Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Materials Testing”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 73 records · Page 4Linked to original sources
PubMed2005

Clinical challenges and the relevance of materials testing for posterior composite restorations.

Posterior composite restorations have been in use for approximately 30 years. The early experiences with this treatment indicated there were more clinical challenges and higher failure rates than amalgam restorations. Since the early days of posterior composites, many improvements in materials, techniques, and instruments for placing these restorations have occurred. This paper reviews what is known regarding current clinical challenges with posterior composite restorations and reviews the primary method for collecting clinical performance data. This review categorizes the challenges as those related to the restorative materials, those related to the dentist, and those related to the patient. The clinical relevance of laboratory tests is discussed from the perspective of solving the remaining clinical challenges of current materials and of screening new materials. The clinical problems related to early composite materials are no longer serious clinical challenges. Clinical data indicate that secondary caries and restoration fracture are the most common clinical problems and merit further investigation. The effect of the dentist and patient on performance of posterior composite restorations is unclear and more clinical data from hypothesis-driven clinical trials are needed to understand these factors. Improvements in handling properties to ensure void-free placement and complete cure should be investigated to improve clinical outcomes. There is a general lack of data that correlates clinical performance with laboratory materials testing. A proposed list of materials tests that may predict performance in a variety of clinical factors is presented. Polymerization shrinkage and the problems that have been attributed to this property of composite are reviewed. There is a lack of evidence that indicates polymerization shrinkage is the primary cause of secondary caries. It is recommended that composite materials be developed with antibacterial properties as a way of reducing failures due to secondary caries. Post-operative sensitivity appears to be more related to the dentin adhesives' ability to seal open dentinal tubules rather than the effects of polymerization shrinkage on cuspal deflections and marginal adaptation.

Bicuspid↗
PubMed1993

Matrix effects on proficiency testing materials. Impact on accuracy of cholesterol measurement in laboratories in the nation's largest hospital system.

The objective of this collaborative study with the Department of Veterans Affairs (VA), College of American Pathologists (CAP), and the Centers for Disease Control and Prevention (CDC) was to quantitate the matrix-induced biases of cholesterol measurements on the CAP Comprehensive Chemistry Surveys materials used in proficiency testing (PT). A total of 174 VA Medical Centers outpatient clinics and clinical laboratories participate in the VA-CDC National Cholesterol Standardization and Certification Program. This study was conducted in 112 VA laboratories that have been standardized for measuring cholesterol accurately (within +/- 3.0% of the CDC reference-method values) using fresh, unfrozen, unadulterated human serum samples. Fresh serum samples and 1990 CAP Surveys materials were sent by overnight mail, and the laboratories were asked to analyze them simultaneously in triplicate in a single analytic batch run. The results showed significant matrix-effect biases with the CAP Surveys materials with six of the eight major peer groups, despite the fact that accuracy of cholesterol measurements was maintained with fresh serum samples. The magnitude and direction (positive or negative) of the matrix-effect biases were instrument, reagent, and method specific using the following peer groups: du Pont Dimension (-8.9%); Beckman CX4, CX5, and CX7 (-5.5%); Kodak Ektachem 400, 500, and 700 (+4.4%); Instrumentation Laboratory Monarch (-3.1%); Baxter Paramax (-2.4%); Technicon SMAC and RA (+1.3%); Hitachi/BMD 704 through 747 (+0.4%); and Abbott Spectrum (-0.3%). The CAP PT materials used currently do not behave in a manner identical to fresh human serum when measuring cholesterol on many, but not all, analytic systems. The observed biases due to "matrix effects" with PT materials will cause incorrect conclusions about the accuracy of many laboratory procedures performed on fresh patient specimens. This matrix-effect phenomenon will severely hamper interlaboratory accuracy transfer, standardization efforts, and monitoring performance of a laboratory's testing accuracy with the use of the current survey materials used in PT programs. Collaborative efforts are needed to (1) improve PT fluids to analytically behave more like fresh, human serum; (2) improve instrument design and reagent formulation; and (3) select methods and methodologic parameters that are more "robust" and less sensitive to the exact character of processed calibrators, quality control, and PT materials.

Bias↗
PubMed1992

[Methods of testing materials made by a knitting technique].

The author describes the methods of testing biomaterials manufactured by TRICOMED, Medical Articles, in Lodz. Examination of raw materials, production control methods, quality control of semi-finished and finished products are discussed.

Biocompatible Materials↗
PubMed1994

Materials testing protocol for small joint prostheses.

In this article, a protocol for the evaluation of new materials for small joint prostheses is introduced. The testing methods employed in the protocol were developed by reviewing reported clinical failure modes and conditions found in vivo. The methods developed quantitatively evaluates the fatigue, fatigue crack propagation, and wear resistance properties of materials. For this study, a silicone elastomer similar to Dow Corning Silastic HP100, a radiation stable polypropylene, and a copolymer of polypropylene and ethylene propylene-diene monomer (EPDM) are evaluated. None of the materials tested demonstrated the ideal properties that are sought in a self-hinging joint prostheses. The silicone elastomer had excellent wear properties; however, cracks quickly propagated, causing catastrophic failure when fatigued. Conversely, the copolymer showed excellent fatigue crack propagation resistance and less than favorable wear properties. The polypropylene did not perform well in any evaluation.

Biocompatible Materials↗
PubMed2005

Double-blind study on materials testing with applied kinesiology.

Applied Kinesiology (AK) is a scientifically unproven method used in complementary medicine to recognize the (in)tolerance of dental materials. Test-retest reliability of AK was examined. The working hypothesis was the assumption that the reliability of AK would not exceed random chance. Two dentists qualified in AK examined 112 volunteers to determine individual (in)tolerance toward two dental composite materials. After the first examination, 31 subjects were excluded from further testing. At the end of the open test phase, 34 of 81 participants had been classified as "tolerant", and seven as "intolerant" to both materials. The remaining 40 individuals showed a combination of either tolerant (to material I)/intolerant (to material II), or the reverse (n = 20 each). Retrieval rate was tested under blind conditions. In 14 cases, the results of the open and blinded tests matched, whereas in 26 cases they did not (95% confidence interval, 21%-52%; p = 0.98). This outcome confirmed our working hypothesis.

Biometry↗
PubMed2003

Dimensional accuracy and surface detail reproduction of two hydrophilic vinyl polysiloxane impression materials tested under dry, moist, and wet conditions.

STATEMENT OF PROBLEM: A major limitation of vinyl polysiloxane (VPS) impression materials is their hydrophobicity. There are 2 aspects to this problem, the wettability of the polymerized impression by dental gypsum materials and the ability of the unpolymerized material to wet intraoral tissues. To address this problem, manufacturers have added surfactants and labeled the new products as hydrophilic vinyl polysiloxane. PURPOSE: The purpose of this investigation was to compare dimensional accuracy and surface detail reproduction of 2 hydrophilic VPS impression materials, when used under dry, moist, and wet conditions. MATERIALS AND METHODS: A total of 102 impressions were made of stainless steel metal dies similar to those described in American Dental Association (ADA) specification 19. The dies had 2 vertical and 3 horizontal lines inscribed on their superior surfaces. Impressions were made under dry, moist, and wet conditions. Dimensional accuracy was measured by comparing the average length of the middle horizontal line in each impression to the same line on the metal die, by use of a measuring microscope with an accuracy of 0.001 mm. A 2-way analysis of variance and least significant difference post hoc test were used to compare mean dimensional changes (alpha=.05). Surface detail reproduction was evaluated in 2 ways: (1) by use of criteria similar to ADA specification 19 for detail reproduction, continuous replication of at least 2 of the 3 horizontal lines, and (2) by use of a method developed for this study that categorized the impressions as satisfactory or unsatisfactory based on their surface characteristics: presence of pits, voids, or roughness. Pearson chi(2) (alpha=.05) was used to compare detail reproduction results. RESULTS: Conditions (dry, moist, and wet) did not cause significant adverse effects on the dimensional accuracy of either material. The mean dimensional change and SD were 0.005% +/- 0.002% or less. With both surface detail analyses, dry, moist, and wet conditions had a significant effect on the detail reproduction of both materials (P<.05). Only under dry conditions did both impression materials continuously replicate at least 2 of the 3 horizontal lines 100% of the time. Under moist conditions, 82% of the Aquasil impressions and 100% of the Reprosil impressions were judged satisfactory, while under wet conditions, only 47% Aquasil and 11% Reprosil impressions were satisfactory. With the additional surface detail characterization, only under dry conditions were impressions produced with clinically acceptable surface quality (Aquasil 77% and Reprosil 100% satisfactory). CONCLUSIONS: Dimensional accuracy of both materials tested was well within ADA standards. Best surface detail results were obtained only under dry conditions for both materials.

Analysis of Variance↗
PubMed1950

The use of raw foods as skin testing material in allergic disorders.

Frozen foods for skin testing were prepared, stored and used by a simple, practicable, and inexpensive method. The capacity of raw foods to produce immunologically positive skin reactions by the scratch test method was reaffirmed. Storage in the frozen state for several months and thawing immediately before using for one series of tests did not affect the allergenic properties of the material. Raw foods were found to be innocuous to the skin and non-urticariogenic in allergic as well as in non-allergic persons. Raw foods, by the scratch test method, induced true positive reactions of a larger size and in greater numbers than the corresponding commercial extracts in the same series of subjects tested.

Allergens↗
PubMed1975

Reaction to Kveim test material in sarcoidosis and other diseases.

81 patients, 24 with sarcoidosis and the remainder with various other diseases, were tested with three batches of Kveim material prepared from the same spleen. Positive Kveim tests were observed in sarcoidosis, tuberculosis, Hodgkin's disease, ulcerative colitis, rheumatoid arthritis, and Weber-Christian disease. These results show that a positive Kveim reaction to the material under test was not specific to sarcoidosis.

Arthritis, Rheumatoid↗
PubMed1999

Compostable packaging materials--test methods and limit values for biodegradation.

In order to classify packaging materials as capable of organic recovery according to the packaging regulation of the European Union, the intended materials must be tested for their compostability. An important prerequisite is the determination of biodegradability by standardized test methods. Details of the intended tests are not comprehensible without further knowledge of the problems of biodegradation testing. The test methods and the limit values used to evaluate the biodegradation results are presented and discussed against the background of established test methods and limit values for chemicals. Furthermore the problem of ecotoxicity tests in connection with compost quality is discussed and an overview of European test laboratories is given.

Biodegradation, Environmental↗
PubMed1982

Evaluation of blood gas quality control and proficiency testing materials by tonometry.

Because of consistent differences found by other investigators and by us, we systematically tonometered, sampled, and measured PO2 and PCO2 concentrations of fresh blood, plasma, and several commercial quality control materials in three models of semiautomated blood gas machines. We found no significant differences between materials or machines for PCO2 between 25 to 72 mm Hg. For tonometered PO2 of approximately 25 to 100 mm Hg, the measured PO2 concentrations were accurate for blood, high for materials with hemoglobin or fluorocarbon (high O2 capacity), and very high for other materials (low O2 capacity). A low O2 capacity material tonometered to a PO2 of 0 mm Hg gave very high values in semiautomated machines and gave correct values only when injected repeatedly without interrupting rinse cycles into a manual machine. These findings indicate significant contamination of blood gas machines with fluids other than the sample so that low O2 capacity quality control materials are inadequate for proficiency testing at degrees of PO2 below 100 mm Hg.

Blood Gas Analysis↗