Urinary fluoride excretion by preschool children in six European countries

Fluoride exposure and factors affecting dental caries in preschool children living in two areas with different natural levels of fluorides

BACKGROUND

Successful oral health interventions must be based on the specific needs of the population that they serve. Evaluation of habits related to dental caries development and estimation of fluoride exposure in a target group of young patients helps to plan effective and safe caries prevention strategies.

OBJECTIVES

The study aimed to evaluate factors affecting dental caries experience and sources of fluoride exposure in preschool children living in two areas: with optimal and low natural content of fluoride in drinking water.

MATERIALS AND METHODS

The study included a group of 73 children of both sexes aged 4-7 years attending two kindergartens in Środa Wielkopolska and Turek (Wielkopolska Voivodeship, Poland), where the content of fluoride in drinking water according to data obtained in the sanitary station ranged from 0.68 to 0.74 mg/L (optimal concentration of fluoride) and from 0.19 to 0.30 mg/L (low concentration of fluoride), respectively. Parents of patients completed a survey about diet, hygiene, and dental care, taking into account the child's fluoride exposure. The calibrated dentist assessed the oral health condition using a mirror, a CPI probe, and a headlamp. Oral hygiene was recorded using the Silness and Löe plaque index, caries experience by calculating the numbers of decayed, missing, and filled primary, and permanent teeth (dmf and DMF, respectively) while caries frequency by calculating the percentage of children with caries experience above 0. In order to assess the fluoride concentrations in urine and drinking water, parents were asked to provide a urine sample collected on fasting and a tap water sample. Fluoride concentrations were assessed using a 09-37 (MARAT) fluoride ion-selective electrode and a RAE 111 silver-chloride reference electrode. Statistical analysis was conducted using the data analysis software system Statistica (version 12, StatSoft, Inc. 2014), assuming a statistical significance level p < 0.05.

RESULTS

No statistically significant differences were found between caries indices of the examined children in each kindergarten (p > 0.05). Urinary fluoride levels were higher in children who tended to swallow toothpaste or used fluoride rinses and positively correlated with fluoride concentrations in the drinking water. Dental caries experience in the examined children depended on the effectiveness and frequency of oral hygiene procedures and dietary habits.

CONCLUSIONS

The strategy aimed at improving the oral health of the examined group of children should include accomplishing oral hygiene, promoting a non-cariogenic diet, and, finally, controlling fluoride exposure from at-home fluoride products. Caries prevention program ought to be adjusted to individual characteristics of each child, taking into consideration oral hygiene practices, dietary habits and total fluoride intake.

Associations between Urinary, Dietary, and Water Fluoride Concentrations among Children in Mexico and Canada

Fluoride, which may be toxic to the developing brain, is added to salt in Mexico and drinking water in Canada to prevent dental caries. We compared childhood urinary fluoride (CUF) concentrations in Mexico City and Canada to characterize patterns of fluoride exposure in these two populations. We also examined associations of CUF with dietary and water fluoride levels in Mexico City and Canada respectively. We included 561 children (ages 4–6; mean age 4.8 years) from the Programming Research in Obesity, Growth, Environment, and Social Stress (PROGRESS) cohort in Mexico City, and 645 children (ages 2–6; mean age 3.7 years) from the Maternal–Infant Research on Environmental Chemicals (MIREC) cohort in Canada. We applied Spearman correlations, T-tests, ANOVA or covariate-adjusted linear regression to examine associations of CUF (mg/L; adjusted for specific gravity) with demographics and dietary or water fluoride concentrations. We used Welch equivalence testing to compare means across cohorts. Mean (SD) CUF was equivalent (t = 4.26, p < 0.001) in PROGRESS: 0.74 (0.42) and fluoridated Canadian communities: 0.66 (0.47), but lower in non-fluoridated Canadian communities: 0.42 (0.31) (t = −6.37, p < 0.001). Water fluoride concentrations were significantly associated with CUF after covariate adjustment for age and sex in MIREC (B = 0.44, 95% CI: 0.30, 0.59, p < 0.001). In contrast, daily food and beverage fluoride intake was not associated with CUF in PROGRESS (p = 0.82). We found that CUF levels are comparable among children in Mexico City and fluoridated Canadian communities, despite distinct sources of exposure. Community water fluoridation is a major source of fluoride exposure for Canadian children.

A systematic review and meta-analysis of 24-h urinary output of children and adolescents: impact on the assessment of iodine status using urinary biomarkers

PURPOSE

Urinary iodine concentration (UIC (μg/ml) from spot urine samples collected from school-aged children is used to determine the iodine status of populations. Some studies further extrapolate UIC to represent daily iodine intake, based on the assumption that children pass approximately 1 L urine over 24-h, but this has never been assessed in population studies. Therefore, the present review aimed to collate and produce an estimate of the average 24-h urine volume of children and adolescents (> 1 year and < 19 years) from published studies.

METHODS

EBSCOHOST and EMBASE databases were searched to identify studies which reported the mean 24-h urinary volume of healthy children (> 1 year and < 19 years). The overall mean (95% CI) estimate of 24-h urine volume was determined using a random effects model, broken down by age group.

RESULTS

Of the 44 studies identified, a meta-analysis of 27 studies, with at least one criterion for assessing the completeness of urine collections, indicated that the mean urine volume of 2-19 year olds was 773 (654, 893) (95% CI) mL/24-h. When broken down by age group, mean (95% CI) 24-h urine volume was 531 mL/day (454, 607) for 2-5 year olds, 771 mL/day (734, 808) for 6-12 year olds, and 1067 mL/day (855, 1279) for 13-19 year olds.

CONCLUSIONS

These results demonstrate that the average urine volume of children aged 2-12 years is less than 1 L, therefore, misclassification of iodine intakes may occur when urine volumes fall below or above 1 L. Future studies utilizing spot urine samples to assess iodine status should consider this when extrapolating UIC to represent iodine intakes of a population.

Current Guidance for Fluoride Intake: Is It Appropriate?

The purpose of this report is to examine critically the appropriateness of the current guidance for fluoride intake in the population (0.05-0.07 mg F/kg bodyweight/d), consider whether changes to the current guidance are desirable, and suggest further research that will strengthen the evidence base for future decisions on guidance/advice in this area. The benefits and the risks of using fluoride particularly concern preschool children because it is at this age that excessive fluoride intake may result in dental fluorosis. Data from mostly cross-sectional studies show a wide variation in exposure and a considerable variation in the amount of fluoride ingested. Fluorosis, mostly mild, is commonly observed. For considering changes in current guidance, there is a need for more knowledge on the relationship between exposure to fluoride at an early age and the development of fluorosis. For that, prospective epidemiological studies with sufficiently large and representative samples of children are required. It is also important to study children in communities both with and without water fluoridation and to include populations where salt or milk fluoridation is used. There is also a need for professional agreement on acceptable levels of mild and moderate/severe fluorosis and a more comprehensive knowledge on the appreciation of mild fluorosis among the public.

The use of urinary fluoride excretion to facilitate monitoring fluoride intake: A systematic scoping review

BACKGROUND

As a recognised effective and economical agent for dental caries prevention, fluoride has been used in many different fluoridation schemes implemented across the world. Considering the narrow 'dose-gap' between the benefit of caries reduction and the risk of dental fluorosis, it is recommended that fluoride intake is monitored by measuring urinary fluoride excretion. The aim of this scoping review is to map the current literature/evidence on fluoride intake and excretion studies in relation to the study population, settings, type of study design, methodology, and analytical approach.

METHODS

Embase/Ovid, MEDLINE/Ovid, CINAHL/EBSCO, Scopus/Elsevier were searched for relevant articles until April 2018. Studies were included if they reported intake and excretion of fluoride in healthy humans of all age groups. Findings were explored using a narrative synthesis to summarise studies characteristics and outcome measures.

RESULTS

Removal of duplicates from the originally 2295 identified records yielded 1093 studies of which 206 articles were included. Only 21.6% of the studies were conducted in children (<8-year-olds). Most studies (38.8%) used drinking water concentration as a proxy for fluoride intake, whereas only 11.7% measured fluoride intake from all sources. Of the 72 studies that measured dietary fluoride intake, only 10 reported the validity of the employed dietary assessment method. Only 14 studies validated the urine sample collection methods. No information on the validity of the employed analytical method was reported by the majority (64.6%) of studies. Only a small proportion (8.7%) of the included studies investigated the association between fluoride intake and excretion.

CONCLUSION

The findings reveal much variability in terms of conducting the studies and reporting the findings, illustrating a high heterogeneity in data collection across settings and populations. Future studies should provide more detail on sampling technique, measurement protocols (including validation), and on clearly defining the relationship between intake and urinary excretion of fluoride.

Urinary fluoride excretion after application of fluoride varnish and use of fluoride toothpaste in young children

BACKGROUND

The efficacy and safety of combined use of topical fluoride products are essential issues that must be monitored.

AIM

To assess urinary excretion of fluoride after application of two different dental varnishes containing 2.26% fluoride in 3- to 4-year-old children and to compare the levels with and without parallel use of fluoride toothpaste.

DESIGN

Fifteen healthy children were enrolled to a randomized crossover trial that was performed in two parts: Part I with twice-daily tooth brushing with fluoride toothpaste and Part II with twice-daily brushing with a non-fluoride toothpaste. After a 1-week run-in period, 0.1 mL of the two fluoride varnishes (Duraphat and Profluorid Varnish) was topically applied in a randomized order. Baseline and experimental urine was collected during 6-h periods. The fluoride content was determined with an ion-sensitive electrode.

RESULTS

There was a statistically significant increase in the 6-h fluoride excretion after application of both experimental varnishes, with and without parallel use of fluoride toothpaste (P < 0.01). When fluoridated toothpaste was used, the mean fluoride excretion was 0.20 mg/6 h after application of Duraphat and 0.29 mg/6 h after application of Profluorid Varnish (P = 0.18).

CONCLUSIONS

Topical applications of 0.1 mL of fluoride varnish significantly increased the 6-h fluoride excretion. As some individuals displayed excretion levels exceeding the optimal fluoride exposure, a restricted use of fluoride toothpaste in connection with the varnish applications would decrease fluoride exposure.

A systematic review on fluoridated food in caries prevention

OBJECTIVE

This paper aims to provide a systematic review of the caries-prevention effect of fluoridated food, excluding water. The main aim of this review was to evaluate the presence of scientific evidence relating to the effects of fluoride intake via food on the occurrence of carious lesions. The outcome was defined as a clinical outcome, so only papers evaluating a decrease in caries indices were included.

MATERIALS AND METHODS

Relevant databases (Medline®, Embase®, The Cochrane Library) were searched. The date range was set from 01.01.1966 to 03.31.2011. One hundred and thirty-nine reports were identified and assessed. Only three papers fulfilled the inclusion criteria and were discussed in detail.

RESULTS

No paper related to the use of fluoridated salt in caries prevention fulfilled the inclusion criteria. The use of milk as a vehicle for providing additional fluoride in a dental public health programme was evaluated in two papers. The consumption of fluoridated milk was an effective measure to prevent caries in the primary teeth. The use of fluoridated sugar demonstrated a reduction in caries increment in the permanent dentition in one paper.

CONCLUSIONS

Literature on the effectiveness of fluoridation in foods in caries prevention is scant and almost all the studies have been conducted in children. There is low evidence that the use of milk fluoridation is effective in reducing the caries increment.

Urinary fluoride excretion in 6- to 7-year-olds ingesting milk containing 0.5 or 0.9 mg fluoride

Effectiveness of 0.5 mg fluoride (F) milk ingestion in preventing caries has been termed only 'moderate'. In this 3-arm partial cross-over intervention, 32 children aged 6-7 years in a non-F area were recruited and urinary F excretion (UFE) measured before and after ingestion of 0.5 or 0.9 mg F milk. Maintaining customary dietary and oral hygiene habits, children underwent a 2-week 'wash-in' with non-F milk, providing a 24-hour urine sample on day 4 of non-F (baseline) and F milk ingestion containing either (i) 0.5 mg or (ii) 0.9 mg F (intervention). A comparative group of thirteen 6- to 7-year-olds living in fluoridated areas provided a 24-hour urine sample on day 4 of daily non-F milk ingestion, following a 2-week non-F milk wash-in. Valid urine samples were analysed for F and UFE estimated from corrected 24-hour urine volume and F concentration. For the 24 test children providing 2 valid urine samples, mean (95% CI) change in corrected 24-hour UFE was 0.130 (0.049, 0.211) and 0.153 (0.062, 0.245) mg/day for 0.5 mg (p < 0.007) and 0.9 mg F (p < 0.001) groups, respectively. Post-intervention, mean (SD) corrected 24-hour UFE was 0.437 (0.153) mg/day and 0.420 (0.188) mg/day for the 0.5 and 0.9 mg F groups, respectively, which were lower than the WHO provisional standards (0.48-0.60 mg F/day). F milk consumption significantly increased UFE; however, the F content of 0.5 and 0.9 mg F milk may be too low to achieve WHO provisional UFE standards concomitant with optimal F exposure in children aged ≥6 years.

Effect of discontinuation of fluoride intake from water and toothpaste on urinary excretion in young children

As there is no homeostatic mechanism for maintaining circulating fluoride (F) in the human body, the concentration may decrease and increase again when intake is interrupted and re-started. The present study prospectively evaluated this process in children exposed to F intake from water and toothpaste, using F in urine as a biomarker. Eleven children from Ibiá, Brazil (with sub-optimally fluoridated water supply) aged two to four years who regularly used fluoridated toothpaste (1,100 ppm F) took part in the study. Twenty-four-hour urine was collected at baseline (Day 0, F exposure from water and toothpaste) as well as after the interruption of fluoride intake from water and dentifrice (Days 1 to 28) (F interruption) and after fluoride intake from these sources had been re-established (Days 29 to 34) (F re-exposure). Urinary volume was measured, fluoride concentration was determined and the amount of fluoride excreted was calculated and expressed in mg F/day. Urinary fluoride excretion (UFE) during the periods of fluoride exposure, interruption and re-exposure was analyzed using the Wilcoxon test. Mean UFE was 0.25 mg F/day (SD: 0.15) at baseline, dropped to a mean of 0.14 mg F/day during F interruption (SD: 0.07; range: 0.11 to 0.17 mg F/day) and rose to 0.21 (SD: 0.09) and 0.19 (SD: 0.08) following F re-exposure. The difference between baseline UFE and the period of F interruption was statistically significant (p<0.05), while the difference between baseline and the period of F re-exposure was non-significant (p>0.05). The findings suggest that circulating F in the body of young children rapidly decreases in the first 24 hours and again increases very fast after discontinuation and re-exposure of F from water and toothpaste.

Urinary fluoride excretion in children exposed to fluoride toothpaste and to different water fluoride levels in a tropical area of Brazil

The aim of this study was to evaluate the urinary fluoride excretion of 2- to 7-year-old children exposed to different water fluoride concentrations in the city of Catolé do Rocha, PB, Brazil. Forty-two children were allocated to 3 groups according to the concentration of fluoride in the water: G1 (n=10; 0.5-1.0 ppm F), G2 (n=17; 1.1-1.5 ppm F) and G3 (n= 15; >1.51 ppm F). The study was carried out in two 1-week phases with 1-month interval between the moments of data collection: in the first phase, the children used a fluoride toothpaste (FT) (1,510 ppm F) for 1 week, whereas in the second phase a non-fluoride toothpaste (NFT) was used. The urine was collected in a 24-h period in each week-phase according to Marthaler's protocol. The urinary fluoride excretion data expressed as mean (SD) in µg/24 h were: G1-FT= 452.9 (290.2); G1-NFT= 435.1 (187.0); G2-FT= 451.4 (224.0); G2-NFT= 430.3 (352.5); G3-FT=592.3 (390.5); and G3-NFT=623.6 (408.7). There was no statistically significant difference between the water fluoride groups, and regardless of the week phase (ANOVA, p>0.05). The use of fluoride toothpaste (1,510 ppmF) did not promote an increase in urinary fluoride excretion. There was a trend, though not significant, as to the increase of urine fluoride concentration in relation to fluoride concentrations in the water. The excretion values suggest that some children are under risk to develop dental fluorosis and information about the appropriate use of fluoride is necessary in this area.