Force decay evaluation of latex and non-latex orthodontic intraoral elastics: in vivo study

ABSTRACT Objective: This clinical study was conducted in order to evaluate force decay over time of latex and non-latex orthodontic intraoral elastics. Methods: Patients (n = 15) were evaluated using latex and non-latex elastics in the periods of : 0, 1, 3, 12 and 24 hours. The rubber bands were transferred to the testing machine (EMIC DL-500 MF), and force values were recorded after stretching the elastic to a length of 25mm. Paired t test was applied and analysis of variance (ANOVA) was used to evaluate the variation of force generated. LSD (Fisher's least significant difference) post-hoc test was thus employed. Results: As regards the initial forces (zero time), the values of force for non-latex elastic were slightly higher than for the latex elastic. In the subsequent times, the forces generated by the latex elastic showed higher values. Regarding the material degradation, at the end of 24 hours the highest percentage was observed for non-latex elastic. Conclusions: The latex elastics had a more stable behavior during the studied period, compared with non-latex.

RESUMO Objetivo: o objetivo deste estudo clínico foi avaliar e comparar o comportamento dos elásticos de látex e não látex quanto à perda de força ao longo do tempo. Método: os pacientes (n = 15) foram avaliados usando ambos os tipos de material (látex e não látex) em cada tempo: 0, 1, 3, 12 e 24 horas. Os elásticos foram transferidos para a máquina de ensaios mecânicos (EMIC DL-500 MF) e os valores de força foram registrados após a distensão dos elásticos a uma distância de 25 mm. Foi aplicado o teste t pareado, e a análise de variância (ANOVA) foi realizada para verificar a variação das forças geradas em todos os tempos estudados. Em seguida, o teste post-hoc LSD (Fisher's least significant difference) foi aplicado. Resultados: quanto às forças iniciais (tempo zero), os valores de força dos elásticos não látex foram ligeiramente maiores do que dos elásticos de látex. Nos tempos subsequentes, as forças geradas pelos elásticos de látex apresentaram valores superiores às geradas pelos elásticos não látex. Em relação à degradação do material, ao fim do período de 24 horas, o maior percentual foi observado pelos elásticos não látex. Conclusões: os elásticos de látex apresentaram comportamento mais estável durante o período de estudo, em comparação aos não látex.

Influence of different beverages on the force degradation of intermaxillary elastics: an in vitro study

Objective: The aim of this study was to evaluate in vitro the effects of frequently ingested beverages on force degradation of intermaxillary elastics. Material and Methods: One hundred and eighty 1/4-inch intermaxillary elastics (TP Orthodontics) were immersed into six different beverages: (1) Coca-Cola®; (2) Beer; (3) Orange juice; (4) Red wine; (5) Coffee and (6) artificial saliva (control). The period of immersion was 15 min for the first and second cycles and 30 min for the third to fifth cycles. Tensile forces were read in a tensile testing machine before and after the five immersion cycles. One-way repeated measures ANOVA was used to identify significant differences. Results: Force degradation was seen in all evaluated groups and at all observation periods (p<0.05). A greater degree of degradation was present at the initial periods, decreasing gradually over time. However, no statistically significant differences were seen among groups at the same periods, showing that different groups behaved similarly. Conclusion: The chemical nature of the evaluated beverages was not able to influence the degree of force degradation at all observation periods.

Biodegradation of a blended starch/natural rubber foam biopolymer and rubber gloves by Streptomyces coelicolor CH13

Background: The growing problem of environmental pollution caused by synthetic plastics has led to the search for alternative materials such as biodegradable plastics. Of the biopolymers presently under development, starch/natural rubber is one promising alternative. Several species of bacteria and fungi are capable of degrading natural rubber and many can degrade starch. Results: Streptomyces coelicolor CH13 was isolated from soil according to its ability to produce translucent halos on a mineral salts medium, MSM, supplemented with natural rubber and to degrade starch. Scanning electron microscope studies showed that it colonized the surfaces of strips of a new starch/natural rubber biopolymer and rubber gloves and caused degradation by forming holes, and surface degradation. Starch was completely removed and polyisoprene chains were broken down to produce aldehyde and/or carbonyl groups. After 6 weeks of cultivation with strips of the polymers in MSM, S. coelicolor CH13 reduced the weight of the starch/NR biopolymer by 92 percent and that of the rubber gloves by 14.3 percent. Conclusions: This study indicated that this bacterium causes the biodegradation of the new biopolymer and natural rubber and confirms that this new biopolymer can be degraded in the environment and would be suitable as a ‘green plastic’ derived from natural sources.

Fundamentos sobre o conhecimento dos aditivos químicos presentes nas luvas de borracha / Fundamentals of the knowledge about chemical additives present in rubber gloves

FUNDAMENTOS: Uma das causas mais frequentes de dermatite de contato alérgica, de origem ocupacional, são os aditivos da borracha, presentes nos Equipamentos de Proteção Individual. Os aditivos das luvas natural e sintética mais alergênicos são tiurams, mercaptos e carbamatos. OBJETIVO: levantar o nível de conhecimento em relação aos aditivos químicos utilizados na fabricação das luvas de borracha sintética. MÉTODOS: Foi aplicado um questionário aberto a profissionais que trabalham com fabricação, pesquisa, prescrição e comercialização das luvas. Foi adotado o método de pesquisa qualitativa. RESULTADOS: Foram entrevistadas 30 pessoas: 4 pesquisadores na área de Medicina do Trabalho, 5 médicos do Trabalho, 2 técnicos de segurança do Trabalho, 1 médico do sindicato de trabalhadores da borracha, 1 engenheiro de Segurança do Trabalho, 1 engenheira de Produção do setor de fabricação de luvas de borracha, 4 empresários importadores de luvas, 1 empresário fabricante de luvas, 3 empresários que comercializavam Equipamentos de Proteção Individual, 3 vendedores de lojas de Equipamentos de Proteção Individual, 2 empresários de lojas que comercializavam produtos para alérgicos e 3 dermatologistas. CONCLUSÃO: O conhecimento da composição química das luvas é pequeno. A rotulagem das luvas, com a descrição da composição química, facilitaria a escolha do melhor tipo de luva para cada pessoa. Esta ação, de baixo custo para as empresas, seria um ganho, do ponto de vista da saúde pública, e teria grande repercussão nos usuários de luvas de borracha.

BACKGROUNDS: One of the most frequent causes of allergic contact dermatitis of occupational origin are rubber additives, which are present in Personal Protective Equipment (PPE). The most allergenic additives of natural and synthetic gloves are thiurams, carbamates and mercapto group. OBJECTIVE: To investigate the state of knowledge about the chemical additives used in the manufacture of synthetic rubber gloves. METHODS: This was a qualitative research study in which professionals working in the manufacture, research, prescription and commercialization of gloves answered an open questionnaire. RESULTS: 30 individuals were interviewed: 4 researchers in occupational medicine, 5 occupational physicians, 2 occupational safety technicians, a rubber workers' union physician, an occupational safety engineer, a pro duction engineer of rubber gloves, 4 importers of gloves, a manufacturer of gloves, 3 businessmen who sell PPE, 3 salesclerks working in stores that sell PPE, 2 businessmen who own stores that sell products for allergic indivi duals, and 3 dermatologists. CONCLUSION: Knowledge of the chemical composition of rubber gloves is scant. The labeling of gloves, with the description of their chemical composition, would facilitate choosing the best type of glove for each person. This low-cost action to businesses would be a gain from the standpoint of public health, with huge repercussions for users of rubber gloves.

Alergia al látex: avances en el desarrollo de inmunoterapias hipoalergénicas especificas / Latex allergy: advances in the development of specific hypoallergenic immunotherapies

This review provides a brief update about the strategies that have been developed for the hipoallergenic immunotherapy against latex allergens. Thus, recombinant mutants, chemically modified molecules, anti IgE monoclonal antibodies and T-cell epitope-based peptides have been used. Additionally, recent finds that show the importance of dendritic cells and their potential applicability to latex allergens are included.

N-nitrosamines in baby bottle nipples and pacifiers

N-nitrosamines - potent carcinogenic, embryopathic, teratogenic and mutagenic agents - hve been detected in baby bottle nipples and pacifiers. Due to children's special vulnerability to the toxic effects of these compounds, some countries have established limits and worked with industries to minimize their levels. However, in several other countries where the problem of high levels still exists, recommendations to minimize exposure are of importance. This article reviews the source as well as the types and levels of N-nitrosamines, nitrosatable amines and nitramines in baby bottle nipples and pacifiers. In addition, the effect of sterilization, migration of these compounds into water, milk, infant formulas, juices and saliva as well as their in vivo formation are discussed

Effect of addition of melamine/formaldhyde resin on the physical and mechanical properties of three rubber formulations

It has been found that the addition of melamine/formaldehyde resin by miling to natural [Pale crepe], synthetic [acrylonitrile-butadiene], and blend of the two [1: 1] vulcanizates gives some improvement in the physical and mechanical properties. These include tensile strength, elongation, modulus 300%, hardness sh, degree of swelling and the extracted soluble matter by some solvents

Modified formulation of natural rubber to be used as parenteral stoppers

Two modified natural rubber formulas were prepared. Ten parts melamine/formaldehyde per hundred parts of rubber were added to get suitable physico-mechanical and chemical properties. A comparative study between the two modified vulcanizates and a commercial rubber closure used by drug companies were carried out to investigate the validity of the suggested formulas to be used as parenteral stoppers