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1.
J Periodontal Res ; 53(1): 1-11, 2018 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-28766712

RESUMEN

This study aimed to assess the literature available on the effects, on peri-implant tissues, of degradation products released from dental implants as a consequence of therapeutic treatment for peri-implantitis and/or of wear-corrosion of titanium. A literature review of the PubMed medline database was performed up to December 31, 2016. The following search terms were used: "titanium wear and dental implant"; "titanium corrosion and dental implant"; "bio-tribocorrosion"; "peri-implantitis"; "treatment of peri-implantitis"; "titanium particles release and dental implant"; and "titanium ion release and dental implant". The keywords were applied to the database in different combinations without limits of time period or type of work. In addition, the reference lists of relevant articles were searched for further studies. Seventy-nine relevant scientific articles on the topic were retrieved. The results showed that pro-inflammatory cytokines, infiltration of inflammatory response cells and activation of the osteoclasts activity are stimulated in peri-implant tissues in the presence of metal particles and ions. Moreover, degenerative changes were reported in macrophages and neutrophils that phagocytosed titanium microparticles, and mutations occurred in human cells cultured in medium containing titanium-based nanoparticles. Debris released from the degradation of dental implants has cytotoxic and genotoxic potential for peri-implant tissues. Thus, the amount and physicochemical properties of the degradation products determine the magnitude of the detrimental effect on peri-implant tissues.


Asunto(s)
Implantación Dental Endoósea/efectos adversos , Implantes Dentales/efectos adversos , Periimplantitis/etiología , Corrosión , Humanos , Interleucina-1beta/metabolismo , Periimplantitis/metabolismo , Periimplantitis/terapia , Titanio
2.
J Periodontal Res ; 52(6): 946-954, 2017 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-28612506

RESUMEN

Two-piece implant systems are mainly used in oral implantology involving an osseointegrated implant connected to an abutment, which supports prosthetic structures. It is well documented that the presence of microgaps, biofilms and oral fluids at the implant-abutment connection can cause mechanical and biological complications. The aim of this review paper was to report the degradation at the implant-abutment connection by wear and corrosion processes taking place in the oral cavity. Most of the retrieved studies evaluated the wear and corrosion (tribocorrosion) of titanium-based materials used for implants and abutments in artificial saliva. Electrochemical and wear tests together with microscopic techniques were applied to validate the tribocorrosion behavior of the surfaces. A few studies inspected the wear on the inner surfaces of the implant connection as a result of fatigue or removal of abutments. The studies reported increased microgaps after fatigue tests. In addition, data suggest that micromovements occurring at the contacting surfaces can increase the wear of the inner surfaces of the connection. Biofilms and/or glycoproteins act as lubricants, although they can also amplify the corrosion of the surfaces. Consequently, loosening of the implant-abutment connection can take place during mastication. In addition, wear and corrosion debris such as ions and micro- and nanoparticles released into the surrounding tissues can stimulate peri-implant inflammation that can lead to pathologic bone resorption.


Asunto(s)
Diseño de Implante Dental-Pilar/efectos adversos , Implantes Dentales/efectos adversos , Titanio , Corrosión , Pilares Dentales/efectos adversos , Implantación Dental Endoósea/efectos adversos , Implantación Dental Endoósea/instrumentación , Fracaso de la Restauración Dental , Humanos
3.
Wear ; 332-333: 643-649, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-26085697

RESUMEN

Tribochemical reactions in a protein lubricated metal-on-metal (MoM) sliding contact may play a significant role for its wear performance. Such reactions lead to the formation of a carbonaceous 'tribofilm', which can act as a protective layer against corrosion and wear. The purpose of this study was to determine the effect of contact load on wear and the formation and retention of tribofilms. Wear tests were performed in a custom-made ball-on-flat testing apparatus that incorporated an electrochemical cell. A ceramic ball was used to articulate against low-carbon wrought CoCrMo alloy pins in bovine serum. Using a range of contact loads at a single potentiostatic condition (close to free potential), weight loss and changes in surface properties were evaluated. We determined that wear was influenced by the loading condition. As expected, wear increased with load, but the association between applied load and measured weight loss was not linear. In the intermediate load region, in the range of 32-48 N (~58-80 MPa), there was more than an order of magnitude drop in the wear per unit load, and the wear versus load data suggested an inflexion point at 49 N. Regression analyses yielded a cubic model (R2=0.991; p=0.0002), where the cubic term, which represents the inflexion, was highly significant (p=0.0021). This model is supported by the observations that the minimum in the friction versus load curve is at 52 N and the highest relative increase in polarization resistance occurred at 49 N. Scanning electron microscopy and Raman spectroscopy indicated the absence of a tribofilm for the low and within the contact area of the high load cases. Synergistic interactions of wear and corrosion seem to play an important role.

4.
Tribol Int ; 91: 235-245, 2015 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-26405372

RESUMEN

Modern hip prostheses feature a modular implant design with at least one tapered junction. This design can lead to several complications due to the introduction of additional interfaces, which are subjected to various loading conditions and micromotion. The main objective of current study is to develop a fretting corrosion apparatus, which is able characterize the mechanical and electrochemical behaviour of various existing metal alloy couples during fretting motion. This study describes the design and the main considerations during the development of a novel fretting corrosion apparatus, as well as determination of the machine compliance and the initial testing results. Machine compliance considerations and frictional interactions of the couples are discussed in detail. For the preliminary tests, metal alloy pins, made of Ti6Al4V and wrought high-carbon CoCrMo were mechanically polished to a surface roughness of less than 20nm. 2 pins (Diameter = 11mm) of either Ti6Al4V or CoCrMo were loaded onto a Ti6Al4V alloy rod at a normal force of 200N. The interface types included: Ti6Al4V-Ti6Al4V-Ti6Al4V, Ti6Al4V-Ti6Al4V-CoCrMo, and CoCrMo-Ti6Al4V-CoCrMo. The Ti6Al4V rod articulated against the metal alloy pins in a sinusoidal fretting motion with a displacement amplitude of ±50µm. Bovine calf serum (30g/L of protein content) was selected as a lubricant and tested at 2 different pH levels (pH 3.0 and 7.6). In all cases, current and friction energy were monitored during the fretting process. The results indicated distinct, material-specific current evolutions and friction energies. No significant differences were observed in electrochemical or mechanical behaviour in response to pH change. In general, Ti6Al4V-Ti6Al4V-Ti6Al4V couples displayed the earliest passivation and superior electrochemical behaviour compared to Ti6Al4V-Ti6Al4V-CoCrMo and CoCrMo-Ti6Al4V-CoCrMo under fretting conditions. In addition, fluctuations in current were observed in specific regions at all instances where Ti6Al4V was coupled with Ti6Al4V. These fluctuations were not observed in instances where Ti6Al4V was coupled with CoCrMo. These findings suggest transitions in the degradation mechanisms at the modular junction as a function of material couples/contacts. The findings may assist in improving the current hip modular junctions.

5.
Wear ; 271(9-10): 1210-1219, 2011 Jul 29.
Artículo en Inglés | MEDLINE | ID: mdl-21921971

RESUMEN

Metal-on-metal (MOM) hip prosthesis bearings have enjoyed renewed popularity, but concerns remain with wear debris and metal ion release causing a negative response in the surrounding tissues. Further understanding into the wear and corrosion mechanisms occurring in MOM hips is therefore essential.The purpose of this study was to evaluate the tribocorrosion behaviour, or interplay between corrosion and wear, of a low-carbon CoCrMo alloy as a function of loading. The tribocorrosion tests were performed using two tribometer configurations. In the first configuration, "System A", a linearly reciprocating alumina ball slid against the flat metal immersed in a phosphate buffer solution (PBS). In the second configuration, "System B", the flat end of a cylindrical metal pin was pressed against an alumina ball that oscillated rotationally, using bovine calf serum (BCS) as the lubricant and electrolyte. System B was custom-built to emulate in vivo conditions. The tribocorrosion tests were performed under potentiostatic conditions at -0.345V, with a sliding duration of 1800 seconds and a frequency of 1Hz. In System A the applied loads were 0.05, 0.5, and 1N (138, 296 and 373MPa, respectively) and in System B were 16, 32, and 64N (474, 597, and 752MPa, respectively). Electrochemical impedance spectroscopy (EIS) and polarization resistance were estimated. The total mass loss (K(wc)) in the CoCrMo was determined. The mass loss due to wear (K(w)) and that due to corrosion (K(c)) were determined. The dominant wear regime for the CoCrMo alloy subjected to sliding changes from wear-corrosion to mechanical wear as the contact stress increases. An attempt was made to compare both system, in their tribochemical responses and formulate some insights in the total degradation processes. Our results also suggest that the proteins in the serum lubricant assist in the generation of a protective layer against corrosion during sliding. The study highlights the need of adequate methodology/guidelines to compare the results from different test systems and translating in solving the practical problems.

6.
Biotribology (Oxf) ; 242020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-33015276

RESUMEN

Tribocorrosion of implants has been widely addressed in the orthopedic and dental research fields. This study is a systematic scoping review about research methods that combine tribocorrosion tests with cells/tissues cultures, aimed to identify related current problems and future challenges. We used 4 different databases to identify 1022 records responding to an articulated keywords search-strategy. After removing the duplicates and the articles that didn't meet the search-criteria, we assessed 20 full-text articles for eligibility. Of the 20 eligible articles, we charted 8 records on cell cultures combined with tribocorrosion tests on implant materials (titanium, CoCrMo, and/or stainless steel). The year of publication ranged from 1991 to 2019. The cell line used was mostly murine. Two records used fretting tests, while 6 used reciprocating sliding with pin-on-disc tribometers. An electrochemical three-electrode setup was used in 4 records. We identified overall two experimental approaches: cells cultured on the metal (5 records), and cells cultured near the metal (3 records). Research activities on tribocorrosion processes in the presence of cells have been undertaken worldwide by a few groups. After a limited initial interest on this topic in the 1990's, research activities have restarted in the last decade, renewing the topic with technologically more advanced setups and analytical tools. We identified the main problems to be the lack of test reproducibility and wear particle characterization. We believe that the main challenges lay in the interdisciplinary approach, the inter-laboratory validation of experiments, and the interpretation of results, particularly in relation to potential clinical significance.

7.
Int J Oral Maxillofac Surg ; 47(8): 1032-1042, 2018 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-29526560

RESUMEN

The aim of this study was to perform a literature review on the use of finite element modeling (FEM) for the evaluation of the biomechanical behavior of temporomandibular joint replacement (TMJR) devices. An electronic search of online medical and scientific literature database was conducted using selected search terms. The search identified 307 studies, of which 19 were considered relevant to this study. Of the 19 selected studies, 10 (52.6%) investigated the influence of geometry and fixation methods, while two (10.5%) evaluated the behavior of artificial condyle-fossa structures. The TMJR devices assessed in these studies included TMJ Inc. (aka Christensen; 63.2%), Zimmer Biomet (15.7%), Stryker (10.5%), and a theoretical intramedullary condylar component (5.3%); 26.3% of the studies evaluated custom TMJR devices. Such studies provided important data on the distribution of strain and stress through TMJR structural components and surrounding bone by using different software systems and methods. The mean stress values were lower on a custom TMJR condyle-ramus component and the supporting bone than on the stock device. FEM proved to be an accurate and valuable biomechanical simulation tool for studying the current TMJR devices and should be considered a useful tool for the improvement and development of future joint replacement devices.


Asunto(s)
Artroplastia de Reemplazo/métodos , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Prótesis Articulares , Articulación Temporomandibular/fisiopatología , Articulación Temporomandibular/cirugía , Humanos , Diseño de Prótesis
8.
Acta Biomater ; 32: 324-335, 2016 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-26768232

RESUMEN

In the management of end-stage temporomandibular joint disorders (TMD), surgeons must often resort to alloplastic temporomandibular joint (TMJ) total joint replacement (TJR) to increase mandibular function and form, as well as reduce pain. Understanding wear and failure mechanisms of TMJ TJR implants is important to their in vivo longevity. However, compared to orthopedic TJR devices, functional wear of failed TMJ TJR implants has not been examined. Not only do wear and corrosion influence TJR implant in vivo longevity, but so does reactivity of peri-implant tissue to these two events. The aim of this study was to examine and report on the wear of retrieved, failed metal-on-metal (MoM), metal-on-polymer (MoP), and titanium-nitride coated (TiN Coated) TMJ TJR implant components. A total cohort of 31 TMJ TJR devices were studied of which 28 were failed, retrieved TMJ TJRs, 3 were never implanted devices that served as controls. The mean time from implantation to removal was 7.24 years (range 3-15), SD 3.01. Optical microscopy, White Light Interferometry (WLI), Scanning Electron Microscopy (SEM), and Raman spectroscopy were utilized to characterize the surfaces of the devices. Data was acquired and evaluated by analyzing alloy microstructure. Substantial surface damage was observed between the articulating areas of the condylar head and the glenoid fossa components. Damage included pitting corrosion, evidence of deposited corrosion products, specific wear patterns, hard phases, surface depressions, and bi-directional scratches. Electrochemical analysis was performed on the MoM Control, retrieved, failed MoM, and TiN Coated devices. Electrochemical tests consisted of open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) tests conducted using the condylar head of the retrieved failed devices. EIS confirmed material properties as well as corrosion kinetics in vivo help to mitigate corrosion as reflected by the Raman spectroscopy results. In summary, this study demonstrated the role of wear and corrosion interactions on the early failure of TMJ TJR devices. Since the materials employed in most orthopedic TJR devices are similar to those used in TMJ TJR implants, studies such as this can provide data that will improve future embodiment paradigms for both. Further studies will include in vitro investigation of corrosion kinetics and the underlying tribocorrosion mechanism of TMJ TJR devices. STATEMENT OF SIGNIFICANCE: An attempt is made in this study, to examine the retrieved TMJ implants and conduct surface and electrochemical analysis; further a translation research approach is employed to compare the observations from the total hip replacement (THR) retrievals. A total cohort of 31 TMJ TJR devices were studied of which 28 were failed, retrieved TMJ TJRs, 3 were never implanted devices that served as controls. Data was acquired and evaluated by analyzing alloy microstructure. Substantial surface damage was observed between the articulating areas of the condylar head and the glenoid fossa components. Electrochemical analysis was performed on the MoM Control, retrieved, failed MoM, and TiN Coated devices. This study demonstrated the role of wear and corrosion interactions on the early failure of TMJ TJR devices. Since the materials employed in most orthopedic TJR devices are similar to those used in TMJ TJR implants, a comparison study was conducted.


Asunto(s)
Prótesis Articulares , Falla de Prótesis , Articulación Temporomandibular/patología , Espectroscopía Dieléctrica , Electricidad , Electroquímica , Humanos , Interferometría , Microscopía Electrónica de Rastreo , Espectrometría Raman
9.
Acta Biomater ; 12: 341-351, 2015 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-25448346

RESUMEN

In uncemented Ti6Al4V hip implants, the bone-stem interface is subjected to cyclic loading motion driven by the daily activities of the patients, which may lead to the complete failure of the implant in the long term. It may also compromise the proliferation and differentiation processes of osteoblastic cells (bone-forming cells). The main objective of this work is to approach for the first time the role of these organic materials on the bio-tribocorrosion mechanisms of cultured Ti6Al4V alloys. The colonized materials with MG63 osteoblastic-like cells were characterized through cell viability/proliferation and enzymatic activity. Tribocorrosion tests were performed under a reciprocating sliding configuration and low contact pressure. Electrochemical techniques were used to measure the corrosion kinetics of the system, under free potential conditions. All tests were performed at a controlled atmosphere. The morphology and topography of the wear scar were evaluated. The results showed that the presence of an osteoblastic cell layer on the implant surface significantly influences the tribocorrosion behavior of Ti6Al4V alloy. It was concluded that the cellular material was able to form an extra protective layer that inhibits further wear degradation of the alloy and decreases its corrosion tendency.


Asunto(s)
Corrosión , Prótesis de Cadera , Osteoblastos/química , Titanio/química , Aleaciones , Humanos , Microscopía Electrónica de Rastreo
10.
Am J Med ; 61(2): 215-20, 1976 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-952294

RESUMEN

Controversy exists regarding the relative safety of intravenously administered lidocaine and procainamide to patients with acutely impaired hemodynamics. Accordingly, their effects were studied in 15 such patients, 14 with acute myocardial infarction and one with cardiomyopathy and severe congestive heart failure. All had elevated levels of pulmonary capillary wedge pressure (greater than 15 mm Hg) and/or low cardiac index (less than 2.5 liters/min/m2). Patients were given lidocaine, a 100 mg bolus followed by a 3 mg/min infusion and, after at least a 30 minute recovery period, procainamide, a 100 mg bolus over 2 minutes followed by a 20 mg/min infusion for 20 to 25 minutes. Hemodynamic measurements were compared early and late in the infusion of each drug. Small, clinically insignificant differences were observed in the hemodynamic responses to the drugs, and no clinically significant deterioration occurred with either. Conventional therapeutic doses of intravenous procainamide can be administered by this regimen, to patients with acute myocardial infarction complicated by cardiac failure or low cardiac output, without producing deleterious hemodynamic effects.


Asunto(s)
Hemodinámica/efectos de los fármacos , Lidocaína/farmacología , Procainamida/farmacología , Enfermedad Aguda , Adulto , Anciano , Presión Sanguínea/efectos de los fármacos , Gasto Cardíaco/efectos de los fármacos , Depresión Química , Electrocardiografía , Corazón/fisiopatología , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Lidocaína/administración & dosificación , Lidocaína/efectos adversos , Masculino , Persona de Mediana Edad , Contracción Miocárdica/efectos de los fármacos , Infarto del Miocardio/fisiopatología , Procainamida/administración & dosificación , Quinidina/farmacología , Resistencia Vascular/efectos de los fármacos
11.
Am J Cardiol ; 38(4): 474-8, 1976 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-823809

RESUMEN

The hemodynamic effects of nitroglycerin ointment were studied in 22 patients with acute myocardial infarction. Control measurements were obtained and observations were made over the ensuing 240 minutes. There was no change in heart rate, cardiac index or stroke index. Ninety minutes after application of the ointment, peak decrements were evident in mean arterial pressure (from 100 to 88 mm Hg) (P less than 0.001), pulmonary capillary wedge pressure (from 19 to 13 mm Hg) (P less than 0.001), right atrial pressure (from 8 to 5 mm Hg) (P less than 0.001) and heart X systolic blood pressure (from 1,155 to 1,044 mm Hg/min X 10(-1) (P less than 0.02); significant changes were still present at 240 minutes. Total peripheral resistance decreased maximally from 19.8 to 17.2 units (P less than 0.02); the transmyocardial gradient (arterial diastolic -- pulmonary capillary wedge pressure) did not decrease during the study. These data indicate that nitroglycerin ointment improves cardiac performance in patients with acute myocardial infarction while reducing the determinants of myocardial oxygen consumption and preserving the transmyocardial gradient for coronary blood flow.


Asunto(s)
Infarto del Miocardio/tratamiento farmacológico , Nitroglicerina/administración & dosificación , Enfermedad Aguda , Adulto , Anciano , Presión Sanguínea/efectos de los fármacos , Gasto Cardíaco/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Femenino , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Hipotensión/inducido químicamente , Infusiones Parenterales , Masculino , Persona de Mediana Edad , Nitroglicerina/efectos adversos , Nitroglicerina/uso terapéutico , Pomadas , Factores de Tiempo , Resistencia Vascular/efectos de los fármacos
12.
Obstet Gynecol ; 48(6): 642-6, 1976 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-1086992

RESUMEN

Acute renal failure of obstetric origin is common among North Indian patients and comprised 72 (22.1%) of 325 patients undergoing dialysis over an 11-year period. Of these, 46 gravidas had developed renal failure following abortion, and 29 cases were due to complications of late pregnancy. The most striking feature of this study was a high incidence of irreversible renal lesions of bilateral diffuse cortical necrosis in early (18.6%) as well as late pregnancy (37.8%). Overall incidence of diffuse cortical necrosis was 25%. In the remainder, acute tubular necrosis was seen in 52 (72.2%), patchy cortical necrosis in 1 (1.4%), and tubular necrosis along with glomerular involvement in 1 patient (1.4%). Pathogenetic factors which contributed to the development of renal failure, either singly or in combination, were loss of blood failure, either singly or in combination, were loss of blood (79.1%), septicemia (31.9%), hypotension due th hemorrhagic and septicemic shock (51.4%), eclamptic toxemia (11.1%), and disseminated intravascular coagulation in 12.5% patients. Infrequent occurrence of disseminated intravascular coagulation in the septic anc eclamptic patients who developed diffuse cortical necrosis was an interesting finding, as was the fact that coagulopathy was more frequently observed in acute tubular necrosis. Late referral, frequent sepsis, and high incidence of bilateral diffuse cortical necrosis contributed significantly to a high mortality (55.3%).


Asunto(s)
Aborto Inducido/efectos adversos , Aborto Espontáneo/complicaciones , Lesión Renal Aguda/etiología , Complicaciones del Embarazo , Lesión Renal Aguda/mortalidad , Lesión Renal Aguda/patología , Eclampsia/complicaciones , Femenino , Humanos , Riñón/patología , Necrosis Tubular Aguda/etiología , Necrosis Tubular Aguda/patología , Hemorragia Posparto/complicaciones , Embarazo , Complicaciones del Embarazo/mortalidad , Complicaciones del Embarazo/patología , Complicaciones Cardiovasculares del Embarazo , Trastornos Puerperales/complicaciones , Sepsis/complicaciones
13.
Am J Trop Med Hyg ; 24(4): 692-7, 1975 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-1155703

RESUMEN

Eight patients with acute renal failure following snakebite were studied. Intravascular hemolysis and disseminated intravascular coagulation contributed to the development of acute renal failure in 6 patients. Direct nephrotoxicity causing acute renal failure is postulated in 2 patients, 1 of whom also revealed evidence of mild, disseminated intravascular coagulation. Three patients had histopathological lesions of acute symmetrical cortical necrosis and 3 had acute tubular necrosis. In 1 patient with acute tubular necrosis, in whom direct nephrotoxicity seemed to be responsible for renal failure, the striking histological feature was a uniform debasement and disappearance of tubular epithelium. In 2 patients with a clinical course of acute tubular necrosis, histological lesions could not be documented. All the 5 patients with acute tubular necrosis regained full recovery of renal function, 3 of them with the help of dialysis and 2 with conservative management. None of the 3 patients with acute cortical necrosis survived in spite of intermittent dialysis therapy.


Asunto(s)
Lesión Renal Aguda/etiología , Mordeduras de Serpientes/complicaciones , Lesión Renal Aguda/sangre , Lesión Renal Aguda/patología , Lesión Renal Aguda/terapia , Adolescente , Adulto , Biopsia , Pruebas de Coagulación Sanguínea , Niño , Coagulación Intravascular Diseminada/etiología , Epistaxis/etiología , Femenino , Fibrinólisis , Hematuria/etiología , Hemorragia/etiología , Humanos , Ictericia/etiología , Riñón/patología , Masculino , Persona de Mediana Edad , Oliguria/etiología , Diálisis Renal , Mordeduras de Serpientes/sangre , Mordeduras de Serpientes/patología , Mordeduras de Serpientes/terapia
14.
J Assoc Physicians India ; 41(2): 122-3, 1993 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-8335605

RESUMEN

Local necrosis and gangrene at the site of the bite are commonly observed after snake envenomation. However, Raynaud's phenomenon and gangrene occurring in a limb other than that bitten by the snake is encountered rarely. So far, there is only one report of such an episode in literature. Here we are reporting a case of patient with snake bite on the right foot following which he developed Raynaud's phenomenon of the left upper limb and dry gangrene of the tips of the left index and middle fingers. The snake was identified as Russel's viper.


Asunto(s)
Gangrena/etiología , Enfermedad de Raynaud/etiología , Mordeduras de Serpientes/complicaciones , Brazo/irrigación sanguínea , Dedos/patología , Humanos , Masculino , Persona de Mediana Edad , Venenos de Víboras
15.
J Mech Behav Biomed Mater ; 29: 199-212, 2014 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-24099949

RESUMEN

The demand for total hip replacement (THR) surgery is increasing in the younger population due to faster rehabilitation and more complete restoration of function. Up to 2009, metal-on-metal (MoM) hip joint bearings were a popular choice due to their design flexibility, post-operative stability and relatively low wear rates. The main wear mechanisms that occur along the bearing surface of MoM joints are tribochemical reactions that deposit a mixture of wear debris, metal ions and organic matrix of decomposed proteins known as a tribolayer. No in-depth electrochemical studies have been reported on the structure and characteristics of this tribolayer or about the parameters involved in its formation. In this study, we conducted an electrochemical investigation of different surfaces (bulk-like: control, nano-crystalline: new implant and tribolayer surface: retrieved implant) made out of two commonly used hip CoCrMo alloys (high-carbon and low-carbon). As per ASTM standard, cyclic polarization tests and electrochemical impedance spectroscopy tests were conducted. The results obtained from electrochemical parameters for different surfaces clearly indicated a reduction in corrosion for the tribolayer surface (Icorr: 0.76µA/cm(2)). Further, polarization resistance (Rp:2.39±0.60MΩ/cm(2)) and capacitance (Cdl:15.20±0.75µF/cm(2)) indicated variation in corrosion kinetics for the tribolayer surface, that attributed to its structure and stability in a simulated body environment.


Asunto(s)
Articulación de la Cadera , Metales Pesados/química , Aleaciones/química , Carbono/química , Corrosión , Electroquímica , Nanopartículas del Metal/química , Propiedades de Superficie
16.
J Long Term Eff Med Implants ; 24(1): 65-76, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24941407

RESUMEN

Adverse local tissue reactions to wear debris and corrosion products have lead to a sharp decline in the use of metal-on-metal (MOM) total hip athroplasties (THAs) clinically. Today, approximately 1 million patients are still carrying such a device. To gain a better understanding of the effect of wear and corrosion products on cells within the joint environment, it is important to generate conditions in vitro that resemble the in vivo system as closely as possible. In this paper, we present a novel tribocorrosion bioreactor that enables the simultaneous conduction of tribocorrosion and cell-culture experiments. In this setup, macrophage cell cultures are located in direct proximity to a tribological interface mimicking the sliding conditions of THA and are exposed to wear and corrosion products as they are generated. These products may include meta-stable species and metallo-organic complexes that have not been considered in earlier studies. The combination of standard tribological, electrochemical, and biological techniques is associated with several challenges that are described here in detail.


Asunto(s)
Reactores Biológicos , Técnicas de Cultivo de Célula , Células Cultivadas , Corrosión , Electroquímica , Reacción a Cuerpo Extraño/inmunología , Prótesis de Cadera/efectos adversos , Humanos , Macrófagos , Ensayo de Materiales , Prótesis Articulares de Metal sobre Metal/efectos adversos , Propiedades de Superficie
17.
J Dent Res ; 90(5): 613-8, 2011 May.
Artículo en Inglés | MEDLINE | ID: mdl-21335537

RESUMEN

UNLABELLED: Lipopolysaccharide (LPS) may induce peri-implantitis and implant failure. However, the role of LPS in titanium (Ti) electrochemical behavior remains unknown. We hypothesized that LPS in saliva with different pHs affects Ti corrosion properties. Thirty-six Ti discs (15 mm × 3 mm) were divided into 12 groups according to saliva pH (3, 6.5, and 9) and Escherichia coli LPS concentration (0, 0.15, 15, and 150 µg/mL). Electrochemical tests, such as open circuit potential, potentiodynamic, and electrochemical impedance spectroscopy, were conducted in a controlled environment. Data were evaluated by Pearson correlation and regression analysis (α = 0.05). LPS and pH affected Ti corrosive behavior. In general, lower pH and higher LPS concentration accelerated Ti corrosion. In the control group, the increase of pH significantly reduced the corrosion rate and increased the capacitance of the double layer. In LPS groups, the decrease of pH significantly increased the corrosion rate of Ti. LPS negatively influenced Ti corrosion behavior. ABBREVIATIONS: C(dl), capacitance of double layer; E(corr), corrosion potential; EIS, electrochemical impedance spectroscopy; I(corr), corrosion current density; I(pass), passivation current density; LPS, lipopolysaccharide; OCP, open circuit potential; R(p), polarization resistance; Ti, titanium.


Asunto(s)
Materiales Biocompatibles Revestidos/química , Lipopolisacáridos/química , Titanio/química , Corrosión , Espectroscopía Dieléctrica , Capacidad Eléctrica , Impedancia Eléctrica , Electroquímica , Escherichia coli , Concentración de Iones de Hidrógeno , Modelos Lineales , Ensayo de Materiales , Análisis de Regresión , Saliva Artificial/química , Estadísticas no Paramétricas , Propiedades de Superficie
18.
Braz J Med Biol Res ; 43(5): 476-82, 2010 May.
Artículo en Inglés | MEDLINE | ID: mdl-20490435

RESUMEN

Carbon nanotubes are highly versatile materials; new applications using them are continuously being developed. Special attention is being dedicated to the possible use of multiwalled carbon nanotubes in biomaterials contacting with bone. However, carbon nanotubes are also controversial in regards to effects exerted on living organisms. Carbon nanotubes can be used to improve the tribological properties of polymer/composite materials. Ultrahigh molecular weight polyethylene (UHMWPE) is a polymer widely used in orthopedic applications that imply wear and particle generation. We describe here the response of human osteoblast-like MG63 cells after 6 days of culture in contact with artificially generated particles from both UHMWPE polymer and multiwalled carbon nanotubes (MWCNT)/UHMWPE nanocomposites. This novel composite has superior wear behavior, having thus the potential to reduce the number of revision hip arthroplasty surgeries required by wear failure of acetabular cups and diminish particle-induced osteolysis. The results of an in vitro study of viability and proliferation and interleukin-6 (IL-6) production suggest good cytocompatibility, similar to that of conventional UHMWPE (WST-1 assay results are reported as percentage of control +/- SD: UHMWPE = 96.19 +/- 7.92, MWCNT/UHMWPE = 97.92 +/- 8.29%; total protein: control = 139.73 +/- 10.78, UHMWPE = 137.07 +/- 6.17, MWCNT/UHMWPE = 163.29 +/- 11.81 microg/mL; IL-6: control = 90.93 +/- 10.30, UHMWPE = 92.52 +/- 11.02, MWCNT/UHMWPE = 108.99 +/- 9.90 pg/mL). Standard cell culture conditions were considered as control. These results, especially the absence of significant elevation in the osteolysis inductor IL-6 values, reinforce the potential of this superior wear-resistant composite for future orthopedic applications, when compared to traditional UHMWPE.


Asunto(s)
Proliferación Celular/efectos de los fármacos , Ensayo de Materiales , Nanocompuestos , Osteoblastos/citología , Polietilenos/farmacología , Técnicas de Cultivo de Célula , Humanos , Osteoblastos/fisiología
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