PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Materials Testing”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed2000

Changes in the mechanical properties and surface texture of compomer immersed in various media.

STATEMENT OF PROBLEM: Limited information is available about the mechanical behavior of compomer under intraoral conditions. PURPOSE: This in vitro study evaluated changes in the mechanical properties and surface texture of compomer and other materials, used in similar clinical circumstances, when immersed in various media. MATERIAL AND METHODS: Hardness measurement for 5 tested materials and 4 immersion media was obtained with a Vickers hardness testing machine. Compressive strength was measured using an Autograph at a crosshead speed of 0.75 mm/min. All readings were taken for up to a 60-day period. An electron probe microanalyzer was used to give an SEM image. RESULTS: The average compressive strength and Vickers surface hardness showed a significant difference between materials. Results showed an overall increase in the solubility of specimens immersed in low pH soft drinks. CONCLUSION: There was a difference in the mechanical properties and surface texture of the materials tested in this study when they were immersed in various media.

Alcoholic Beverages↗
PubMedDate not supplied

Determination of 3-chloro-1,2-propanediol in foods and food ingredients by gas chromatography with mass spectrometric detection: collaborative study.

The results of a collaborative study are reported for the determination of 3-chloro-1,2-propanediol (3-monochloropropane-1,2-diol; 3-MCPD) in a wide range of foods and food ingredients, using gas chromatography with mass spectrometric detection and incorporating the use of a deuterated internal standard. After a pretrial study, 12 laboratories (6 United Kingdom, 1 Switzerland, 1 Japan, 2 United States, 1 The Netherlands, and 1 from the European Commission) were asked to analyze 12 test materials (as known duplicates or split-level samples) by using a prescribed procedure. The test materials consisted of duplicate samples of acid-hydrolyzed vegetable protein (containing 3-MCPD at 0.029 mg/kg), malt extract (0.055 mg/kg), wholemeal bread crumbs (0.030 mg/kg), salami (0.016 mg/kg), cheese alternative (0.043 mg/kg), and soup powder (split levels at 0.045 and 0.041 mg/kg). Repeatability ranged from 0.005 to 0.013 mg/kg and reproducibility, from 0.010 to 0.027 mg/kg, for the samples tested. Precision values were well within statistically predicted levels (HORRAT values of <1 for 5 of the 6 matrixes tested) and within method criteria prepared by a joint working group composed of the United Kingdom Ministry of Agriculture, Fisheries and Food and industry representatives. The study demonstrated the satisfactory validation of the method for quantifying 3-MCPD at levels of > or = 0.010 mg/kg. The limit of detection derived from separate in-house studies was estimated to be 0.005 mg/kg. The method was adopted First Action by AOAC INTERNATIONAL.

Animal Feed↗
PubMedDate not supplied

Effect of 1.23 percent APF gel on fluoride-releasing restorative materials.

This study evaluated the effect of a 1.23 percent APF gel on the surface morphological characteristics and surface roughness of one high-viscosity (Fuji IX GP), three polyacid-modified resin-based composites (Dyract AP, F2000 and Compoglass F) (PMRC), and two resin-modified glass-ionomer cements (Vitremer and Fuji II LC). A microfilled nonfluoridated resin-based composite (Silux Plus) was used as a control. All materials were handled according to the manufacturers' instructions. The fluoride gel used in the study was a 1.23 percent acidulated phosphate fluoride gel (APF) (Nupro APF). The specimens were repeatedly exposed to the APF gel with cotton applicators for a period that simulated the equivalent of 4 yrs (1 min/6 mo) under prophylactic fluoride treatment. Average surface roughness (Ra) of the control and treated specimens was measured. Three separate Ra measurements along the direction of rotation of the finishing and perpendicular to the finishing direction and edge of the mold were made for each specimen surface. In each group, specimens with Ra closest to the mean were removed from the molds, sputter-coated with gold and examined using a scanning electron microscope. The results showed that all tested materials, except Vitremer, displayed increased surface roughness values following APF treatment. However, this was not statistically significant for Compoglass F, Vitremer and Fuji II LC. Among PMRC materials, F2000 displayed the highest Ra average value, although the differences between F2000 and Dyract AP and of Compoglass F and Dyract AP was not statistically significant. Comparisons of the Ra values between Silux Plus and the other test materials revealed statistically significant differences except for Dyract AP and Compoglass F. No statistically significant difference was found between the Ra values of Vitremer and Fuji II LC following APF treatment. Among all groups, Fuji IX GP displayed the highest surface roughness.

Acidulated Phosphate Fluoride↗
PubMed1989

A predictive mouse ear-swelling model for investigating topical phototoxicity.

Predictive models should be used to determine the phototoxic potential of consumer products intended for topical exposure and outdoor use. To determine the potential of a compound to elicit a phototoxic reaction, a mouse ear-swelling model, which uses a xenon arc ultraviolet (UV) solar simulator as the radiation source, was used. The UV solar simulator delivered UV radiation from 290 to 400 nm (UVB + UVA) or from 320 to 400 nm (UVA) when appropriate filters were used. With this model, the phototoxic potential of nine known phototoxins and three negative test materials was successfully demonstrated. Based on the time of onset of the phototoxic response following test material application and irradiation, both immediate (20-30 min) and delayed-type (48-96 hr) phototoxic responses were demonstrated using this model with anthracene and 8-methoxypsoralen, respectively. The optimal time for irradiation after application of 8-methoxypsoralen to the ears was 30-60 min. Irradiation of ears immediately after treatment with 8-methoxypsoralen or 6 hr after application resulted in little or no phototoxic response. The phototoxic response to 8-methoxypsoralen was dependent upon the UVA dose and, when tested at a constant UVA dose, the response was concentration dependent. To obtain an optimal phototoxic response to 7-methoxycoumarin, both UVB and UVA radiation were required. These results show that the mouse ear-swelling model, which is quantifiable and more objective than models based on subjective evaluation of skin changes, is an excellent model for investigative and predictive phototoxicity testing.

Administration, Cutaneous↗
PubMed1988

Experimental contact sensitization with 3,4,5-trichloropyridazine.

The potential of 3,4,5-trichloropyridazine to induce contact sensitization was assessed in the guinea pig maximization test of Magnusson and Kligman and also in the closed patch test described by Buehler. The test material was a 1% solution of 3,4,5-trichloropyridazine in a highly refined mineral oil. The test material elicited moderate to severe irritation when diluted in mineral oil to concentrations of 15-25% and minimal irritation at concentrations of 1-3%. Both tests clearly indicated that 3,4,5-trichloropyridazine was a contact sensitizer to guinea pigs, although the response was stronger in the maximization test. Sensitization was distinguished from irritation by the use of concurrent irritation control groups.

Animals↗
PubMed1996

Estimating the removal and biodegradation potential of radiolabeled organic chemicals in activated sludge.

A two-step procedure is described to characterize the removal and biodegradation potential of nonvolatile 14C-labeled organic compounds in activated sludge. In the first step, trace concentrations of radiolabeled test materials are dosed in influent wastewater to continuous-flow activated sludge (CAS) systems which have been previously exposed or acclimated to unlabeled test material. Radiolabel is quantified in influent, effluent, and activated sludge mixed liquor to determine total 14C removal and partitioning of radiolabel in solid and liquid compartments. The 14C data are used to calculate the amount of removal due to sorption and biodegradation and to estimate the apparent sorption coefficients for 14C activity to activated sludge solids. The 14C-labeled CAS studies are followed by biodegradation studies in batch-activated sludge (BAS) systems using sludge derived from the CAS system. The kinetics of biodegradation (defined as mineralization to 14CO2) are measured in the BAS system to confirm the CAS biodegradation results and generate mineralization rate constants for kinetic modeling. The two-step procedure was applied to radiolabeled anionic (linear alkylbenzene sulfonate) and cationic (dodecyltrimethylammonium chloride, distearyldimethylammonium chloride) surfactants which differed greatly in their biodegradation and sorption profiles. Laboratory removal figures for these materials were comparable to values measured in full-scale wastewater treatment systems, although the amount of removal due to sorption and biodegradation varied significantly for the different surfactants. In general, the 14C method has several advantages over standard methods used in the United States and Europe which employ unlabeled materials. These advantages include the use of realistic concentrations and test conditions for acclimating and dosing activated sludge microorganisms and the ability to generate partitioning and kinetic constants that can be used more broadly in environmental fate and exposure models.

Biodegradation, Environmental↗
PubMed1985

Measurement of ionized calcium with five types of instruments. An external quality assessment.

An external quality assessment for ionized calcium determinations was carried out in 24 laboratories in Northern Europe. Both protein-free and protein-containing test materials were included in the study. The average within-laboratory variation (CV) for all test materials was 3.1, 1.7, 1.2, 1.8 and 1.3% for the AVL 980 (AVL, Graz, Austria), the Microlyte (Kone, Espoo, Finland), the Nova 2 (Nova Biomedical, Newton, Ma USA), the Orion SS-20 (Orion, Cambridge, Mass., USA), and the ICA1 (Radiometer, Copenhagen, Denmark) respectively. The corresponding interlaboratory CV was 3.1, 2.9, 3.1 and 2.4%. The variation between types of instruments was even larger and caused differences of up to 33%. The results indicate a need for well-defined protein-containing control material.

Calcium↗
PubMed1998

Comparison of sealing ability of three different root canal sealers--an in vitro study.

The main objective of endodontic therapy is complete obturation of the root canal system after it has been adequately prepared and sterilised. A wide variety of root canal sealers are available for obturation of the root canal system. A number of different invitro methods have been used to evaluate the sealing ability of endodontic filling materials. By combining one or two tests it may be possible to obtain information about sealing ability of the test material. Therefore, the present invitro study compared the sealing ability of three different root canal sealers, namely Sealapex, AH-26 and ZnOE by two different methods, bacterial leakage and dye penetration. The results showed that AH-26 has the maximum sealing ability followed by Sealapex and ZnOE.

Bismuth↗
PubMed1994

Gingival absorption of triclosan following topical mouthrinse application.

This study assessed the gingival uptake and urinary excretion of triclosan in dogs following topical applications of a mouthrinse containing 0.03% of triclosan. Five different phases were conducted to define the time course of plasma concentration. The effect of plaque on gingival absorption was also measured. Phase I: Animals' teeth were cleaned of plaque via scraping. Blood sampling time was 0-2 hours. Phase II: Plaque was not removed from the animals' teeth. Blood sampling time was 0-2 hours. Phase III: Plaque was not removed from the animals' teeth. Blood sampling time was 0-6 hours. Phase IV: Plaque was not removed from the animals' teeth. Blood sampling time was 0-12 hours. Phase V: Animals' teeth were cleaned of plaque via scraping. Blood sampling time was 0-12 hours. The test substance was administered to 1 male and 1 female dog in Phases I, II, IV and V, and to 1 male dog in Phase III. The same animals were used in each phase. On the first day of each phase, the animals were treated with distilled water for a 15-minute period. The animals were exposed daily to the test material for a 15-minute period during the remaining 7 days of each phase. The test material was administered using custom-made acrylic applicator trays to enclose the maxillar premolars and molars and gingiva of one-half of the upper jaw. A leak-proof seal along the mucogingival junction and palatal mucosa was established and maintained during the exposure period.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed2003

Biological response to wear debris generated in carbon based composites as potential bearing surfaces for artificial hip joints.

UHMWPE wear particles have been implicated in osteolysis, implant loosening, and long-term failure of total hip arthroplasties in vivo. This study examined four carbon-based composite materials as alternatives for UHMWPE in joint bearings. These materials were HMU-CVD, SMS-CVD, P25-CVD, and CFR-PEEK. New bearing materials should satisfy certain criteria: they should have good wear properties that at least match UHMWPE, and produce wear particles with low levels of biological activity. Of the four materials tested in multidirectional pin-on-plate tribological tests, SMS-CVD, P25-CVD, and CFR-PEEK showed lower volumetric wear factors than UHMWPE. P25-CVD had the lowest wear factor of 0.54 +/- 0.34 x 10(-7) mm(3)/Nm. Analysis of P25-CVD wear particles by transmission electron microscopy showed that the debris was very small, with the vast majority of particles being under 100 nm in size, which was similar in size to metal wear particles. The P25-CVD particles were isolated and cultured with L929 fibroblasts and U937 monocytic cells to assess their effect on cell viability. P25-CVD particles were significantly less cytotoxic (p < 0.01, ANOVA) to both cell types than CoCr metal wear particles. This work suggests that carbon-carbon composite materials may have potential for use in total hip replacement bearings. Of the materials tested P25-CVD had the lowest wear factor, and produced very small wear debris that had minimal cytotoxic effect on L929 and U937 cells in vitro. Therefore carbon-carbon composites, such as P25-CVD, may be important in the development of next-generation implants with lower wear rates and reduced cytotoxic potential.

Animals↗
PubMed1985

Saudi Arabic speech audiometry for children.

Phonetically balanced mono and disyllabic Classical Arabic word lists were chosen to construct a Saudi Arabic speech test for children. These words were taken from children's stories. They were first evaluated by primary and pre-school children in the urban and rural areas of the Province and then divided in eight subgroups of 10 words each. The articulation curves obtained from the children with this test material are similar in course and value to that of the German language using similar speech-test material under the same conditions.

Audiometry, Speech↗
PubMed1993

Children with specific language impairment: linguistic impairment or short-term memory deficit?

This study is concerned with characteristics of short-term memory (STM) in children with specific language impairment (SLI). The linguistic requirements of the test procedure, the characteristics of the test materials, and the development of linguistic representations were considered. Two experimental tasks were used: a verbal-repetition and a picture-pointing procedure. The tasks used auditory presentation and were designed to explore different underlying processes during immediate recall. The linguistic characteristics of the test materials were designed to explore the influence of semantic, lexical, and phonological factors on STM. Six SLI children (aged 6:1 to 9:6) (years:months) were individually matched on comprehension and expression of language to 17 younger children (age 3:4 to 6:5). Both groups were differentially influenced by the materials as a function of the test procedure. In general, both group and individual analyses found no significant difference between the performance of the SLI children and language-age (LA) controls. The implications of the results in relation to previous findings from investigations of STM and the underlying cause of SLI in children are discussed.

Child↗
PubMed2003

The safety of the use of ethyl oleate in food is supported by metabolism data in rats and clinical safety data in humans.

The absorption, distribution, and excretion of radiolabeled ethyl oleate (EO) was studied in Sprague-Dawley rats after a single, peroral dose of 1.7 or 3.4 g/kg body weight and was compared with a radiolabeled triacylglycerol (TG) containing only oleic acid as the fatty acid (triolein). Both test materials were well absorbed with approximately 70-90% of the EO dose absorbed and approximately 90-100% of the TG dose absorbed. At sacrifice (72 h post-dose), tissue distribution of EO-derived radioactivity and TG-derived radioactivity was similar. The tissue with the highest concentration of radioactivity in both groups was mesenteric fat. The other organs and tissues had very low concentrations of test material-derived radioactivity. Both test materials were rapidly and extensively excreted as CO(2) with no remarkable differences between their excretion profiles. Approximately 40-70% of the administered dose for both groups was excreted as CO(2) within the first 12 h (consistent with beta-oxidation of fatty acids). Fecal elimination of EO appeared to be dose-dependent. At the dose of 1.7 g/kg, 7-8% of the administered dose was eliminated in the feces. At the dose of 3.4 g/kg, approximately 20% of the administered dose was excreted in the feces. Excretion of TG-derived radiolabel in the feces was approximately 2-4% for both doses. Overall, the results demonstrate that the absorption, distribution, and excretion of radiolabeled EO is similar to that of TG providing evidence that the oleic acid moiety of EO is utilized in the body as a normal dietary TG-derived fatty acid. To confirm the expected safety of EO in humans, a total of 235 subjects participated in a 12-week trial where two levels of ethyl oleate in a milk-based beverage were investigated: 8 g/day in a single serving (approximately 0.1 g/kg) and 16 g/day taken in two divided servings (approximately 0.2 g/kg). Adverse events (AEs) were recorded throughout the 12-week trial. In addition, a brief physical exam (including vital signs and body weight), ECGs, fasting serum chemistry profile, serum lipid profile, and urinalysis were performed at baseline and after study completion. Results showed the incidence of reported AEs was similar between the EO groups and the control groups. Analysis of comprehensive laboratory data revealed no EO exposure-related, clinically significant adverse changes in laboratory parameters. These studies demonstrated that EO has a highly favorable safety profile and is well tolerated in the diet.

Administration, Oral↗
PubMed2006

Primary irritant and delayed-contact hypersensitivity reactions to the freshwater cyanobacterium Cylindrospermopsis raciborskii and its associated toxin cylindrospermopsin.

BACKGROUND: Freshwater cyanobacteria are common inhabitants of recreational waterbodies throughout the world; some cyanobacteria can dominate the phytoplankton and form blooms, many of which are toxic. Numerous reports in the literature describe pruritic skin rashes after recreational or occupational exposure to cyanobacteria, but there has been little research conducted on the cutaneous effects of cyanobacteria. Using the mouse ear swelling test (MEST), we sought to determine whether three toxin-producing cyanobacteria isolates and the purified cyanotoxin cylindrospermopsin produced delayed-contact hypersensitivity reactions. METHODS: Between 8 and 10 female Balb/c mice in each experiment had test material applied to depilated abdominal skin during the induction phase and 10 or 11 control mice had vehicle only applied to abdominal skin. For challenge (day 10) and rechallenge (day 17), test material was applied to a randomly-allocated test ear; vehicle was applied to the other ear as a control. Ear thickness in anaesthetised mice was measured with a micrometer gauge at 24 and 48 hours after challenge and rechallenge. Ear swelling greater than 20% in one or more test mice is considered a positive response. Histopathology examination of ear tissues was conducted by independent examiners. RESULTS: Purified cylindrospermopsin (2 of 9 test mice vs. 0 of 5 control mice; p = 0.51) and the cylindrospermopsin-producing cyanobacterium C. raciborskii (8 of 10 test mice vs. 0 of 10 control mice; p = 0.001) were both shown to produce hypersensitivity reactions. Irritant reactions were seen on abdominal skin at induction. Two other toxic cyanobacteria (Microcystis aeruginosa and Anabaena circinalis) did not generate any responses using this model. Histopathology examinations to determine positive and negative reactions in ear tissues showed excellent agreement beyond chance between both examiners (kappa = 0.83). CONCLUSION: The irritant properties and cutaneous sensitising potential of cylindrospermopsin indicate that these toxicological endpoints should be considered by public health advisors and reservoir managers when setting guidelines for recreational exposure to cyanobacteria.

Alkaloids↗
PubMed2005

Viability testing of material derived from Mycobacterium tuberculosis prior to removal from a containment level-III laboratory as part of a Laboratory Risk Assessment Program.

BACKGROUND: In the field of clinical mycobacteriology, Mycobacterium tuberculosis (MTB) can be a difficult organism to manipulate due to the restrictive environment of a containment level 3 (CL3) laboratory. Tests for rapid diagnostic work involving smears and molecular methods do not require CL3 practices after the organism has been rendered non-viable. While it has been assumed that after organism deactivation these techniques can be performed outside of a CL3, no conclusive study has consistently confirmed that the organisms are noninfectious after the theoretical 'deactivation' steps. Previous studies have shown that initial steps (such as heating/chemical fixation) may not consistently kill MTB organisms. METHODS: An inclusive viability study (n = 226) was undertaken to determine at which point handling of culture extraction materials does not necessitate a CL3 environment. Four different laboratory protocols tested for viability included: standard DNA extractions for IS6110 fingerprinting, crude DNA preparations for PCR by boiling and mechanical lysis, protein extractions, and smear preparations. For each protocol, laboratory staff planted a proportion of the resulting material to Bactec 12B medium that was observed for growth for 8 weeks. RESULTS: Of the 208 isolates initially tested, 21 samples grew within the 8-week period. Sixteen (7.7%) of these yielded positive results for MTB that included samples of: deactivated culture resuspensions exposed to 80 degrees C for 20 minutes, smear preparations and protein extractions. Test procedures were consequently modified and tested again (n = 18), resulting in 0% viability. CONCLUSIONS: This study demonstrates that it cannot be assumed that conventional practices (i.e. smear preparation) or extraction techniques render the organism non-viable. All methodologies, new and existing, should be examined by individual laboratories to validate the safe removal of material derived from MTB to the outside of a CL3 laboratory. This process is vital to establish in house biosafety-validated practices with the aim of protecting laboratory workers conducting these procedures.

Clinical Laboratory Techniques↗
PubMed1998

Bonding efficiency and interfacial morphology of one-bottle adhesives to contaminated dentin surfaces.

PURPOSE: To evaluate the effect of dentin contamination with water, saliva or blood on the bond strength of one-bottle dentin adhesives and interfacial morphology. MATERIALS AND METHODS: The tested materials were Scotchbond 1, One-Step, Prime & Bond 2.1 and Syntac SC. The three-step bonding system Scotchbond Multi-Purpose Plus (SMP) was also included as control. Extracted human molars were used. For each tooth, enamel was removed by sectioning with a diamond saw and a smear layer was created by grinding on wet 600 grit SiC paper. Before the adhesive materials were applied and cured, the dentin was dried with air for 3 s, dried with a damp cotton pellet, or contaminated with saliva or blood. Cylinders of the composite resin Z100 were applied onto the adhesive dentin surfaces using Teflon split molds. After 24-hour water storage, the shear bond strength of the specimens was determined using an Instron testing machine at a crosshead speed of 0.5 mm/min. The morphology of the dentin-resin interface was examined using SEM. RESULTS: Wetting of the substrate significantly increased the bond strength produced by One-Step, while the bond strength of Syntac SC was significantly decreased. The bond strength produced by Scotchbond 1, Prime & Bond 2.1 and SMP showed a slight increase or decrease, which was not significant. Saliva contamination decreased the bond strength significantly of only Syntac SC, while blood contamination significantly decreased the bond strengths of all materials. SEM evaluation of the dentin-resin interface showed a relation between resin tag formation and bond strength.

Adhesives↗