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 883 records · Page 49Linked to original sources

PubMed1996

In vivo comparison of hemocompatibility of materials used in mechanical heart valves.

BACKGROUND AND AIMS OF THE STUDY: Most studies of mechanical heart valve prostheses in recent years have focused on the hydrodynamic and clinical performance of different valve designs. Little attention has been paid to the hemocompatibility (thrombogenicity) of materials used in the prostheses. METHODS: In the present study, three materials currently used in mechanical heart valves, titanium, cobalt-chromium alloy (Haynes 25) and pyrolytic carbon (Pyrolite), together with a surface-modified (methylated) titanium, were evaluated and compared for their hemocompatibility in a sheep model. The test materials in the form of discs were glued to plastic buttons and implanted into the intrathoracic venae cavae of anesthetized sheep. Four different materials were tested simultaneously in each animal: two in the superior and two in the inferior vena cava. Eight animals were used. After two hours of exposure to flowing blood, the discs were explanted and evaluated for their hemocompatibility using close-up photography and scanning electron microscopy (SEM). Thrombus formation and blood cell adhesion were studied quantitatively. RESULTS: The results showed that there was significantly more thrombus on pyrolytic carbon and methylated titanium than on titanium and cobalt-chromium (p < 0.05). More leukocytes adhered on pyrolytic carbon and cobalt-chromium than on titanium and methylated titanium (p < 0.05). CONCLUSION: The results indicate that titanium and cobalt-chromium under the present condition were more hemocompatible than pyrolytic carbon. The clinical significance of the finding remains to be investigated.

Adhesiveness↗

PubMed1995

Biological testing of dental materials: development of national and international standards.

Testing of dental materials helps to ensure that they are of satisfactory quality. Most standardized testing programs have focused on the physical, chemical, and mechanical properties of the materials, and started at the National Bureau of Standards, USA, in 1919. The need for biological evaluation of dental materials became evident after some material-related adverse incidents. The first document concerning standardized testing of the biological properties of dental materials was published by the American Dental Association in 1972. During the last twenty-five years, increased attention has been focused on the evaluation of biological properties by standardized testing. The development of standards concerning biological testing of dental materials since 1972 at the national and international level is described.

American Dental Association↗

PubMed2004

Diametral tensile strength of a resin composite core with nonmetallic prefabricated posts: an in vitro study.

STATEMENT OF PROBLEM: A number of prefabricated nonmetallic posts are currently available for use in conjunction with resin composite cores before fabrication of crowns for endodontically treated teeth. Information is needed regarding the strength of the composite and the nature of attachment between its components. PURPOSE: The aim of this study was to determine the influence of different types of posts on the fracture resistance of a resin composite core material using the diametral tensile strength (DTS) test. MATERIAL AND METHODS: Cylindrical specimens, 6 mm in diameter and 3 mm high, were prepared from resin composite (Tetric Ceram) and a group of prefabricated posts (n=10) as follows: resin composite only (control); Vectrispost (VTS); FiberKor (FKR); AEstheti-Plus post (ATP); Light-Post (LTP); Dentorama post (DRM), and Para-Post (PRP) as a second control. Specimens were stored for 7 days in water at 37 degrees C and then subjected to DTS test in a universal testing machine until failure occurred and load was recorded (N). Mean values and SD for DTS values (MPA) were calculated, and data were analyzed statistically with 1-way analysis of variance, followed by the Tukey test (alpha=.05). Representative specimens from each group were examined with SEM to determine nature of failure. RESULTS: Mean values (SD) in MPa for DTS were as follow: CONTROL GROUP: 49.64 (3.36); VTS: 29.77 (3.36); FKR: 31.9 (2.39); ATP: 28.92 (2.2); LTP: 34.26 (3.37); DRM: 33.45 (2.46), and PRP: 27.90 (2.40). Analysis of variance indicated significant differences among the groups (P<.05). SEM examination indicated that for PRP failure was adhesive in nature, whereas with all nonmetallic posts, cohesive failure was more predominant. CONCLUSION: The use of posts did not result in reinforcement of resin composite core when diametral tensile force was applied. When used with the core material, LTP, DRM, and FKR resulted in the highest DTS values, whereas PRP resulted in the lowest values.

Analysis of Variance↗

PubMed1988

[Clinical testing of drainage tubes following abdominal surgery interventions].

The properties of soft rubber, silicone latex, and silicone rubber were investigated by material testing and clinical observation with regard to suitability for use in drainage tubes. Silicone latex proved to be the softest of the three materials but was also characterised by very low elongation values, which caused problems in tube withdrawal. Soft rubber tubes should be used only for short periods in indwelling time for their inferior biocompatibility and trend to lumen incrustation. Silicone rubber, while somewhat harder than silicone latex, was characterised by excellent biocompatibility and safe drainage functionality.

Biocompatible Materials↗

PubMed2006

Comparison of biomechanical properties of alloderm and enduragen as static facial sling biomaterials.

BACKGROUND: Static slings are one of the most commonly used surgical rehabilitation methods in the management of chronic facial paralysis. Acellular human cadaveric dermis (Alloderm; Life Cell Corp., Branchburg, NJ) is used for this purpose; however, it has variable stretching properties that may necessitate additional "tuning-up" procedure(s). Acellular porcine dermis (Enduragen; Tissue Sciences Laboratories, plc., Aldershot, U.K.) was recently introduced as a biologic implant and it is compositionally similar to Alloderm. However, no data currently exist regarding its biomechanical properties and potential use as an alternative implant to Alloderm in static facial sling procedures. OBJECTIVE: The objective of this study was to compare the biomechanical properties of Alloderm and Enduragen for static facial sling procedures in the management of the paralytic face. STUDY DESIGN: This study consisted of an in vitro prospective study in an academic medical research setting. METHODS: Same size and thickness Alloderm and Enduragen samples were tested with MTS 858 Bionix materials test system for load-to-failure, displacement under increasing and constant stress, and stiffness. RESULTS: Enduragen showed significantly less elongation under increasing stress and at the beginning of constant stress. Load-to-failure and stiffness were significantly higher in Alloderm; however, both biomaterials have adequate stiffness and load-to-failure for a static facial sling procedure. CONCLUSIONS: Enduragen may serve as another potential static facial sling material, because it stretches significantly less than Alloderm under stress. Clinical experience is needed with Enduragen to determine its potential use as a static facial sling material.

Biocompatible Materials↗

PubMed2005

Intrinsic constraint of unlinked total elbow replacements--the ulnotrochlear joint.

BACKGROUND: Many unlinked total elbow replacement designs with radically differing articular geometries exist, suggesting that there is no consensus regarding an optimal design. A feature inherent to the articular design is the intrinsic constraint afforded to the joint by the implant. Our aim was to compare the intrinsic constraints of unlinked implants with that of the normal ulnotrochlear joint. METHODS: We tested twelve cadaveric ulnotrochlear joints with a custom-made multiple-axis materials testing machine. With compressive loads ranging from 10 to 100 N, the joints were moved in either valgus or varus directions at 90 degrees of flexion. The ulnotrochlear components from a single example of five medium-sized unlinked elbow replacements (Ewald, Kudo, Pritchard ERS, Sorbie-Questor, and Souter-Strathclyde) were also tested. The recorded measurements included the torques and forces, angular displacement, and axial displacement of the humerus relative to the ulna. RESULTS: In general, the peak torque and the constraint ratio significantly increased with increasing compressive load for the implants as well as for the normal elbow. In valgus displacement, the Souter-Strathclyde implant had the highest and the Sorbie-Questor had the smallest peak torque and the Souter-Strathclyde had the highest and the Ewald had the smallest constraint ratio. In varus displacement, the Kudo had the highest and the Ewald had the smallest peak torque and constraint ratio. CONCLUSIONS: The constraint ratio is a characteristic that is useful for describing elbow joint behavior and for comparing the behavior of implants with that of the human elbow. Of the unlinked implants tested, the Souter-Strathclyde and Kudo prostheses most closely approximated the behavior of the human elbow joint. Implants that resemble the human elbow in appearance do not replicate normal behavior consistently, whereas other implants that do not resemble the human elbow closely do not deviate markedly from human behavior. Thus, much basic information about elbow form and function is needed to improve the performance of total elbow prostheses.

Aged↗

PubMed1988

A comparative biomechanical study of spinal fixation using the combination spinal rod-plate and transpedicular screw fixation system.

A biomechanical study was performed comparing the stiffness and stability of the three-level combination spinal rod-plate and transpedicular screw (CSRP-TPS) fixation system with those of three anterior stabilization constructs that spanned three vertebral levels: iliac strut grafting, polymethylmethacrylate and anterior Harrington rod instrumentation (technique of Siegal et al.), and the Kaneda anterior device. The CSRP-TPS fixation system was also compared with five posterior instrumentation systems that spanned five vertebral levels: Harrington distraction rod instrumentation, segmentally wired Luque rectangular instrumentation, Cotrel-Dubousset transpedicular instrumentation. Steffee transpedicular screws and plates, and R. Roy-Camille plates under conditions of single-level instability. The relative stability of each instrumentation system was compared by mounting the fixation systems on calf spine segments containing five motion segments destabilized by complete L3 anterior corpectomies and L2-L3 and L3-L4 anterior diskectomies to simulate the two-column instability found clinically in spine fractures. Mechanical nondestructive cyclical testing in rotation, axial compression, and flexion was performed on 12 spines. All biomechanical tests were performed on a biaxial servo-controlled MTS 858 Bionix hydraulic materials testing device with a biaxial load cell. Intervertebral displacements between L2 and L4 were continuously recorded utilizing an extensometer with the knife edges placed directly adjacent to the L3 corpectomy defect during testing. This biomechanical study showed that CSRP-TPS instrumentation spanning three vertebral levels could restore the torsional, compressive, and flexural rigidity of the destabilized calf spines to that of the intact calf spines and provided more in vitro stability than either the traditional five-level Harrington distraction rod or the segmentally wired Luque rectangular instrumentation. The greatest torsional rigidity occurred with the five-level Cotrel-Dubousset instrumentation, the five-level Steffee plate and screw system, and the three-level Kaneda anterior device. In axial compression and flexural testing, the three-level CSRP-TPS system provided fixation comparable with the five-level Cotrel-Dubousset instrumentation, the five-level Steffee transpedicular screw and plate system, the five-level R. Roy-Camille plate and screw system, and the three-level Kaneda anterior device. Satisfactory levels of rigidity can be restored by three-level CSRP-TPS instrumentation under conditions of single-level instability in unstable thoracolumbar and lumbar spine fractures.

Analysis of Variance↗

PubMed1996

Tensile properties of the interosseous membrane of the human forearm.

The interosseous membrane is a structure deep in the forearm that joins the radius and the ulna. It is made up of membranous and ligamentous regions. Two main ligamentous structures have been described: a prominent central fiber group, the "central band," and a smaller proximal fibrous band, the "oblique cord." Many authors believe that the central band plays a biomechanical role in the normal and fractured forearm and that it may function much like a ligament. The objective of this study was to determine the tensile properties of the central band. Eighteen fresh frozen forearms from cadavers (45-70 years of age, both sexes) were used. A fiber bundle of the central band was subjected to a uniaxial tensile test to failure in a materials testing machine, and its tensile properties were calculated. Stiffness, ultimate load, and energy absorbed to failure were expressed as a function of specimen width. The central band structure had a stiffness of 13.1 +/- 3.0 N/mm per mm width and an ultimate load of 56.6 +/- 15.1 N per mm width (mean +/- SD). The tissue of the central band displayed a modulus of 608.1 +/- 160.2 MPa, ultimate tensile strength of 45.1 +/- 10.3 MPa, and strain at failure of 9.0 +/- 2.0%. This study demonstrated that the central band is comprised of strong tissue. The material properties of the central band compare with those of patellar tendon: modulus is 120% and ultimate tensile strength is 84% that of patellar tendon. As a structure, the interosseous membrane is stiff and capable of bearing high loads. Although load distribution across the central band is unknown, a 1.7 cm wide, evenly loaded homogenous portion of the central band would possess a stiffness comparable with that of the anterior cruciate ligament. The results of this study provide a basis for future analyses of radioulnar stability and load transfer.

Aged↗

PubMed2006

[In vitro cytotoxicity of different self-etching dental adhesive systems].

The study evaluated the cytotoxicity of five self-etching dentin adhesive systems applied on dentin specimens of different thicknesses. The test materials (A: Adper Prompt-L-Pop, B: Xeno II, C: Clearfil SE Bond, D: One up Bond F, E: Resulcin Aqua Prime & Monobond) and a positive control (35% H202) were applied on 1.0, 1.5 and 2.5 mm thick bovine dentin specimens (each subgroup n = 5) in a dentin barrier test device. The experiments were performed with perfusion (2 ml/h) of the pulpal part of the chamber. The eluates were obtained before (baseline) and 15, 30, 45, 60 and 120 min after application of the adhesives and pipetted onto L-929 fibroblasts. Cytotoxicity of the materials was determined in relation to the baseline value using the MTT assay and statistical analysis was performed by ANOVA. After 15 min perfusion, test materials B-E applied on 1.0 mm and B and E applied on 1.5 mm dentin specimens exhibited cytotoxic potential. However, after 30 min perfusion none of the adhesives showed any toxicity. Cytotoxicity decreased with increasing thickness of the dentin slices and was lower for Adper Prompt-L-Pop compared to adhesives B-E. Self-etching adhesive systems might exhibit cytotoxic potential when applied on dentin of less than 1.5 mm thickness. However, cytotoxicity of the materials decreased with increasing dentin thickness and increasing duration of perfusion.

Acid Etching, Dental↗

PubMed1991

In vitro methods for the assessment of primary local effects of topically applied preparations.

Three 'alternative' methods for the screening of the primary irritation potentials of topically applied preparations and raw materials are presented as a test battery and their in vitro endpoints are compared with in vivo data. The first method is the intermediate test on the chorioallantoic membrane of hens' fertilized eggs, which is generally proposed for the prediction of the irritation potential of chemicals. Relevant test parameters, such as the time-dependent appearance of hemorrhages, vascular lysis and coagulation, are used to classify the test substances. Secondly, cytotoxicity tests with Balb/c 3T3 fibroblasts are used to characterize the influence of test materials on cellular homeostasis and viability, which is quantified by the dose-dependent uptake of Neutral red. As a second parameter changes in the cellular protein level can be easily measured by subsequent staining with Kenacid blue. Finally, the third approach to in vitro evaluation is presented in the form of the red blood cell assay, a rapid photometric assay which permits distinguishing basically between damage to the membrane and to proteins as endpoints which correlate with lesions observed on the conjunctiva, iris and cornea in the eye and the acute inflammatory responses evoked during epicutaneous irritancy testing. Changes in the optical behavior of oxyhemoglobin are used as the inherent indicator for monitoring both endpoints and their interrelations. These methods are proposed and can be used advantageously for testing newly developed topical preparations and their ingredients in view of their local irritation potential without further use of animal testing. Moreover, they can also be used for screening chemicals.

Administration, Topical↗

PubMed1992

Tissue responses to Hydron, assessed by intramuscular implantation.

Freshly mixed polymerized Hydron root canal filling material, fully set AH26 and Teflon were implanted in the quadriceps muscle of guinea pigs and assessed histologically at 2 days, 1, 2, 3, 12 and 26 weeks after implantation. All materials were characterized by peri-implant fibrous connective tissue capsule formation. Von Kossa-positive calcific material was observed at the implant-tissue interface of Hydron implants. The amount of apparently calcified material increased with time. Inflammation was not a prominent tissue response for any of the test materials, nor was a foreign body giant cell response.

Animals↗

PubMed1991

Effects of gamma radiation on the in vitro wear of composite restorative materials.

The effects of gamma radiation at therapeutic dosage levels on the wear of three anterior (two light-cured and one autocured) composites and a light-cured posterior composite were studied in vitro. Specimens were subjected to successive sets of 100 abrades to a maximum of 500 abrades on a reciprocating arm abrader, with the dimensional change being recorded between the sets of abrades. The data showed that there were no significant effects on the wear rates of any of the materials tested. The rate of height loss was similar for the two hybrid composites tested (P less than 0.05), as was that for the microfilled and conventional material (P less than 0.05). There was, however, a significant difference (P greater than 0.001) in the wear behaviour between the two groups.

Acrylic Resins↗

PubMed2001

An ex vivo biomechanical evaluation of a hydroxyapatite cement for use with vertebroplasty.

STUDY DESIGN: Comparative ex vivo biomechanical study. OBJECTIVE: To determine the strength and stiffness of osteoporotic vertebral bodies subjected to compression fractures and stabilized via bipedicular injections of the following: 1) Simplex P (Stryker-Howmedica-Osteonics, Rutherford, NJ), 2) Simplex P formulated consistent with the practice of vertebroplasty (F2), or 3) BoneSource (Stryker-Howmedica-Osteonics). SUMMARY OF BACKGROUND DATA: Little is known about the mechanical stabilization afforded by new materials proposed for use with vertebroplasty. METHODS: Vertebral bodies (T8-T10 and L2-L4) from each of 10 fresh spines were harvested from female cadavers (81 +/- 12 years), screened for bone density (t score, -3.8 +/- 1.1; bone mineral density, 0.75 +/- 15 g/cm2), disarticulated, and compressed to determine initial strength and stiffness. The fractured vertebral bodies were stabilized via bipedicular injections of 4 mL (thoracic) or 6 mL (lumbar) and then recrushed. RESULTS: Vertebral bodies repaired with Simplex P resulted in significantly greater strength (P < 0.05) relative to their prefracture states, those repaired with BoneSource resulted in the restoration of initial strength for both the thoracic and lumbar level, and those repaired with F2 resulted in significantly greater strength (P < 0.05) in the thoracic region and restoration of strength in the lumbar region. All cement treatments resulted in significantly less stiffness compared with initial values. CONCLUSIONS: All three materials tested restored or increased vertebral body strength, but none restored stiffness. Both new materials show promise for use in percutaneous vertebroplasty, but they need clinical evaluation.

Aged↗

PubMed1993

Thermal diffusivity of glass ionomer cement systems.

The thermal diffusivity has been measured for 10 glass ionomer and resin-based materials: three conventional (water-hardened) glass ionomer cements, two silver-reinforced glass ionomers, an experimental stainless steel-reinforced glass ionomer, three visible light-cured (VLC) glass ionomer-resin hybrid materials, and a VLC resin-based product developed for the same clinical uses as the hybrid materials. Cube-shaped specimens, c. 10 x 10 x 10 mm, initially at room temperature were immersed in mercury surrounded by an ice-water bath. From the experimental cooling curve a semi-log plot of relative temperature decrease vs. time yielded a straight line whose slope is proportional to the thermal diffusivity. The values ranged from 1.74-5.16 x 10(-3) cm2 s-1, and all of the materials tested would have adequate insulating properties provided normal clinical thickness levels for lining materials are maintained. It was found that the thermal diffusivities for the three metal-reinforced glass ionomers, where composition information is available, do not follow a rule of mixtures applied to the individual components.

Cermet Cements↗

PubMed1998

A two-dimensional model of cyclic strain accumulation in ultra-high molecular weight polyethylene knee replacements.

As new methods of sterilization of the ultra-high molecular weight polyethylene (UHMWPE) component in knee replacements are introduced, reported incidents of delamination will decrease. The prediction of plastic strain accumulation and associated failure mechanisms will then become more important in knee replacement design. The finite element analysis reported in this paper aims to advance the modelling of strain accumulation in UHMWPE over repeated gait cycles and seeks to determine the effects of the knee replacement design variables of geometry and kinematics. Material testing was performed under cyclic and creep conditions to generate the elastic, viscoplastic material model that has been used in this time-dependent analysis. Non-conforming geometries were found to accumulate plastic strains at higher rates than conforming geometries. The anatomical motion known as rollback initially produced lower strain rates, but predictions of the long-term response indicated that designs which allow rollback may produce higher strains than static designs after only about a week of loading for a knee replacement patient.

Biocompatible Materials↗

PubMed1990

[Quantitative evaluation by measuring affected area for cytotoxicity of dental materials].

The agar overlay method was modified and employed in this study to quantitatively evaluate the cytotoxicity of dental materials. The area of fibroblasts affected by the release of toxic substances from tested materials was determined with an image analysis system in order to compare the relative cytotoxicity of amalgams and composite resins. The cytotoxicity of amalgams decreased by 50% or more with aging time. Zinc appeared to be the major contributor to the cytotoxicity of amalgams. The cytotoxicity of chemically cured composite resins was also reduced with hardening time. However, even after 24 hours, the cytotoxicity of all chemically cured composite resins was still apparent. The cytotoxicity of light cured composite resins was dramatically reduced after illumination with the light source. The cytotoxicity of both amalgams and composite resins was strongly dependent upon their hardening process, since aging and curing produced a more stable material which was less likely to release toxic substances into the culture medium. The technique developed in the present study for measuring the area of affected cells to quantitatively evaluate the cytotoxicity of dental materials is simple and reproducible.

Composite Resins↗

PubMed2001

An in-vitro study of the pressure-relieving properties of four wound dressings for foot ulcers.

This in-vitro study reports on a selection of mechanical tests on four wound dressings: Allevyn (Smith and Nephew), Biatain (Coloplast), Lyofoam (Seton Scholl) and Tielle (Johnson and Johnson). The aim of the study was to investigate these dressings in the laboratory by subjecting them to dry and wet compression tests, shearing tests and a cyclical test. As predicted, all dressings performed differently in the range of tests, with Lyofoam deforming the most when subjected to compression testing (5.6 mm). During wet compression, differences in the physical properties of all the materials tested were identified. During shearing testin, Allevyn and Tielle withstood the greatest shear deflection before failure, but Biatain withstood the greatest force before failing. During the cyclical testing, Lyofoam only reduced by 1% of its original thickness, while Biatain reduced by 30%. No one dressing performed better in all the tests. However, as an all-round 'pressure-relieving' dressing, Allevyn consistently outperformed the others in the study.

Bandages↗

PubMed1998

Experimental testing of a DEXA-derived curved beam model of the proximal femur.

This study was designed to test whether, using curved beam theory, a structural model of the proximal femur derived from two-dimensional dual energy x-ray absorptiometry could be used to predict femoral strength in an experimental simulation of a fall on the greater trochanter. A set of 22 fresh cadaveric femoral specimens were scanned with use of two-dimensional dual energy x-ray absorptiometry and then were tested to failure in a materials testing system, under three-point loading, with the ground impact vector aligned within the plane and along the bisector of the femoral neck-shaft angle. Failure locations generally corresponded to stress peak locations predicted by the curved beam model. Predicted failure loads correlated well with measured failure loads for femoral neck fractures (r=0.89; percent SE of estimate=23%) and some-what less well for intertrochanteric fractures (r=0.83; percent SE of estimate=29%). Overall predictions for failure load calculated from the maximum stress peak value over both locations corresponded to measured failure loads with an r value of 0.91 (percent SE of estimate=21%). This kind of structural approach to the analysis of data for hip bone mass has the potential to provide mechanistic interpretations of the statistical associations frequently shown between conventional bone mineral measures and either hip fracture risk in vivo or bone strength in vitro.

Absorptiometry, Photon↗