Publications

Radiation crosslinking of ultrahigh molecular weight polyethylene (UHMWPE) has been used to decrease the wear of joint implant bearing surfaces. While radiation crosslinking has been successful in decreasing femoral head penetration into UHMWPE acetabular liners in vivo, postirradiation thermal treatment of the polymer is required to ensure the oxidative stability of joint implants in the long term. Two types of thermal treatment have been used: (i) annealing below the melting point preserves the mechanical properties but the residual free radicals trapped in the crystalline regions are not completely eliminated, leading to oxidation in the long-term and (ii) annealing above the melting point (melting) eliminates the free radicals but leads to a decrease in mechanical properties through loss of crystallinity during the melting process. In this study, we hypothesized that free radicals could be reduced by annealing below the melting point under pressure effectively without melting due to the elevation of the melting point. By avoiding the complete melting of UHMWPE, mechanical properties would be preserved. Our hypothesis tested positive in that we found the radiation-induced free radicals to be markedly reduced (below the detection limit of state-of-the-art electron spin resonance) by thermal annealing under pressure in radiation crosslinked virgin UHMWPE and UHMWPE/vitamin-E blends without loss of mechanical properties.

BACKGROUND

Modelling is widely used to inform decisions about management of malaria and acute febrile illnesses. Most models depend on estimates of the probability that untreated patients with malaria or bacterial illnesses will progress to severe disease or death. However, data on these key parameters are lacking and assumptions are frequently made based on expert opinion. Widely diverse opinions can lead to conflicting outcomes in models they inform.

METHODS AND FINDINGS

A Delphi survey was conducted with malaria experts aiming to reach consensus on key parameters for public health and economic models, relating to the outcome of untreated febrile illnesses. Survey questions were stratified by malaria transmission intensity, patient age, and HIV prevalence. The impact of the variability in opinion on decision models is illustrated with a model previously used to assess the cost-effectiveness of malaria rapid diagnostic tests. Some consensus was reached around the probability that patients from higher transmission settings with untreated malaria would progress to severe disease (median 3%, inter-quartile range (IQR) 1-5%), and the probability that a non-malaria illness required antibiotics in areas of low HIV prevalence (median 20%). Children living in low transmission areas were considered to be at higher risk of progressing to severe malaria (median 30%, IQR 10-58%) than those from higher transmission areas (median 13%, IQR 7-30%). Estimates of the probability of dying from severe malaria were high in all settings (medians 60-73%). However, opinions varied widely for most parameters, and did not converge on resurveying.

CONCLUSIONS

This study highlights the uncertainty around potential consequences of untreated malaria and bacterial illnesses. The lack of consensus on most parameters, the wide range of estimates, and the impact of variability in estimates on model outputs, demonstrate the importance of sensitivity analysis for decision models employing expert opinion. Results of such models should be interpreted cautiously. The diversity of expert opinion should be recognised when policy options are debated.

BACKGROUND AND OBJECTIVES

Recent studies suggest an overall association between chronic kidney disease (CKD) and periodontal disease, but it is unknown whether this association is similar across various subpopulations.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study was a cross-sectional analysis of 2001 to 2004 National Health and Nutrition Examination Survey data. CKD was defined as a urinary albumin-to-creatinine ratio ≥30 mg/g or estimated GFR of 15 to 59 ml/min per 1.73 m(2). Adjusted odds ratios were calculated using multivariable logistic regression with U.S. population-based weighting.

RESULTS

These analyses included 6199 dentate adult participants (aged 21 to 75 years) with periodontal exams. The estimated prevalences of moderate/severe periodontal disease and CKD were 5.3% and 10.6%, respectively. Periodontal disease was associated with >2-fold higher risk of CKD that was moderately attenuated after adjustment for age, gender, race/ethnicity, tobacco use, hypertension, diabetes, educational attainment, poverty index ratio, and dental care use. There were no statistically significant interactions between periodontal disease and race/ethnicity, educational attainment, or poverty status. Less-than-recommended dental care use was associated with periodontal disease and CKD and was increasingly prevalent among nonwhites, lower educational attainment, and lower poverty status.

CONCLUSIONS

The association between periodontal disease and CKD is not significantly different among subgroups. However, because nonwhites, those with a lower educational level, and the poor less frequently report use of recommended dental care, the association between periodontal disease and kidney function over time may become stronger among these groups and warrants further investigation.