Characterisation at the Bonding Zone between Fly Ash Based Geopolymer Repair Materials (GRM) and Ordinary Portland Cement Concrete (OPCC)

In recent years, research and development of geopolymers has gained significant interest in the fields of repairs and restoration. This paper investigates the application of a geopolymer as a repair material by implementation of high-calcium fly ash (FA) as a main precursor, activated by a sodium hydroxide and sodium silicate solution. Three methods of concrete substrate surface preparation were cast and patched: as-cast against ordinary Portland cement concrete (OPCC), with drilled holes, wire-brushed, and left as-cast against the OPCC grade 30. This study indicated that FA-based geopolymer repair materials (GRMs) possessed very high bonding strength at early stages and that the behavior was not affected significantly by high surface treatment roughness. In addition, the investigations using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy have revealed that the geopolymer repair material became chemically bonded to the OPC concrete substrate, due to the formation of a C–A–S–H gel. Fundamentally, the geopolymer network is composed of tetrahedral anions (SiO₄)⁴⁻ and (AlO₄)⁵⁻ sharing the oxygen, which requires positive ions such as Na⁺, K⁺, Li⁺, Ca²⁺, Na⁺, Ba²⁺, NH⁴⁺, and H₃O⁺. The availability of calcium hydroxide (Ca(OH)₂) at the surface of the OPCC substrate, which was rich in calcium ions (Ca²⁺), reacted with the geopolymer; this compensated the electron vacancies of the framework cavities at the bonding zone between the GRM and the OPCC substrate.     

Survival of patients receiving fibrinolytic therapy for acute ST-segment elevation myocardial infarction in a developing country – patient characteristics and predictors of mortality

There is paucity of outcomes data on patients receiving fibrinolytic therapy (FT) for acute ST-elevation myocardial infarction (STEMI) in Indo-Asians. We conducted this study to determine survival as well as correlates of mortality in this population. Hospital charts of 230 patients receiving FT for acute STEMI between January 2002 and December 2004 were reviewed. Primary outcome variable was total mortality. Cox proportional hazards regression models were constructed. At a median follow-up of 717 days, 13.5% died, majority (23) during the in-hospital period. Multivariate predictors of mortality included (adjusted hazards ratio [HR], 95% confidence interval [CI]) age (HR 1.06, 95% CI 1.01–1.13), ejection fraction (HR 0.93, 95% CI 0.89–0.97), admission white cell count (HR 1.02, 95% CI 1.01–1.04) and change in ST-segment elevation (HR 0.96, 95% CI 0.92–0.99). We conclude that patients receiving FT for acute STEMI in Pakistan are a relatively high-risk group with a 10% in-hospital mortality and high frequency of recurrent events. Comparison data with primary angioplasty as an alternative strategy are needed.     

Interplay between toothbrush stiffness and dentifrice abrasivity on the development of non-carious cervical lesions

Objective

This study investigated the effect of toothbrush stiffness and dentifrice slurry abrasivity on the development and progression of simulated non-carious cervical lesions (NCCLs).

Materials and methods

Human maxillary premolars were allocated to 12 groups generated by the association between toothbrushes, soft, medium, and hard stiffness, and simulated dentifrice slurries, lower, medium, and higher; deionized water (DI) served as negative control. Teeth were mounted on acrylic blocks, and their root surfaces partially covered with acrylic resin to simulate gingiva, leaving a 2-mm area apical to the cemento-enamel junction exposed to toothbrushing. Specimens were brushed with the test slurries for 35,000 and 65,000 double strokes. Impressions taken at baseline and after both brushing periods were scanned by a 3D optical profilometer. Dentin volume loss (mm³) was calculated by image subtraction. Data were analyzed using three-way ANOVA and Fisher’s PLSD tests.

Results

All toothbrushes caused higher volume loss when associated to higher abrasive slurry, compared to medium- and lower-abrasive slurries. Medium caused more volume loss than lower-abrasive slurry, which led to more volume loss than DI. Hard and medium toothbrushes were not different when used with medium- or higher-abrasive slurries. There were no differences among toothbrushes when used with DI and lower-abrasive slurry. Overall, 35,000 brushing strokes resulted in significantly less volume loss than 65,000.

Conclusions

Toothbrush stiffness was an important factor on NCCL development, especially when brushing with medium- and higher-abrasive slurries.

Clinical relevance

Medium and hard toothbrushes associated with medium- and high-abrasive toothpastes can yield more severe NCCLs.

     

Perspectives of physicians practicing in low and middle income countries towards generic medicines: A narrative review

Objectives

This review was conducted to document published literature related to physicians’ knowledge, attitudes, and perceptions of generic medicines in low- and middle-income countries (LMICs) and to compare the findings with high-income countries.

Methods

A systematic search of articles published in peer-reviewed journals from January 2001 to February 2013 was performed. The search comprised nine electronic databases. The search strategy involved using Boolean operators for combinations of the following terms: generic medicines, generic medications, generic drugs, generic, generic substitution, generic prescribing, international non-proprietary, prescribers, doctors, general practitioners, physicians, and specialists.

Results

Sixteen articles were included in this review. The majority (n = 11) were from high income countries and five from LMICs. The main difference between high income countries and LMICs is that physicians from high income countries generally have positive views whereas those from LMICs tend to have mixed views regarding generic medicines. Few similarities were identified among different country income groups namely low level of physicians’ knowledge of the basis of bioequivalence testing, cost of generic medicines as an encouraging factor for generic medicine prescribing, physicians’ concerns towards safety and quality of generic medicines and effect of pharmaceutical sales representative on generic medicine prescribing.

Conclusion

The present literature review revealed that physicians from LMICs tend to have mixed views regarding generic medicines. This may be due to differences in the health care system and pharmaceutical funding system, medicine policies, the level of educational interventions, and drug information sources in countries of different income levels.