery. However, commercially available glasses used in dental cements suffer from the loss of fluorine during the melting procedure and from phase separation of the glass upon quenching, giving rise to inter- and intra-batch variation. A model glass was examined in which minimal loss of fluorine is observed. This results in a glass whose composition is reproducible between batches. This glass will crystallize both above and below the glass transition temperature following heat treatments. Cements can be produced whose properties vary with the degree of crystallinity of the glass-ceramic. A commercial glass was also examined and was found to crystallize to an apatite phase.

Bone Cements↗

PubMed1992

Behaviour of fetal rat osteoblasts cultured in vitro on bioactive glass and nonreactive glasses.

We examined the behaviour of fetal rat osteoblasts cultured upon bioactive glass and nonreactive glasses, and the supposed stimulatory effects of bioactive glass on osteoblasts. Nonreactive glass cultures showed flattened cells with almost no dorsal ruffles. Bioactive glass cultures showed compact cells with dorsal ruffles and filapodia resulting in the formation of a denser cell layer. For confluent nonreactive glass cultures the osteoblast expression was mainly concentrated in the clustered cells which were formed upon the monolayer, whereas for confluent bioactive glass cultures the osteoblast expression was more generally distributed. The production of type I collagen, osteocalcin and an osteoblast-specific antigen was shown by immunocytochemistry for all cultures, although differences in distribution were observed. The bioactive layer of bioactive glass is responsible for a better osteoblast-like morphology, a higher proliferation rate and generally a better osteoblast expression.

Alkaline Phosphatase↗

PubMed1992

Role of the glass phase in bioactive glass-ceramics.

Glass-ceramics, or composites with a glass-ceramic matrix prepared by controlled crystallization, almost invariably contain a residual glass phase. A suitable composition for the residual glass phase of bioactive glass-ceramics can be found approximately and controlled on the basis of calculation of a structural parameter Y, which in the simplified concept of the glass structure corresponds to the mean number of bridging oxygens per polyhedron in the glass lattice.

Biocompatible Materials↗

PubMed1989

Bone bonding behavior of MgO-CaO-SiO2-P2O5-CaF2 glass (mother glass of A.W-glass-ceramics).

In this study, it was found that a Ca-P layer and a Si layer were formed on the interface of the mother glass of apatite-wollastonite containing glass-ceramics (designated AW) and bone tissue. The dissolution of Si, Ca, and P from glass (MgO-CaO-SiO2-P2O5-CaF2) is necessary to form a chemical film (a Si layer and a Ca-P layer). The three kinds of glasses used were 1) a mirror surface of the mother glass (MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF 0.5 weight ratio) of AW (designated G-AW (mirror], 2) an abraded surface of G-AW (designated G-AW (#2000)), 3) a mirror surface SiO2 glass (designated G-Si, 100% SiO2). The glass plates (15 mm x 10 mm x 2 mm) were implanted into the metaphysis of tibia of mature male rabbits for 10 and 25 weeks. The failure load, when an implant detached from the bone or when the bone itself broke, was measured by a detaching test and the interface of glass/bone was observed by SEM-EPMA. Failure loads in G-Si, G-AW (mirror), and G-AW (#2000) 10 weeks after implantation were 0.18 +/- 0.24, 3.06 +/- 1.29, and 2.94 +/- 1.77 kg, respectively. Those in G-Si, G-AW (mirror), and G-AW (#2000) 25 weeks after implantation were 1.30 +/- 1.18, 3.88 +/- 1.06, and 3.55 +/- 1.51, respectively. The failure loads in G-Si vs. G-AW (mirror) and those in G-Si vs. G-AW (#2000) differed significantly (P less than 0.01). There were no significant differences in the failure load according to the surface roughness of G-AW. As shown by SEM-EPMA observation, a Si layer next to G was adjacent to a Ca-P layer next to the bone. The chemical film showed no increase in thickness as time passed. A Ca-P layer did not form on the interface of Si-G and bone.

Biocompatible Materials↗

PubMed1989

[Basic studies on CaO-P2O5-MgO-SiO2-CaF system glass ceramics. 2. Ultrastructural study on interface between culture cells and glass ceramics].

The aim of this study was to determine biocompatibility of glass ceramics and adhesion of cultured cells to glass ceramics. Four established cultured cell lines, human fibrosarcoma cells (HT-1080), human gingival carcinoma cells (Ca9-22), human osteosarcoma cells (NY) and mouse osteoblasts (MC3T3-E1), were used. For phase-contrast and electron microscopic observation they were cultured on substrates of glass ceramics or polystyrene coverslips as a control. The results obtained were as follows. Glass ceramics caused neither cellular degeneration nor death, as revealed by phase-contrast microscopy. By transmission electron microscopy an amorphous structure similar to the basal lamina was observed at the interface between the substrates and Ca9-22, and between glass ceramics and NY. A similar structure sometimes existed between the substrates and MC3T3-E1. On the other hand HT-1080 showed no such structure. The findings suggest that the biocompatibility of glass ceramics was satisfactory. Furthermore, from the clinical point of view it seems to be possible to close the material-tissue interface with epithelial, fibrocytic and osteocytic cells.

Animals↗

PubMed1991

A glass wool-based method for purifying Trypanosoma cruzi trypomastigotes and identification of an epimastigote-specific glass-adherent surface peptide.

Glass wool, hydrophilic cotton wool, non-electrically charged BIO-GEL P2 and common tissue paper columns were used to purify trypomastigotes from a mixed Trypanosoma cruzi population grown in axenic culture medium. With all these columns, highly purified (up to 98%) trypomastigote preparations were obtained. Trypomastigote yields from cotton wool, BIO-GEL P2 and common tissue paper columns were not as high as from glass wool columns, from which yields varied from 69 to 80%. Purification on glass wool did not affect trypomastigote infectivity or virulence. Dead trypomastigotes could not be purified on glass wool columns. A glass-adherent amphiphilic peptide of 45 kDa, present in the cell membrane, was isolated from epimastigote but not from trypomastigote preparations.

Animals↗

PubMed1988

Histological and histomorphometrical analysis of bioactive glass and fibre reinforced bioactive glass dental root implants.

Bioactive glass has the ability to bond with bone, but it cannot be used as a load bearing device due to its limited mechanical properties. By reinforcing bioactive glass with a ductile second phase, a structurally reliable material is obtained. The aim of the present study was to evaluate histologically and morphometrically the interfacial behaviour of submerged composite dental root implants. Therefore, bulk and composite implants were subgingivally installed in the partially edentulous jaws of Beagle dogs and harvested after 4 and 16 months. Histologically, the connection between the implants and bone tissue could be clearly demonstrated. This bone connection is mainly located at the cortical bone level. In the vicinity of the infraalveolar nerve a fibrous tissue contact was found. It is shown that surgical trauma, motion at the glass to tissue interface, and gross ion dissolution from the material adversely affect the interfacial osteogenesis. If these factors are controlled, bone bonding is found over a larger area than the initial area of contact between the implant and bone tissue. This means that bone grows out along the implant surface, starting from the initial contact area. No difference was observed between the interfacial behaviour of bulk bioactive glass and intact fibre reinforced bioactive glass implants.

Animals↗

PubMed1992

A study of fracture and inelastic behavior of bioactive glass-ceramics and glasses.

The fracture and inelastic behavior of A-W glass-ceramics, phosphate glasses, silicate glasses, and borate glasses were determined in simulated body fluid (SBF), kerosene, and water. By using the stable crack growth technique, an inelastic behavior was observed on the diagram of load versus load-point displacement. From these studies, it was suggested that the inelastic behavior of bioactive glass-ceramics was produced by the plastic deformation of glassy phase on the grain boundary.

Apatites↗

PubMed1985

The interface of various glasses and glass ceramics with a bony implantation bed.

Basing on histomorphological evaluations and morphometrical quantifications in a standardized model experiment, a comparison is made between the reactions of skeletal tissues to various glasses, glass-ceramics and enamels. On the surface of these so-called reactive biomaterials either a direct bonding to mineralized bone or also different amounts of osteoid or chondroid tissue formation can be observed, depending on the composition of the material. It is shown that the solubility of the glasses cannot directly be related to the reactivity and the resulting bone bonding; bone binds only to glasses with a controlled release of constituents and which exhibit a seam of extracellular matrix on their surface, in which normal primary mineralization can occur; the release of constituents such as Al2O3, Ta2O5, ZrO2, or phosphates from the material can inhibit this normal mineralization and the transformation of chondroid tissue to bone; if connective tissue instead of bone is present at the interface (either primarily or after bone remodelling), the dissolution (or corrosion) of the material may be no longer controllable, and the tissue reacts with a continuous inflammatory response to the corrosion products.

Animals↗

PubMed1990

[Glass ionomer cements as orthodontic bracket adhesives. An in vitro study with 4 glass ionomer cements (GIC) and 2 conventional orthodontic bracket adhesives as the comparative group].

240 orthodontic brackets were bonded to buccal surfaces of bovine teeth. As bonding material we used four glass ionomer cements without etching and two normal orthodontic bracket bonding materials with etching of enamel. Brackets of group 1 were tested with a material testing machine for shear and tensile strength after ten minutes. Brackets of group 2, 3 and 4 were tested after one day, 28 days and 98 days, respectively. In the average the bonding strength of glass ionomer cements was 50% less than the bonding strength of the comparison group with etching. The fracture of the bonding took place to 80% between the mesh base and the glass ionomer cements. Defects of the enamel surface were never observed. The bonding between mesh-base and glass ionomer cements has to be improved before the use of this bonding material can be recommended for the use in a busy practice.

Animals↗

PubMed1992

Glass fibre versus non-glass fibre splinting bandages.

We have assessed the current range of synthetic splinting bandages, comparing glass with non-glass fabrics and plaster-of-Paris. Physical and mechanical tests have been carried out and the opinions of patients, volunteers and orthopaedic staff were recorded. Modern bandages have some better properties than standard plaster bandage but do not conform as well, are more expensive and potentially more hazardous. However, non-glass bandages are lighter, less brittle, more radiolucent and less hazardous than glass fibre bandages and are preferred by both patients and applicators.

Attitude to Health↗

PubMed1991

The biocompatibility of glass-poly(alkenoate) (Glass-Ionomer) cements: a review.

The literature describing the biocompatibility of glass-poly(alkenoate) ('Glass-Ionomer') cements has been reviewed. This literature shows that these materials have generally good biocompatibility for both dental and orthopaedic use, this latter observation being very recent. There have, though, been a few reports showing that in certain circumstances these materials may cause pulpal irritation and the reasons for these particular findings are considered. Following discussion of the biocompatibility of Glass-Ionomer cements, consideration is given to the likely underlying causes of this feature. Three factors are identified as contributing to the biocompatibility of these cements. They are: (i) minimal exotherm on setting; (ii) rapid neutralization following mixing; and (iii) slow release of ions which are generally biologically beneficial or, at least, benign. This last point is considered in some detail. Previous studies of leaching of ions from Glass-Ionomer cements have shown that only inorganic species are released. The biological effects of each of these inorganic ions are described and their influence on biocompatibility discussed.

Aluminum↗

PubMed1989

Evaluation of the ability of glass-ionomer cement to bond to glass-ionomer cement.

This study investigated the cohesive bond strengths of glass-ionomer cement at three setting and etching intervals and compared these bonds to the shear strength of the material itself. Bonded cylinders were created and then sheared using the Instron Universal Testing Machine. Analysis of bond values of glass ionomer added to glass ionomer indicate bond variability and low cohesive bond strength of the material. Bond values of unbonded glass-ionomer material indicate that the material itself is stronger than bonds established between bonded samples.

Dental Bonding↗

PubMed1991

From contacts and bondings between bone and bioactive glass to bonding of bioactive glass and porcelain to metal alloys, different methods of fracture repair.

Bioactive glass has the ability to bond to bone. In this article the contact between glass and bone is discussed and the development of core alloy for an implant coated with bioactive glass and the oxidation of metal surface in ceramic fusion has been studied. Good bonding of coating materials to core alloys is necessary in dental implants. Using a pull test method we studied the bond strengths between various alloys and some composite materials clinically used to repair fractures of porcelain-veneered dental crowns. An experimental bioglass material was also studied. The bonding of composite materials to metal surfaces etched with hydrofluoric acid was almost as good as the bonding between metal and porcelain, or glass.

Adhesives↗

PubMed1992

Microleakage of glass ionomer/composite resin restorations: a laboratory study. 1. The influence of glass ionomer cement.

Acid-etching of enamel margins, often combined with bevelling and use of a low viscosity resin, has resulted in improved sealing of composite restorations. When enamel is absent and margins involve dentine or cementum, microleakage is more often observed. The use of glass ionomer cement, as both a restorative material and as a base combined with a veneer of composite resin, has been advocated as a means of minimizing microleakage where margins are placed in dentine or cementum. Four restorative techniques incorporating glass ionomer cement were used, in vitro, to restore cervical cavities. After thermal cycling, dye penetration was scored along occlusal and gingival margins. In all instances the gingival margin exhibited a less reliable seal than the occlusal margin. The sandwich restorations produced a superior seal at both occlusal and gingival margins when compared with glass ionomer restorative cement.

Acid Etching, Dental↗

PubMed1977

Modifications of glass microelectrodes: a self-filling and a semifloating glass microelectrode.

A simple and inexpensive method for constructing a double capillary was developed for preparing a self-filling glass microelectrode. The modified method uses a thin capillary instead of a bundle of glass fibers and fuses it to the outer capillary wall with flame before pulling the latter with a puller. The validity of the new electrode was proven by measuring the proximal cell PD of the rat kidney slices (mean of the stable cell PDs lasting longer than 30 min,--69 mV). A semifloating electrode was modified from the original floating electrode to be applicable to the in vivo kidney preparation whose pulsatile and respiratory movements had hindered yielding a stable cell PD. This electrode is constructed simply by replacing the shaft of the Ling-Gerard glass microelectrode with a length of flexible silcone-rubber tubing. The cell PD recorded by this electrode is found to be more stable and can withstand minor tissue distortion in mammalian kidney cells in vivo and also in such a contractile tissue as the secretory coil of the eccrine sweat gland.

Animals↗

PubMedDate not supplied

[Biomechanic and histomorphometric studies of HIP titanium glass ceramic, a new implant material, compared with glass ceramics, titanium and titanium alloy].

Interfacial tensile strength and quantitative histomorphological properties of alloplastic implant materials for hard tissue application were studied in animal models. Physico-chemical bonding in the order of 1 N/mm2 of bone to glass-ceramic (Ceravital) was demonstrated independent of magnitude of surface roughness with mineralized bone in excess of 80% at the implant interface. No bone-bonding, but contact of mineralized bone at the metal surface was observed in pure titanium and titanium alloys (Ti6Al4V, Ti5Al2, 5Fe) with smooth surfaces. Rough or porous surfaced specimens, however, exhibited mechanical interlocking and interdigitation, thus yielding interfacial tensile strength of up to 4 N/mm2 in geometrically porous or madreporic surfaces. The new composite material HIP-Titanium-glass-ceramic (Ceravital) displayed physico-chemical bonding to bone as well as mechanical interdigitation within the secondary porous structure, thus giving support to expectations that HIP-Titanium-glass-ceramic coated implants should perform superior than bulk materials.

Animals↗