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 1,045 records · Page 58Linked to original sources

PubMed1991

The adaptation and sealing ability of light-cured glass ionomer retrograde root fillings.

The adaptation and sealing ability of a light-cured glass ionomer cement when used as a retrograde root filling was assessed using a confocal optical microscope with and without a fluorescent dye. This material was compared with a conventional glass ionomer cement and amalgam. The root canals of 60 extracted human single-rooted teeth were prepared and filled with gutta-percha and sealer. All the teeth were apicected, retrograde cavities were prepared, and then divided into three groups of 20 teeth each and filled with the test materials. The light-cured glass ionomer cement was well adapted to the retrograde cavity and apicected root surface. Within the retrograde cavity the cement was often well adapted to one wall, but gaps were found on the opposite cavity wall. This was probably caused by the polymerization contraction of the material. In contrast, the amalgam retrograde root fillings were poorly adapted to the cavities, with gaps between the cavity walls and amalgam. This group exhibited the poorest sealing ability as measured by the extent of dye penetration. The conventional glass ionomer cement was often found smeared over the root face, and there were unfilled voids at the base of some retrograde cavities. The results of the dye leakage study were analysed statistically. The sealing ability of the light-cured glass ionomer cement was significantly better than that of amalgam (P less than 0.001). The dye penetration around the light-cured glass ionomer cement and the conventional glass ionomer cement was not significantly different (P greater than 0.05). However, the sealing ability of the conventional glass ionomer cement was significantly better than that of amalgam (P less than 0.05).

Analysis of Variance↗

PubMed1995

[The chemical solubility and stability of low-melting dental porcelains].

The aim of this investigation was to study the chemical solubility of 3 new low-fusing ceramics (Duceram-LFC, Duceragold and Vita Omega 800) in comparison with a conventional PFM-ceramic (Vita Omega) together with different surface treatments. Additionally, the three-point flexure strengths were measured. Although the test conditions were very stringent in comparison to the standard solubility test, all ceramics comply with ISO/DIS 6872 specifications, and are thus deemed to be well tolerated in the oral environment. Vita Omega demonstrated the lowest chemical solubility. Mechanical polishing of the surfaces of LFC and Duceragold ceramics produced lower solubility results as compared to glazing. Vita Omega and Omega 800 behaved contrarily. After repeated hydrolysis testings Ducera-LFC demonstrated the highest disintegration resistance. The three-point flexure strengths of low-fusing ceramics were generally higher than that of the conventional PFM-ceramic. As opposed to the other ceramic materials tested, the flexure strength of Duceram-LFC increased significantly after hydrolysis testing.

Dental Porcelain↗

PubMed2006

[Significance of microbial colonisation in materials for orthopaedic technology. New insights].

A great problem in the treatment of diabetes are infections of diabetic feet. A likely reservoir of microorganisms are contaminated orthopaedic materials. Insoles from 70 patients were examined for potential microbial colonisation. Commonly employed materials were contaminated in vitro under standardised conditions using known microorganisms. After treating with an alcoholic skin disinfectant, the organisms were counted semiquantitatively. In addition to pathogens, the surfaces showed mainly microorganisms present in the normal skin flora. In all materials tested, disinfection reduced the number of organisms by 4-5 log orders. It could be shown that simple disinfection (wiping) reduces the microorganisms present on orthopaedic materials to an acceptable number. Further studies are needed to determine whether this also reduces the incidence of diabetic skin and soft tissue infection.

Bacteria↗

PubMed1995

Effects of method of internal fixation of symphyseal disruptions on stability of the pelvic ring.

This study tested different methods of internal fixation of a symphyseal disruption, in comparison with the mechanics of the intact pelvis. Unembalmed cadaveric pelves were tested in simulated bilateral stance in a servohydraulic materials-testing machine. Motion of the superior and inferior pubic symphysis, and at two levels of the posterior sacroiliac complex, was measured using high resolution displacement transducers. The fixations tested were (1) double plating (4.5 mm reconstruction plates), (2) wire loops around two 6.5 mm, fully threaded cancellous screws, and (3) an absorbable suture material (polydioxanone). Each pelvis was first tested intact, recording displacements in response to a cyclic axial load up to a maximum of 500 N applied through the proximal sacrum. The pubic symphysis was then sectioned and the sacrum fractured to produce an unstable pelvis (Tile C-type). Recordings were then repeated, following fixation of the sacral fracture with lag screws and sequential fixation of the symphysis with each of the test methods. The results from eight pelves revealed that internally fixed symphyseal motion was generally greater than intact, regardless of fixation method. The superior symphysis was usually compressed, while there was distraction inferiorly. Wiring resulted in significantly less symphyseal motion than the other methods (P < 0.02), provided four loops were used, reducing the separation inferiorly. There was no significant difference in sacral fracture motion between the three methods. The results indicate that in osteoporotic bone, as used in this study, symphyseal wiring is best able to oppose the tensile loads in the inferior symphysis that are associated with bilateral stance loading. These biomechanical findings must be interpreted within the broader context of surgical management of these complex injuries.

Aged↗

PubMed1982

[Comparative studies in vitro of the toxic effect of water extracts from synthetic materials in biological tests on living cells].

Synthetic materials for medicine and pharmacy described as medical grade materials are constantly improved and new materials appear every year. There are various kinds of synthetic materials within the same group and they differ in qualitative and quantitative choice of chemical compounds used for their synthesis, and in technology of their production. These factors influence physico-chemical and biological properties of the materials. There is also a possibility of qualitative changes in synthetic products caused by depolimerization and migration of chemical compounds which depends on the conditions and time of their storage, and on the method of sterilization. The production of a new synthetic item is connected with the necessity of selective choice of the proper material. The choice is made on the basis of complex physico-chemical and biological investigations. Systematic controls of multimolecular materials after polimerizations and controls of ready products should be made in the course of series production. Controls of toxicity are usually made according to chosen one or few biological testing methods in vitro. The results of parallel investigations performed according to different methods are not sufficient for univocal evaluation of the material since they can be either divergent or contradictory. Therefore new tests and expanding methods of biological investigations are constantly looked for. A new technique of synthetic materials toxicity evaluation with the fresh diluted bulls semen has been developed after for several years, of research. The results indicated that the bulls semen was useful in toxicity evaluation. This present work constitutes a continuation and recapitulation of the investigations which had the following goals to be attained. 1. Improvement of investigations technique, development of the criteria of results evaluation and presentation of the basic principles of our method of toxicity investigation of synthetic materials water extracts on the bull semen. 2. Evaluation of the toxicity of various synthetic products used in animals insemination and biomedical products on bull semen. 3. The comparison of the results of toxicity investigation of synthetic materials water extracts on bulls semen with the results of investigations performed on cell cultures HF, mouse cells L929, chicken embryo cells CEC and the results of hemolytic test. 4. The complex evaluation of the own method of toxicity investigation of synthetic materials water extracts with the application of the fresh bulls semen. 55 various materials and products used in medicine, in animals insemination and in the food industry were chosen for the investigation.(ABSTRACT TRUNCATED AT 400 WORDS)

Anaphylaxis↗

PubMed1993

Some physical properties of an improved facial elastomer: a comparative study.

An attempt was made to evaluate some properties of clinical importance of a new facial elastomer, Cosmesil HC2. A comparative study versus Silskin II and Cosmesil SM4 was also carried out and took into account the effect of weathering after exposure to ultraviolet radiation. The results showed that Cosmesil HC2 is a resilient material and yet displays good tensile characteristics. The results also showed that weathering does not significantly affect Cosmesil HC2 elastomer's tear strength. The overall effect of irradiation was moderate in all materials tested.

Chemical Phenomena↗

PubMed2005

The influence of calcium fluoride (CaF2) on biaxial flexural strength of apatite-mullite glass-ceramic materials.

OBJECTIVE: The aim of this study was to evaluate the effect of varying the molar percentage of calcium fluoride (CaF2) on the biaxial flexural strength (BFS) of apatite-mullite glass-ceramics. METHODS: Three apatite-mullite glass-ceramic materials were produced based on a formula of 4.5SiO(2)-3Al2O(3)-1.5P2O(5)-3CaO-XCaF2, where X=0.5, 1 and 3 and called HG 1-3, respectively. These materials were used to produce discs of 2 mm thickness and 12 mm diameter using the lost-wax casting process. 30 discs per material were produced, 10 discs per material were cast and then left to bench cool (glass state), 10 discs per material were given a heat treatment at 765, 679 and 629 degrees C for 1h and then heat treated at 890, 860 and 824 degrees C for the HG 1-3, respectively, for another hour to form apatite. Ten discs per material were heat treated as previously described (765, 679 and 629 degrees C) then heat treated for 1h at 1022, 987 and 892 degrees C for the HG 1-3, respectively, to form apatite-mullite. The heat treatment temperatures were obtained from differential thermal analysis data. A lithium disilicate glass-ceramic was used as a control. Biaxial flexural strength (BFS) was determined using a LIoyd 2000R tester. RESULTS: Data showed that the BFS increased as the fluoride content increased, and the apatite-mullite samples had significantly higher BFS values than the as cast glass or apatite samples (p<0.05), with the control having significantly higher BFS values than all the HG glass-ceramic materials for every condition (p<0.05). The fictive glass transition temperature (Tg) was observed to drop with increasing fluoride content. SIGNIFICANCE: Increasing the CaF2 content increased the BFS and decreased the Tg of the glass-ceramic materials tested.

Aluminum Silicates↗

PubMed1996

A prospective clinical evaluation of the longevity of resorbable sutures in oral mucosa.

A prospective, randomised and controlled clinical investigation was undertaken to evaluate the longevity of resorbable sutures in the oral environment. The sutures investigated were gut, polyglycolic acid and polyglactin 910, were of standard gauge and needle type, and were placed using a standard technique by trained clinicians. The sutures were monitored following apical surgery in 55 patients (110 sutures) and the median survival values were: gut - 4 days, polyglycolic acid - 15 days, polyglactin 910 - 28 days. These differences were highly statistically significant. A postal survey of 30 randomly selected oral and maxillofacial surgeons reveal most prefer to use resorbable sutures, with softgut the most popular choice. Most would like an ideal resorbable suture to last 5 to 14 days and in this respect none of the materials tested appears satisfactory.

Absorption↗

PubMed1993

Influence of dentinal fluid and stress on marginal adaptation of resin composites.

The influence of dentinal fluid and of a number of stress procedures on the quality of the margins of class V restorations located in both enamel and dentin was quantitatively assessed in vitro with the aid of a scanning electron microscope. The materials tested were GLUMA 2000 experimental, Prisma Universal Bond 3, and Syntac, together with the fine hybrid composites supplied by the respective manufacturers (Pekafill, AP.H, and Tetric). All materials achieved over 95% of "continuous margin" in enamel before and after stressing. In dentin, the initial values, with as well as without dentinal fluid simulation, were situated between 93.2 and 98.2%. With GLUMA 2000 experimental after stressing, a "continuous margin" occurred in only 50.2%, but with Prisma Universal Bond 3 and Syntac, the value was 79.0%. The influence of dentinal fluid simulation was dependent on the dentinal adhesive used. The effects of the various stress procedures were not significantly different.

Body Fluids↗

PubMedDate not supplied

The effect of polishing on surface roughness of tissue conditioners.

PURPOSE: Surface roughness can affect microbial colonization of long-term denture liners, alloys, and denture acrylic. The purpose of the present study was to examine the effect of finishing and polishing procedures on surface roughness of 4 temporary resilient denture liners (tissue conditioners). MATERIALS AND METHODS: Mean surface roughness was measured for 4 materials (Lynal, Visco-gel, Coe-Soft, and Functional Impression Tissue Toner [FITT]) finished in 4 ways: unfinished (control); polished; reduced, unpolished; and reduced, polished. Samples were allowed to polymerize at 37 degrees C for 24 hours, and the surface roughness was measured using a Mitutoyo Surftest 212. RESULTS: Mean surface roughness ranged from 1.8 +/- 0.8 microns for polished Lynal to 7.8 +/- 1.1 microns for reduced, unpolished FITT. All polished samples were smoother than unpolished samples (including controls), whether or not the samples were reduced with a bur. CONCLUSION: Polished samples of tissue conditioning material had lower mean surface roughness measurements than control or reduced, unpolished samples at the 95% level of confidence. There was no difference in mean surface roughness measurements of control samples and unpolished samples reduced with a bur at the 95% level of confidence. Mean surface roughness differed significantly between the materials tested.

Acrylic Resins↗

PubMedDate not supplied

In vitro evaluation of pH changes induced by calcium hydroxide liners.

OBJECTIVES: Since the highly alkaline pH of calcium hydroxide is considered by many to be responsible for its biologic activity, the possible variations of pH induced by the different calcium hydroxide liners are accepted as a major concern. The aim of the present study was to determine the pH changes of five different calcium hydroxide liners and variations of pH levels at different time intervals. METHOD AND MATERIALS: The materials tested were Dycal, Life, Calic, Dycal VLC, and Calcident 450. Samples were prepared according to manufacturer instructions and by using plastic molds; five standard samples from each material were prepared. The samples were then placed in separate vials, containing 10 mL deionized water (pH 7.0), and stored at room temperature (200C). The pH measurements were taken 1 hour, 24 hours, 3 days, and 7 days after mixing. The pH variations of each material at the given time intervals were recorded, and the means were calculated. RESULTS: Statistical analysis showed significantly high differences between the mean pH values induced by each material at all time intervals. The highest value for the first-hour measurement was for Dycal VLC, and the highest values for the other time intervals were for Calcident 450. The pH values of the materials exhibited statistically significant differences among all the time intervals. CONCLUSION: All materials changed the pH of deionized water toward alkaline.

Calcium Hydroxide↗

PubMed1989

[Risks and benefits of polymeric inlays].

Class I inlays were produced according to the direct method using six white light-cured composite, one inlay material and one veneer acrylic. They were subjected to extraoral heat treatment at 125 degrees C for 150 s. In addition, heat-cured inlays were produced according to the indirect method. In all cases heat treatment resulted in a considerable increase in transverse strength and modulus of elasticity as well as a material specific decrease in the specimen volume between 0.15% and 1.05%, and it facilitated finishing. With one exception heat-treated and heat-cured inlays could be inserted without open margins; even 5000 threshold load cycles of 500 N failed to cause marginal defects. However, these inlays also had no open margins when inserted without previous heat treatment. While in the case of four materials this resulted in no measurable reduction in fatigue strength, it reduced this value to a maximum of 100 N in three materials. Swelling of the polymeric inlays due to high water absorption resulted in extensive enamel cracks with one of the materials tested.

Acrylic Resins↗

PubMed2005

Fatigue testing of enamel bonds with self-etch and total-etch adhesive systems.

OBJECTIVE: Etching of enamel by self-etching adhesive systems is not as pronounced as with phosphoric acid employed with most total-etch adhesive systems. This may result in differences in the effectiveness of the bonds for the two types of systems. The aim of this study was to compare two such systems by bond strength and fatigue testing. MATERIALS AND METHODS: Shear bond strengths for Single Bond (SB) and Adper Prompt-L-Pop (PLP) were obtained on bovine enamel surfaces. Fatigue measurements were made with the same test fixtures using cyclical loading at 2 Hz for a maximum of 10(5) cycles or until the bond failed. Four selected loads between 40 and 70% of the shear bond strength were tested for each adhesive and the number of cycles to failure was recorded. S-N curves were constructed from the data and fatigue stress limits were determined. The Mann-Whitney U-test and t-tests were used for statistical comparisons of the results. SEM analysis of resin tag formation into enamel surfaces was carried out. RESULTS: A significantly greater bond strength was found for SB (25.3 MPa) than for PLP (19.2). Sustainable stresses after 10(5) load cycles were substantially lower than the corresponding shear bond strengths and fatigue limits were found to be 8.4 MPa for PLP and 14.6 MPa for SB. The ratio of fatigue limit to bond strength was less for PLP (44%) than for SB (57%). Resin tag penetration into enamel was substantially less for PLP than for SB. SIGNIFICANCE: Fatigue testing in conjunction with bond strength testing can provide a better means for assessing the performance of adhesive systems used for bonding to enamel.

Acid Etching, Dental↗

PubMed1990

[Cytotoxic effects of restorative materials on early passage cultured cells derived from human gingiva (in vitro)].

This study evaluated the cytotoxic effects of three common restorative materials on early passage cultured cells derived from human gingiva (HG cells). Other early passage cultured cells derived from human dental pulp tissues (HP cells) and L cells established obtained from mouse subcutaneous tissues, were also examined. Cytotoxicity was assessed according to the uptake of neutral red and dye exclusion with nigrosin. The cytotoxicity was in the order of glass ionomer cement (highest), light cured composite resin and dental amalgam. HG cells were the least sensitive to the materials tested. Both filtration of extracts and addition of serum into the extract affected the cytotoxicity. Glass ionomer cement increased the acidity of the extract, but the two other materials did not. Dissolution of metal ions, aluminium, tin, copper, mercury and zinc occurred from the materials. The extract of the composite resin had a different absorbance. This study disclosed differences in the cellular reaction to the restorative materials. Thus, utilization of early passage cultured cells is necessary for biological evaluation of the dental materials in vitro.

Animals↗

PubMed2004

Cyclic testing of arthroscopic knot security.

PURPOSE: Arthroscopic soft tissue repairs undergo many cycles of tensioning and relaxation before significant tissue healing occurs, and knot security under cyclic loads is essential for good results after these repairs. The current study was designed to assess the security of arthroscopic knots under stepwise cyclic loading. TYPE OF STUDY: In vitro materials testing. METHODS: Three types of arthroscopic knots--sliding knots with loop reversal but without post switching (S=SxSxSxS), modified Revo knots with loop reversal and post switching twice (S=S//xSxS//xS), and the SMC knot backed by 2 throws with loop reversal and post switching (S//xS//xS)--were compared with five-throw square knots tied with an open technique. All knots were tied with No. 2 braided nonabsorbable suture around 2 aluminum rods. They were pretensioned to 10 N, and initial displacement was recorded. The knots were then cycled at 1 Hz for 9 different load levels, with 250 cycles at each level, followed by a 30-second rest period to allow recording of permanent laxity of the suture loop. The first step of cyclic loading was from 10 to 40 N, and the upper limit was increased by 10 N for each successive load level. Any knot surviving cyclical loading was pulled to failure. RESULTS: Ten knots of each configuration were tested. All 3 arthroscopic slip knots showed significantly less initial displacement compared with the square knots (0.26 mm compared with 0.45 mm, respectively, P <.005). All square and modified Revo knots reached the ninth (120 N) loading level, whereas only 6 of the SMC knots and 3 of the arthroscopic knots without post switching reached the ninth loading level. Furthermore, all square and modified Revo knots failed by suture breakage at the knot, whereas 8 arthroscopic knots without post switching and 5 SMC knots failed by slipping. In fact, 3 of the arthroscopic knots without post switching and 1 of the SMC knots failed during the initial cyclic loading from 10 to 40 N. The modified Revo knots reached 3 mm of permanent laxity at significantly higher load levels than the square knots tied with an open technique (96 N v 78 N, P <.005). The SMC knots reached 3 mm of permanent laxity at statistically similar load levels compared with the square knots, but showed considerably more variability. None of the arthroscopic knots without post switching survived the entire cyclic-loading protocol. Four square, 5 modified Revo, and 5 SMC knots that survived cyclic loading reached ultimate failure at statistically similar load levels (157, 156, and 152 N, respectively). CONCLUSIONS: Post switching and loop reversal are key to arthroscopic knot security. Arthroscopic slip knots may be tighter at the time of knot construction than openly hand-tied square knots. The modified Revo knots appear to be as durable as openly hand-tied square knots regarding resistance to loosening under cyclic loading conditions. Security of arthroscopic knots without post switching is quite variable, making these knots less reliable. The SMC knot also proved not to be as reliable as the square and modified Revo knots when cyclically tested.

Arthroscopy↗

PubMed2004

Flexural strength of dental composite restoratives: comparison of biaxial and three-point bending test.

This study compared two test methods used to evaluate the flexural strength of resin-based dental composites. The two test methods evaluated were the three-point bending test4 and the biaxial flexural test. Materials used in this investigation were from the same manufacturer (3M ESPE) and included microfill (A110), minifill (Z100 and Filtek Z250), polyacid modified (F2000), and flowable [Filtek Flowable (FF)] composites. Flexural strength was determined with the use of both test methods after 1 week of conditioning in water at 37 degrees C. Data were analyzed with the use of an ANOVA/Scheffe test and an independent-samples t test at significance level 0.05. Mean flexural strength (n = 7) ranged from 66.61 to 147.21 and 67.27 to 182.81 MPa for three-point bending and ball-on-three-ball biaxial test methods, respectively. In both test methods, Z100 was significantly stronger than all other composites evaluated. In the three-point bending test, flexural strength of Z250 was significantly higher than A110, F2000 and FF, and FF was significantly stronger than A110 and F2000. The biaxial test method arrived at the same conclusions except that there was no significant difference between Z250 and FF. Pearson's correlation revealed a significantly (p < 0.01) positive and good correlation (R2 = 0.72) in flexural strength between the two test methods. Although the biaxial test has the advantage of utilizing small specimens, the low reproducibility of this test method does not support the proposition that it is a more reliable test method when compared to the ISO three-point bending test.

Algorithms↗

PubMed1997

Effect of irradiation time on tensile properties of stiffness and strength of composites.

PURPOSE: We compared the effect of irradiation time on the diametral tensile strength and stiffness of three visible light-cured composites. The sensitivity of the two mechanical properties to differentiate between the materials was also investigated. MATERIAL AND METHODS: Cylindrical specimens of three composites were cured for 20, 40, 80, and 120 seconds (n = 10) and loaded up to failure in a diametral tensile strength test. Stiffness and diametral tensile strength values were recorded. RESULTS: Irradiation time significantly influenced diametral tensile strength (p = 0.0017) and stiffness (p = 0.0002). With the same irradiation times the three tested materials demonstrated no significant difference when diametral tensile strength was studied (p = 0.31). However, stiffness values did show a significant difference (p = 0.0002). CONCLUSIONS: This study found that stiffness is more sensitive in disclosing differences in tensile properties between the materials than diametral tensile strength.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1996

A comparison of the dimensional stability of three inlay pattern materials.

This study investigates the dimensional stability of 3 inlay pattern materials stored for different periods of time. Three indices were formulated to assess changes. These were: deviation and area change which both indicate a proportional contraction or expansion, and ratio which shows distortion. A brass master model was constructed to represent a cavity with 4 intersecting reference lines on the base, which were transferred to the bottom of the inlay pattern. The materials tested were Kerr's Type II blue inlay casting wax, Duralay (an autopolymerizing acrylic resin) and Modilux (a light-curing resin). Ten inlay patterns were prepared from each material in the brass master model cavity. Measurements of pre-determined points on the reference lines were recorded with a reflex microscope immediately after removal of the inlay patterns and then repeated at intervals of 1 hour and 24 hours. These measurements were compared to corresponding measurements on the brass master model and then converted into the three indices previously mentioned. Analysis of data showed that none of the materials distorted and that all the patterns underwent a proportional contraction, with wax contracting more than Duralay and Modilux. Significantly more contraction occurred at 24 hours than between onset (0 hour) and 1 hour. As contraction only occurred after 1 hour and wax contracted the most, it is recommended that Duralay or Modilux be used as the pattern material, especially if a delay in investing is anticipated.

Analysis of Variance↗