Vacuum cleaner friction injuries in paediatrics: A 10 year review of national trends

Our regional burns service has gained experience in managing paediatric hand friction burns due to vacuum cleaners (VC).We aimed to evaluate our 10 year experience managing these injuries as well as reviewing national data trends in order to identify those at risk of injury.Materials and MethodsA International Burns Injury Database (IBID) request was made to review the number of burn injuries recorded due to Vacuum cleaner injuries (VCIs). In addition, a local IBID request was made to identify the number of burn injuries managed within our regional burns service.ResultsWe identified 288 VCIs which have increasingly occurred in England and Wales between 1996–2020 and 32 children who sustained these injuries within our regional burns service. A general theme from both national and local data highlighted that these injuries occurred in males (78%, n=25) with a mean age of 20 months (9 months–4.5 years) affecting children’s hands (94%). In 25 cases (78%) these injuries involved an interphalangeal joint. 85% (n = 27) of injuries were deep dermal/full thickness with eleven children (34%) undergoing surgical excision and skin grafts.DiscussionSignificant paediatric burn injuries can be sustained from VCs. Greater awareness is indicated for these injuries and legislation should be considered in order to improve the safety of vacuum cleaners. International burn societies are urged to collect data of these injuries in order to co-ordinate improved prevention strategies and change within the VC industry.     

Biotribology of artificial hip joints

Hip arthroplasty can be considered one of the major successes of orthopedic surgery, with more than 350000 replacements performed every year in the United States with a constantly increasing rate. The main limitations to the lifespan of these devices are due to tribological aspects, in particular the wear of mating surfaces, which implies a loss of matter and modification of surface geometry. However, wear is a complex phenomenon, also involving lubrication and friction. The present paper deals with the tribological performance of hip implants and is organized in to three main sections. Firstly, the basic elements of tribology are presented, from contact mechanics of ball-in-socket joints to ultra high molecular weight polyethylene wear laws. Some fundamental equations are also reported, with the aim of providing the reader with some simple tools for tribological investigations. In the second section, the focus moves to artificial hip joints, defining materials and geometrical properties and discussing their friction, lubrication and wear characteristics. In particular, the features of different couplings, from metal-on-plastic to metal-on-metal and ceramic-on-ceramic, are discussed as well as the role of the head radius and clearance. How friction, lubrication and wear are interconnected and most of all how they are specific for each loading and kinematic condition is highlighted. Thus, the significant differences in patients and their lifestyles account for the high dispersion of clinical data. Furthermore, such consideration has raised a new discussion on the most suitable in vitro tests for hip implants as simplified gait cycles can be too far from effective implant working conditions. In the third section, the trends of hip implants in the years from 2003 to 2012 provided by the National Joint Registry of England, Wales and Northern Ireland are summarized and commented on in a discussion.     

表面等离子渗氮处理钛的生物相容性评价：2.耐摩擦磨损性能

本文对用N2-H2混合气体在钛表面进行等离子氮化化学热处理获得的含氮表层进行了硬度、摩擦系数和耐磨损性能研究。结果表明，在镣表面生成的含氮层可以降低摩擦系数，显著提高了钛表层的硬度；在低负荷干摩擦条件下，含氮表层的磨损率有较大程度的改善。     

口腔正畸托槽与弓丝之间最大静摩擦力与静摩擦系数的实验研究

目的 设计一种体外装置,研究正畸托槽与弓丝之间的最大静摩擦和静摩擦系数.方法 实验选择了一种方丝托槽与两种直径0.4 mm的正畸钢丝,设计实验装置在干燥和有唾液条件下测量托槽与弓丝之间在不同正压力下的最大静摩擦力和静摩擦系数.结果 研究发现,在干燥条件下,国产弓丝与托槽之间产生的最大静摩擦力和静摩擦系数显著大于3 M弓丝,在有唾液时两者无显著区别.结论 不同条件下,弓丝与托槽之间产生的静摩擦力与静摩擦系数不同.     

Evaluation of the effect of collagen network degradation on the frictional characteristics of articular cartilage using a simultaneous analysis of the contact condition

Background. Superficial conditions and integrity of collagen network play an important role on the lubrication performance of articular cartilage. In this work, a technique based on the evanescent waves is used for the evaluation of contact condition during friction tests.

Methods. The frictional and superficial characteristics of the normal and degraded articular cartilages with high and low concentration of collagenase were evaluated. The optical apparatus was set in order to decrease the intensity of a light reflected at the interface between a prism and specimens when collagen fibers are found near the interface.

Findings. For all conditions, an increase in the attenuation of reflectance as the friction coefficient increases was observed with reasonable correlation. For the specimens degraded with collagenase, low friction and reduced attenuation of reflectance were observed at the beginning of sliding followed by a gradual increase in both friction and attenuation of reflectance. In comparison to the degraded specimens, normal specimens presented high friction at beginning and low friction at the end of test.

Interpretation. The superficial conditions and the presence of water at the articular surface play an important role in the lubrication of synovial joints. The ability to retain water for degraded specimens is impaired due to the loss of proteoglycan observed in the histological sections and hence, their low friction observed at the beginning of the test is not sustained for a long time. The use of evanescent waves demonstrated to be very useful in the analysis of the contact condition of articular cartilage.     

Studying the non-uniform expansion of a stent influenced by the balloon

Non-uniform expansion of cardiovascular stents, which exists widely in experiments, has a large influence on stent safety, but has seldom been studied in depth until now. In this paper we use a folded balloon with friction to expand a stent through finite element method (FEM), and study how this influences non-uniform expansion of the stent. The simulations were carried out using ABAQUES software. The results show that the stent expands non-uniformly only when the fold and friction are considered together in the FEM model. The extent of non-uniformity during expansion increases with rising friction coefficient values; with the same friction coefficient but different stent locations on the balloon the extent of non-uniform deformation is different. On the other hand, compared to a tri-folded balloon, a six-folded balloon clearly decreases the expansive non-uniformity, which means that by increasing the number of the folded parts of balloon the stent expands more uniformly.     

The economic burden of schizophrenia in Canada in 2004

ABSTRACT

Objective: To estimate the financial burden of schizophrenia in Canada in 2004.

Methods: A prevalence-based cost-of-illness (COI) approach was used. The primary sources of information for the study included a review of the published literature, a review of published reports and documents, secondary analysis of administrative datasets, and information collected directly from various federal and provincial government programs and services. The literature review included publications up to April 2005 reported in MedLine, EMBASE and PsychINFO. Where specific information from a province was not available, the method of mean substitution from other provinces was used. Costs incurred by various levels/departments of government were separated into healthcare and non-healthcare costs. Also included in the analysis was the value of lost productivity for premature mortality and morbidity associated with schizophrenia. Sensitivity analysis was used to test major cost assumptions used in the analysis. Where possible, all resource utilization estimates for the financial burden of schizophrenia were obtained for 2004 and are expressed in 2004 Canadian dollars (CAN$).

Results: The estimated number of persons with schizophrenia in Canada in 2004 was 234?305 (95% CI, 136?201–333?402). The direct healthcare and non-healthcare costs were estimated to be CAN$2.02 billion in 2004. There were 374 deaths attributed to schizophrenia. This combined with the high unemployment rate due to schizophrenia resulted in an additional productivity morbidity and mortality loss estimate of CAN$4.83 billion, for a total cost estimate in 2004 of CAN$6.85 billion. By far the largest component of the total cost estimate was for productivity losses associated with morbidity in schizophrenia (70% of total costs) and the results showed that total cost estimates were most sensitive to alternative assumptions regarding the additional unemployment due to schizophrenia in Canada.

Conclusions: Despite significant improvements in the past decade in pharmacotherapy, programs and services available for patients with schizophrenia, the economic burden of schizophrenia in Canada remains high. The most significant factor affecting the cost of schizophrenia in Canada is lost productivity due to morbidity. Programs targeted at improving patient symptoms and functioning to increase workforce participation has the potential to make a significant contribution in reducing the cost of this severe mental illness in Canada.     

Sliding contact fracture of dental ceramics: Principles and validation

Ceramic prostheses are subject to sliding contact under normal and tangential loads. Accurate prediction of the onset of fracture at two contacting surfaces holds the key to greater long-term performance of these prostheses. In this study, building on stress analysis of Hertzian contact and considering fracture criteria for linear elastic materials, a constitutive fracture mechanics relation was developed to incorporate the critical fracture load with the contact geometry, coefficient of friction and material fracture toughness. Critical loads necessary to cause fracture under a sliding indenter were calculated from the constitutive equation, and compared with the loads predicted from elastic stress analysis in conjunction with measured critical load for frictionless normal contact—a semi-empirical approach. The major predictions of the models were calibrated with experimentally determined critical loads of current and future dental ceramics after contact with a rigid spherical slider. Experimental results conform with the trends predicted by the models.     

Probing the interfacial strength of novel multi-layer zirconias

ObjectivesThe rapidly increasing use of zirconia-based CAD/CAM multi-layer structures in dentistry calls for a thorough evaluation of their mechanical integrity. This work examines the effect of the multi-layering architecture as well as variations in composition and inclusion of pigments among the layers on the flexural strength of multi-layer zirconias.MethodsA modified 4-point bending test, aided by a Finite Element Analysis (FEA), was used to probe the interfacial strength of 3 classes of yttria-partially-stabilized zirconia: Ultra Translucent Multi-Layer (UTML—5Y-PSZ), Super Translucent Multi-Layer (STML—4Y-PSZ), Multi-Layer (ML—3Y-PSZ). In accord with the size limitation (22-mm height) of CAD/CAM pucks, test samples were prepared in the form of “long” (25 × 2 × 3 mm) and “short” (17.8 × 1.5 × 2 mm) beams. Homogeneous beams (both long and short) were produced from either the Enamel (the lightest shade) or Dentin (the darkest shade) layer, whereas multi-layer beams (short beam only) were obtained by cutting the pucks along their thickness direction, where the material components of various shades were stacked.ResultsThe Enamel and Dentin layers exhibited similar flexural strength for a given material class, with ML amassing the highest strength (800–900 MPa) followed by STML (560–650 MPa) and UTML (470–500 MPa). The 3 classes of multi-layer zirconia showed a trade-off between strength and translucency, reflecting different yttria contents in these materials. The failure stress of the cross-sectional multi-layer beams was, however, ∼30% lower than that of their Enamel or Dentin layer counterparts, regardless of material tested.SignificanceThe weakness of interfaces is a drawback in these materials. Additionally, when measuring strength using short beam flexure, friction between the specimen and supporting pins and accuracy in determining loading span distances may lead to major errors.     

陶瓷托槽槽沟形貌及滑动摩擦现象的观察

目的对四种托槽和两种弓丝滑动前后进行外貌和槽沟微观形貌的分析,探讨影响托槽与弓丝间摩擦力大小的因素。方法对四种托槽用立体显微镜对外观形貌及其与两种弓丝滑动前后扫描电镜的微观形貌进行观察,用微硬度测量仪测量四种托槽槽沟、托槽体部位的硬度。结果四种托槽形貌及滑动前后槽沟部位的微观形貌不同,硬度也有差异,硬度由小到大分别为A托槽的金属槽沟部位（F）213．72±57．33HV,D托槽305．76±46．65HV,B托槽1087．12±139．86HV,A托槽体部1111．26±182．52HV,C托槽1309．81±225．56HV。结论硬度和表面粗糙度是影响托槽与弓丝间摩擦力的因素。陶瓷托槽硬度大,表面粗糙,与金属弓丝间的摩擦力大。