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Background and Objective: Resistance to corrosion is an advantageous property of orthodontic brackets;however, due to low levels of pH found in the mouth of a patient, localized corrosion may occur. This can affect tooth movement by increasing friction between the arch wire and bracket slot and initiate enamel discoloration. Additionally, corrosion causes the release of elements that may lead to cytotoxic and biological side effects. The aim of this study was to compare the amount of corrosion caused by lemon juice, vinegar and Coca-Cola® on orthodontic brackets in vitro and then to recommend the most suitable diet during orthodontic treatment. Method: Sixty orthodontic brackets in three groups of twenty were immersed in a test solution (Fusamaya-Meyer artificial saliva plus lemon juice, vinegar or Coca-Cola) at a temperature of 37°C±1. Moreover, a negative control consisting of twenty brackets were put in pure artificial saliva. After 6 weeks the amount of corrosion was determined by measuring δW of mean weights of brackets and the results were analyzed by general linear models (repeated measurement). Results: Significant differences were seen during different weeks of the study (P<0.001) and different solutions(P<0.001). This study showed the amount of corrosion in orthodontic brackets was the most for cola followed by vinegar and then lemon juice. In addition, mean differences for cola versus lemon juice was -0.010(sig. <0.001), vinegar versus lemon juice was -0.006 (sig. =0.001) and cola versus vinegar was -0.004(sig. =0.013). Conclusion: Acidic effervescent soft drinks such as cola have to be eliminated or minimized in the nutritional diet of orthodontic patients because of their harmful effects on their brackets.

Introduction: Multiple and sometimes contradictory evidence exists on the relationship between dust exposure and respiratory symptoms with pulmonary disorders. The study was conducted to examine the effects of chronic exposure to street dust on the pulmonary parameters and respiratory complaints in sweepers. Methods: This cross-sectional study was conducted on 100 sweepers working in district 3 Bandar Abbas municipality in 2014. The control group was selected from the staff of the same municipality with an office/administrative position who lacked occupational respiratory exposures. In order to investigate pulmonary parameters, spirometry with Spirolab MIR3 were performed and FVC, FEV1, FEV1/FVC, PEF and FEF25-75 parameters were measured. Data were analyzed using STATA 12 software. Two Way ANOVA was used to compare respiratory parameters between two groups. Results: Prevalence of respiratory symptoms including cough, sputum, shortness of breath and wheezing had no significant differences in two groups. Values of FEV1, FEF25-75 and PEF showed significant decrease when adjusted for the effect of smoking on sweeper compared with administrative personnel (P<0.05). There were no statistically significant differences between two groups and other variables of FVC and FEV1/FVC. Conclusion: It seems that sweepers cleaning street, who are constantly exposed to dust, are at risk of developing respiratory symptoms and decline in spirometric indices. It is useful to apply protective measures to prevent exposure to dust and to perform annual spirometry for early detection of respiratory disorders in sweepers.

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