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PubMed1998

The lubricating ability of biomembrane models with dipalmitoyl phosphatidylcholine and gamma-globulin.

Two kinds of friction tests were conducted to investigate the lubricating effect of the injection of amphiphilies on the osteoarthritic joint. The effects of the addition of L alpha-dipalmitoyl phosphatidyl-choline (L alpha-DPPC) riposomes and gamma-globulin in a saline solution of sodium hyaluronate (HA) were evaluated through pendulum friction tests. The frictional characteristics of pig shoulder joints were confirmed to depend on the viscosity of the lubricants only in the physiologically low load condition and in the condition immediately after loading. Detergent (polyoxyethylene p-t-octylphenyl ether) was successfully used to remove adsorbed films from the articular surfaces. The friction coefficient of natural synovial joints was significantly increased in a mode of mixed lubrication with the HA solution of 0.2 g/dl by the treatment of the surface with the detergent. The addition of L alpha-DPPC riposomes or gamma-globulin significantly improved the boundary lubricating ability of the articular surfaces treated with the detergent, depending on the quantity of those additives. It appears that the L alpha-DPPC riposomes and gamma-globulin can form protective films on the articular surfaces like a biomembrane. Moreover, the reciprocating frictional behaviour in sliding pairs of pig articular cartilages and glass plates was studied in order to elucidate the tribological role of those constituents in the boundary lubricating film on the articular surface. Pig synovial fluid and water solutions of HA were used as lubricants. The synovial fluid had superior lubricating ability compared to the HA solution of equivalent viscosity under a physiologically high load condition. This fact seems to be responsible for the boundary lubricating ability of constituents other than hyaluronic acid. Langmuir-Blodgett (LB) films of L alpha-DPPC on the glass plate were kept at a low and stable friction coefficient, depending on the number of film layers. In conditions of mixed films with L alpha-DPPC and gamma-globulin, the frictional behaviour was improved by increasing the quantity of gamma-globulin. A model is proposed in which the effective adsorbed films are composed of proteins, phospholipids and other conjugated constituents on the articular surfaces to be accurate in describing the boundary lubricating mechanism. The mechanism is controlled by hydrophobic groups in those amphiphilies.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

The effects of proteins on the friction and lubrication of artificial joints.

The tribological testing of artificial hip and knee joints in the laboratory has been ongoing for several decades. This work has been carried out in an attempt to simulate the loading and motion conditions applied in vivo and, therefore, the potential for the success of the joint. However, several different lubricants have been used in these tests. The work documented in this paper compares results obtained using different lubricants and makes suggestions for future work. Hip joints and knee joints of different material combinations were tested in a friction simulator to determine their friction and lubrication properties. Both carboxymethyl cellulose (CMC) fluids and bovine serum (with CMC fluids added) were used as the lubricants. These were prepared to various viscosities to produce the Stribeck plots. Human synovial fluid, of just one viscosity, was used as the lubricant with some of the joints to give a true comparison with physiological lubricants. The results showed that, in most cases, the lubricant had a significant effect on the friction developed between the joint surfaces. This is thought to be due to the proteins that are present within the bovine serum adsorbing to the bearing surfaces, creating 'solid-like' films which rub together, protecting the surfaces from solid-to-solid contact. This would be beneficial in terms of wear but can either increase or decrease the friction between the contacting surfaces. It is important to simulate the conditions in vivo as closely as possible when testing these joints to try to obtain a better comparison between the joints and to simulate more accurately the way that these joints will operate in the body. In an attempt to simulate synovial fluid, bovine serum seems to be the most popular lubricant used at present. It would be beneficial, however, to develop a new synthetic lubricant that more closely matches synovial fluid. This would allow us to predict more accurately how these joints would operate long-term in vivo.

Body Fluids↗

PubMed2004

[In vitro evaluation of lubrication properties of a suction catheter].

BACKGROUND: Lubrication is an important factor for passage of a suction catheter through a tracheal tube. This study was carried out to evaluate the effects of lubricants on resistance against removal of a suction catheter from a tracheal tube in an experimental setting. METHODS: A tracheal tube (I.D. of 7.5mm) was inserted into a mannequin, and the resistance against removal of a suction catheter from the tube was measured. RESULTS: Lubrication was improved by using a lubricant (lidocaine jelly or KY jelly), but there was no difference between the effects of the two lubricants. The use of water as lubricant markedly decreased lubrication. Differences in lubrication depending on the type of tracheal tube used, probably due to differences in coating, were also found. CONCLUSIONS: The use of water as a lubricant is not recommended for tracheal suction.

Catheterization↗

PubMedDate not supplied

Vaginal lubricants for the infertile couple: effect on sperm activity.

OBJECTIVE: To determine the effects of natural vegetable oils and vaginal lubricants on sperm motion and viability. DESIGN: Four widely used vaginal lubricants (K-Y Jelly, Astroglide, Replens, and Touch) and two vegetable oil products that have been used as vaginal lubricants were purchased through local vendors. Sperm was obtained by masturbation without lubrication from normal, healthy donors. Lubricants were mixed with sperm from individual donors and the effects on sperm motility were determined at 1, 15, 30, and 60 minutes. SETTING: Southwestern Fertility Associates of The University of Texas Southwestern Medical Center at Dallas. MAIN OUTCOME MEASURES: Sperm motility was evaluated by manual motility counts and by computer-assisted semen analysis. Sperm viability was evaluated with Hoechst 33258 dye. The effects of the various lubricants were compared with those of a spermicidal agent, Gynol II (negative control) and Ham's F-10 (positive control). RESULTS: Commercial lubricants inhibited sperm motility by 60-100% after 60 minutes of incubation. Sperm exposed to Replens or Astroglide were nonmotile and nonviable after incubation for 60 minutes, similar to the control, nonoxynol-9 containing product Gynol II. Canola oil had no detrimental effects and was indistinguishable from Ham's F-10 in terms of sperm viability and motility. CONCLUSIONS: For couples with infertility, the use of vaginal lubricants during intercourse is not recommended. In cases where a lubricant is required, careful selection can maximize sperm motility and viability.

Cell Survival↗

PubMed2004

Mesophilic aerobic degradation of a metal lubricant by a biological consortium.

The metal-forming industries require the use of greases to lubricate metal surfaces during manufacturing operations, and the residues of these lubricants must be removed prior to finishing processes to protect and improve the appearance of the final product. An aqueous, biological metal-cleaning process operating under mild conditions (pH 9, 42 degrees C) eliminates the use of environmentally unfriendly cleaning materials such as chlorinated solvents by employing microorganisms to degrade greases and oils naturally. This process was characterized in terms of initial degradation rates of a representative metal lubricant and by phylogenetic identification of the active bacteria. The metal lubricant in a surfactant solution was degraded by a bacterial consortium, and its concentration was determined by a novel gas chromatography assay. The maximum degradation rate Vmax and the apparent Km were obtained as 45 mg/(day mg protein) and 24 g/l on cellular basis, and 4.6 g/(day l) and 33 g/l on a volumetric basis, respectively. Mineralization of the metal lubricant was shown by analyzing the evolved CO2 and Cl-, and the bacterial consortium utilized the metal lubricant as a sole carbon and energy source (micro=0.05+/-0.01 h(-1) at 0.5 vol% lubricant concentration). The active bacteria in the biological metal-cleaning process were identified as Bacillus licheniformis for the higher lubricant concentrations (3, 5, and 7.5 vol%), Bacillus cereus at 1 vol%, and Pseudomonas aeruginosa, Rhizobiaceae strain M100, and Achromobacter sp. LMG 5431 at 0.3 vol%.

Achromobacter↗

PubMed2006

Effect of synovial fluid on boundary lubrication of articular cartilage.

OBJECTIVES: The lubrication of articulating cartilage surfaces in joints occurs through several distinct modes. In the boundary mode of lubrication, load is supported by surface-to-surface contact, a feature that makes this mode particularly important for maintenance of the normally pristine articular surface. A boundary mode of lubrication is indicated by a kinetic friction coefficient being invariant with factors that influence formation of a fluid film, including sliding velocity and axial load. The objectives of this study were to (1) implement and extend an in vitro articular cartilage-on-cartilage lubrication test to elucidate the dependence of the friction properties on sliding velocity, axial load, and time, and establish conditions where a boundary mode of lubrication is dominant, and (2) determine the effects of synovial fluid (SF) on boundary lubrication using this test. METHODS: Fresh bovine osteochondral samples were analyzed in an annulus-on-disk rotational configuration, maintaining apposed articular surfaces in contact, to determine static (mu(static) and mu(static),(N(eq)) and kinetic ([mu(kinetic)] and [mu(kinetic),(N(eq))]) friction coefficients, each normalized to the instantaneous and equilibrium (N(eq)) normal loads, respectively. RESULTS: With increasing pre-sliding durations, mu(static) and mu(static),(N(eq)) were similar, and increased up to 0.43 +/- 0.03 in phosphate buffered saline (PBS) and 0.19 +/- 0.01 in SF, whereas [mu(kinetic)] and [mu(kinetic),(N(eq))] were steady. Over a range of sliding velocities of 0.1-1 mm/s and compression levels of 18% and 24%, [mu(kinetic)] was 0.072 +/- 0.010 in PBS and 0.014 +/- 0.003 in SF, and [mu(kinetic),(N(eq))] was 0.093 +/- 0.005 in PBS and 0.018 +/- 0.002 in SF. CONCLUSIONS: A boundary mode of lubrication was achieved in a cartilage-on-cartilage test configuration. SF functioned as an effective friction-lowering boundary lubricant for native articular cartilage surfaces.

Animals↗

PubMed2001

Do bacteriostatic urethral lubricants affect the clinical efficacy of intravesical bacillus Calmette-Guérin therapy?

OBJECTIVES: To investigate the effect of a bacteriostatic urethral lubricant on the clinical efficacy of intravesical bacillus Calmette-Guérin (BCG) therapy. METHODS: Between July 1987 and August 1999, 389 patients with superficial urothelial carcinoma of the bladder (pTa [multilocular, size greater than 2 cm, recurrent tumor], pT1, pTis) were treated adjuvantly with BCG in a 6-week intravesical cycle after complete transurethral tumor resection of the bladder. Within the framework of a prospective study on recurrence and progression of superficial urothelial carcinoma of the bladder after transurethral resection and BCG therapy, we retrospectively studied the clinical value of the observation that the use of bacteriostatic urethral lubricants reduces the viability and thus the efficacy of BCG. If a lubricant induces a clinically relevant reduction in the viability of BCG, instillation without lubricant should lead to a lower rate of recurrence and possibly a lower rate of progression. Lubricant (11 mL) was used during catheterization in every male patient in our population (group 1, n = 317, 81.5%); no lubricant was used in the women serving as the control group (group 2, n = 72, 18.5%). The two groups were similar with respect to age, distribution of tumor stage and grade, multifocality, and frequency of previous bladder carcinoma (Levene test, P = 0.008). The median follow-up was 54 months (range 4 to 143). RESULTS: Of the 389 patients, 90 (23.1%) developed recurrence during the follow-up period: 73 (23%) in group 1 and 17 (23.6%) in group 2 (P value not significant). Progression occurred in 14 patients in group 1 (4.4%) and in 8 patients in group 2 (11%) (P = 0.043). In groups 1 and 2, 19.2% and 47.1%, respectively, of the recurrences were progressive (P = 0.026). CONCLUSIONS: The use of bacteriostatic lubricants in the usual dose before BCG instillation had no detectable adverse effect on the clinical efficacy of intravesical BCG immunotherapy. To avoid traumatic catheterization with possible systemic BCG administration, we therefore recommend, especially in men, the additional use of a sufficient quantity of urethral lubricant.

Adjuvants, Immunologic↗

PubMed2004

Alkalinization of intra-cuff lidocaine and use of gel lubrication protect against tracheal tube-induced emergence phenomena.

BACKGROUND: We sought to determine the benefits of using alkalinized lidocaine 40 mg to fill the cuff of a tracheal tube (ETT) in combination with water-soluble gel lubrication to prevent post-intubation sore throat. METHODS: The work included an in vitro study of the diffusion of alkalinized lidocaine solution through the low-pressure, high-volume cuff of an ETT. We also performed a randomized controlled study (n=20 patients in each group) that included a group who received an alkalinized lidocaine-filled ETT cuff with lubrication of the tube using water-soluble gel (Group G), and two control groups who received an alkalinized lidocaine-filled cuff with ETT lubrication with water (Group W) or an air-filled cuff with ETT lubrication with water (Group C). RESULTS: Water-soluble gel lubrication (Group G) produced a lower incidence of sore throat during the 24-h post-extubation period than lubrication with water alone in the cuffs filled with alkalinized lidocaine (Group W), and compared with the air control group. The ability of lidocaine to pass through the cuff of an ETT when water-soluble gel and/or water alone was used as a lubricant was similar, as determined by lidocaine plasma concentrations (C(max) 45 ng x ml(-1)). Cough and restlessness before tracheal extubation were decreased in patients with the alkalinized lidocaine-filled cuffs compared with the air-filled cuffs. After extubation, nausea, vomiting, dysphonia and hoarseness were greater for patients with air-filled cuffs compared with the lidocaine-filled cuffs. No significant difference between the groups was recorded in arterial blood pressure and heart rate. In vitro data suggest that the lower the NaHCO(3) injection volume, the greater the release of lidocaine across a low-pressure, high-volume cuff. CONCLUSIONS: These data show benefits of using an alkalinized lidocaine-filled ETT cuff in combination with water-soluble gel lubrication in preventing post-intubation sore throat.

Adult↗

PubMed2006

Increased total knee arthroplasty ultra-high molecular weight polyethylene wear using a clinically relevant hyaluronic acid simulator lubricant.

In this study, osteoarthritic and periprosthetic synovial fluid samples were rheologically and biochemically compared to develop a hyaluronic acid (HA) supplemented bovine serum (BS) lubricant that mimicked the properties of human joint synovial fluid. The effect of this BS + HA lubricant (50 per cent bovine calf serum + 1.5 g/l HA) on the wear rate of ultra-high molecular weight polyethylene (UHMWPE) during a total knee replacement wear test was then investigated. In conjunction with biochemical similarities, the rheological analysis showed that the BS + HA lubricant viscosity was not statistically different to aspirated total knee arthroplasty (TKA) revision joint fluid viscosity over a range of physiologic shear rates. Gravimetric results at 5 million wear testing cycles showed that the BS + HA lubricant produced an average of 6.88 times more UHMWPE wear than 50 per cent bovine serum lubricant alone. The BS + HA lubricated CoCr femoral component surfaces revealed pitting and surface roughening that was not observed using standard bovine serum only lubricants, but that was similar to the metallic surface corrosion observed on in vivo CoCr femoral component retrievals. These findings support the hypothesis that the addition of HA to simulator lubricant is capable of producing CoCr femoral component surface damage similar to that observed in vivo.

Arthroplasty, Replacement, Knee↗

PubMed1975

Influence of stone mixing agents, impression materials and lubricants on surface hardness and dimension of a dental stone die material.

The influence of different stone mixing agents, impression materials and lubrication methods on the surface hardness of a stone die material has been evaluated. For one impression material the dimensional effect of the mixing agents and lubrication on the dies was also studied. The stone die material was mixed with water or a gypsum hardener and allowed to set on surfaces of glass, agar-agar, polyether, polysulfide and silicone impression materials. The lubrication methods for the stone were mineral oil, water soluble lubricant and mineral oil followed by water soluble lubricant. The surface hardness was measured according to the Brinell test. The Brinell test was chosen after a comparative study of the Brinell, Vickers and Knoop hardness test methods. The results showed that gypsum hardener was preferable to distilled water. The impression materials appear to have influence on the surface hardness of stone. The effect differed on water mixed and hardener mixed stone which emphasizes the importance of the mixing agent. All lubrication decreased the surface hardness of stone. With hardener mixed stone the combination of mineral oil followed by water soluble lubricant seemed preferable. Neither the gypsum hardener nor the lubrication influenced the dimension of the stone die material.

Dental Impression Materials↗

PubMed2005

Association of articular cartilage degradation and loss of boundary-lubricating ability of synovial fluid following injury and inflammatory arthritis.

OBJECTIVE: To study the relationship between the boundary-lubricating ability of synovial fluid (SF) and articular cartilage damage in a rabbit knee injury model, to correlate collagen markers of such damage with SF boundary-lubricating ability and elastase activity, and to examine the lubricating ability of SF, together with collagen markers of articular cartilage damage, under the inflammatory conditions of knee joint synovitis (KJS) and rheumatoid arthritis (RA). METHODS: SF was aspirated weekly from the affected knee joints of 10 adult rabbits following transection of the anterior and posterior cruciate ligaments. The boundary-lubricating ability of SF was determined in vitro using a previously described friction apparatus. Lubricin concentrations and type II collagen (CII) peptides were quantified by sandwich enzyme-linked immunosorbent assays (ELISAs). Levels of the C-terminal neoepitope 9A4 (derived from collagenase degradation of CI, CII, and CIII) and of epitope 5-D-4 of keratan sulfate (a marker of proteoglycan depletion) were quantified by inhibition ELISAs. Elastase activity was measured spectrophotometrically. The sensitivity of purified human lubricin to digestion by neutrophil elastase (NE) was examined by Western blotting. RESULTS: The lubricating ability of SF from injured rabbit knees was significantly decreased at weeks 2 and 3 compared with week 1 after injury. Lubricin concentrations were significantly higher at week 1 than at weeks 2 and 3. CII peptide concentrations increased significantly at weeks 2 and 3 compared with week 1, while 9A4 neoepitope concentrations increased significantly at week 3 compared with weeks 1 and 2. There were no significant differences in epitope 5-D-4 concentrations among the 3 weeks. Elastase activity in SF increased significantly at weeks 2 and 3 compared with week 1. Elastase activity correlated significantly with diminishing lubrication at weeks 1, 2, and 3. SF from patients with KJS or RA exhibited deficient lubrication and elevated levels of CII peptides compared with SF from normal controls. NE was shown to completely degrade purified human lubricin in vitro. CONCLUSION: Loss of boundary-lubricating ability of SF after injury is associated with damage to the articular cartilage matrix. This can be attributed to inflammatory processes resulting from the injury, particularly in the early phases. This association also exists in patients with acute knee injuries or progressive chronic inflammatory arthritis.

Animals↗

PubMed2001

Design of a simulated urethra model for the quantitative assessment of urinary catheter lubricity.

Catheters designed for intermittent urological catheterization should possess appropriate lubricity and mechanical properties to ensure optimal clinical performance. However, the lack of a reproducible in vitro method that simulates clinical use makes it difficult to evaluate the lubricity of urinary catheters and other devices for urethral insertion. Therefore, this study describes a suitable method based on use of a Texture Analyzer to characterize the lubricity of such devices. The novel method was susequently applied to the evaluation of commercially-available intermittent urinary catheters. In addition, other important physicochemical properties of these catheters were examined, namely Young's modulus, degree of hydration and morphology. Catheter lubricity was quantified, using a Texture Analyzer, by measurement of the forces required for insertion and removal of the device from two model substrates, agar and mucin-coated silicone tubing. Significant differences in lubricity were identified between the commercially-available catheters, with Aquacath and Lofric exhibiting the lowest forces of insertion and removal. There were no significant differences between the extent of hydration between the catheters, with the exception of Uro-flo which exhibited the lowest hydration. Therefore, the differences in lubricity were not directly related to the extent of hydration. The forces required for insertion/removal of all catheters were markedly greater in the simulated mucin model than in the agar substrate and the former, simulated urethra model, was accepted to mimic more accurately, the in vivo situation. Significant differences were observed between the Young's Moduli of the catheter biomaterials, with Aquacath possessing the largest value. In conclusion, this study has described the use of a texture analyzer and polymeric substrates for the evaluation of biomaterial lubricity. Using these methods, Aquacath and Lofric catheters exhibited greatest lubricity. However, following additional consideration of the mechanical properties of these biomaterials, Aquacath possessed the most appropriate physicochemical properties for use in intermittent catheterization.

Journal Article↗

PubMed1997

Effect of tear lubricating solutions on in vivo corneal epithelial permeability.

PURPOSE: The rabbit corneal epithelial permeability was measured noninvasively following exposure to commercially available tear lubricating solutions. METHODS: The normal unanesthetized rabbit's corneal surface was either bathed in the tear lubricating solution for 5 min or received multiple applications of 2 drops per 30 min for 6 h for one or five days. The corneal epithelial permeability to carboxyfluorescein after a 5-min bath was measured with the Fluorotron Master. Fifteen commercially available tear preparations were tested. RESULTS: The baseline corneal epithelial permeability was 0.0455 +/- 0.0114 nm/s. The epithelial permeability values for the corneas bathed for 5 min in control solution (BSSplus) was 0.0798 +/- 0.0074 nm/s, in the preservative-free tear lubricating solutions the range was 0.512 to 0.542 nm/s, and in the preserved tear lubricating solutions the range was 0.3518 to 11.8873 nm/s. The preservative-free tear lubricating solutions had epithelial cell permeabilities up to 6 times greater than the control solution. Whereas, the preserved tear lubricating solutions had epithelial cell permeabilities up to 149 times greater than the control solution. Multiple applications of the tear lubricating solutions for 5 days were less damaging to the epithelial permeability than the 5 min bath applications. The resulting epithelial permeabilities were up to 2 fold greater than the control with the corresponding preservative-free solution and up to 29 fold greater than control with the corresponding preserved solution. CONCLUSION: An extended exposure of 5 min to various tear lubricating solutions demonstrated significant differences in epithelial cell permeability between preserved solutions and unpreserved solutions, whereas the multiple drop application technique demonstrated all of the preservative-free solutions and some of the preserved solutions to be insignificantly different from the control solution.

Animals↗

PubMed2005

Application of surface plasmon resonance sensing to studying elastohydrodynamic lubricant films.

We present a new technique based on the spectral characteristics associated with the surface plasmon resonance (SPR) effect for studying lubricants in elastohydrodynamic (EHD) dimples. The pressure inside the EHD dimple causes a localized change of the refractive index (RI) of the entrapped lubricant. This also results in a shift in the spectral SPR absorption dip. By monitoring the color changes within the SPR image, one can obtain a direct measurement of the RI of the entrapped lubricant, from which the pressure distribution within the elastohydrodynamic lubrication (EHL) dimple can be deduced by means of a predetermined relation of pressure and RI of the tested lubricant. Dimples formed with the lubricants PB 2400 and H 1900 were studied in our experiments. Because SPR is sensitive only to the RI variation within a thin region (approximately one wavelength) close to the sensor's surface, the new technique does not require any measurement of the absolute film thickness of the lubricant. This is much simpler than the existing two-beam interferometric technique for measuring the RI of lubricants in EHD dimples, which requires simultaneous measurements of optical film thickness by use of two beams of different angles of incidence. In light of this advantage we anticipate that the new technique can be applied to pressure field mapping in highly loaded rolling and sliding EHL contacts.

Journal Article↗

PubMed1994

A new model for synovial joint lubrication.

A new approach to synovial joint lubrication is presented using Bingham fluid as lubricant between the approaching porous cartilagenous surfaces. It is presumed that the thickness of the core formed, due to thickly concentrated hyaluronic acid molecules, increases as the surfaces come closer. This is due to the withdrawal of the base fluid through the boosted lubrication mechanism, leading to the formation of lubricating gel. This gel ultimately acts as boundary lubricant which prevents cartilage-to-cartilage contacts very briefly during a gait cycle. For most of the gait cycle, fluid film lubrication persists, and this fluid supports greater loads which are due to the development of increased pressures as compared with viscous lubricants. Thus, normal joints possess an in-built mechanism to support greater loads, at the load-bearing joints, with less friction and wear.

Cartilage, Articular↗

PubMed2004

Testing the ecotoxicology of vegetable versus mineral based lubricating oils: 2. Induction of mixed function oxidase enzymes in barramundi, Lates calcarifer, a tropical fish species.

An increasing number of vegetable-based oils are being developed as environmentally friendly alternatives to petroleum products. However, toxicity towards key tropical marine species has not been investigated. In this study we used laboratory-based biomarker induction experiments to compare the relative stress of a vegetable-based lubricating oil for marine 2-stroke engines with its mineral oil-based counterpart on tropical fish. The sub-lethal stress of 2-stoke outboard lubricating oils towards the fish Lates calcarifer (barramundi) was examined using liver microsomal mixed function oxidase (MFO) induction assays. This study is the first investigation into the use of this key commercial species in tropical North Queensland, Australia in stress assessment of potential hydrocarbon pollution using ethoxyresorufin O-deethylase (EROD) induction. Our results indicated that barramundi provide a wide range of inducible rates of EROD activity in response to relevant organic stressors. The vegetable- and mineral-based lubricants induced significant EROD activity at 1.0 mg kg(-1) and there was no significant difference between the two oil treatments at that concentration. At increasing concentrations of 2 and 3 mg kg(-1), the mineral-based lubricant resulted in slightly higher EROD activity than the vegetable-based lubricant. The EROD activity of control and treated barramundi are found to be within ranges for other species from temperate and tropical environments. These results indicate that vegetable-based lubricants may be less stressful to barramundi than their mineral counterparts at concentrations of lubricant > or =2 mg kg(-1). There is great potential for this species to be used in the biomonitoring of waterways around tropical North Queensland and SE Asia.

Animals↗

PubMed2003

Elastohydrodynamic lubrication analysis of metal-on-metal hip-resurfacing prostheses.

The elastohydrodynamic lubrication analysis was carried out in this study for a typical metal-on-metal hip-resurfacing prosthesis under a simple steady-state rotation. Both the Reynolds equation and the elasticity equation were coupled and solved numerically by the finite difference method. The finite element method was used to determine the elastic deformation of both the femoral and the acetabular components required for the lubrication analysis. The effect of the radial clearance between the femoral head and the acetabular cup on the predicted film thickness and pressure distribution was investigated. The predicted minimum lubricating film thickness was found to compare favourably with the prediction using the Hamrock and Dowson [J. Lubrication Technol. 100 (1978) 236] formula based on the assumption of ball-on-plane semi-infinite solids. This implies that the non-metallic materials such as bone and cement underlying the metallic components have a small effect on the predicted lubrication performance for the particular metal-on-metal hip-resurfacing prosthesis considered in this study. Under realistic physiological walking conditions, a decrease in the radial clearance from 150 to 50 microm resulted in a 137% increase in the predicted minimum film thickness from 19 to 45 nm. Consequently, given a surface roughness of 0.01 microm for both the metallic femoral and acetabular bearing surfaces, the predicted mixed lubrication regime for the larger clearance was changed to a full fluid film lubrication regime for the smaller clearance. This clearly highlighted the importance of the design and manufacturing parameters on the tribological performance of these hard-on-hard hip prostheses.

Algorithms↗

PubMed1996

Effect of dowel lubrication on resistance to dislodgment of dowels cemented with a 4-META resinous cement.

Dentatus stainless steel dowels were cemented 5 mm into prepared canals of extracted human teeth with C&B Metabond cement. One half the dowels were lubricated before cementation to ensure easy subsequent retrieval. Significantly less tensile force was required to dislodge the lubricated dowels (p = 0.0209). Retrievable lubricated dowels could provide dentists the option of nonsurgical endodontic retreatment in lieu of endodontic surgery. However, lubrication cannot be recommended for clinical use at this time because of the potential for the dowel to unscrew during normal oral function. Further studies are required to determine the effects of rotational forces on the lubricated dowel, surface design of the dowel on retention, and chemical interaction of the lubricant on the resinous cement. Long-term effects of the lubricant on the cement are unknown.

Acrylic Resins↗