Probability statements regarding the ratio of standard deviations and correlation coefficient in a bivariate normal population

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Antibacterial nanosilver coated orthodontic bands with potential implications in dentistry

Background & objectives: Fixed orthodontic treatment, an indispensable procedure in orthodontics, necessitates insertion of dental bands. Insertion of band material could also introduce a site of plaque retention. It was hypothesized that band materials with slow-release antimicrobial properties could help in sustained infection control, prevention of dental plaque formation and further associated health risks. Considering the known antimicrobial proprieties of silver, a coating of silver nanoparticle (SNP) onto the stainless steel bands was done and characterized for its beneficial properties in the prevention of plaque accumulation. Methods: Coatings of SNPs on conventional stainless steel dental bands were prepared using thermal evaporation technology. The coated dental bands were characterized for their physicochemical properties and evaluated for antimicrobial activity and biocompatibility. The physiochemical characterization of band material both coated and uncoated was carried out using scanning electron microscope, energy dispersive spectroscopy, atomic force microscopyand contact angle test. Biocompatibility tests for coated band material were carried using L929 mouse fibroblast cell culture and MTT [3-(4, 5-dimethyl thiazol-2-yl)-2, 5-diphenyl tetrazolium bromide] assay. Antimicrobial activity of coated band material against Gram-positive bacteria was tested. Results: A stable and uniform coating of SNPs was obtained. The coated band materials were biocompatible as well as possessed distinct antimicrobial activity. Interpretation & conclusions: The SNP coated dental bands could be potential antimicrobial dental bands for future clinical use. Further studies need to be done to validate the efficiency of coated band materials in oral environments

Genetic polymorphisms and metabolism of endocrine disruptors in cancer susceptibility Polimorfismos genéticos e metabolismo dos desreguladores endócrinos na suscetibilidade ao câncer

Epidemiological studies have estimated that approximately 80% of all cancers are related to environmental factors. Individual cancer susceptibility can be the result of several host factors, including differences in metabolism, DNA repair, altered expression of tumor suppressor genes and proto-oncogenes, and nutritional status. Xenobiotic metabolism is the principal mechanism for maintaining homeostasis during the body's exposure to xenobiotics. The balance of xenobiotic absorption and elimination rates in metabolism can be important in the prevention of DNA damage by chemical carcinogens. Thus the ability to metabolize and eliminate xenobiotics can be considered one of the body's first protective mechanisms. Variability in individual metabolism has been related to the enzymatic polymorphisms involved in activation and detoxification of chemical carcinogens. This paper is a contemporary literature review on genetic polymorphisms involved in the metabolism of endocrine disruptors potentially related to cancer development.<br>Estudos epidemiológicos estimam que cerca de 80% dos cânceres estão relacionados a fatores ambientais. A suscetibilidade individual ao câncer pode resultar de vários fatores relacionados ao metabolismo de xenobióticos, reparo do DNA, expressão de genes supressores de tumor e protoncogenes e estado nutricional. O metabolismo é o principal mecanismo para manter a homeostasia durante a exposição dos organismos aos xenobióticos. O equilíbrio das taxas de absorção e eliminação dos xenobióticos tem um papel importante na prevenção de danos no DNA, provocados por carcinógenos químicos. Sendo assim, a habilidade de metabolizar e eliminar os xenobióticos pode ser considerada uma das primeiras linhas de defesa dos organismos. Variações no metabolismo individual têm sido relacionadas aos polimorfismos enzimáticos, envolvidos na ativação e desintoxicação de carcinógenos químicos. Neste trabalho, é realizada uma revisão da literatura contemporânea sobre os polimorfismos genéticos envolvidos no metabolismo de desreguladores endócrinos, potencialmente associados ao desenvolvimento do câncer