Objective:To evaluate the effect of different water-improving methods on dental fluorosis of children aged 8 to 12 in drinking-water-borne fluorosis areas in Xi'an City, and provide basis for making fine prevention and control measures.Methods:In 2018, 50 drinking-water-borne fluorosis villages in Xi'an City with water improvement time from 2011 to 2013 were selected as survey sites. The condition and the way of water improvement were surveyed, water fluoride content was determined and the prevalence of dental fluorosis in children aged 8 to 12 was examined, and the rates of dental fluorosis were compared before and after the water improvement in the 50 villages.Results:The water-improving projects were in normal operation in 50 villages. The medians of water fluoride content were 0.31, 0.88 and 1.14 mg/L in villages with municipal water supply, low fluorine well and defluoridation treatment water supply (the villages of different water-improvement methods were 12, 24 and 14, respectively), the differences were statistically significant ( H = 75.54, P < 0.01). The qualification rates of water fluoride in villages with different water-improvement methods were 100.00% (12/12), 79.17% (19/24) and 57.14% (8/14), and the difference was statistically significant (χ 2 = 6.95, P < 0.05). The detection rate of dental fluorosis was 43.17% (218/505) in the 11 villages with excessive water fluoride content, and the detection rate was 20.77% (331/1 594) in the 39 villages with qualified water fluoride content, the difference was statistically significant (χ 2 = 99.66, P < 0.01). After water improvement, the total detection rate of dental fluorosis (26.16%, 549/2 099) in the 50 villages was lower than that before water improvement (41.66%, 959/2 302), the difference was statistically significant (χ 2 = 117.17, P < 0.01). The detection rates of dental fluorosis were reduced after the water improvement in villages with municipal water supply and low fluorine well, the differences were statistically significant (χ 2 = 74.37, 69.36, P < 0.01). The detection rate was declined after water improvement in villages with defluoridation treatment water supply, but the difference was not significant (χ 2 = 0.78, P > 0.05). There was a statistically significant difference in the detection rate of dental fluorosis among children in villages with different water-improvement methods (χ 2 = 72.79, P < 0.01). The detection rate of dental fluorosis in villages with defluoridation treatment water supply [39.53% (200/506)] was higher than that in villages with municipal water supply [17.97% (133/740)] and low fluorine well [25.32% (216/853)], the differences were statistically significant ( P < 0.017); the detection rate of dental fluorosis in villages with municipal water supply was lower than that in villages with low fluorine well ( P < 0.017). Conclusions:The dental fluorosis of children's has been effectively controlled in the villages after water improvement in Xi'an City. The fluoride content in the water and the detection rate of dental fluorosis in children in some endemic areas are still high. It is necessary to further improve the water quality or consolidate the improvement effect as soon as possible.

Objective To assess the effects of defluoridation on prevalence of children's dental fluorosis in Xi'an City and study related influencing factors.Methods In 2017,the survey results of 2013 were collected from the previous investigation of drinking water type fluorosis in Xi'an Center for Disease Control and Prevention,and villages from drinking water type fluorosis areas were divided into five groups:0.0-,0.2-,0.5-,1.0-,and ≥ 1.5 mg/L,according to the fluoride concentrations of water.Four villages were randomly selected from each group,a total of 20 villages were selected as the investigation sites.A cross-sectional analytical study was conducted in the 20 villages,the fluoride in drinking water,the dental fluorosis of children aged 8-12 years and fluoride content in urine were detected,and the survey results were compared with those of 2013.Children were divided into five groups according to urinary fluoride contents as:0.0-(control),0.4-,0.8-,1.2-,and ≥ 1.6 mg/L,and the logistic regression model was used to evaluate the risk of dental fluorosis.Results There were no significant differences in water fluoride content between 2013 and 2017 (P ＞ 0.05).The rates of dental fluorosis among the study population in 2013 and 2017 were 25.35％ (200/789) and 20.58％ (164/797),and the difference was significant (x2 =5.11,P＜0.05).The prevalence rate and severity of dental fluorosis in 2013 [3.52％ (9/256),13.28％ (17/128),31.62％ (43/136),37.82％(45/119),57.33％(86/150)] and 2017[4.02％(10/249),11.82％(13/110),18.05％(24/133),29.13％(37/127),44.94％ (80/178)] were significantly increased with increase of water fluoride concentration (x2 =168.02,117.83,P ＜ 0.01).The prevalence rate of dental fluorosis was higher than 30％ in the three groups with water fluoride content 0.5-,1.0-and ≥ 1.5 mg/L in 2013,and the prevalence rates were decreased in these groups in 2017.The prevalence rate of dental fluorosis was lower than 30％ in the groups with water-fluorine content of 0.5-,1.0-＜1.5 mg/L,while the rate of dental fluorosis in the group with water-fluorine content of higher than 1.5 mg/L was still over 40％.The geometric mean of urinary fluoride of children in 2013 and 2017 were 1.02,0.67 rg/L,and the difference was significant (t =10.24,P ＜ 0.01).There were significant differences in children urinary fluoride between water fluoride groups in 2013 and 2017 (F =85.36,151.14,P ＜ 0.01).The risk of dental fluorosis increased with increase of urinary fluoride content,the odds ratio (OR) values were 5.26,7.83 and 13.28 in the three groups with the urinary fluoride 0.8-,1.2-,≥1.6 mg/L in 2013;the OR values in 2017 were 5.18,7.65 and 13.36,the differences were statistically significant (P ＜ 0.05).Conclusions The situation of water fluoride and dental fluorosis are not optimistic after defluoridation of drinking water.It is necessary to reinforce the measures of water defluoridation,and carry out classified management in endemic fluorosis areas.

Objective: To evaluate the dynamic prevalence of dental fluorosis of children and levels of fluoride in drinking water after improvement of water in Xi an City, to provide scientific basis for water fluoridation improvement. Methods: A total of 35 fluorosis endemic villages were selected as fixed monitor sites in 2014-2018, the ways of water improvement were surveyed, water fluorine content were detected and the prevalence of dental fluorosis in children aged 8 to 12 years were examined. Results: Rates of excess fluoride in drinking water from 2014 to 2018 were 22.86%, 14.29%,11.43%, 11.43% and 8.57%, the difference were significant(χ2=16.44, P<0.01).The dental fluorosis detection rates of children aged 8 to 12 years were 20.89%,18.22%,17.46%,18.13% and 16.76% in 2014-2018 which showed a obvious descending trend by year(χ2=10.02, P<0.01). The detection rate of dental fluorosis in children aged 8 and 9 years showed a decreasing trend by year(χ2=6.53, 4.54, P<0.05).The difference of total rate of dental fluorisis,rate of mild cases rate of moderate-to-severe cases were statistically between the villages without qualified water and the villages with normal fluorine water(χ2=179.22, 167.93,10.35, P<0.01). The rate of detection in the villages with the water fluorine exceed standard in 2014-2018 showed a declining trend year by year(χ2=28.50, P<0.01). The detection rate were significant different across water improvement methods(χ2=197.76, P<0.01). Detection rate of dental fluorosis decreased from 2014 to 2018 in the areas with municipal water supply showed a decreasing after year(χ2=12.16, P<0.01). Conclusion The improvement of municipal water supply shows significant effects on water fluorosis control, the detection rate of water fluoride and children s dental fluorosis in some villages with the other ways of water improvement are still higher than expected, the continuously monitor of fluoride content in water and dental fluorosis in children should be strengthened.

Objective:To assess the implementation of control measures and dental fluorosis of children in drinking-water-borne endemic fluorosis areas in Xi'an City, and to evaluate the implementation effects of the prevention and control measures.Methods:All drinking-water-borne endemic fluorosis villages in Xi'an were selected as the investigation sites. The progress and running condition of all water-improved projects were investigated, fluoride concentration in all the water-improved projects and tap water were tested. "Standard Test Method for Drinking Water" (GB/T 5750.5-2006) was used to test the water fluoride. A cross-sectional analytical study was conducted on school children aged 8 - 12 years old, the dental fluorosis was determined according to "Diagnosis of Dental Fluorosis" (WS/T 208-2011).Results:There were 273 drinking-water-borne endemic fluorosis villages, the rate of water improved villages was 91.58% (250/273), and all of the water-improved projects were operating normally (100.00%, 196/196). The rate of water-improved projects with qualified water fluoride was 88.27% (173/196), 237 villages had fluoride safe drinking water and the qualified rate was 86.81% (237/273). The median of water fluoride in the 250 villages with water-improved projects was 0.78 mg/L, the median was 0.83 mg/L in the 23 villages without water-improved projects, and the difference was not significant ( Z = 1.475, P > 0.05) . The overall prevalence of dental fluorosis among children aged 8 - 12 years old was 19.86% (1 960/9 871), and the dental fluorosis index was 0.39. The prevalence of dental fluorosis in the villages with qualified water fluoride was 16.13% (1 377/8 539), and the rate was 43.77% (583/1 332) in the villages with unqualified water fluoride, and the difference was significant (χ 2 = 553.283, P < 0.01). The prevalence of dental fluorosis in children with water fluoride content of 0.00 - 1.20, 1.21 - 1.50, and ≥1.51 mg/L was 16.13% (1 377/8 539), 41.20% (281/682), 46.46% (302/650), and the difference was significant (χ 2 = 559.011, P < 0.01), the severity of the disease was positively correlated with water fluorine concentration ( r = 0.273, P < 0.01). The epidemic situation in 202 villages was effectively controlled and 71 villages did not reach the control standard. Conclusions:The progress of water-improved projects and the rate of qualified water fluoride are not optimistic in Xi'an, the dental fluorosis of children is still higher than the government standard in the high fluoride drinking-water areas. The measures for water improving defluorination and disease surveillance should be strengthened.