Eine biomechanische Evaluation von porösen Ti6Al7Nb-Gussimplantaten für orthopädische Anwendungen unter Verwendung einer vergleichenden Finite-Elemente-Analyse

Over the past decade, new developed and refined titanium casting technologies make it possible to produce dental and medical implants. Avoiding impurities and changes of the surface layer by α case formation are major challenges in titanium casting. In this context, the present results show the effect of four types of investments on the α case layer of Ti67-castings. In brief, Y2O3 based investment materials are a reliable and promising choice for the production of titanium castings compared to Invest-Ti-T, Al2O3 and ZrSiO4 based investment materials, although the processing of this material is comparatively difficult. It can be concluded that an α case layer with a suitable thickness has a positive effect on titanium castings and can help to improve mechanical properties such as Young’s modulus, flexure stress, and fatigue resistance. In the light of these results, 15 µm was determined as a critical thickness value for an α case layer. The main objective of this study was to evaluate the implant stability numerically after four weeks and six months implantation time for rat and sheep implants, respectively. The FEA was performed to simulate biomechanical push-out tests. The simulated average maximum push-out forces are higher than the experimentally measured values. Both 3D model curves reach the maximum push-out force at larger displacements. The computationally predicted stiffness values for both 3D models exhibited a high agreement with the experimentally calculated stiffness. The second stage of 2D model curves were similar to that of measured curves. However, no clear non-linear behavior was observed for both 3D model curves. Meanwhile, 2D models showed a uniform and continuous sliding stage, while implants eluding occurred faster and sliding stages curves were narrow in 3D models. Even though different stress magnitudes were obtained for both groups of rat and sheep implants, the stress distribution at the bone interface was similar. It can be concluded that 3D simulations were more sensitive than the 2D FE analyses. It should be noted that a detailed bone model is crucial and unit cell assumptions enhances the accuracy of FE analyses. Elongated tetrakaidecahedron unit cells improved the prediction of cancellous bone behavior and the highest accuracy of FE prediction was also achieved. FEA results allow to make statements about the average behavior of the implant bone interface. High correlations were found between push-out strength as estimated from FE and the experimentally measured push-out strength.In den letzten Jahrzehnten, ermöglichen neu entwickelte und verfeinerte Titan-Gusstechnologien die Herstellung verschiedenen Zahn- und medizinischer Implantate. Allerdings sind noch viele praktische Probleme zu lösen. Vermeidung der Verunreinigungen und Veränderungen der Oberflächenschicht durch α-Case Bildung sind große Herausforderungen in Titanguss. In diesem Zusammenhang umfassen die vorliegenden Ergebnisse die Auswirkung von vier verschiedenen keramischen Formmaterialien auf die Entstehung der α- Case-Schicht von Ti67-Gussteilen. In Kürze, Y2O3-basierte Formmaterialien sind eine zuverlässige und vielversprechende Wahl für die Herstellung von Titan-Gussteilen im Vergleich zu Invest-Ti-T-, Al2O3- und ZrSiO4-basierten Formmaterialien, obwohl die Verarbeitung dieses Materials vergleichsweise schwierig ist. Es lässt sich feststellen, dass eine α-Case-Schicht mit einer optimalen Dicke einen positiven Effekt auf Titan-Gussteile hat und dazu beitragen kann, die mechanischen Eigenschaften wie den Elastizitätsmodul, die Biegebeanspruchung und die Ermüdungsbeständigkeit zu verbessern. Angesichts dieser Ergebnisse wurden 15 μm als kritischer Dickenwert für eine α-case Schicht bestimmt. Das Hauptziel dieser Arbeit war es, die Implantatstabilität nach vier Wochen und sechs Monaten Implantationszeit für Ratten bzw. Schafimplantate numerisch zu bewerten. Die FEA wurde durchgeführt, um biomechanische push-out Tests zu simulieren. Die simulierten durchschnittlichen maximalen push-out Kräfte sind höher als die experimentell gemessenen Werte. Beide 3D-Modellkurven erreichen die maximale push-out Kraft bei größeren Verschiebungen. Die rechnerisch vorhergesagten Steifigkeitswerte für beide 3D-Modelle zeigten ein hohes Übereinstimmung mit der experimentell festgestellten Steifigkeit. Die zweite Stufe der 2D-Modellkurven ähnelte denen der gemessenen Kurven. Für beide 3D-Modellkurven wurde jedoch kein klares, nichtlineares Verhalten beobachtet. Mittlerweile zeigten 2D-Modelle ein gleichmäßiges und kontinuierliches Gleitreibungsverhalten, während die Trennung der Implantate von Knochenaufbau schneller auftraten und Gleitreibungsverhaltenkurven in 3D-Modellen schmal waren. Obwohl für beide Gruppen von Ratten- und Schafimplantaten unterschiedliche Stressgrößen erhalten wurden, war die Spannungsverteilung an der Knochenoberfläche ähnlich. Es lässt sich feststellen, dass 3D-Simulationen empfindlicher waren als die 2D-FE-Analysen. Es ist anzumerken, dass ein detailliertes Knochenmodell entscheidend ist und die Einheitszell Annahme die Genauigkeit von FE-Analysen erhöht. Langgestreckte Tetrakaidecahedron-Einheitszellen verbesserten die Vorhersage des spongiösen Knochenverhaltens und die höchste Genauigkeit der FE-Vorhersage wurde ebenfalls erreicht. FEA-Ergebnisse erlauben es, Aussagen über das durchschnittliche Verhalten der Implantat-Knochen-Grenzfläche zu machen. Es wurden hohe Korrelationen zwischen der von FE geschätzten Push-out Festigkeiten und der experimentell gemessenen Push-out Festigkeiten gefunden

Socioeconomic indicators are strong predictors of hepatitis A seroprevalence rates in the Middle East and North Africa

The goal of this analysis was to examine the association between age-specific hepatitis A virus (HAV) seroprevalence rates and various socioeconomic indicators within the Middle East and North Africa (MENA) region. We conducted a systematic review of all recently published studies on HAV conducted in the MENA region and identified the highest quality studies for inclusion in our analysis. We calculated the age at midpoint of population immunity (AMPI) for each study and estimated seroprevalence rates at the ages of 5, 10, and 15 years. Next, we identified the correlations between these metrics and several socioeconomic variables. HAV data collected in or after 2000 were available for 14 of the 19 countries in the MENA region. Four of the 14 included countries had intermediate HAV endemicity (Algeria, Saudi Arabia, Turkey, and UAE), five had high endemicity (Iran, Jordan, Lebanon, Morocco, and Tunisia), and five had very high endemicity (Egypt, Iraq, Palestine, Syria, and Yemen). Water and sanitation were not significant predictors of AMPI or seroprevalence, most likely because most countries in this region have high rates of access to these utilities. However, gross domestic product (GDP), gross national income (GNI), and the human development index (HDI) were all highly associated with AMPI and prevalence. The observed correlations suggest that of the MENA countries without recent HAV data, Bahrain, Kuwait, and Qatar most likely have low endemicity, Oman likely has intermediate endemicity, and Libya likely has high endemicity. While it is unlikely that a single correlation model would be suitable for use in all world regions, the approach utilized in this analysis might provide a simple but accurate method for using economic data to impute the endemicity profiles of countries without recent data in regions where at least several neighboring countries have conducted recent serostudies. Keywords: Drinking water, Hepatitis A, Middle East and North Africa, Seroprevalence, Socioeconomic statu

A national survey of surgical antibiotic prophylaxis in Turkey

OBJECTIVE: To assess the quality of antibiotic prophylaxis for clean and clean-contaminated elective surgical procedures. DESIGN: A cross-sectional, country-wide survey. SETTING: Thirty-six hospitals in 12 cities in Turkey. PARTICIPANTS: Four hundred thirty-nine surgeons from 6 different specialties who performed selected procedures of interest. METHODS: A random sample of surgeons from different hospitals was selected. A standardized data collection form was used to record the type of procedure, the names, doses, timing of the first doses, and duration of antibiotics, important decisive factors, and problems in the management of prophylactic antibiotic use for surgical procedures. RESULTS: Fifty-five percent of surgeons addressed completed the survey. For clean-contaminated procedures, 6% of surgeons did not use antibiotic prophylaxis, whereas 88% used more than a single dose. Inappropriate antibiotics were chosen for 32% of procedures. In 39% of procedures, the first dose of antibiotics was not administered during induction of anesthesia. Duration of prophylaxis was longer than 24 hours in 80% and longer than 48 hours in 46% of all procedures. Only 112 surgeons (26%) were using definitely appropriate prophylaxis in all ways. Multivariate analysis revealed that surgeons in university hospitals (OR, 2.353; CI95, 1.426-3.884; P = .001) and general surgeons (OR, 4.986; CI95, 2.890-8.604; P ;lt; .001) used antibiotic prophylaxis more appropriately. Patients not covered by health insurance (OR, 0.417; CI95, 0.225-0.772; P ;lt; .001) were associated with inappropriate prophylaxis. CONCLUSION: Given the high frequency of antibiotics prescribed for surgical prophylaxis in Turkey, adherence to surgical prophylaxis guidelines is urgently needed

Comparative evaluation of the Brucella Coombs gel test in laboratory diagnosis of human brucellosis

Brucellosis is widespread among humans and animals. Diagnosis of brucellosis mostly depends on serological methods. Serological tests are preferred over time-consuming and hazardous bacterial cultures in routine laboratory practice. However, these tests are somehow challenging due to ‘incomplete/blocking antibodies’ that prevent agglutination. Brucella Coombs gel test (BCGT) is newly developed test that contains Coombs antibodies (anti-human IgG) in gel microtubes and depends on gel centrifugation methods for the serological diagnosis of brucellosis. Here, performance of the BCGT is compared with standard serum tube agglutination (STA), standard serum tube agglutination with Coombs (C-STA) and immune capture agglutination (Brucellacapt). In total, 78 positive samples for study group and 16 samples for the control group were enrolled in the study. The samples were tested at dilutions of 1:40–1:5120. Titres at 1:160 and above were considered positive for brucellosis, whereas those lower than 1:160 were considered negative. Excellent agreement levels were determined between BCGT test and C-STA (κ, 0.894; p < 0.001), and BCGT and Brucellacapt (κ, 0.802; p < 0.001), when the diagnostic titre was accepted as 1:160. BCGT is easy to apply and interpret and provides reliable titre results in less than 2 h. It is also advantageous for screening

Molecular characterization of rotaviruses in mid-western Turkey, 2006-2007

Altindis, Mustafa/0000-0003-0411-9669; Banyai, Krisztian/0000-0002-6270-1772WOS: 000285418300019Vaccines against rotaviruses are now available in numerous countries, including Turkey. As the vaccines may show various efficiencies against different type specificities and routine vaccination in infants might result in selection and immune escape of wild-type rotavirus strains, strain surveillance has been initiated before and during the vaccine introduction. We aimed to provide corresponding information on local strain prevalence in Anatolia, mid-western Turkey during the introduction of rotavirus vaccines. Stool samples positive for group A rotavirus by commercial enzyme immunoassay were subjected to reverse transcription-polymerase chain reaction based genotyping of the outer capsid antigens, VP7 and VP4, determining G and P type specificities respectively. Among 36 fully and 5 partially typeable strains we detected genotype G1, G2, and G9 VP7 specificities and genotype P[4], P[6] and P[8] VP4 specificities in 5 individual and 4 mixed combinations. The most common strain was G2P[4] (n=17), followed by G9P[8] (n=9). Other strains were G1P[8] (n=2), G2P[8] (n=2), G1+2P[8] (n=2), G9P[4] (n=1), G2+9P[8] (n=1), G4+9P[6] (n=1), and G2P[4+8] (n=1). Partially typed strains included 2 G1P[NT] and 3 G2P[NT] strains. Our data may help determine a baseline of the rotavirus genotype prevalence in Turkey and see if changes in the incidence of individual strains will be observed after routine use of vaccine.Hungarian Scientific Research Fund (OTKA)Orszagos Tudomanyos Kutatasi Alapprogramok (OTKA) [T049020]We would like to thank Dr Ahmet Gayretli for his contributions to improve the paper. The helpful remarks of the anonymous Reviewer of our paper are also acknowledged. The study was supported in part by the Hungarian Scientific Research Fund (OTKA, T049020)

Serologic and Molecular Diagnosis of Human Parvovirus B19 in Rheumatoid Arthritis Patients

Objective: To investigate Human Parvovirus (HPV) B19 IgG and IgM antibody levels and B19 viral DNA using PCR method in the serum of Rheumatoid arthritis (RA) patients to determine the role of B19 in the ethiopathogenesis of RA

Comparative Usefulness of High Sensitivity C-Reactive Protein and C-Reactive Protein to Evaluate Inflammation in Patients with Rheumatoid Arthritis

Objective: Assessment of disease activity is very important for successful management of rheumatoid arthritis (RA). The use of high sensitivity C-reactive protein (hs-CRP) assays was recently recommended as a measure to identify low disease activity in RA. The aim of this study was to compare hs-CRP and C-reactive protein (CRP) levels to evaluate inflammation in patients with RA and to investigate their association with disease activity and the number of swollen/tender joints. Material and Methods: Eighty-six patients with RA and 65 age and sex matched healthy controls were enrolled in this study. All patients fulfilled the American College of Rheumatology (ACR) classification criteria for RA. Disease Activity Score (DAS) 28 was used for the assessment of disease activity. Number of swollen joints, number of tender joints and global assessment of the patient by using visual analog scale (VAS) were noted. CRP, hs-CRP, erythrocyte sedimentation rate (ESR) of the patients with RA and controls were measured. We analyzed the association between hs-CRP, CRP and ESR versus other clinical variables. Results: The patients with RA had significantly higher levels of ESR, hs-CRP and CRP compared with controls (p<0.05). The hs-CRP was more closely associated with DAS 28 (r: 0.73, p<0.001), VAS (r: 0.69, p<0.001), number of swollen joints (r: 0.46, p=0.005) and number of tender joints (r: 0.42, p=0.001) than CRP. Conclusion: Our findings suggested that hs-CRP might be used to evaluate disease activity and inflammation in RA and that hs-CRP testing might reflect systemic inflammation in a more accurate way than routine CRP assays