Dental caries and fluorosis experience of 8-12-year-old children by early-life exposure to fluoride

The role of FGF9-mediated TGF-β1/Smad signaling in enamel hypoplasia induced by exposure to fluoride and SO2 in rats

Many geographical areas of the world are polluted by both fluoride and sulfur dioxide (SO2). However, the effects of simultaneous exposure to fluoride and SO2 on teeth are unknown. Fibroblast growth factor-9 (FGF9) and transforming growth factor-β1 (TGF-β1) are key signaling molecules in enamel development. The purpose of the study was to explore the effects of co-exposure to fluoride and sulfur dioxide on enamel and to investigate the role and mechanism of FGF9 and TGF-β1. First, sodium fluoride (NaF) and SO2 derivatives were used to construct rat models and evaluate the enamel development of rats. Then, TGF-β1 (cytokine) treatment, SIS3 (inhibitor) treatment and FGF9 gene knockdown were used to explore the mechanism of enamel damage in vitro. The results showed that enamel column crystals in the exposed group were characterized by enamel hypoplasia, as indicated by alterations such as disarrangement of enamel column crystals, space widening and breakage. Ameloblasts also showed pathological changes such as ribosome loss, mitochondrial swelling, nuclear fragmentation and chromatin aggregation. The protein expression of FGF9 was higher and the protein expression of AMBN, TGF-β1 and p-Smad2/3 protein was lower in the groups treated with fluoride and SO2 individually or in combination compared with the control group. Further studies showed that TGF-β1 significantly upregulated p-Smad2/3 and AMBN protein expression and reduced the inhibitory effects of fluoride and SO2; furthermore, SISI blocked the effect of TGF-β1. In addition, knockdown of FGF9 upregulated TGF-β1 protein expression, further activated Smad2/3 phosphorylation, eliminated the inhibitory effects of fluoride and SO2, and increased the protein expression of AMBN. In brief, the study confirms that co-exposure to fluoride and SO2 can result in enamel hypoplasia in rats and indicates that the underlying mechanism may be closely related to the effect of FGF9 on enamel matrix protein secretion through inhibition of the TGF-β1/Smad signaling pathway.

Relationship between fluoride exposure and count of Streptococcus mutans in supragingival biofilm of mexican scholar children

Background/purpose

The use of fluoride is known to reduce the risk of dental caries. There is limited information on the relationship between Streptococcus mutans (S. mutans) and fluoride exposure. This study investigated the association between the count of S. mutans on supragingival biofilm and fluoride exposure of scholar children.

Materials and methods

In this cross-sectional study, 56 children from 9 to 11 years of age were selected. Fluoride concentration in drinking water, urine and saliva of each participant were assessed. The count of S. mutans was estimated by calculating the DNA copy number through a quantitative real time polymerase chain reaction (qPCR) assay. Also, sociodemographic data, oral and general health information and variables related to caries risk were evaluated. A stepwise multiple linear regression was performed in all caries related predictor variables with the count of S. mutans as the dependent variable.

Results

The multiple linear regression analysis showed that the concentration of fluoride in saliva (β = −3.029, p < 0.001) and urine (β = −2.057, p = 0.017), time of last visit to the dentist (β = 1.968, p = 0.001), plaque index (β = 1.637, p = 0.006) and number of surfaces with codes 3–6 (D_3-6MFS) of ICDAS II criteria (β = 0.283, p = 0.076) were significantly associated with the count of S. mutans (Adjusted R square = 0.427, p < 0.001).

Conclusion

Fluoride levels in urine and saliva were negatively associated with the count of S. mutans in supragingival biofilm. Plaque index, D_3-6MFS and time of last visit to the dentist showed a positive association.

NaF reduces KLK4 expression by decreasing Foxo1/Runx2 expression in LS8 cells

OBJECTIVE

This study aimed to investigate the effect of high fluoride on runt-related transcription factor 2 (Runx2) expression and to explore the possible relationship among Runx2, forkhead box o1 (Foxo1) and kallikrein 4 (KLK4) in high fluoride-treated ameloblasts.

DESIGN

Ameloblast-like cells (LS8 cells) were exposed to various concentrations of sodium fluoride (NaF) for up to 48 h. Runx2 expression was downregulated by gene silencing, and Foxo1 expression was up- and downregulated by gene overexpression and silencing, respectively. The mRNA and protein levels of Runx2, Foxo1, KLK4 and matrix metalloproteinase 20 (MMP20) were detected by qRT-PCR and western blotting.

RESULTS

Runx2 expression was decreased in a dose- and time-dependent manner in NaF-treated LS8 cells. The knockdown of Runx2 markedly decreased KLK4 expression in LS8 cells under NaF conditions. However, the variation trend of MMP20 was unclear. In addition, forced Foxo1 expression led to significant upregulation of Runx2 in LS8 cells under NaF conditions. In contrast, the knockdown of Foxo1 markedly decreased the Runx2 protein levels under NaF conditions. Moreover, Foxo1 downregulation markedly decreased runx2 mRNA levels, and this inhibition in LS8 cells was intensified when combined with NaF treatment.

CONCLUSION

The results indicated that NaF reduces Runx2 expression in LS8 cells and that decreased Foxo1/Runx2 expression induced by high fluoride is a cause of low KLK4 expression.

Excess Risk of Dental Caries from Higher Free Sugars Intake Combined with Low Exposure to Water Fluoridation

The study aimed to quantify the excess risk of interaction between high free sugars (sugars) intake and lack of exposure to water fluoridation on child dental caries. Data from the Australian National Child Oral Health Study, a population-based survey of 24,664 children aged 5 to 14 y, were collected using parental questionnaires and oral epidemiological examinations by trained examiners. Information on socioeconomic status, dental health behaviors, and dental service use was used as covariates. The number of servings of sugars-containing foods and drinks consumed in a usual day was assessed as the main exposure, categorized into 5 groups. Residential history was used to calculate lifetime exposure to fluoridated water (LEFW), categorized as low (<25%), medium (25% to <75%), or high (75%-100%). Caries prevalence (dmfs/DMFS >0) and experience (dmfs/DMFS) in the primary (ages 5-10 y) and permanent (ages 8-14 y) dentitions were the main dependent variables. The association of sugars intake and LEFW with each outcome was estimated in multivariable log-Poisson regression models with robust standard error estimation, adjusted for covariates. The relative excess risk due to interaction (RERI) between sugars intake and LEFW was estimated. Strong positive gradients in all outcomes were observed across sugars intake groups. Relative to the lowest intake group, the 3 highest intake groups had significantly higher adjusted prevalence ratios for having caries and higher adjusted mean ratios of caries experience in both dentitions, after controlling for all covariates. LEFW strongly and consistently attenuated the effects of all levels of sugars intake on the outcomes. RERI estimates indicated that a combination of lack of exposure to fluoridated water and high sugars intake resulted in greater excess risk of primary and permanent caries than if there was no interaction. Evidently, children with high sugars intakes and low exposure to water fluoridation are at disproportionately higher risk of dental caries.

Ultra-processed foods and early childhood caries in 0–3‐year‐olds enrolled at Primary Healthcare Centers in Southern Brazil

Objective:

To investigate the relationship between ultra-processed food consumption and early childhood caries.

Design:

Cross-sectional analysis of baseline data from a cluster randomised controlled study. Outcomes included the prevalence of children with non-cavitated and cavitated caries. The main exposure was the total daily consumption of ultra-processed foods (up to three times and four times or more), assessed through a FFQ. Potential confounders were socio-demographic characteristics of the child and caregiver/family, child breast-feeding, oral hygiene and use of dental services. Poisson regression using robust variance adjustment was used to estimate prevalence ratios (PR) and their respective 95 % CI.

Setting:

Primary Healthcare Centers in an urban area of Pelotas, Southern Brazil.

Participants:

Children aged 0–3 years (n 309).

Results:

Consumption of ultra-processed foods four times or more a day was found in 67·6 % of children; 24·4 and 12·0 % presented non-cavitated and cavitated caries, respectively. After adjustment, children who consumed ultra-processed foods four times or more a day were more likely to present both non-cavitated caries (PR 2·25, 95 % CI 1·19, 4·27, P = 0·013) and cavitated caries (PR 3·48, 95 % CI 1·18, 10·30, P = 0·024) compared with those who have consumed them up to three times a day.

Conclusions:

Consumption of ultra-processed foods is associated with early childhood caries. Interventions aiming at reducing ultra-processed food consumption should be implemented to improve children’s oral health.

Community-level predictors of Australian children's dental caries and injury

BACKGROUND

Social determinants of oral health are complex and have been described by conceptual frameworks. A widely embraced model of children's oral health was published by Fisher-Owens et al. (2007), identifying theoretical constructs influencing oral health. The current study aimed to investigate community-level constructs described in the conceptual model.

METHODS

The Longitudinal Study of Australian Children is a cross-sequential dual cohort study, with a representative sample (n = 10090) of Australian children. Generalized estimating equations were applied to model seven waves of carer-reported oral health and community measures.

RESULTS

In the final model, children living in Queensland had a 1.48 (CI 1.35-1.62) increased odds of dental caries over time. Children in low socio-economic status (SES) areas (OR 1.32 CI 1.20-1.44) had an increased odds of caries. The state of Queensland (OR 1.24 CI 1.05-1.46) and poor neighbourhood liveability (OR 1.17 CI 1.05-1.31) were predictors of dental injury.

CONCLUSION

By modelling available community measures, this study found SES and rurality were predictors of caries over childhood. Our results highlight the difficulty of applying conceptual models to oral health. The use of qualitative studies and realist reviews should be considered to complement statistical models to provide contextualized insights into funding, policy and service delivery on children's oral health.

Brick tea consumption is a risk factor for dental caries and dental fluorosis among 12-year-old Tibetan children in Ganzi

Brick tea contains high concentration of fluoride. The aim of the present work was to explore whether and how the brick tea is a risk factor for dental caries and dental fluorosis among Tibetan children in Ganzi. A cross-sectional study was conducted with 368 12-year-old Tibetan children in Ganzi. Dental caries was measured by DMFT index, and dental fluorosis severity was measured by Dean's Index. Community Fluorosis Index was used to estimate public health significance of dental fluorosis. Oral health-related behaviors and awareness, dietary habits and socioeconomic status were determined by a questionnaire. Bivariate and multivariate analyses were used to determine risk factors associated with dental caries and dental fluorosis. Dental caries prevalence was 37.50%, mean DMFT was 0.84 ± 1.53, while dental fluorosis prevalence was 62.23%. Community Fluorosis Index was 1.35, indicating a medium prevalent strength of dental fluorosis. Dental fluorosis was associated with mother's regular consumption of brick tea and residence altitude, and dental caries was associated with mother's regular consumption of brick tea. Mother's regular consumption of brick tea was a risk factor for both dental fluorosis and dental caries among children. Reducing mother's brick tea consumption during pregnancy and lactation may improve oral health status of their children.

A comparison of dental fluorosis in adult populations with and without lifetime exposure to water fluoridation

OBJECTIVES

There is a lack of evidence on the proportion and severity of fluorosis in adult populations exposed and not exposed to fluoridated water over their lifetimes. The aim of this study was to compare the proportion and severity of fluorosis in adults with lifetime exposure to water fluoridation with a nonexposed sample. A secondary aim was to report the gradient of fluorosis severity by age.

METHODS

A cross-sectional study recruited a sample with lifetime exposure to water fluoridation and a matched, nonexposed group. 580 participants, aged 18-52 years (mean 34.3, SD 9.4) and 64% female, were recruited in general dental practices located in fluoridated (Birmingham and County Durham) and nonfluoridated areas (Manchester). Three digital images were taken of their incisors and an experienced examiner who was blind to exposure status viewed the images remotely and allocated fluorosis scores using the Thylstrup and Fejerskov (TF) scale.

RESULTS

At TF ≥ 1 (any fluorosis), a significantly higher proportion of participants from the fluoridated area had fluorosis (F 39% NF 21.3%, P < 0.001), at the threshold TF ≥ 3 ("aesthetic concern"), the difference was no longer statistically significant (F 4.1%, NF 2.2%, P = 0.25). There was a gradient by age, whereby fluorosis was highest in the youngest and lowest in the oldest age group.

CONCLUSIONS

Although fluorosis is more common in adults with lifetime exposure to water fluoridation than those with no exposure, the aesthetic impact of fluorosis seems to diminish with age.

Interpreting Poisson Regression Models in Dental Caries Studies

Oral epidemiology involves studying and investigating the distribution and determinants of dental-related diseases in a specified population group to inform decisions in the management of health problems. In oral epidemiology studies, the hypothesis is typically followed by a cogent study design and data collection. Appropriate statistical analysis is essential to demonstrate the scientific association between the independent factors and the target variable. Analysis also helps to develop and build a statistical model. Poisson regression and its extensions have gained more attention in caries epidemiology than other working models such as logistic regression. This review discusses the fundamental principles and basic knowledge of Poisson regression models. It also introduces the use of a robust variance estimator with a focus on the "robust" interpretation of the model. In addition, extensions of regression models, including the zero-inflated model, hurdle model, and negative binomial model, and their interpretation in caries studies are reviewed. Principles of model fitting, including goodness-of-fit measures, are also discussed. Clinicians and researchers should pay attention to the statistical context of the models used and interpret the models to improve the oral and general health of the communities in which they live.