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At least 253 records · Page 14Linked to original sources

PubMed1980

Comparison of a microbicidal povidone-iodine gel and a placebo gel as catheter lubricants.

A comparison of povidone-iodine to a placebo gel as urinary catheter lubricants focused on the effects of urethral bacterial counts and on patient comfort. The 50 patients were divided into 2 parallel groups in a single blind study. Both lubricants lowered the bacterial counts, with the reduction achieved by povidone-iodine gel significantly greater than the reduction associated with the placebo (p less than 0.02). The numbers of patients experiencing discomfort from the 2 preparations did not differ nor was there any difference in the degree of discomfort, which was minimal for both groups. No other adverse side effects were reported for either lubricant.

Adult↗

PubMed2002

Biodegradability testing of synthetic ester lubricants--effects of additives and usage.

The optimised biodegradability test system "O2/CO2 Headspace Test with GC-TCD" is used for the assessment of synthetic ester lubricants. The effects of both additives and usage on biodegradability are examined and discussed. Ester based cutting fluids and hydraulic fluids with and without additives are used under defined conditions at machine tools and hydraulic and plain bearing test benches. The lubricants are characterised additionally with respect to kinematic viscosity, acidity and elemental composition. Furthermore, a formulated mineral oil is characterised before and after usage at an hydraulic test bench. The results clearly show that the mineral oil is far less biodegradable than the ester oils and that their biodegradability is not affected by usage. Biodegradability of the ester oils is mainly depending on the characteristics of the base fluids and not affected by the additives. Antioxidants are influencing stability respectively biodegradability indirectly, since they prevent oxopolymerisation effects. Other effects of usage on biodegradation are not detected. In this context, the antioxidants ensure ready biodegradability and have a positive effect on the environmental fate of synthetic ester lubricants.

Antioxidants↗

PubMed1999

Molecular weight independence of the effect of additive hyaluronic acid on the lubricating characteristics in synovial joints with experimental deterioration.

OBJECTIVE: To assess the molecular weight dependence of the lubricating characteristics of additive hyaluronic acid in animal joints with experimental deterioration. DESIGN: An experimental study in rabbits stifles in vitro. BACKGROUND: Hyaluronic acid is used as a drug for osteoarthritis. However, the molecular weight dependence of the effect of hyaluronic acid has been unclear. METHODS: Using a robotic arm under force-control, frictional coefficients were measured in fourteen rabbit stifles. The experimental conditions examined were: (1) intact joint surfaces; (2) after the joint surfaces were washed with physiological saline; (3) after the addition of 1% hyaluronic acid solution with a molecular weight of one million daltons and two million daltons, respectively. RESULTS: The increased frictional coefficient produced by washing with saline was decreased significantly by the addition of hyaluronic acid to the joint surfaces. This effect was observed regardless of the molecular weight of the hyaluronic acid. CONCLUSION: The lubricating characteristics of hyaluronic acid in synovial joints do not change with molecular weight. RELEVANCE: Hyaluronic acid solution is used clinically for the treatment of osteoarthritis. In the present study, the molecular weight dependency of the lubricating characteristics of hyaluronic acid was tested using the friction in synovial joints.

Animals↗

PubMed1987

Lubrication and viscosity features of human saliva and commercially available saliva substitutes.

The lubricating features and viscosity of human saliva and five commercially available saliva substitutes were compared. The results indicate that little correlation exists between these parameters. Saliva substitutes based on carboxymethylcellulose do not appear to lubricate biocompatible hard interfaces well and, therefore, might not protect against the rapid attrition observed in xerostomic individuals. In contrast, a mucin-based substitute proved to be a better lubricant with values comparable to whole human saliva.

Adult↗

PubMed2001

A protocol for the forensic analysis of condom and personal lubricants found in sexual assault cases.

In sexual assault cases, lubricant trace evidence may supplement biological evidence, or may be the primary physical evidence where biological evidence is unavailable. This study considered a total of 50 lubricants from condoms and personal lubricant products available in Australia. Differentiation of the samples was attempted using fluorescence examination, Fourier transform infrared spectroscopy (DRIFTS), gas chromatography-mass spectrometry, liquid chromatography-tandem mass spectrometry, and pyrolysis gas chromatography-mass spectrometry. Eleven of the samples were uniquely identified by the analysis scheme, while the remainder of the samples were separated into nine groups. As a result of this study, a recommended protocol for the detection and analysis of an "unknown" biological swab was produced.

Australia↗

PubMed2003

Normal and prosthetic synovial joints are lubricated by surface-active phospholipid: a hypothesis.

Much evidence supports the hypothesis that surface-active phospholipid (SAPL), which imparts the thin hydrophobic outermost lining to the normal articular surface, is the boundary lubricant reducing friction to remarkably low levels. We review this evidence and further hypothesize that SAPL produced in type B synoviocytes will also lubricate prostheses after implantation. This could explain why implanted hips display far less wear than hips in simulated wear trials do, even using protein as the lubricant whereas rougher surfaces can be tolerated in vivo. We introduce the concept that a deficiency of SAPL might explain the selective failure of prostheses just as osteoarthritic articular surfaces are deficient. This, in turn, leads to the replenishment of SAPL, as tested in OA, and the concept of prelubricating prostheses before implantation.

Cartilage, Articular↗

PubMed2001

Influence of wet granulation and lubrication on the powder and tableting properties of codried product of microcrystalline cellulose with beta-cyclodextrin.

The individual influence of wet granulation and lubrication on the powder and tableting properties of codried product of microcrystalline cellulose (MCC) with beta-cyclodextrin (beta-CD) was examined in this study. Avicel PH 101 and 301 were included for comparison. The codried product, Avicel PH 101 and 301 were granulated with water, and the granules were milled to retain three different size fractions: 37-60 microm, 60-150 microm, and 150-420 microm. The original Avicels and codried product were lubricated with magnesium stearate in three different percentages (0.2, 0.5, and 1.0%). The results showed that the powder flowability and disintegration of codried product and Avicels were significantly improved after wet granulation. However, the compactibility of codried product and Avicels decreased with increasing particle size. Nevertheless, the compactibility of the codried excipient after granulation was still better than the non-granulated Avicel PH 101 and 301. On the other hand, codried product and Avicels were sensitive to lubrication and resulted in decreasing compactibility and increasing disintegration. Because of the rounder shape of particles, the codried excipient was more sensitive to magnesium stearate and produced weaker tablets than did Avicels.

Analysis of Variance↗

PubMed1998

Optimization of an effervescent tablet formulation containing spray dried L-leucine and polyethylene glycol 6000 as lubricants using a central composite design.

A rotatable central composite design is used to evaluate the effects of lubricants and compression force on the physical characteristics of effervescent tablets. Effervescent tablets lubricated with a combination of spray dried L-leucine and polyethylene glycol 6000 are prepared by direct compression and examined. Residual force, crushing strength and disintegration time are considered as response variables and related to the L-leucine and polyethylene glycol concentrations and to the compression force. The calculated models are used to assess the influence of the production factors on tablet properties. As increasing amounts of L-leucine, showing good lubricating properties, reduce the crushing strength and prolong tablet disintegration, the L-leucine concentration is kept at a low level. An optimum tablet formulation contains 2% L-leucine and 3% polyethylene glycol 6000. The tablets have a tensile strength of 0.47 MPa and disintegrate in less than 2 min. Predicted and experimental results are in agreement within a 95% CI.

Chemistry, Pharmaceutical↗

PubMed2006

Evaluation of risk and benefit in the implementation of near-infrared spectroscopy for monitoring of lubricant mixing.

On-line near-infrared spectroscopy (NIRS) was used to monitor lubricant blending to ensure the quality of the final dosage form. A quantitative multivariate NIR model was developed using different lubricant concentration levels. Real-time model predictions correlated well with the expected lubricant concentration during blending, which allowed determination of blend quality. The significance of sensor location on the blender at different fill levels was evaluated. The capability of this application was further assessed by real-time study of blending dynamics under varying process conditions and raw material attributes. The response of the developed NIR method to sudden spikes in analyte concentration, changes in raw material attributes, and perturbations to standard mixing procedures was evaluated. This study allows an understanding of risk factors associated with the implemented technology, and its ability to accurately monitor the process events. Furthermore, it highlights the importance of proper selection of processing conditions and raw material attributes to improve process robustness.

Evaluation Studies as Topic↗

PubMed2000

Lubricant susceptibility of Cellactose and Avicel PH-200: a quantitative relationship.

The lubricant susceptibility of two direct compression excipients, Avicel PH-200 and Cellactose, was determined using a model mix with metamizol sodium (dipyrone) and designed experiments to obtain a quantitative relationship by multiple regression. As a result, a new constant called specific lubricant sensibility Ls is proposed for the comparison of lubricant susceptibility in other drug-excipient systems.

Cellulose↗

PubMed2004

Influence of the valve lubricant on the aerodynamic particle size of a metered dose inhaler.

Presented in this work are the results of a study designed to investigate the impact of valve lubricant (i.e., silicone oil) on the aerodynamic particle size distribution (PSD) of a steroid suspension metered dose inhaler (MDI) containing propellant HFA-227. The objective of this study was to explore whether the valve lubricant, which is often used in MDI products to prevent valve sticking, can enter an MDI product and potentially impact the aerosol spray dynamics. The results of this work have shown that samples containing valves with high silicone levels produced a larger aerodynamic particle size (by cascade impaction) than samples with low-silicone or silicone-free valves. It is postulated that the presence of silicone in the product may increase the propensity for drug aggregation, thereby leading to an increase in the aerodynamic particle size of the emitted aerosol. These findings stress the importance of evaluating the effects of valve lubricant on the aerodynamic PSD in the early formulation development stage of an MDI.

Adrenal Cortex Hormones↗

PubMed1986

Evaluation of lubricants for the prosthetic eye wearer.

We evaluated the need for additional lubrication in 200 consecutive patients using an ocular prosthesis. Of these patients, 154 (77%) required no additional lubrication, while 46 patients (23%) required supplemental lubrication. Enuclene, the only product manufactured specifically for the patient with an ocular prosthesis, has been reported by the majority of our patients to be inadequate for comfort and wearability. Other solutions for contact lens use were compared with Enuclene and found to be far superior by patients using an ocular prosthesis.

Adolescent↗

PubMed1988

A comparison of different methods of lubrication of glass syringes used to identify the epidural space.

Measurement of loss of resistance in glass syringes is a method widely used to locate the epidural space in epidural anaesthesia. Static and dynamic forces were measured under four experimental conditions in new glass syringes: unpolished, dry; polished, dry; unpolished, saline lubricated; and polished, saline lubricated. The unpolished saline lubricated syringes had a mean (SD) static force of 53.18 (15.0) g and dynamic force of 40.88 (15.2) g. These values were significantly greater than for polished dry syringes where the values were 5.27 (2.1) g and 4.38 (0.94) g, respectively. The results show that the least amount of resistance to plunger movement is obtained by dry polishing glass syringes.

Anesthesia, Epidural↗

PubMed1975

Some new evidence on human joint lubrication.

Theoretical consideration has been given to the use of pendulum machines which are used to examine the frictional properties of human joints by incorporating them as fulcra. As a result, a new type of pendulum machine has been built which incorporates the facility to apply sudden loads to the joint on starting the swinging motion, and also the ability to measure directly the frictional torque experienced by the joint. The results obtained from natural hip joints indicate the presence of squeeze film lubrication under conditions of sudden loading of a joint. In addition, a self-generated fluid film process was observed at low loads while at higher loads boundary lubrication appeared to be important. These results have been used to describe the lubrication regimens occurring in a normal activity such as walking. A single experiment carried out on a hip from a patient suffering from severe rheumatoid arthritis has also been reported and the frictional resistance was seen to be increased fifteenfold compared to a normal hip.

Arthritis, Rheumatoid↗

PubMed2001

Elastohydrodynamic lubrication analysis of metal-on-metal hip prostheses under steady state entraining motion.

The elastohydrodynamic lubrication problem of metal-on-metal hip joint replacements was considered in this study. A simple ball-in-socket configuration was used to represent the hip prosthesis. The Reynolds equation in a spherical coordinate was adopted for the fluid-film lubrication analysis, to account for the ball-in-socket geometry. The corresponding elastic deformation was calculated by means of the finite element method in order to consider the complex ball-in-socket geometry as well as the backing materials underneath the acetabular cup. Both the Reynolds and the elasticity equations were solved simultaneously using the Newton-Raphson finite difference method. The general methodology developed was then applied to a recent experimental prototype metal-on-metal hip implant. It was shown that the backing materials underneath the acetabular cup had little influence on the predicted contact pressure and the elastic deformation at the bearing surfaces for this particular example. Both the film thickness and the hydrodynamic pressure distributions were obtained under various loads up to 2500 N. The predicted minimum lubricating film thickness from the present study was compared with a simple estimation using the Hamrock and Dowson formulae based upon an equivalent ball-on-plane model and excellent agreement was found. However, it was pointed out that for some forms of metal-on-metal hip prostheses with a thin acetabular cup, a polyethylene inlay underneath a metallic bearing insert or a taper connection between a bearing insert and a fixation shell, the general methodology developed in the present study should be used and this will be considered in future studies.

Elasticity↗

PubMed2002

Analysis of elastohydrodynamic lubrication in a novel metal-on-metal hip joint replacement.

Elastohydrodynamic lubrication (EHL) analysis was carried out in this study for a novel metal-on-metal hip prosthesis, which consists of a cobalt-chrome alloy femoral head articulating against a cobalt-chrome alloy acetabular insert connected to a titanium fixation shell through a taper. Finite element models were developed to investigate the effect of the pelvic bone and the load on the predicted contact pressure distribution between the two bearing surfaces under dry conditions. The finite element method was used to develop elasticity models for both the femoral and the acetabular components; it was found that the elastic deformation of the acetabular insert was mainly dependent on the load, rather than the detailed pressure distribution. A modified solution methodology was accordingly developed to couple the elasticity models for both the femoral and the acetabular surfaces with the Reynolds equation and to solve these numerically by the finite difference method. It was found that a load increase from 500 to 2500 N had a negligible effect on the predicted maximum contact pressure and the minimum film thickness, due to the relatively flexible and accommodating structure of the acetabular insert. Furthermore, the predicted minimum film thickness was shown to be significantly greater than the simple estimation based on the assumption of semi-infinite solids (mono-block design) using the Hamrock and Dowson formula. The effects of the viscosity of the lubricant and the radial clearance between the femoral and the acetabular components on the predicted lubricating film thickness were investigated under both in vitro simulator testing and in vivo walking conditions.

Algorithms↗

PubMed1998

Adaptive multimode lubrication in natural synovial joints and artificial joints.

To examine the lubrication mechanisms in both natural synovial joints and artificial joints with artificial cartilages, pendulum tests of pig shoulder joints and simulator tests of sliding pairs of a stainless steel spherical component and natural articular cartilage or artificial cartilage have been conducted. Firstly, it was shown in pendulum tests of pig shoulder joints that both concentration of hyaluronic acid or viscosity and adsorbed film formation of proteins and phospholipids exerted a significant effect on frictional behaviour in swinging motion immediately after a loading of 100 N. Under a high load of 1 kN, low friction was observed under wide-ranging viscosity conditions, since a high load similar to body weight probably enhanced the squeeze film effect due to improved congruity. Next, frictional behaviour of sliding pairs in knee joint models, consisting of a stainless steel spherical surface and either specimens of pig tibial cartilage or polyvinylalcohol (PVA) hydrogel, was examined during walking in simulator tests. In these tests, the influences of lubricant viscosity and addition of protein on frictional behaviour were evaluated. For both compliant materials, the appropriate addition of gamma-globulin to sodium hyaluronate (HA) solution maintained low friction and protected rubbing surfaces under thin film conditions. These phenomena are discussed from the viewpoint of adaptive multimode lubrication.

Animals↗

PubMed1997

Friction of composite cushion bearings for total knee joint replacements under adverse lubrication conditions.

Conventional joint replacements consist of a polished metallic or ceramic component articulating against a layer of polyethylene. Although the friction in the contact between these articulating surfaces is low, polyethylene wear is produced as a result of a boundary/mixed lubrication regime. Wear debris is generated by direct asperity contact, abrasion, adhesion and fatigue, and has been shown to cause adverse tissue reactions which can lead to joint failure. The introduction of soft compliant materials, similar in stiffness to articular cartilage, has shown that with cyclic loading and relative motion between the articulating surfaces typical of normal walking, a fluid film can be maintained through combined entraining and squeeze-film actions, and hence wear can be minimized. For 95 per cent of the time, however, we are not walking but standing still or moving slowly. A pendulum simulator has been used in the present study to investigate the effect of adverse tribological conditions which may lead to fluid film breakdown, such as severe cyclic loading, particularly in the swing phase, reduced sliding velocity, reduced stroke length and start-up after a period of constant loading. Friction of a model composite cushion knee bearing, manufactured from a graded modulus (20-1000 MPa) layer of polyurethane, sliding against a polished metal cylinder has been measured for various lubricants and the results have been analysed using a Stribeck assessment. Severe cyclic loading, decreased sliding velocity and decreased stroke length have been found to limit the degree of fluid entrainment previously allowed during the swing phase of normal walking, thus allowing breakdown of fluid films and elevated levels of friction and surface damage. Soft layer joint replacements must therefore be designed to operate with thick elastohydrodynamic fluid films to provide some degree of protection when tribological conditions become severe, or alternatively incorporate alternative boundary or mixed lubrication mechanisms. This study quantifies a potential limitation of the cushion bearing concept.

Elasticity↗