Background. Elastomeric chains and NiTi coil springs are two major traction aids in orthodontic tooth movements. Force degradation occurs over time in both groups, with higher percentages in elastic chains. The effects of environmental factors and some mouth rinses on this force decay have been previously studied. No study has been performed to evaluate the effect of current popular mouth rinses such as Orthokin, Sensikin and Persica on this force degradation.Methods. Forty pieces of elastic chains consisting of 5 loops (Ortho Technology, USA) and 40 NiTi closed coil springs (3M Unitek, Germany) were divided into 4 groups: control (artificial saliva), Orthokin mouthwash, Sensikin mouthwash and Persica mouthwash. All the groups were kept in an incubator at 37°C for 3 weeks. In the test groups, the samples were immersed in mouthwash twice a day. Force degradation was measured at 5 time intervals: baseline, 1 hour, 24 hours, 1 week and 3 weeks, using a digital force gauge. Repeated-measures ANOVA and one-way ANOVA were used for statistical analysis.Results. Force decay occurred over time in both elastic chainand coil spring groups. In elastic chain group, after 3 weeks, Orthokin mouth rinse had significantly lower force degradation compared to other groups (P < 0.05) and in coil spring group there were no statistically significant differences in force degradation after 3 weeks between the subgroups (P > 0.05).Conclusion. Based the results of this study, these three mouthwashes did not increase the force degradation of orthodontic traction aids under study.

Transmission of leachate from municipal solid waste landfills can potentially threaten ecosystems and human societies when the landfill has no system for collecting and treating leachate. Leachate produced from landfills finds its way through the soil to groundwater and surrounding surface waters, leading to pollution of water resources. This study aimed to investigate the effects of leachate from Khalkhal landfill (a city in Ardabil province, northwestern Iran) on the quality of groundwater and surrounding surface water. During 2019-2020, 4 wells (one control well located upstream of the landfill and three wells located downstream of the landfill) and two stations of the surface water resource of the Herochai river were spots for sampling. First, we did sampling during high and low rainfall seasons in accordance with the standards. Second, we analyzed the values of some physical, chemical, and biological quality parameters according to standard methods. The sampling of the soil texture was conducted following ASTM D 422 standards. Then, the soil was analyzed at Reference Laboratory of Water, Soil, and Plant in Ardabil province. The value of most parameters measured in the water of downstream wells was lower than the limit recommended by the Iranian and World Health Organization, indicating no limitation for drinking and agricultural uses. The quality of the Herochai river water was also relatively undesirable in terms of turbidity and total coliform in some samples. Additionally, consistent with the study results, no difference was observed between high and low rainfall seasons. According to the results obtained from different parameters, Schuler and Wilcox diagrams, and landfill water pollution index (LWPI), the quality of upstream and downstream water resources of Khalkhal municipal solid waste landfill was not much different. In other words, the landfill did not affect water.