Wear particle-induced inflammation leading to periprosthetic osteolysis remains a major cause of hip implant failure. As polyethylene particles from conventional metal-on-polyethylene implants have been associated with these failures, an interest in lower wear metal-on-metal (MM) bearings has emerged. However, the biological effects of nanometer-size chromium oxide particles, predominant type of wear particles produced by MM implants, remain mostly unknown. Therefore, this study aimed to determine the cytotoxicity of nanometer-size Cr2O3 particles on macrophages in vitro, by analyzing their effects on cell mortality and cytokine release and comparing them with those of similarly-sized alumina (Al2O3) particles (known to be relatively bioinert). Results showed that at high concentrations, nanometer-size Cr2O3 particles can be cytotoxic to macrophages, inducing significant decreases in total cell numbers and increases in necrosis. Results also showed that, at high concentrations, the cytotoxicity of Cr2O3 particles was overall higher than that of Al2O3 particles, even though Cr2O3 and Al2O3 are both stable forms of ceramic materials. However, it appeared to be lower than that of previously reported conventional polyethylene and CoCrMo particles. Therefore, chromium oxide particles may not be the main culprit in initiating the inflammatory reaction in MM periprosthetic tissues.

Wear particle-induced inflammation leading to periprosthetic osteolysis remains a major cause of hip implant failure. As polyethylene particles from conventional metal-on-polyethylene implants have been associated with these failures, an interest in lower wear metal-on-metal (MM) bearings has emerged. However, the biological effects of nanometer-size chromium oxide particles, predominant type of wear particles produced by MM implants, remain mostly unknown. Therefore, this study aimed to determine the cytotoxicity of nanometer-size Cr2O3 particles on macrophages in vitro, by analyzing their effects on cell mortality and cytokine release and comparing them with those of similarly-sized alumina (Al2O3) particles (known to be relatively bioinert). Results showed that at high concentrations, nanometer-size Cr2O3 particles can be cytotoxic to macrophages, inducing significant decreases in total cell numbers and increases in necrosis. Results also showed that, at high concentrations, the cytotoxicity of Cr2O3 particles was overall higher than that of Al2O3 particles, even though Cr2O3 and Al2O3 are both stable forms of ceramic materials. However, it appeared to be lower than that of previously reported conventional polyethylene and CoCrMo particles. Therefore, chromium oxide particles may not be the main culprit in initiating the inflammatory reaction in MM periprosthetic tissues.

Wear particle-induced inflammation leading to periprosthetic osteolysis remains a major cause of hip implant failure. As polyethylene particles from conventional metal-on-polyethylene implants have been associated with these failures, an interest in lower wear metal-on-metal (MM) bearings has emerged. However, the biological effects of nanometer-size chromium oxide particles, predominant type of wear particles produced by MM implants, remain mostly unknown. Therefore, this study aimed to determine the cytotoxicity of nanometer-size Cr2O3 particles on macrophages in vitro, by analyzing their effects on cell mortality and cytokine release and comparing them with those of similarly-sized alumina (Al2O3) particles (known to be relatively bioinert). Results showed that at high concentrations, nanometer-size Cr2O3 particles can be cytotoxic to macrophages, inducing significant decreases in total cell numbers and increases in necrosis. Results also showed that, at high concentrations, the cytotoxicity of Cr2O3 particles was overall higher than that of Al2O3 particles, even though Cr2O3 and Al2O3 are both stable forms of ceramic materials. However, it appeared to be lower than that of previously reported conventional polyethylene and CoCrMo particles. Therefore, chromium oxide particles may not be the main culprit in initiating the inflammatory reaction in MM periprosthetic tissues.

Total hip replacement is a common orthopedic surgery today with a population with an increasing life expectancy and a more active lifestyle. Most implants have a life expectancy of 10 years or longer, however after 25 years one out of four implants has been revised. This means that the risk of a secondary surgery is high for young patients. In many cases the reason for revision is the formation of nanometer to micrometer sized particles that activate the immune system to resorb bone.   The implants today usually consist of a femoral head of a cobalt chromium alloy and a cup of polyethylene. Replacing these materials with a cobalt chromium alloy with a silicon nitride coating is hoped to generate less and smaller wear particles that will not activate the immune system to resorb bone. This study compares wear particles from three different silicon nitride coatings with wear particles from polyethylene and a cobalt chromium alloy. The first was a standard coating, the second had a layered structure and the third had a nitrogen content gradient.   This study uses a reciprocating motion with an alumina ball that slides against a sample of cobalt chromium with a silicon nitride coating in a serum solution to generate wear particles. The particles are then analyzed with a scanning electron microscope. In order to separate the particles from the serum solution two different methods were used. The first one used hydrochloric acid and the second used the enzyme proteinase K. Apart from the particles the wear tracks were investigated with vertical scanning interferometry and the adhesion was studied with scratch tests and light microscopy.   The results show that the wear particles do not differ between the coatings. All coatings show a high wear volume, which is believed to be a consequence of the material combination, movement pattern or surface roughness of the counter surface. In conclusion the test set up generates particles of a relevant size and both methods for serum digestion were successful.

Wear particle-induced inflammation leading to periprosthetic osteolysis remains a major cause of hip implant failure. As polyethylene particles from conventional metal-on-polyethylene implants have been associated with these failures, an interest in lower wear metal-on-metal (MM) bearings has emerged. However, the biological effects of nanometer-size chromium oxide particles, predominant type of wear particles produced by MM implants, remain mostly unknown. Therefore, this study aimed to determine the cytotoxicity of nanometer-size Cr2O3 particles on macrophages in vitro, by analyzing their effects on cell mortality and cytokine release and comparing them with those of similarly-sized alumina (Al2O3) particles (known to be relatively bioinert). Results showed that at high concentrations, nanometer-size Cr2O3 particles can be cytotoxic to macrophages, inducing significant decreases in total cell numbers and increases in necrosis. Results also showed that, at high concentrations, the cytotoxicity of Cr2O3 particles was overall higher than that of Al2O3 particles, even though Cr2O3 and Al2O3 are both stable forms of ceramic materials. However, it appeared to be lower than that of previously reported conventional polyethylene and CoCrMo particles. Therefore, chromium oxide particles may not be the main culprit in initiating the inflammatory reaction in MM periprosthetic tissues.

During braking, both the rotor and the pads in disc brakes are worn. Since disc brakes are not sealed, some of the wear particles generated can become airborne. Several studies have found an association between adverse health effects and the concentration of particles in the atmosphere, so it is of interest to improve our knowledge of the airborne wear particles generated by disc brakes. However, in field tests it is difficult to distinguish these particles from others in the surrounding environment, so it may be preferable to use laboratory test stands and/or simulation models to study the amount of airborne wear particles generated. This thesis deals with a simulation methodology for prediction of airborne wear particles from disc brakes and three experimental methods for testing disc brake materials with focus on airborne wear particles. The four appended papers discuss the possibility to both measure and predict the number and size distribution of airborne wear particles that originate from the pad to rotor contact. The objective is to develop a simulation methodology that predicts the number and size distribution of airborne wear particles from disc brakes. Paper A describes how a modified pin-on-disc machine was used to study airborne wear particles originating from different disc brake materials. The results indicate that the test setup can be used to measure and rank the number concentration and size distribution of the airborne wear particles generated. Paper B describes a disc brake assembly test stand for measurements of airborne wear particles from disc brakes. The results indicate that the test setup can be used to measure the number concentration and size distribution of airborne wear particles generated from disc brake materials. The results also indicate a promising ability to rank different pad/rotor material combinations with respect to the number concentration of airborne wear particles. Paper C compares measurements made in passenger car field tests with measurements made in a disc brake assembly test stand and in a pin-on-disc machine. A promising correlation between the three different test methods is found. Paper D presents a simulation methodology for predicting the number and size distribution of airborne wear particles using finite element analysis (FEA). The simulated number distribution is compared with experimental measurements at component level. The result indicates that the proposed methodology may be used to predict the number concentration and size distribution of airborne particles generated in the pad-to-rotor contact.

Over the last decades, there has been much attention on air quality, especially in urban environments. A significant factor effecting the air quality in the urban environment is airborne particulate matter (PM). Long-term exposure to PM causes increased risk for heart disease, decreased lung function, exacerbation of asthma, and lung cancer. Therefore, many countries have implemented exposure limits to the concentration of ambient PM in the urban environments. The toxicity of PM is dependent on several factors such as chemical composition, shape, adsorbed materials, and particle sizes (usually divided in ultrafine, fine and coarse particles). However, the relationship between different PM properties and developing health hazards are not clear. Therefore, further studies to investigate different properties of PM may contribute to understanding the influence of PM on human health.  In the present work, different novel methods to investigate sampled airborne PM and to investigate potential health effects have been used to increase the knowledge regarding street and wear particles. In study I, a sampling plan involving collecting one filter from Tapered Element Oscillating Microbalance (TEOM) monitoring stations used for Environmental monitoring each month for 20 months were developed. Particles on the filters were extracted into a suspension. TEOM particles were then studied with respect to constituents and variables that reflect their toxicity. The constituent and toxicity was found to be spatial and seasonal dependent. As a follow-up, in study II, TEOM filters from three geographical different cities were collected once a month for a year. The variation in particle mass measured with TEOM monitor, cadmium and lead contents, as well as endotoxin levels between locations and time points over the year was studied. The correlation between studied variables and biological effect was investigated. The results show that the concentration of metals and endotoxin in TEOM particles have no relationship to particle mass, while endotoxin levels coincided with pro-inflammatory response. These studies show that results from analyzing different variables on obtained particles from TEOM filters in combination with information about the ambient particle concentration, could be helpful in the evaluation of differences in the risk of breathing air at various locations.  The dominant road traffic particle sources are wear particles from the road and tyre interface, and from vehicle brake pads. The particle concentrations are highest in cities with high traffic amounts and a high frequency of braking. There are a few cell studies that have investigated the toxicological and biological effect of these wear particles, but there is a lack of knowledge regarding their effect on tissue level. Furthermore, the knowledge about importance of rock materials in pavement is deficient. To mitigate these knowledge gaps, the effect of different wear particles from pavement and brake pad were tested using a model with isolated perfused rat lungs in study III. The wear particles from the pavement showed a significant decrease of tidal volume compared to unexposed controls. The largest effect were found with quartzite stone material. Wear particles from brakes instead showed a larger effect on released proinflammatory cytokines. The study shows that the toxic effect on lungs exposed to airborne particles can be investigated using repetitive measurements of tidal volume. Furthermore, the study shows that the choice of rock material in road pavements has the potential to affect the toxicity of road wear particles. This should be considered in environments where the concentrations and exposures are high. The brake particles showed a different effect than stone particles, indicating the need to differentiate wear particles from different sources in relation to health effects. In summary, the present work have investigated different aspects of airborne particles collected from streets as well as generated wear particles. These indicate different important aspects of the particles that may be of importance to better understand their health effects.

Aseptic loosening due to polyethylene wear presents one of the most frequently occurring joint replacement complications requiring a revision surgery. Numerous scientific works and publications deal with the issue of morphology, determination and distribution of wear particles. Few studies, however, determine reliably amounts of particles in individual periprosthetic zones. The objective of this work was to evaluate the correlation between amounts of wear particles and periprosthetic osteolysis findings. Description of distribution of these particles in the surroundings of joint replacement presented further objectives of the work. Wear particles were isolated from granuloma obtained during revisions of total hip replacements. Amounts of wear particles were determined using IRc. These findings were correlated with X-ray examinations and intraoperative findings. Method of progressive enzymatic degradation of tissue was used in order to describe wear particles distribution in polyethylene granuloma and surrounding periprosthetic tissues. Results showed uneven incidence of wear particles in the surroundings of the total joint replacement. The incidence correlated with X-ray examinations and intraoperative findings. Distribution of particles was described as well as new determination methods and further...

<p>During braking, both the rotor and the pads in disc brakes are worn. Since disc brakes are not sealed, some of the wear particles generated can become airborne. Several studies have found an association between adverse health effects and the concentration of particles in the atmosphere, so it is of interest to improve our knowledge of the airborne wear particles generated by disc brakes. However, in field tests it is difficult to distinguish these particles from others in the surrounding environment, so it may be preferable to use laboratory test stands and/or simulation models to study the amount of airborne wear particles generated.</p><p>This thesis deals with a simulation methodology for prediction of airborne wear particles from disc brakes and three experimental methods for testing disc brake materials with focus on airborne wear particles. The four appended papers discuss the possibility to both measure and predict the number and size distribution of airborne wear particles that originate from the pad to rotor contact. The objective is to develop a simulation methodology that predicts the number and size distribution of airborne wear particles from disc brakes.</p><p>Paper <strong>A</strong> describes how a modified pin-on-disc machine was used to study airborne wear particles originating from different disc brake materials. The results indicate that the test setup can be used to measure and rank the number concentration and size distribution of the airborne wear particles generated.</p><p>Paper <strong>B</strong> describes a disc brake assembly test stand for measurements of airborne wear particles from disc brakes. The results indicate that the test setup can be used to measure the number concentration and size distribution of airborne wear particles generated from disc brake materials. The results also indicate a promising ability to rank different pad/rotor material combinations with respect to the number concentration of airborne wear particles.</p><p>Paper <strong>C</strong> compares measurements made in passenger car field tests with measurements made in a disc brake assembly test stand and in a pin-on-disc machine. A promising correlation between the three different test methods is found.</p><p>Paper <strong>D</strong> presents a simulation methodology for predicting the number and size distribution of airborne wear particles using finite element analysis (FEA). The simulated number distribution is compared with experimental measurements at component level. The result indicates that the proposed methodology may be used to predict the number concentration and size distribution of airborne particles generated in the pad-to-rotor contact.</p>

During braking, both the disc and pads in disc brakes are worn. Since disc brakes are not sealed,some of the wear particles generated can become airborne. Several studies have found anassociation between adverse health effects and the concentration of particles in the atmosphere,so it is of interest to improve our knowledge of the airborne wear particles generated by discbrakes. This thesis deals with experimental and computational methods focusing on airborne wearparticles from disc brakes. The eight appended papers discuss the possibility to both measure andnumerically determine the concentration and size distribution of airborne wear particles thatoriginate from the pad-to-disc contact. The objective is to increase the scientific knowledge ofairborne wear particles generated from disc brakes. Papers A, B and C describe tests of disc brake materials conducted in a modified pin-on-discmachine. The results show that the test set-up can be used to measure and rank disc brakematerials with respect to the concentration of airborne particles generated. Ultrafine (nanosized),fine and coarse airborne wear particles that contain metals such as iron, copper and tin werefound. Papers D and E describe a novel disc brake assembly test stand and tests of disc brake materialsconducted in it. The results show that the test set-up can be used to measure the concentrationand size distribution of airborne wear particles generated from disc brake materials. The resultsalso indicate an ability to rank different pad/disc combinations with respect to the concentrationof airborne wear particles. Furthermore, the results suggest that this test stand can be used tostudy rust layer removal from the disc and that airborne particles are generated even at low brakepressures, such as used to remove dirt from the disc. Paper F compares measurements made in passenger car field tests with measurements made in adisc brake assembly test stand and in a pin-on-disc machine. A promising correlation between thethree different test methods is found. Paper G presents and discusses a simulation methodology that numerically determines theconcentration and size distribution of airborne wear particles generated from the pad-to-disccontact in disc brakes by using general-purpose finite element software. Paper H discusses a cellular automaton model that describes the microscopic contact situationbetween the pad and disc in disc brakes. This model is used to numerically determine the amountof wear that leaves the contact. The results correlate qualitatively with experimental observationsfound in the literature. / QC 20110317