The Quantification of Physiologically Relevant Cross-Shear Wear Phenomena on Orthopaedic Bearing Materials Using the MAX-Shear Wear Testing System

2005 ◽  
Vol 127 (4) ◽  
pp. 740-749 ◽  
Author(s):  
Matthew R. Gevaert ◽  
Martine LaBerge ◽  
Jennifer M. Gordon ◽  
John D. DesJardins
Keyword(s):  
Wear Test ◽  
Quantitative Relationship ◽  
Surface Damage ◽  
Sem Analysis ◽  
Wear Testing ◽  
Testing System ◽  
Linear Wear ◽  
Shear Surface ◽  
Wear Damage

Background: The occurrence of multi-directional sliding motion between total knee replacement bearing surfaces is theorized to be a primary wear and failure mechanism of ultra-high molecular weight poly(ethylene) (UHMWPE). To better quantify the tribologic mechanisms of this cross-shear wear, the MAX-Shear wear-testing system was developed to evaluate candidate biomaterials under controlled conditions of cross-shear wear. Method of approach: A computer controlled traveling x-y stage under a 3 degree-of-freedom statically loaded pin is used to implement the complex multi-directional motion pathways observed during TKR wear simulation. A MHz collection of dynamic x-y friction was available on all six environmentally controlled stations. The functionality of this testing platform was proven in a 100,000 cycle, 11.6 MPa, wear test using 15.0 mm diameter polished stainless steel spheres against flat GUR4150 UHMWPE. A five-pointed star wear pattern was used to incorporate the physiologically relevant cross-shear sliding conditions of stop/start, 50mm∕s entraining velocity and five crossing angles of 72°. Using normalized volumetric reconstruction of the resulting surface damage, a direct quantitative relationship between linear and cross-shear surface damage intensity was obtained. Results: Cross-shear surface damage volume loss was found to be 2.94 (±0.88) times that associated with linear sliding under identical tribologic conditions. SEM analysis of linear wear damage showed consistent fibril orientation along the direction of sliding while cross-shear wear damage showed multi-directional fibril orientations and increased surface roughness. Significant increases in discrete crossing-point friction coefficients were recorded throughout testing. Conclusions: This scientific approach to quantifying the tribologic effects of cross-shear provides fundamental wear mechanism data that are critical in evaluating potential biomaterials for use as in vivo bearings. Relevant multi-axis, cross-shear wear testing is necessary to provide quantifiable measures of complex biomaterials wear phenomena.

The Effect of Motion Path on the Wear Rate of UHMWPE for Orthopaedic Implants

1999 ◽  
Author(s):  
Jeff A. Sprague ◽  
Willard L. Sauer
Keyword(s):  
Wear Rate ◽  
Wear Test ◽  
Axial Rotation ◽  
Wear Testing ◽  
Motion Path ◽  
Orthopaedic Implant ◽  
Wear Rates ◽  
Nonlinear Motion ◽  
Pin On Disk

Abstract The effect of adding a second axis of motion was investigated for pin-on-disk wear testing of ultra-high-molecular-weight polyethylene (UHMWPE) for orthopaedic implant applications. In addition to linear reciprocation of the UHMWPE or metal disk, axial rotation of the metal or UHMWPE pin was conducted. The added rotation reproduces the cross-shear on the UHMWPE surface that is generated in clinically relevant wear simulator tests and in vivo. The wear rates that result from the multi-axis pin-on-disk tests are significantly higher (one to two orders of magnitude) than those seen in the linear-only tests. This supports the findings of other researchers (Bragdon et al., 1996; McKellop, 1995; Walker et al., 1996; Wang et al. 1997) in that the application of nonlinear motion increases the wear of UHMWPE substantially. This is further validated by the comparison of a hip simulator wear test conducted with three axes of motion — rotation, flexion, and abduction — to a test conducted with two axes of motion — rotation and flexion. The absence of the abduction eliminated a significant degree of nonlinear motion (cross-shear) and, consequently, the wear rate was significantly lower than that seen in the test with abduction.

scholarly journals Effect of Polypropylene Modification by Impregnation with Oil on Its Wear and Friction Coefficient at Variable Load and Various Friction Rates

2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Paweł Sędłak ◽  
Beata Białobrzeska ◽  
Tomasz Stawicki ◽  
Piotr Kostencki
Keyword(s):  
Friction Coefficient ◽  
Sliding Friction ◽  
Wear Test ◽  
Friction Torque ◽  
Engine Oil ◽  
Wear Testing ◽  
Wear Behaviour ◽  
Linear Wear ◽  
Variable Load ◽  
Fatigue Wear

Laboratorial two-body wear testing was carried out in order to assess effects of polypropylene modification by impregnating it with oils on friction coefficient and wear in comparison to those parameters of unmodified polypropylene, Teflon, and polyamide during operation under conditions of sliding friction without lubrication. Wear behaviour of the tested specimens was investigated using ASTM G77-98 standard wear test equipment. Recording program made it possible to visualise and record the following parameters: rotational speed and load, linear wear, friction coefficient, temperature of the specimen, and ambient temperature. In addition, wear mechanisms of the analysed materials were determined with use of scanning electron microscopy. In the case of the remaining tested polymers, the most important mechanism of wear was adhesion (PP, PTFE, PA 6.6, and PA MoS2), microcutting (PTFE, PA 6.6, and PA MoS2), fatigue wear (PTFE), forming “roll-shaped particles” combined with plastic deformation (PA 6.6 and PA MoS2), and thermal wear (PP). Impregnation of polypropylene with engine oil, gear oil, or RME results in significant reduction of friction coefficient and thus of friction torque, in relation to not only unmodified polypropylene but also the examined polyamide and Teflon.

scholarly journals Friction and Wear Properties of Plasma Sprayed YSZ/Ni-Cr-Al Coated 6063-T6 Aluminum Alloy

2017 ◽  
Vol 17 (3) ◽  
pp. 168-174
Author(s):  
E. Erzi ◽  
D. Dispinar ◽  
S. Yilmaz
Keyword(s):  
Plasma Spray ◽  
Wear Test ◽  
Substrate Material ◽  
Sem Analysis ◽  
Spindle Speed ◽  
Wear Testing ◽  
Wear Properties ◽  
Spray Technique ◽  
Ysz Coating ◽  
Working Distance

AbstractIn this study T6 heat treated 6063 aluminum alloys were used as substrate material. In order to form a bond between the substrate and the main coating, all samples were coated with Ni-Cr-Al powders. 8 wt% Yttria Stabilized Zirconia powders (YSZ) were coated with plasma spray technique. Thickness of YSZ was 150 μm and bond coating was 36 m. XRD and SEM-EDS analyses were performed to characterize the coating layers. These YSZ coated and uncoated samples were subjected to wear testing under different spindle speed, loading and working distance. Wear test results were compared with the kinetic friction coefficients and weight loss values. Wear marks on YSZ coated and uncoated samples were investigated by SEM analysis. By coating with plasma spray technique, the wear resistance of Al alloys was increased without changing the friction coefficient. It was found that spindle speed had significant effect over the wear properties than the load applied. By YSZ coating, wear properties were increased 10 times.

Effect of Nano-ZrO2 Particulates on Wear Characteristics of Al7075 Metal Matrix Composite

2020 ◽  
Vol 12 (4) ◽  
Author(s):  
M.S. Prashanth Reddy ◽  
H.P Raju
Keyword(s):  
Weight Ratio ◽  
Wear Test ◽  
Stir Casting ◽  
Light Metal ◽  
Vital Role ◽  
Sem Analysis ◽  
Working Environment ◽  
Wear Testing ◽  
Dry Sliding Wear ◽  
Gas Supply

The demands in application-oriented areas lead to evolution of many light metal alloys which are capable of maintaining strength to weight ratio in an adequate manner. Out of all light metal aluminium alloys plays a vital role with the addition of hard ceramic particulates. In this view an attempt has been made to synthesis the aluminium nano composites with the addition of ZrO2 with a particle size of 80nm by using stir casting methodology by adopting specific working environment using argon gas supply. The addition of ceramic particles found uniform in distribution wise. The specimens are subjected to dry sliding wear test using Ducom wear test equipment which results in significant improvement in the resistance for wear. The composite was prepared for 0.75, 1.00, 1.25, 1.50, 1.75 and 2.00 wt.% addition of reinforcement. As % of addition of reinforcement the wear rate is gradually decreasing, the worn-out surfaces are subjected to SEM analysis after wear testing.

Formulation, Development and Characterization of Floating Beads of Diltiazem Hydrochloride

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Anamika Saxena Saxena ◽  
Santosh Kitawat ◽  
Kalpesh Gaur ◽  
Virendra Singh
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Drug Delivery Systems ◽  
Entrapment Efficiency ◽  
Repeated Administration ◽  
Alginate Beads ◽  
Delivery Systems ◽  
Sem Analysis ◽  
Formulation Development

The main goal of any drug delivery system is to achieve desired concentration of the drug in blood or tissue, which is therapeutically effective and nontoxic for a prolonged period. Various attempts have been made to develop gastroretentive delivery systems such as high density system, swelling, floating system. The recent developments of FDDS including the physiological and formulation variables affecting gastric retention, approaches to design single-unit and multiple-unit floating systems, and their classification and formulation aspects are covered in detail. Gastric emptying is a complex process and makes in vivo performance of the drug delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug-delivery systems for more than 12 hours. The floating or hydrodynamically controlled drug delivery systems are useful in such application. Background of the research: Diltiazem HCL (DTZ), has short biological half life of 3-4 h, requires rather high frequency of administration. Due to repeated administration there may be chances of patient incompliance and toxicity problems. Objective: The objective of study was to develop sustained release alginate beads of DTZ for reduction in dosing frequency, high bioavailability and better patient compliance. Methodology: Five formulations prepared by using different drug to polymer ratios, were evaluated for relevant parameters and compared. Alginate beads were prepared by ionotropic external gelation technique using CaCl2 as cross linking agent. Prepared beads were evaluated for % yield, entrapment efficiency, swelling index in 0.1N HCL, drug release study and SEM analysis. In order to improve %EE and drug release, LMP and sunflower oil were used as copolymers along with sodium alginate.

scholarly journals In vitro and in vivo evaluation of diamond-coated strips

2016 ◽  
Vol 87 (3) ◽  
pp. 455-459 ◽  
Author(s):  
Roberta Lione ◽  
Francesca Gazzani ◽  
Chiara Pavoni ◽  
Stefano Guarino ◽  
Vincenzo Tagliaferri ◽  
...  
Keyword(s):  
Contact Point ◽  
Sem Analysis ◽  
Tribological Test ◽  
In Vivo Evaluation ◽  
Wear Performance ◽  
Abrasive Grains ◽  
Abrasive Power ◽  
In Vivo Analysis

ABSTRACT Objective: To test in vitro and in vivo the wear performance of diamond-coated strips by means of tribological testing and scanning electronic microscope (SEM). Materials and Methods: To evaluate the in vitro wear performance, a tribological test was performed by a standard tribometer. The abrasive strips slid against stationary, freshly extracted premolars fixed in resin blocks, at a 2-newton load. At the end of the tribological test, the residual surface of the strip was observed by means of SEM analysis, which was performed every 50 meters until reaching 300 meters. For the in vivo analysis, the strip was used for 300 seconds, corresponding to 250 meters. Results: The strips presented a fenestrated structure characterized by diamond granules alternating with voids. After the first 50 meters, it was possible to observe tooth material deposited on the surface of the strips and a certain number of abrasive grains detached. The surface of the strip after 250 meters appeared smoother and therefore less effective in its abrasive power. After 300 seconds of in vivo utilization of the strip, it was possible to observe the detachment of diamond abrasive grains, the near absence of the grains and, therefore, loss of abrasive power. Conclusions: Under ideal conditions, after 5 minutes (300 meters) of use, the strip loses its abrasive capacity by about 60%. In vivo, a more rapid loss of abrasive power was observed due to the greater load applied by the clinician in forcing the strip into the contact point.

scholarly journals How affinity of the ELT-2 GATA factor binding to cis-acting regulatory sites controls Caenorhabditis elegans intestinal gene transcription

Development ◽  
2020 ◽  
Vol 147 (14) ◽  
pp. dev190330
Author(s):  
Brett R. Lancaster ◽  
James D. McGhee
Keyword(s):  
Transcription Factor ◽  
Caenorhabditis Elegans ◽  
Binding Affinity ◽  
Experimental System ◽  
Quantitative Relationship ◽  
Gata Factor ◽  
Unknown Parameters ◽  
Cis Acting ◽  
Complicated Model

ABSTRACTWe define a quantitative relationship between the affinity with which the intestine-specific GATA factor ELT-2 binds to cis-acting regulatory motifs and the resulting transcription of asp-1, a target gene representative of genes involved in Caenorhabditis elegans intestine differentiation. By establishing an experimental system that allows unknown parameters (e.g. the influence of chromatin) to effectively cancel out, we show that levels of asp-1 transcripts increase monotonically with increasing binding affinity of ELT-2 to variant promoter TGATAA sites. The shape of the response curve reveals that the product of the unbound ELT-2 concentration in vivo [i.e. (ELT-2free) or ELT-2 ‘activity’] and the largest ELT-XXTGATAAXX association constant (Kmax) lies between five and ten. We suggest that this (unitless) product [Kmax×(ELT-2free) or the equivalent product for any other transcription factor] provides an important quantitative descriptor of transcription-factor/regulatory-motif interaction in development, evolution and genetic disease. A more complicated model than simple binding affinity is necessary to explain the fact that ELT-2 appears to discriminate in vivo against equal-affinity binding sites that contain AGATAA instead of TGATAA.

scholarly journals Scanning electron microscopic examination of enamel surface after fixed orthodontic treatment: In-vivo study

2012 ◽  
Vol 140 (1-2) ◽  
pp. 22-28 ◽  
Author(s):  
Tijana Sessa ◽  
Jelena Civovic ◽  
Tina Pajevic ◽  
Jovana Juloski ◽  
Milos Beloica ◽  
...  
Keyword(s):  
Electron Microscopic Examination ◽  
Surface Damage ◽  
Multivariate Regression Analysis ◽  
Enamel Surface ◽  
Orthodontic Appliances ◽  
Electron Microscopic ◽  
Fixed Orthodontic Appliances ◽  
Tooth Surfaces ◽  
Scanning Electron

Introduction. Therapy with fixed orthodontic appliances starts with bracket bonding and ends with debonding of brackets, leaving enamel surface varied. Objective. The aim of this pilot study was to examine enamel surface before and after debonding of orthodontic brackets by the use of scanning electron microscopy (SEM). Methods. Epoxy replicas of four patients? premolars indicated for therapy with fixed orthodontic appliances were made and brackets were bonded to their teeth with a different adhesives (Enlight, No-mix, Fuji Ortho LC and Heliosit Orthodontic) (n=4). Two months later, brackets on premolars were debonded and amounts of adhesive left on the tooth surfaces and the bracket bases were evaluated with the adhesive remnant index (ARI). After resin removal, epoxy replicas were made and the surface of premolars was evaluated with the enamel surface index (ESI). All replicas of premolars (n=32) were prepared for SEM examination and compared under different magnifications. Tooth damage was estimated based on correlation between ARItooth and ESI. Results. Pearson?s ?2 test showed no significant differences between ARItooth and ARIbracket of four materials used. Nonparametric correlations showed significant differences between ARItooth and ARIbracket, ESI and ARItooth, and between ESI and ARIbracket. Increasing of ARItooth is followed with the descent of ARIbracket and the ascent of ESI. Multivariate regression analysis showed a significant correlation between ESI and ARItooth. Conclusion. Most bond failures took place at enamel-adhesive interface. ARItooth was a predictor to enamel surface damage. The type of material did not affect enamel surface damage.

Calcium absorption and intestinal calcium-binding protein: quantitative relationship.

1979 ◽  
Vol 236 (5) ◽  
pp. E556 ◽  
Author(s):  
J J Feher ◽  
R H Wasserman
Keyword(s):  
Vitamin D ◽  
Vitamin D3 ◽  
Calcium Binding ◽  
Calcium Absorption ◽  
Binding Protein ◽  
Quantitative Relationship ◽  
Calcium Binding Protein ◽  
Vitamin D Status ◽  
Loop Technique

The concentration of the vitamin D-induced calcium-binding protein (CaBP) and calcium absorption from the duodenum were investigated in chicks with an in vivo ligated-loop technique. The relation between CaBP and calcium absorption was dependent on a) source of vitamin D activity (either vitamin D3 or 1,25-dihydroxycholecalciferol); b) dosage of vitamin D3; c) time after administration of vitamin D3 to rachitic animals. To aid in the interpretation of these results, a phenomenological model was developed in which CaBP was viewed as being linearly related to a portion of calcium absorption. The model, when applied to the data, suggests that there is a "nonfunctional" pool of CaBP the size of which is determined by the vitamin D status of the animal. After correction for this nonfunctional pool, the proportionality between CaBP and calcium absorption is independent of the vitamin D status of the animal.

scholarly journals In VitroEvaluations andIn VivoToxicity and Efficacy Studies of MFM501 against MRSA

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Saiful Azmi Johari ◽  
Mastura Mohtar ◽  
Sharifah Aminah Syed Mohamad ◽  
Mohd Fazli Mohammat ◽  
Rohana Sahdan ◽  
...  
Keyword(s):  
Inhibitory Activity ◽  
Lethal Dose ◽  
Sem Analysis ◽  
Bacterial Colony ◽  
Dose Oral ◽  
Low Cytotoxicity ◽  
Time Kill ◽  
Oral Acute Toxicity ◽  
Peritonitis Model

Previously we have discovered a synthetically derived pyrrolidone alkaloid, MFM501, exhibiting good inhibitory activity against 53 MRSA and MSSA isolates with low cytotoxicity against three normal cell-lines with IC50values at >625 µg/ml. Time-kill assay, scanning electron microscopy (SEM) analysis,in vivooral acute toxicity test, and mice peritonitis model were carried out in this study. In the time-kill study, MFM501 showed a less than 3 log10decrease in bacterial colony concentration value (CFU/ml) which represented a bacteriostatic action while displaying a time-dependent inhibitory mechanism. Following that, SEM analysis suggested that MFM501 may exert its inhibitory activity via cytoplasmic membrane disruption. Moreover, MFM501 showed no toxicity effect on treated mice at an estimated median acute lethal dose (LD50) value of more than 300 mg/kg and less than 2000 mg/kg. For the efficacy test, a mean effective dose (ED50) of 87.16 mg/kg was obtained via a single dose oral administration. Our data demonstrated that MFM501 has the potential to be developed further as a new, safe, and effective oral-delivered antibacterial agent against MRSA isolates.

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