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PubMedDate not supplied

Preload loss in gold prosthesis-retaining screws as a function of time.

PURPOSE: Screwed joints are widely used in implant dentistry, and their failure is a significant problem that may be related to loss of preload. Preload is the compressive force generated across a joint when a screw is tightened and is responsible for keeping a joint closed. For a given torque, preload is limited by the frictional resistance of the contacting screw threads, flange, and opposing joint surfaces. This study tested the hypothesis that following correct placement, prosthetic gold screws lose preload over time. MATERIALS AND METHODS: The study used standard Nobel Biocare components. Strain gauges mounted on a standard abutment formed a transducer to measure preload. Five sets of new prosthetic gold screws, gold cylinders, and standard abutment screws were assembled in turn on the top of an implant body, using the transducer abutment. The gold screws were tightened with a Nobel Biocare Torque Controller set to 10 Ncm, when it had an output of 12.06 +/- 0.8 Ncm with 95% repeatability. Preload was monitored for 15 hours; then the screws were removed and examined under a scanning electron microscope. RESULTS: Preload ranged from 157.5 to 488.9 N (mean 319.6 N), with a mean reduction over 15 hours of 24.9%, with 40.2% of this occurring within 10 seconds of tightening. DISCUSSION: Torsional relaxation of the screw shaft, embedment relaxation, and localized plastic deformation of the gold alloy and opposing titanium threads were the most likely explanation for this phenomenon. CONCLUSIONS: New prosthetic gold screws suffer significant loss of preload following placement.

Compressive Strength↗
PubMedDate not supplied

A retrospective observational study of the effect of surface treatments and cementing media on the durability of gold palatal veneers.

This paper reports on the results of a retrospective observational study that sought to determine both the longevity and effects of surface treatments of gold palatal veneers used to restore tooth surface loss. Details of all gold palatal veneers fabricated from Mattident 60 were sourced from hospital records spanning 11 years and 9 months. The case notes of each individual were accessed and, for each restoration, a note was made of the date and method of cementation, together with the period of patient follow-up. When patients continued their routine checkups, the records were scrutinized closely for evidence of restoration failure. This yielded a data set of 151 palatal gold veneer cementations for which the surface treatments and/or cementing media were known. Survival analysis by the Kaplan-Meier method of alumina blasted veneers revealed median survival times of 4,663 days when cemented with Panavia 21 and 687 days if cemented with Aquacem. Veneers that were alumina blasted, oxidized and cemented with Panavia 21 had a survival probability of 1.0. A Logrank test revealed highly statistically significant differences between the survival curves (p<0.0001). It was concluded that: (1) Alumina blasting the fit surface of a gold veneer prior to cementation with Panavia 21 resulted in a significantly more durable restoration compared to alumina blasting and cementation with Aquacem and no etching of tooth substance. (2) Due to low MST cementing, gold palatal veneers with a conventional glass polyalkenoate cement are not recommended. (3) Pre-treatment of gold palatal veneers by alumina blasting and oxidation prior to cementing with Panavia 21 appears to improve the chances of obtaining a dependable restoration. A greater number of restorations would be required to statistically test this trend.

Acid Etching, Dental↗
PubMed1991

[A case of oral gold tablet-induced interstitial pneumonitis].

A 76-year-old woman was admitted with exertional dyspnea and chest roentgenographical abnormal shadows appearing after oral gold therapy (total 720 mg) for rheumatoid arthritis. Based on the patient's clinical course, chest roentgenograms, chest CT and pathological findings of TBLB specimens, gold pneumonitis was diagnosed. Steroid therapy improved symptoms and pulmonary function and cotton-like shadows on chest roentgenograms and chest CT scanning. However, linear and large ringed shadows on chest roentgenograms and chest CT scan remained, even after steroid therapy. This case is the first case of oral gold tablet-induced pneumonitis. Although the mechanism of oral gold tablet-induced pneumonitis is considered to be almost the same that of gold injection therapy-induced pneumonitis, this case suggested that fibrotic changes in oral gold tablet-induced pneumonitis may be delayed over a long period.

Administration, Oral↗
PubMed1991

Separation of periportal and perivenous rat hepatocytes by fluorescence-activated cell sorting: confirmation with colloidal gold as an exogenous marker.

Periportal and perivenous hepatocytes are known to display various functional differences. In this study we present a new method to separate periportal and perivenous cells: after selectively loading zone 1 or zone 3 with the fluorescent label acridine orange in an antegrade or retrograde perfusion, respectively, we separated the isolated hepatocytes on a fluorescence-activated cell sorter. The common way to check on proper separation is to estimate activities of enzymes known to exhibit a heterogeneous acinar distribution. Using enzyme histochemistry, however, we found that already on short collagenase perfusion, some enzymes displayed a more shallow gradient than in vivo, making enzyme activities less suitable as zonal markers. We therefore used colloidal gold granules (17 nm) injected intravenously (2.5 mg) into the rat 2 to 3 hr before cell isolation. The gold is taken up predominantly by perivenous hepatocytes, probably because of the efficient removal of gold granules in zone 1 by competing Kupffer cells. We compared acridine orange fluorescence, presence of gold particles and activities of six marker enzymes, three biochemically and three histochemically determined. Acridine orange and gold both pointed to a high enrichment of the fractions, whereas most enzyme activities were more randomly distributed among the cells as a result of the isolation procedure. Our separation procedure yielded fractions highly enriched in either viable periportal or perivenous cells, both from one liver. The use of colloidal gold as a marker to monitor separation is a valuable alternative to the more risky estimation of enzyme activities.

Acridine Orange↗
PubMed1991

Intramuscular gold therapy is associated with long survival in patients with rheumatoid arthritis.

To investigate whether the premature death of patients with rheumatoid arthritis (RA) was associated with intramuscular (im) gold treatment or side effects due to gold, a sample of 573 adult patients with RA treated at hospital for the first time during 1961-66 was retrospectively studied for the duration and side effects of im gold treatment as well as death and causes of death. By 1989 a total of 251 patients had died. Gold treatment was not associated with premature death. On the contrary, longterm gold treatment was associated with a high survival rate. Secondary amyloidosis was diagnosed in 28 out of 63 patients, who had gold associated renal disease and who died.

Adult↗
PubMed1989

Effects of gold coordination complexes on neutrophil function are mediated via inhibition of protein kinase C.

Previous studies have shown that the gold compounds auranofin (AUR) and gold sodium thiomalate (GST) inhibit responses of various cells and tissues. We found that superoxide anion generation induced in human neutrophils by the chemotactic tripeptide fmet-leu-phe (1 microM), fluoride (18 mM), or phorbol myristate acetate (PMA, 100 nM) was inhibited by pretreatment of cells with 5-100 microM AUR. The extent of inhibition was dependent on AUR concentration and duration of the preincubation. GST was much less potent, inasmuch as only weak effects were observed at 5 times higher concentrations. The ineffectiveness of GST was attributed to its slower rate of penetration into cells, compared with AUR. The finding that mobilization of internal Ca2+ stores was not blocked in AUR-treated cells suggests that phospholipase C-mediated hydrolysis of polyphosphoinositides to inositol 1,4,5-trisphosphate was not inhibited by the drug. Because PMA is known to mimic the action of diacylglycerol in activating protein kinase C (PKC), we investigated the possibility that gold compounds might be interfering with signal transduction at this level. Enzymatic assays indicated that both gold compounds reduced the level of PKC activity associated with the cytosol; however, translocation of PKC to the plasma membrane was not found. Immunoblot analyses carried out with polyclonal anti-PKC antisera revealed that the gold compounds did not cause degradation of PKC or increase translocation to the membrane. Further studies indicated that enhanced endogenous protein phosphorylation resulting from PMA stimulation was attenuated in cells co-treated with AUR. Finally, in vitro enzymatic assays showed that both AUR and GST inhibited partially purified PKC in a concentration-dependent manner. It is suggested that modulation of PKC represents a mechanism of action of gold coordination complexes at the cellular level.

Auranofin↗
PubMed1989

Observations of colloidal gold labelled platelet microtubules: high voltage electron microscopy and low voltage-high resolution scanning electron microscopy.

18 nm colloidal gold-antitubulin and 4 nm colloidal gold-antitubulin were used to label microtubules in adherent, fully spread platelets. Both sizes of marker effectively labelled microtubules in the partially extracted platelets. However only the 4 nm gold penetrated the dense microfilament matrix of the inner filamentous zone so that portions of microtubules within this cytoskeletal zone could be tracked. The gold marker could be visualized well with 1 MeV high voltage transmission EM and with 5 kV or greater secondary imaging or 20 kV backscattered imaging of carbon only coated samples. 1 kV secondary imaging permitted high resolution imaging of the surface of tubules and the microfilaments with their respective associated material. Individual gold-antibody complexes were difficult to identify by shape alone due to the tendency of the antibody coats to blend together when in very close approximation and due to the presence of other molecules or molecular aggregates similar in size to the gold-antibody labels. Microtubules were seen to wind in and out of the inner and outer filamentous zones as they encircled the granulomere. Some tubules were seen to "dead end" at the peripheral web. Numerous smaller microtubule loops were present principally in the outer filamentous zone and tubules could be followed as they went from the outer filamentous zone through the inner filamentous zone and into the granulomere.

Blood Platelets↗
PubMed1989

A colloidal gold labeling technique for the direct determination of the surface area of eukaryotic cells.

We have developed a colloidal gold labeling technique for the direct quantitation of the cell surface area. The method is based on coating the cell surface with [195Au] colloidal gold-protein complexes followed by morphometric determination of the labeling density (gold particles/micron2 cell surface) and radiometric determination of the total number of gold particles bound per cell. The ratio of both values directly gives the cell surface area. The accuracy of the method was shown using Staphylococcus aureus cells as a model system, where the cell surface area determined with our assay (4.0 microns2) corresponded well to the value calculated from the radius of the cells (3.6 microns2). In a more complex model system J-774 mouse macrophages were labeled with different amounts of [195Au] gold-protein complexes to show that the assay is independent of the degree of saturation of the cell surface binding sites. Both high (135 Au/microns2) and low (65 Au/microns2) labeling densities resulted in a surface area of about 1200 microns2. The technique finally was applied to L-929 fibroblasts to determine the increase of the cell surface area when the cells change from a spherical to a flat monolayer state. We found that the cell surface area increased 3-fold during the spreading process. The results show that the colloidal gold labeling technique allows the direct determination of the surface area of complex eukaryotic cells. The technique is suitable for the quantitation of changes in the surface architecture known to occur in different functional states of eukaryotic cells.

Animals↗
PubMed1988

A novel approach to the ultrastructural localization of cell surface receptors: affinity-gold labeling of Na, K-ATPase.

We describe here a novel method of affinity-gold labeling for the ultrastructural localization and biochemical characterization of functional cell surface receptors. This approach combines the widely used colloidal gold technique, a previously published method for coating the gold with a matrix of derivatized dextran, small receptor-specific ligands, and a photoactivatable cross-linker. The resulting gold-affinity probe directed to a selected receptor by the ligand, is subsequently attached to the receptor by light activation of the cross-linker. As a specific example, a gold affinity probe prepared with ouabain, a selective inhibitor of Na,K-ATPase, as the directing ligand was used to investigate the ultrastructural localization of this enzyme complex in cell membranes. The biological activity of ouabain covalently linked to derivatized dextran containing the photoactivatable cross-linker was examined by its action on ion transport across dog trachea epithelium and on the enzyme activity of Na,K-ATPase preparations obtained from the rectal gland of the elasmobranch, Mustelus californicus. By these tests the probe mimics the effects of free ouabain. Electron micrographs of labeled human erythrocytes and cultured human foreskin fibroblasts showed an apparent random distribution of Na,K-ATPase on the plasma membranes of these cells. Binding of the probe was blocked in the presence of excess ouabain, a result demonstrating that the affinity probe binds at the same sites as free ouabain. Covalent attachment of probe by light activation of the nitroarylazido groups greatly enhanced retention during washing and standard procedures of fixation and dehydration. The high density of the gold probe was utilized to isolate the covalently attached membrane components from labeled human foreskin fibroblasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Affinity Labels↗
PubMed1985

Demonstration of receptor binding of two apo-B containing lipoproteins by differential labelling with colloidal gold.

The interaction of two types of apo-B containing lipoproteins, human low density lipoprotein (LDL) and lipoprotein-a (Lp(a], with cultured human skin fibroblasts was studied by differential colloidal gold labelling in conjunction with thin sectioning and surface replication techniques. After separate exposure of the fibroblasts to either gold labelled LDL or Lp(a) for 15 to 30 min at 37 degrees C, labelled lipoproteins were predominantly found in coated pit areas. Excess of unlabelled LDL or Lp(a) completely displaced the gold labelled lipoproteins, indicating specific binding by the LDL-receptor. Simultaneous exposure of fibroblasts to LDL-16 nm gold and Lp(a)-40 nm gold conjugates revealed that both LDL and Lp(a) are bound in the same coated pit and internalized into the same endosome. In contrast to native lipoproteins, gold labelled acetylated lipoproteins were found diffusely distributed on membrane surface areas predominantly representing fibronectin-containing fibrils.

Apolipoproteins B↗
PubMed1987

Effects of weekly and daily pretreatment with gold sodium thiomalate on adjuvant induced arthritis.

The effect of gold sodium thiomalate on adjuvant induced arthritis in DA rats was investigated. Ten mg/kg gold given in either weekly or daily injections before the administration of adjuvant was able to decrease the severity of arthritis in these animals. One mg/kg gold given as daily injections had no effect on adjuvant induced arthritis. One mg/kg gold given as weekly injections before adjuvant administration reduced the severity of arthritis to a level which was intermediate between that seen in the placebo control and the 10 mg/kg gold groups. The proliferative responses of spleen cells to mitogens in these animals were not altered by in vivo gold therapy.

Animals↗
PubMed1987

Gold pharmacokinetics in breast milk and serum of a lactating woman.

During 20 weeks of aurothioglucose therapy, gold in a mother's serum and breast milk and her nursing infant's serum and urine were measured. The mother's steady state plasma gold was 4.05 mg/l; it was 0.041 mg/l in breast milk. Only 0.0255 mg gold appeared in the breast milk/24 h. We calculated that only 0.1785 mg gold (0.71% of the weekly dose) would appear in the breast milk over a week. No gold (less than 5 X 10(-7) mg/l) was found in the infant's plasma or urine. It is very unlikely that more than minute amounts of gold are absorbed from the mother's breast milk when breast feeding an infant.

Adult↗
PubMed1988

Comparison of etretinate (Tigason) and parenteral gold in the treatment of psoriatic arthropathy.

Etretinate is a synthetic vitamin A derivate given orally for the treatment of severe skin psoriasis. This drug has been reported to be effective also in psoriatic arthropathy and in this study we compared the efficacy and side-effects of etretinate with those of parenteral gold. Sixteen out of 18 patients completed 6 months of therapy with etretinate (initial dose 0.7 mg/kg/day) whereas only 7/9 patients completed 6 months of therapy with parenteral gold. A statistically significant decrease in the joint index occurred in both groups. In the etretinate group, the musculoskeletal symptoms improved considerably in 12 (67%) patients completing the treatment, and at the end of therapy also the skin lesions had healed or improved markedly in most patients. In two patients the reasons for terminating etretinate treatment were hypertriglyceridaemia and epigastric pain. In the gold group, seven patients could not complete the treatment regimen due to the common toxic side-effects of gold. The results of this study confirm that both etretinate and parenteral gold are effective in treating psoriatic arthropathy, and show that etretinate treatment seems to cause fewer harmful side-effects than chrysotherapy with parenteral gold.

Adult↗
PubMed1977

Gold thioglucose obesity syndrome.

Parenteral administration of gold thioglucose to mice produces an area or necrosis in the ventromedial portion of the hypothalamus. The lesion, like lesions produced by electrocautery of this area, causes hyperphagia and consequent obesity. The glucose moiety of gold thioglucose is essential for production of the lesion. Glucose analogues (2-deoxy-glucose, sodium thioglucose and phlorizin) prevent the gold thioglucose-induced lesion, and by themselves produce a transient hyperphagia. Insulin deficiency prevents the lesion. Either adrenalectomy or hypophysectomy counteracts the effect of insulin deficiency. Electron microscopic studies, in which general necrosis is avoided by administration of aspirin before gold thioglucose or by administration of subnecrotic doses of gold thioglucose, reveal that gold thioglucose primarily affects neural elements contiguous with capillaries in the ventromedial hypothalamus. The experimental observations indicate the presence of special glucoreceptor cells in the ventromedial hypothalamus that are involved in the regulation of food intake.

Adrenalectomy↗
PubMed1988

Alternatives to high noble dental casting gold alloys type 3. An in vitro in vivo study.

For economic reasons a large number of cheaper alternatives to the high noble dental casting gold alloys have been introduced on the market. The main problem with these alternative alloys is their chemical stability. This is a most important property as degradation of an alloy may release substances which can be harmful to the wearer. Thus, the corrosion behavior of four dissimilar alternative dental casting alloys together with a high-gold reference alloy was evaluated in the as-cast, hardened, and annealed conditions by means of potentiodynamic polarization analysis, partly supplemented by electron spectroscopy for chemical analysis. In order to facilitate interpretation of the results of the corrosion study, the composition and metallographic structure of specimens in the specimens in the dissimilar conditions had to be determined. The methods used were light microscopy, electron probe microanalysis, and X-ray diffractometry. Biocompatibility, which is related to the release of metal ions, was evaluated by subcutaneous implantation of specimens from the five alloys in guinea-pigs. Thus, the in vivo toxicity of the different alloys could be assessed. The chemical stability of an alloy also determines its tarnish resistance and as tarnish apart from creating esthetic problems, also may result in changes in the wetting characteristics of the alloy surface the in vivo tarnish of as-cast and annealed specimens inserted into complete mandibular dentures was estimated after up to 16 weeks. Castability, an important factor in an alloy's clinical performance, was measured as the marginal sharpness of cast simulated crowns from the five alloys. Finally, the clinical performance of crowns and bridges made from one low-gold and one silver-palladium alloy as experimental materials together with a high-gold alloy as a reference material was evaluated using specific periodontal parameters, a tarnish index, and CDA's guidelines for the assessment of clinical quality. The findings may be summarized as follows: The metallographic evaluation for the low-gold alloys Midas and Rajah indicated that these alloys may contain more than one phase. The two silver-palladium alloys Albacast and Alba V were heterogeneous in the three conditions studied. In most cases, the pre-treatment of the alloys had a decisive influence on their proneness to corrosion. The castability of the silver-palladium alloys was inferior to that of the gold-based alloys. The biocompatibility as revealed by subcutaneous implantation showed that one of the silver-palladium alloys (Albacast) produced the least tissue response, while the other one (Alba V) exhibided the worst tissue response.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1987

Detection of the low density lipoprotein (LDL) receptor on nitrocellulose paper with colloidal gold-LDL conjugates.

Gold-low density lipoprotein (LDL) conjugates were used to detect the LDL receptor on nitrocellulose paper. Solubilized rat liver membrane proteins were subjected to electrophoresis and electroblotted onto nitrocellulose paper. The receptor was then detected as a red band (within 10 min) by overlaying with the LDL conjugates. The coloration was prevented by unlabeled LDL, EDTA, and suramin but not by unlabeled HDL3. In the dot blot assay, detection with the colloidal gold-LDL conjugates was as sensitive as both the autoradiographic method with 125I-labeled LDL and the biotinylated LDL method; the estimated limit of detection by scanning densitometry was 1.6 femtomoles of receptor protein. When the coloration obtained with the colloidal gold-LDL conjugates was intensified by photochemical silver staining, down to 200 attomoles of the LDL receptor could be detected. In this assay, the EDTA-sensitive binding of colloidal gold-LDL to solubilized hepatic membrane proteins was 12 times higher for rats treated with 17 alpha-EE than for normal rats. The use of colloidal gold-LDL conjugates is therefore a very easy, safe, inexpensive, fast and sensitive method for the detection of the LDL receptor on nitrocellulose paper. Furthermore, with silver staining and scanning densitometry, the colloidal gold-LDL conjugates could be used in a dot blot assay to quantify tissue and cell LDL receptors down to attomolar levels.

Animals↗
PubMedDate not supplied

[Lysosomotropism and anti-inflammatory action of gold salts].

Gold salts have been widely used in the past 70 years in the treatment of various connective tissue diseases and more particularly in rheumatoid arthritis. However their mechanism of action remains poorly understood. Gold salts are transported in the blood linked with several serum proteins including immunoglobulins. Methods of analytical electron microscopy (Castaing probe) have shown that gold is actively concentrated in the lysosomes of various cell types, including the proximal tubular cells of the kidney and certain bone marrow cells. These data, together with those provided by biochemical techniques, suggest that sodium aurothiopropanol sulfonate modifies the stability of lysosome membranes. In the present study it is shown that the stability of kidney lysosomes of treated rats was increased by 42.4 per cent after treatment for 3 days. This protective action was also seen when lysosomes were subjected to lysis by digitonin. The protective effect of gold salts on the lysosomal membrane may be explained by the formation of chemical complexes between gold and sulfhydryl groups present in the membrane, resulting in stable mercaptic bonds. These findings suggest that the increase in stability of lysosomal membranes plays a significant role in the anti-inflammatory action of gold salts.

Animals↗
PubMed1970

[Further facts in pleural recurrence prevention by radio-colloidal gold in operated breast cancer].

The communication deals with endoscopical facts making recognizable that the intrapleural incorporation of colloidal radio-gold after the so-called radical mastectomy corresponds to a preventive-curative act. There is an analysis and proof of lymphogenous nature of the threatening, in it's manifest stage always lethal early and late pleural metastasis. The special and various features of the pleural cavity in postoperative endoscopy are demonstrated as a basis for the following dosage of radio-gold in a preventive-curative sense. Original, spectacular pictures are represented. On the basis of an experience for decades and because of the insufficient results of surgical therapy and conventional radiotherapy, unsatisfactory quoad sanationem et vitam, it must be pointed out that an additional, intrapleural radio-gold therapy is imperative. The application must be done early after operation. The effectiveness of this application is beyond question, since the pioneer-work of J. H. Müller and the ten years results with his preoperative radio-gold infiltration of the breast and my own endoscopically developed intrapleural radio-gold infusion. Both methods make possible true healing and ten years survival. For this reasons I recommend the employ of the more practicable intrapleural infusion on a big collective. The question of a long-term effectiveness of the therapy with fast electrons (betatron) is still to be decided on the ten years parameter. But I don't doubt that radio-gold is superior to all kind of radiotherapy controlling the contralateral pleural dissemination.

Adenocarcinoma, Scirrhous↗