Dental caries status and related factors among 5-year-old children in Shanghai.

BACKGROUND: Dental caries in young children is a difficult global oral health problem. In the last decade, China has put a great deal of effort into reducing the prevalence of dental caries. This study, which is part of the China Population Chronic Disease and Nutrition Surveillance 2021, aimed to investigate the prevalence of dental caries among children aged 5 in Shanghai, China, and its associated factors. METHODS: A total of 1281 children aged 5 years from 6 districts in Shanghai were selected by a stratified sampling method. The survey consisted of an oral health questionnaire and an oral health examination. The questionnaire included questions on oral health knowledge, attitudes, and behaviours. The oral health examination used WHO standards. After screening, the data were input and analysed. Chi-square tests and logistic regression analyses were used to study the relevant factors affecting dental caries. RESULTS: The prevalence of dental caries among 1281 children was 51.0%, the dmft index score was 2.46, the Significant Caries Index (SiC) score was 6.39, and the SiC10 score was 10.35. Dental caries experience was related to the frequency of sweet drink consumption, the age of starting tooth brushing, eating habits after brushing, whether the children had received an oral examination provided by the government (p < 0.05), and the mother's education level but was not related to sex, the use of fluoride toothpaste, the frequency of brushing, whether the parents assisted brushing, or the frequency of flossing (p > 0.05). Logistic regression analysis showed that the region of residence, eating after brushing and the age of starting brushing were associated with dental caries. CONCLUSIONS: Dental caries remained prevalent among 5-year-old children in Shanghai, China. Prevention strategies that target the associated factors including region of residence, eating after brushing, and the age of starting brushing should be considered.

A survey on knowledge and attitudes towards molar-incisor hypomineralization among undergraduate and postgraduate students at the School of Stomatology, Wuhan University.

BACKGROUND: Molar incisor hypomineralization (MIH) is a developmental dental disease, and its clinical management challenges dentists. This study aimed to investigate the knowledge about MIH and the attitudes towards learning more about MIH among undergraduate and postgraduate students attending the School of Stomatology, Wuhan University. METHODS: This survey was based on a questionnaire modified based on previous studies. The questionnaire was sent to 540 undergraduate and postgraduate students from the School of Stomatology, Wuhan University. The questions covered their clinical experience, perceptions, clinical management, and preferences for further training. Data were analysed with the Chi-square test. RESULTS: We collected 368 questionnaires (response rate: 68%). Among them, 89% (328/368) were eligible for analysis. Most respondents (80%) had heard of MIH, primarily from classroom teaching. However, only 40% of the students had observed the disease clinically, and a relatively low proportion of students were familiar with the aetiology, prevalence, differential diagnosis, and treatment of MIH. Most respondents were highly enthusiastic and had great expectations about further systematic teaching about MIH. CONCLUSION: Most students in this study had heard of MIH, but few were familiar with the principles of its differential diagnosis. Systematic teaching about MIH is warranted.

Establishing mainstream partial nitrification in the membrane aerated biofilm reactor by limiting the oxygen concentration in the biofilm.

The proliferation of nitrite oxidizing bacteria (NOB) still remains as a major challenge for nitrogen removal in mainstream wastewater treatment process based on partial nitrification (PN). This study investigated different operational conditions to establish mainstream PN for the fast start-up of membrane aerated biofilm reactor (MABR) systems. Different oxygen controlling strategies were adopted by employing different influent NH4+-N loads and oxygen supply strategies to inhibit NOB. We indicated the essential for NOB suppression was to reduce the oxygen concentration of the inner biofilm and the thickness of aerobic biofilm. A higher NH4+-N load (7.4 g-N/(m2·d)) induced higher oxygen utilization rate (14.4 g-O2/(m2·d)) and steeper gradient of oxygen concentration, which reduced the thickness of aerobic biofilm. Employing closed-end oxygen supply mode exhibited the minimum concentration of oxygen to realize PN, which was over 46% reduction of the normal open-end oxygen mode. Under the conditions of high NH4+-N load and closed-end oxygen supply mode, the microbial community exhibited a comparative advantage of ammonium oxidizing bacteria over NOB in the aerobic biofilm, with a relative abundance of Nitrosomonas of 30-40% and no detection of Nitrospira. The optimal fast start-up strategy was proposed with open-end aeration mode in the first 10 days and closed-end mode subsequently under high NH4+-N load. The results revealed the mechanism of NOB inhibition on the biofilm and provided strategies for a quick start-up and stable mainstream PN simultaneously, which poses great significance for the future application of MABR.

Study on enhanced denitrification using particulate organic matter in membrane bioreactor by mechanism modeling.

Particulate organic matter (POM) in wastewater is a potential denitrification carbon source, while the optimal operational mode using denitrification mechanism with POM is still unclear in wastewater treatment plants. In this work, we investigated the denitrification rates (DNRs) in a full-scale membrane bioreactor (MBR) coupled with two-stage pre-anoxic (pre-AN), and then evaluated the POM denitrification efficiency using mechanism modeling. The results indicate that POM related fraction accounted for the majority of the obtained specific DNR of 1.39±0.46mgNg(-1) MLVSS h(-1) in the second pre-AN without available soluble carbon source. The modeling approaches with calibration and validation procedures estimated a high residual POM concentration of 0.17g COD g(-1) MLVSS in the activated sludge, which provided specific DNR of 1.14mgNg(-1) MLVSS h(-1). High POM retention time in the reactor was the result of high solid retention time used in the MBR. In particular, post-AN of high biomass concentration could provide the highest POM denitrification efficiency in MBR. The MBR process combined with additional sludge reduction technology could further enhance denitrification by POM.