Comparison of vacuum-formed and Hawley retainers: a systematic review.

INTRODUCTION: Hawley retainers (HRs) and vacuum-formed retainers (VFRs) are the 2 most commonly used retainers in orthodontics. However, the basis for selection of an appropriate retainer is still a matter of debate among orthodontists. In this systematic review, we evaluated the differences between VFRs and HRs. METHODS: Electronic databases (PubMed, EMBASE, Cochrane Library, ISI Web of Science, LILACS, and Pro-Quest) were searched with no language restriction. The relevant orthodontic journals and reference lists were checked for all eligible studies. Two article reviewers independently screened the retrieved studies, extracted the data, and evaluated the quality of the primary studies. RESULTS: A total of 89 articles were retrieved in the initial search. However, only 7 articles met the inclusion criteria. Some evidence suggested that no difference exists to distinguish between the HRs and VFRs with respect to changes in intercanine and intermolar widths after orthodontic retention. In terms of occlusal contacts, cost effectiveness, patient satisfaction, and survival time, there was insufficient evidence to support the use of VFRs over HRs. CONCLUSIONS: Additional high-quality, randomized, controlled trials concerning these retainers are necessary to determine which retainer is better for orthodontic procedures.

The effects of sub-lethal UV-C irradiation on growth and cell integrity of cyanobacteria and green algae.

The effects of UV-C irradiation on algal growth and cell integrity were investigated to develop a potential method for preventing cyanobacterial blooms. The toxic cyanobacterium Microcystis aeruginosa and three common freshwater green algae Chlorella ellipsoidea, Chlorella vulgaris, and Scenedesmus quadricanda were exposed to UV-C irradiation at 0-200mJcm(-2) and subsequently incubated for 9-15 d under normal culture conditions. Cell density and cell integrity were assessed using flow cytometry. The results suggested that UV-C irradiation at 20-200mJcm(-2) can suppress M. aeruginosa growth for 3-13 d in a dose-dependent manner. UV-C irradiation at 20 and 50mJcm(-2) is sub-lethal to M. aeruginosa cells as over 80% of the exposed cells remained intact. However, UV-C irradiation at 100 and 200mJcm(-2) induced severe cell disintegration in more than 70% of the irradiated cells. Neither significant suppression nor disintegration effects on green algae were observed for UV-C irradiation at 20-200mJcm(-2) in this study. Taken together, the sensitivity of M. aeruginosa to UV-C irradiation was significantly higher than that of the non-toxic C. ellipsoidea, C. vulgaris, and S. quadricauda, suggesting the potential application of sub-lethal UV-C irradiation for M. aeruginosa bloom control with a predictable low ecological risk.

[Dynamic experiment on controlling of Microcystis aeruginosa by UV-C irradiation].

A plug-flow UV-C reactor equipped with low pressure UV lamp was utilized to study the suppression effect after UV-C irradiation under the dynamic conditions on Microcystis aeruginosa, a typical cyanobacterium in algae blooms in China. The culture fluid of Microcystis aeruginosa was exposed to UV-C irradiation when pumped through the reactor. After that, the fluid was incubated under the normal culture condition, and sampled at 2 h, 1 d, 3 d, 5 d, 7 d, 9 d for determination of cell density using the inverted system fluorescence microscope. The experiments showed that, UV-C irradiation did not cause severe cell lysis, and UV-C irradiation at dose ranged from 36 to 115 mW x s x cm(-2), and 31 to 50 mW x s x cm(-2) could suppress Microcystis aeruginosa biomass growth for the 2.6 x 10(5)-2.7 x 10(5) cells x mL(-1) and 9.0 x 10(5)-1.15 x 10(6) cells x mL(-1) fluid in 9 days, respectively.

Verification of an improved method for determination of urinary iodine by As3+-Ce4+ catalytic spectrophotometry / 中国地方病学杂志

Objective To verify the feasibility and application value of an improved method for determination of urinary iodine by As3+-Ce4+ catalytic spectrophotometry.Methods Adults urine samples were collected,iodine calibration curves of 0-300 μg/L and 300-1200 μg/L were prepared,and urinary iodine was determined by the improved As3+-Ce4+ catalytic spectrophotometric method.Lyophilized human urinary iodine ingredient standards were used to validate linearity and range,limit of detection,precision and accuracy of this improved detection method.Results The linear range of the calibration curve was 0-300 μg/L,the detection limit was 1.8 μg/L,and the range of correlation coefficient was-0.9995--0.9997.When measuring urinary iodine at 40-80,100-149,200-280 μg/L,the relative standard deviations were 1.5％,0.8％ and 0.5％.When measuring urinary iodine at 40-80,100-149,150-180 μg/L,the average recoveries were 97.8％,99.8％ and 96.6％.Two given values of urinary iodine of national standard samples were (73.0± 9.0) and (206.0± 10.0)μg/L,and the results determined by this method were (75.5 + 0.9) and (207.5 ± 1.9)μg/L,and the relative deviation was 3.4％ and 0.7％,respectively,the results determined were all within the given value range.The linear range of the calibration curve was 300-1200 μg/L,the detection limit was 305.2 μg/L,the range of the correlation coefficient was-0.9996--0.9999.When measuring urinary iodine at 300-400,500-600 and 1000-1200μg/L,the relative standard deviations were 0.6％,1.0％ and 0.7％.When measuring urinary iodine at 300-499,500-599 and 600-700 μg/L,the average recoveries were 99.7％,99.2％ and 100.4％.Two given values of urinary iodine of national standard samples were (558.3 ± 3.5) and (884.8 ± 4.7)μg/L,the results determined by this method were (556.0 + 17.0) and (883.0 ± 28.0)μg/L,and the relative deviation was 0.4％ and 0.2％,respectively,the results were all within the given value range.Conclusions This method extends the detection range of iodine concentration,and improves precision and accuracy.This method greatly reduces the amount of arsenic used therefore reduces environmental pollution,which is suitable for promotion.

Application of global positioning systems and geographic information systems in drinking water defluoridation project in Liaoning province / 中国地方病学杂志

Objective To establish information management systems of drinking water defluoridation project in water-related endemic fluorosis areas and investigate the status of drinking water defluoridation project in Liaoning, provide the basis for the development of control measures. Methods Global positioning systems (GPS)and geographic information systems(GIS) were used in the study in August 2006 - July 2008. Water defluoridation projects of 1234 in 48 counties(cities, districts) in drinking water type of fluorosis areas were positioned. Latitude and longitude, water samples, water fluoride content were collected or tested. GIS was used to establish information management system of water defluoridation projects. Results We have established information management system for the facilities of decreasing water fluorine in drinking water type of endemic fluorosis regions in Liaoning. One thousand two hundred and thirty four defluoridation facilities distributed in east longitude between 39.39° - 43.37°,north latitude between 119.25° - 125.50°, and altitude between - 6.60 and 801.14 meter in 48 endemic fluorosis counties in 13 cities. Nine hundred and twenty seven facilities for decreasing fluorine were able to supply water regularly, accounting for 75.1% of investigated projects;29 facilities was .not yet completely rebuilt, accounting for 2.4%;278 facilities(supply water for 344 villages) were out of order or discarded for 22.5% of investigated projects.Water fluorine contents of 63 facilities were greater than 1.2 mg/L, accounting for 6.8% of investigation project.Facilities working regularly and water fluorine was in accord with hygienic standard for drinking water facilities were 70.0%. Conclusions The establishment of Liaoning province defluoridation project information management system in the whole province of drinking water type of fluorosis areas provides scientific basis for accurate decision-making on prevention and control of the disease.