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 1,027 records · Page 57Linked to original sources

PubMed2003

First metatarsal-phalangeal joint arthrodesis: a biomechanical assessment of stability.

BACKGROUND: First metatarsal phalangeal joint (MTP) arthrodesis is a commonly performed procedure for the treatment of hallux rigidus, severe and recurrent bunion deformities, rheumatoid arthritis and other less common disorders of the joint. There are different techniques of fixation of the joint to promote arthrodesis including oblique lag screw fixation, lag screw and dorsal plate fixation, crossed Kirschner wires, dorsal plate fixation alone and various types of external fixation. Ideally the fixation method should be reproducible, lead to a high rate of fusion, and have a low incidence of complications. METHODS: In the present study, we compared the strength of fixation of five commonly utilized techniques of first MTP joint arthrodesis. These were: 1. Surface excision with machined conical reaming and fixation with a 3.5 mm cortical interfragmentary lag screw. 2. Surface excision with machined conical reaming and fixation with crossed 0.062 Kirschner wires. 3. Surface excision with machined conical reaming and fixation with a 3.5 mm cortical lag screw and a four hole dorsal miniplate secured with 3.5 mm cortical screws. 4. Surface excision with machined conical reaming and fixation with a four hole dorsal miniplate secured with 3.5 mm cortical screws and no lag screw. 5. Planar surface excision and fixation with a single oblique 3.5 mm interfragmentary cortical lag screw. Testing was done on an Instron materials testing device loading the first MTP joint in dorsiflexion. Liquid metal strain gauges were placed over the joint and micromotion was detected with varying loads and cycles. RESULTS: The most stable technique was the combination of machined conical reaming and an oblique interfragmentary lag screw and dorsal plate. This was greater than two times stronger than an oblique lag screw alone. Dorsal plate alone and Kirschner wire fixation were the weakest techniques. CONCLUSIONS: First MTP fusion is a commonly performed procedure for the treatment of a variety of disorders of the first MTP joint. The most stable technique for obtaining fusion in this study was the combination of an oblique lag screw and a dorsal plate. This should lead to higher rates of arthrodesis.

Analysis of Variance↗

PubMedDate not supplied

Assessing the application of an additive model to estimate toxicity of a complex effluent.

A number of industries monitor levels of chemicals in their effluent, but few have undertaken prolonged biological monitoring of this wastewater. The focus of the present study was to determine whether past chemical data for effluent from a lead smelter could be used to estimate its past toxicity. Since the interactive effects of metals in effluents are often assumed to be additive, it was hypothesized that an additive model, 100/[sigma(metal concentration in effluent/EC50 for individual metal)], could be used to generate an EC50 from chemical data (where EC50 is the concentration of test material that affects 50% of the test organisms). To test the approach, a larval development toxicity test with the marine polychaete, Galeolaria caespitosa, was used to test 26 separate samples of effluent from a lead smelter, generating empirical EC50 values. EC50 values for each individual metal in the effluent were also generated using the larval development toxicity test. The concentrations of trace metals in each effluent sample were determined and, using the additive model, EC50 values were calculated. For the majority of effluent samples tested, the additive model underestimated toxicity, suggesting the presence of additional unidentified contaminants in the effluent samples. Additionally, a nonlinear rather than linear regression curve was found to best describe the relationship between the model and empirically derived EC50 values. This relationship was then used to estimate past trends in toxicity of the smelter effluent. Forty-eight percent of the variability in measured toxicity was explained by the model, with the model underestimating toxicity in the majority of samples.

Animals↗

PubMedDate not supplied

Performance of high frequency impaired listeners with conventional and extended high frequency amplification.

This study sought to determine if a high-pass hearing aid can provide increased improvement in word recognition and consonant discrimination over that of a conventional high frequency emphasis hearing aid in listeners with hearing loss limited to frequencies above 1 000 Hz. Word and consonant discrimination were assessed in quiet and in the presence of 12 talker speech babble for 10 subjects under three listening conditions: (1) unaided; (2) wearing a conventional high frequency emphasis hearing aid, and (3) wearing an experimental high-pass instrument. The speech testing materials included: (1) Northwestern University Auditory Test No. 6; (2) California Consonant Test, and (3) eight voiceless English consonants. Results suggested that both instruments provided similar benefit in quiet for improving word recognition and resolving consonant errors. For the noise condition, however, the experimental high-pass aid provided a considerable advantage in both word recognition and consonant identification and was particularly sensitive to reducing within- and between-manner voiceless consonant confusions. Furthermore, measurements of real-ear gain revealed that the high-pass aid afforded considerably greater acoustic gain above 4 000 Hz than that shown for the conventional high frequency emphasis hearing aid,20

Adult↗

PubMed1996

Use of the Arizona Battery for Communication Disorders of Dementia in the UK.

The Arizona Battery for Communication Disorders of Dementia (ABCD) (Bayles & Tomoeda, 1993) was given to groups of young and old normal subjects and to subjects with moderate Alzheimer's disease in the UK. Very few significant differences were found between their raw scores and those of the original standardisation sample in the USA, which makes the ABCD an appropriate test to use in the UK. Although some subjects commented on several of the test stimuli, cultural differences in pictures and vocabulary did not produce notable effects on test performance and so alterations to test materials are not required for the test to be used in the UK.

Adult↗

PubMed2004

Below Knee Impact Responses using Cadaveric Specimens.

Knee injuries represent about 10% of all injuries suffered during car crashes. Efforts to assess the injury risk to the posterior cruciate ligament (PCL) have been based on a study available in the literature (Viano et al., 1978), in which only two of the five knees tested had PCL ruptures. The aims of the current study were to repeat the study with a higher number of samples, study the effects of other soft tissues on knee response, and assess the adequacy of the experimental setup for the identification of a PCL tolerance. A total of 14 knees were tested using a high-speed materials testing machine. Eight were intact knees (with the patella and all the muscular and ligamentous structures), three were PCL-only knees (patella and all the muscular and ligamentous structures other than the PCL removed), and the last three were PCL-only knees with the tibia protected from bending fracture. Of the eight intact knees tested, only one had PCL mid substance rupture, one had a partial articular fracture of the tibia below the plateau, and six had simple transverse fracture of the tibial metaphysis. Of the three PCL-only knees without tibial protection, one had PCL mid substance rupture, one had avulsion at the posterior intercondylar attachment point, and the last one had a simple oblique fracture of the tibial metaphysis. Of the three PCL only knees with tibia protection, two had PCL mid-substance ruptures and the third one had an avulsion at the tibial insertion site with partial articular fracture of the lateral plateau. Overall, the results of the current study were similar to those observed by Viano et al. (1978). The average displacement at failure for all PCL related injuries was 17.2+/-2.8 mm for the current study (n=6) and 16.2+/-3.9 mm for Viano et al. (1978) (n=4). This value is higher than the Injury Assessment Reference Value of 15 mm proposed by Mertz (1984) and used in various regulations. Both studies suggest that the existence of the soft tissues other than the PCL affect the injury outcome and that the intact knee would suffer predominantly tibial metaphyseal fractures possibly due to bending. Consequently, it is concluded that the current experimental setup can produce isolated PCL injuries but the data available are inadequate to characterize PCL tolerance. A Hybrid III knee equipped with a ball bearing knee slider was also tested using a pendulum setup. Apart from the initial higher stiffness, the overall response of this knee lies within the force-deflection corridors defined using the response of the cadaver knees with PCL mid-substance failure.

Journal Article↗

PubMed2005

Screening mammography interpretation test: more frequent mistakes.

PURPOSE: To present the mammographic cases most commonly misinterpreted by the participants in the mammography self-test proposed by the Italian Society of Medical Radiology (SIRM) National Congress in Rimini, Italy, 2002, by analysing the findings responsible for errors, suggesting reasons for the errors, and assessing possible inadequacies in the format of the test. MATERIALS AND METHODS: The self-test was performed on the mammograms of 160 cases (32 positive and 128 negative for cancer as confirmed by histology). The mammograms had been taken in the four standard projections and placed on four multi-panel diaphanoscopes, each displaying a set of 40 cases comprising benign and malignant cases in equal proportions. The participants were given pre-printed forms on which to note down their diagnostic judgement. We evaluated a total of 134 fully-completed forms. Among these, we identified the 23 cases most frequently misread by over 15 participants in percentages varying between 40-90%. Of these cases, 10 were malignancies and 13 were negative mammograms. On review, we also assessed the diagnostic contribution of complementary investigations (not available the participants). RESULTS: The 134 fully-completed forms (all of the 40 cases) yielded a total of 5360 responses, 1180 of which (22.01%) were incorrect. Of these, 823 out of the 4288 cases expected to be negative (19.2%) were false positive, and 357 out of the 1072 cases expected to be positive (33.3%) were false negative. As regards the 23 most frequently misread cases, these were 10/32 (31.25%) mammograms positive for malignancy and 13/128 (10.15%) negative mammograms or mammograms showing benign disease. The 10 malignancies included 7 infiltrating ductal carcinomas, 1 infiltrating cribriform carcinoma, 1 infiltrating tubular carcinoma, and 1 carcinoma in situ. The 13 cases of benign disease--as established by histology or long-term follow-up--mistaken for malignancies by the test participants were fibrocystic breast disease in 5 cases, surgical scar in 1 case, ABBI scar in 1 case, radial scar in 2 cases, microcalcifications that had remained stable for years in 2 cases, focal sclero-adenosis in 1 case and sclero-elastosis in 1 case. CONCLUSIONS: The errors were due to microcalcifications, benign disease simulating a neoplasm, overlapping tissue, visibility of a lesion in one projection only, lesion site in relation to the corpus mammae, missed areas of asymmetry. Attention must be paid to these signs of focal breast disease since, if correctly evaluated, they enable the early diagnosis of low-grade carcinomas that frequently carry a favourable prognosis.

Adenocarcinoma↗

PubMed2005

A study to assess the colour stability of acetal resins subjected to thermocycling.

The purpose of this study was to compare colour stability of pink and white acetal resin with one conventional poly (methylmethacrylate) resin. Five specimen disks 50 +/- 0.1 mm in diameter and approximately 1.0 mm thick were prepared from each material. The discs were hydrated for a period of 30 days in distilled water and were then desiccated to a constant weight. Total of fifteen specimens were thermocycled for 100 and 300 hours (4000-12000 cycle) between water baths of 5-55 degrees C. Changes from baseline colour readings were recorded at each interval. Data were analysed with descriptive statistic, repeated measured analysis of variance and single factor analysis of variance. The colour changes for all materials at 100 hours were in the categories of slight, based upon the National Bureau of Standard System (NBS) for expressing colour difference. At 300 hours, the colour changes of materials were significantly different (p = 0.0001). All the materials tested showed clinically acceptable discolouration values.

Color↗

PubMedDate not supplied

Factors influencing the cytotoxicity of anti-bacterial sera for lymphocytes from ankylosing spondylitis patients.

Rabbit antisera to certain strains of Gram-negative bacteria are reported to be cytotoxic for the lymphocytes of about 80% of HLA-B27 positive patients with ankylosing spondylitis (AS) but not for the lymphocytes of healthy HLA-B27 positive individuals. The lymphocytes of normal individuals can, however, be made susceptible to lysis by antibacterial sera by incubation in spent supernatant from appropriate bacterial cultures. In an attempt to explain the failure of certain laboratories to reproduce these results we have tested a number of variables in the 51Cr-release complement-dependent cytotoxicity assay. We conclude that AS patients in London and Sydney carry the same antigen, that several different incubation media can be used for both the cytotoxicity assay of HLA-B27 positive AS cells and modification of normal B27 positive cells and that the cells used may be collected either in heparin containing media or after defibrination. Major requirements for success include a healthy sample of lymphocytes (preferably at a fairly high concentration), suitable antiserum from a rabbit repeatedly immunised with large numbers of bacteria, appropriate complement and efficient technique. However, as we have failed to repeat this test consistently in London, even using materials tested in this study, it seems that another, probably non-biological, factor is also important.

Bacteria↗

PubMed1986

[Suitability of speech audiometry study procedures for current demands in clinical and general practice].

The quality of the recorded audiometric test material (the "Freiburg" and "Marburg" language test) meets the High Fidelity standards of the 1960's. In the light of current technology (digital technique, compact disc, etc.), the question arises whether speech-audiometry can still contribute to diagnosis, medico-legal assessment and fitting of hearing aids. Results of the "Freiburg" language test are presented, which analyse the comparability of the individual groups in quiet and in noisy surroundings, the technical and technological aspects of the sound systems, orthophonic reproduction and the practical performance of audiometric speech tests. Finally, recommendations of the commission for speech-audiometry and hearing aids of the ADANO are presented and discussed. These may explain present and future demands and possibilities of a broad-band audiometric investigation spectrum in hospital and practice.

Audiometry, Pure-Tone↗

PubMedDate not supplied

[Allergic reaction to products made of natural rubber].

In the previous few years, there has been a startling escalation in intraoperative and radiologic anaphylactic episodes, some of them lethal, that have been assigned to rubber exposure. Immediate hypersensitivity reactions to natural rubber pose a significant risk to patient with spina bifida and urogenital abnormalities, health care workers, and rubber industry workers. It has been estimated that 2% to 10% of physicians and nursing personnel are latex allergic. The clinical syndromes associated with reactions to latex may be divided into three broad categories a) contact dermatitis--limited to skin directly in contact with latex, b) contact urticaria syndrome a broad spectrum of contact reactions including not only immediate wheal and flare reactions, but also dyshidrotic vesiculation, and accelerated contact reactions including erythema, burning or pruritus occurring within 10-30 minutes after contact, c) systemic allergic reactions-including generalized urticaria or pruritus, rhinoconjunctivitis or asthma, as well as the multiple presentations of anaphylaxis. Contact dermatitis reactions are thought to be a T-cell mediated type IV reaction, systemic reactions to latex appear to be an IgE-mediated phenomenon. Contact urticaria syndrome seems to be a heterogeneous group of reactions. Diagnosis of latex allergy is made on clinical grounds, however, history alone is insufficient to recognize all patients at risk, and conscientious testing materials are not yet available. Prick tests utilizing extracts from latex gloves or from raw latex preparation can be used but the specificity of this test remains unknown. Skin prick testing must be considered experimental and should be only done by experienced physician. Serologic testing for latex allergy remains a safe alternative, although the sensitivity and specificity of this procedure is still undefined. Prophylactic regimes to avoid rubber exposure and decrease the antigen content of natural rubber products by the rubber industry should be implemented to decrease the rate of sensitization in the future and prevent allergic reactions.

Anaphylaxis↗

PubMedDate not supplied

Physical properties of self locking and conventional surgical knots.

OBJECTIVE: To assess some of the physical properties of three types of self locking knots and two types of conventional surgical knots. DESIGN: Experimental in vitro study. OUTCOME MEASURES: Knot efficiency (knot strength: suture strength ratio), slippage, and volume. MATERIALS: Test knots tied with the suture materials polyglactin, polydioxanone and nylon in USP sizes 1,2/0, and 4/0. RESULTS: Self locking knots performed significantly better (p < 0.01) than conventional knots in all combinations of material and size, except for 4/0 nylon. Efficiency of the self locking knots tied with the monofilament polydioxanone and nylon ranged from 0.88-0.96. With the multifilament polyglactin, it ranged from 0.71-0.90, and it increased proportionally with the thickness of the material. The mean efficiency of the conventional knots was 0.51 (0.06) for polyglactin, and 0.70 (0.17) for the monofilament materials. The self locking knots did not slip. The conventional starting knot often slipped partly, but came undone only when the conventional terminating knot was tied with monofilament material. The self locking knots were significantly smaller than the conventional knots. CONCLUSION: Self locking knots are safer than conventional surgical knots, and considerably smaller.

Humans↗

PubMed1996

Stability of cereal allergens.

BACKGROUND: Ingested cereals and inhaled cereal dusts can cause IgE-mediated allergy. Testing for these allergies yields variable, often undependable results, which could be due to the use of unsuitable or degraded testing materials. OBJECTIVE: We studied the effect of storage media, time and temperature on the stability of protein allergens extracted from wheat, rye, barley and oats flour. We also examined the effect of heat processing similar to that used when preparing foods on the stability of allergenic proteins present in wheat flour. METHODS: After storage experiments proteins in allergen extracts were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and then visualized using immunoblotting or staining with Coomassie brilliant blue. After heat processing wheat flour proteins were extracted and their IgE-binding capacity was estimated. RESULTS: Extracted proteins from wheat, rye and barley flour appeared stable for at least 21 months when stored at 4 degrees C in an aqueous solution containing 50% glycerol and 0.45% sodium chloride. In a medium with 0.4% phenol and 0.9% sodium chloride degradation of many proteins became apparent already after 1 month of storage. Oats extracts lost their IgE-binding capacity more rapidly and the maximal storage time appeared to be 10 months at 4 degrees C in a solution containing 50% glycerol and 0.45% sodium chloride. The IgE-binding capacity of the allergenic proteins decreased as heat-processing temperature and heating time increased. No processing conditions entirely abolished IgE-binding. CONCLUSION: Cereal allergen preparations can be stored either in lyophilized form or at 4 degrees C in 50% glycerol. Unheated materials should be used also when testing for food allergy, as heating reduces allergenicity and thus sensitivity at testing.

Adolescent↗

PubMed1998

Investigation into the cercariacidal and miracidiacidal properties of Endod (Phytolacca dodecandra) berries (type 44).

Aqueous extract of ground Endod (Phytolacca dodecandra) berries (Type 44) was investigated for its cercariacidal and miracidiacidal properties. Aqueous extract of the berries prevented snails from being infected by miracidia at a concentration of 4 ppm. Assessment of cercariacidal activity of Endod berries indicated that mortality of cercariae exposed to aqueous extract of Endod berries increased with increase in concentration of the test material and exposure time. Viability assessment test showed that pre-treatment of the cercariae with 12 ppm of the extract completely inhibited infection of mice by cercariae and significantly reduced tissue egg deposition and worm establishment in the mice (ANOVA, P < 0.05) The potential use of (Phytolacca dodecandra) berries against schistosome larval stages in fresh water in a schistosomiasis control program is discussed.

Analysis of Variance↗

PubMed1989

New dynamic corrosion test for dental materials.

A new laboratory technique has been developed in an effort to simulate the deterioration processes occurring in dental amalgam restorations while they are exposed to attack by the oral environment and simultaneously subjected to biting forces during mastication. This combined mechanical wear and corrosion action may be one of the major contributors to the degradation of dental amalgam restorations. The technique provides the capability of varying and measuring electrochemical and mechanical parameters during a sliding-wear process in a corrosive environment. A high-copper dental amalgam was selected and tested to demonstrate the applicability of the method in evaluating and studying the effects of the combined action of wear and corrosion processes on dental materials. For the particular amalgam material tested in the present study, it was found that sliding-wear significantly lowered its corrosion potential and increased corrosion rates by at least one order of magnitude.

Copper↗

PubMed2005

Engineering properties and performance of dental crowns.

Dental crowns are used to replace damaged natural crowns of teeth and are fixed to prepared teeth with luting cements, which should provide an adhesive bond to the tooth structure giving reliable retention and minimal microleakage. Mechanical testing of crowns in vitro gives failure load distributions that are well described by Weibull models, comparing probabilities of survival and reliability. Fatigue testing of crowns is time consuming, but regression analysis to interpolate functions through data points quoting probability limits or applying Weibull analysis is achievable. A complementary approach is to conduct materials tests with appropriate interfacial geometries. Luting cements are used in thin layers of 40-150 microm. Contraction during polymerization is restrained by adhesion to substrates, allowing little relaxation of stresses. Conventional and resin-modified glass ionomer cements create thin zones of interaction with dentine and fail cohesively. The chevron notch short rod technique has been used to measure fracture toughness and rank cements. A development of this method, using chevron notch short bar specimens, permitted fracture toughness to be determined for luting cement--dentine substrate interfaces. Representative fracture experiments need to be developed to apply mixed mode conditions. The basic challenge to predict long-term performance from short-term laboratory tests remains.

Biomedical Engineering↗

PubMed2006

The effect of temperature on viscosity of root canal sealers.

AIM: To test the hypothesis that there was no significant (alpha = 0.05) change in viscosity of commercially available root canal sealers with increase in temperature using a high-performance Advanced Rheometric Expansion System (ARES) rheometer. METHODOLOGY: Materials tested were Apexit, Tubliseal EWT, Grossman's, AH Plus and Ketac-endo. Cone-and-plate geometry was used (25-mm diameter, 0.1 radian and gap 0.051 mm). Measurements were carried out for steady-state viscosity at 25 and 37 degrees C in the shear rate range of 0.001-50 s(-1) at standardized relative humidity and within 30 min from the start of mixing. Five samples were taken for each sealer at each temperature. RESULTS: At 25 degrees C all sealers demonstrated shear thinning. At 37 degrees C Grossman's (powder : liquid ratio 2 : 1 and 3 : 1) and Ketac-endo had a rapid rise in viscosity and early set whereas the other sealers were shear thinning. On increasing temperature from 25 degrees C to 37 degrees C, Apexit, Tubliseal and AH Plus had reduced viscosity whereas Grossman's 2 : 1, Grossman's 3 : 1 and Ketac-endo had increased viscosity, which varied with the shear rate. The change in viscosity with change in temperature was significant (P < 0.05) for all sealers except AH Plus. CONCLUSIONS: There was a variation in the effect of increasing temperature on each sealer depending on the shear rate. With the exception of AH Plus, a significant (P < 0.05) change in viscosity was found, and the null hypothesis was rejected.

Calcium Hydroxide↗

PubMed2002

[Fracture strength of custom-fabricated celay all-ceramic post and core].

OBJECTIVE: The purpose of this study is to compare the fracture strengths of custom-fabricated Celay all-ceramic post-core, custom cast metal post-core, and prefabricated stainless steel post (Parapost) plus composite resin core with or without a 2.0 mm dentine ferrule. METHODS: A total of 60 recently extracted human maxillary central incisors were endodontically treated and divided into five groups of 12. They were given the following treatments: Group A: Celay ceramic post-core with 2.0 mm dentine ferrule, Group B: Celay ceramic post-core with no dentine ferrule, Group C: cast metal post-core with 2.0 mm dentine ferrule, Group D: cast metal post-core with no dentine ferrule, and Group E: prefabricated post and composite core with 2.0 mm dentine ferrule. All specimens were stored at 100% humidity at room temperature for 30 days before testing. Each specimen was in a special jig at a 45 degrees angle to the long axis and subjected to a load on MTS 810 universal material testing machine until failure, with crosshead speed of 0.02 cm/min. Analysis of variance followed by the Newman-Keuls pairwise multiple comparison test was used to compare the results of the groups tested. RESULTS: There was a statistically significant difference between five groups (P < 0.01). Celay ceramic post-core with 2.0 mm dentine ferrule (758.35 N +/- 119.26 N) and cast metal post-core with 2.0 mm dentine ferrule (756.63 N +/- 166.22 N) had a significantly larger mean failure threshold for fracture than the other three groups which had no significant difference between each other. There was a statistically significant difference between the fracture resistance of Celay post-core restored teeth with and without 2.0 mm dentine ferrule. CONCLUSION: The custom-fabricated Celay post-core could be a choice for clinical use in endodontically treated tooth when the final restoration is an all-ceramic crown and the preparation has a 2.0 mm dentine ferrule.

Ceramics↗

PubMed1992

Linear dimensional variability and tensile strengths of three solder index materials.

This study compared the linear dimensional change and tensile strengths of three indexing materials used for aligning joints to be soldered. Sixty rods 6 mm in diameter and 18 mm in length were made from base metal. The rods were divided into three groups of 10 pairs each, and a simulated solder gap was created between the rods in each pair. Ten simulated gaps were indexed with Duralay resin, 10 were indexed with Relate resin, and 10 were indexed with ZAPIT cyanoacrylate material. Measurements were made of each pair, before and after indexing, and the tensile strength of each indexed pair was measured and recorded. Linear measurements showed no significant difference between any of the groups. However, significant differences in tensile strength were found among all the materials tested.

Acrylic Resins↗