Use of fluoride by young children and prevalence of mottled enamel

Comparison of the remineralizing potential of child formula dentifrices

BACKGROUND

Although child formula fluoridated dentifrices can be used safely by young children their remineralizing capability remains questionable.

AIMS

To evaluate the remineralizing potential of child formula dentifrices on primary teeth.

DESIGN

In vitro single-section technique utilizing a 7 days pH-cycling model.

METHODS

Primary teeth were placed in demineralizing solution for 96 h to produce artificial carious lesions 100 μm deep, and then cut longitudinally into 50 sections 100-150 μm thick and randomly assigned to five groups. Sections in Groups A to D were treated with dentifrices containing 500 ppm AmF, 500 ppm MFP, 500 ppm MFP and xylitol, or 500 ppm NaF, respectively. Group E sections were treated with a nonfluoridated dentifrice.

OUTCOME MEASUREMENTS

Lesions were evaluated using polarized light microscopy and microradiography.

RESULTS

Group D (500 ppm NaF) sections exhibited a significant decrease in lesion depth, whereas those in Group E (nonF) showed a significant increase in depth (P<0.05, paired t-test). Decrease in lesion progression was observed in Groups A, B and C.

CONCLUSIONS

The 500 ppm NaF dentifrice demonstrated remineralization of carious lesions by virtue of a significant decrease in lesion depth; whereas dentifrices that contained AmF, MFP and MFP with xylitol decelerated the progression of demineralization.

Fluoride reduces the expression of enamel proteins and cytokines in an ameloblast-derived cell line

OBJECTIVE

To investigate the effects of two different fluoride concentrations on the expression of enamel proteins, alkaline phosphatase (ALP), cytokines and interleukins by an ameloblast-derived cell line.

METHODS

Murine ameloblast-derived cells (LS-8), mouse odontogenic epithelia, were exposed to 1 or 5ppm sodium fluoride (NaF) (0.46 and 2.25ppm F, respectively) for 1, 3 and 7 days. The effect of NaF on the mRNA expression of enamel proteins was quantified; the secretion of cytokines, and interleukins, and the alkaline phosphatase (ALP) activity, into the cell culture medium was measured and compared to untreated controls. The effect on cell growth after 1- and 3-days in culture was measured using BrdU incorporation.

RESULTS

Fluoride at 2.25ppm reduced mRNA expression of the structural enamel matrix proteins amelogenin (amel), ameloblastin (ambn), enamelin (enam), and the enamel protease matrix metallopeptidase-20 (MMP-20). Similarly several vascularisation factors (vascular endothelial growth factor (VEGF), monocyte chemoattractant proteins (MCP-1) and interferon inducible protein 10 (IP-10), was also reduced by 2.25ppm fluoride. ALP activity and proliferation were stimulated by 0.46ppm fluoride but inhibited by 2.25ppm fluoride.

CONCLUSIONS

These results indicate that fluoride may impact on the expression of structural enamel proteins and the protease responsible for processing these proteins during the secretory stage of amelogenesis and go some way to explaining the mineralization defect that characterises fluorotic enamel.

Topical fluoride as a cause of dental fluorosis in children

BACKGROUND

For many years, topical use of fluorides has gained greater popularity than systemic use of fluorides. A possible adverse effect associated with the use of topical fluoride is the development of dental fluorosis due to the ingestion of excessive fluoride by young children with developing teeth.

OBJECTIVES

To describe the relationship between the use of topical fluorides in young children and the risk of developing dental fluorosis.

SEARCH STRATEGY

Electronic search of the Cochrane Oral Health Group Trials Register, CENTRAL, MEDLINE, EMBASE, BIOSIS, Dissertation Abstracts and LILACS/BBO. Reference lists from relevant articles were searched. Date of the most recent searches: 9th March 09.

SELECTION CRITERIA

Randomised controlled trials (RCTs), quasi-RCTs, cohort studies, case-control studies and cross-sectional surveys, in which fluoride toothpastes, mouthrinses, gels, foams, paint-on solutions, and varnishes were compared to an alternative fluoride treatment, placebo or no intervention group. Children under the age of 6 years at the time topical fluorides were used.

DATA COLLECTION AND ANALYSIS

Data from all included studies were extracted by two review authors. Risk ratios for controlled, prospective studies and odds ratios for case-control studies or cross-sectional surveys were extracted or calculated. Where both adjusted and unadjusted risk ratios or odds ratios were presented, the adjusted value was included in the meta-analysis.

MAIN RESULTS

25 studies were included: 2 RCTs, 1 cohort study, 6 case-control studies and 16 cross-sectional surveys. Only one RCT was judged to be at low risk of bias. The other RCT and all observational studies were judged to be at moderate to high risk of bias. Studies were included in four intervention/exposure comparisons. A statistically significant reduction in fluorosis was found if brushing of a child's teeth with fluoride toothpaste commenced after the age of 12 months odds ratio 0.70 (random-effects: 95% confidence interval 0.57 to 0.88) (data from observational studies). Inconsistent statistically significant associations were found between starting using fluoride toothpaste/toothbrushing before or after the age of 24 months and fluorosis (data from observational studies). From the RCTs, use of higher level of fluoride was associated with an increased risk of fluorosis. No significant association between the frequency of toothbrushing or the amount of fluoride toothpaste used and fluorosis was found.

AUTHORS' CONCLUSIONS

There should be a balanced consideration between the benefits of topical fluorides in caries prevention and the risk of the development of fluorosis. Most of the available evidence focuses on mild fluorosis. There is weak unreliable evidence that starting the use of fluoride toothpaste in children under 12 months of age may be associated with an increased risk of fluorosis. The evidence for its use between the age of 12 and 24 months is equivocal. If the risk of fluorosis is of concern, the fluoride level of toothpaste for young children (under 6 years of age) is recommended to be lower than 1000 parts per million (ppm).More evidence with low risk of bias is needed. Future trials assessing the effectiveness of different types of topical fluorides (including toothpastes, gels, varnishes and mouthrinses) or different concentrations or both should ensure that they include an adequate follow-up period in order to collect data on potential fluorosis. As it is unethical to propose RCTs to assess fluorosis itself, it is acknowledged that further observational studies will be undertaken in this area. However, attention needs to be given to the choice of study design, bearing in mind that prospective, controlled studies will be less susceptible to bias than retrospective and/or uncontrolled studies.

Total fluoride intake and urinary excretion in 4–year–old Iranian children residing in low-fluoride areas

Knowledge of levels of fluoride ingestion and excretion is important in planning optimum fluoride therapy for young children. In previous literature, it has been assumed that only about one-third of ingested fluoride is excreted in young children. The aims of the present study were (a) to measure total fluoride intake, urinary fluoride excretion and fluoride balance, and (b) to investigate the effect of air temperature on fluoride intake and urinary fluoride excretion, in young children. Children (4 years old) living in a city, a small town and rural areas of Fars province, Iran, where drinking water contained 0·30–0·39 mg F/l, were invited to participate. Selection of subjects was by random sampling of kindergartens or health centres. The children were surveyed twice, once in summer and once in winter. Diet was obtained by 3 d diaries with interview. Samples of most foods and drinks were analysed for fluoride content. Ingestion of fluoride from toothpaste was estimated for each child. Each child's urine was collected over 24 h and analysed for fluoride content. Seventy-eight of the 116 volunteers completed all aspects of the study, which was conducted in 1995–6. For all children, the mean fluoride ingestion from diet was 0·390 (sd 0·122) mg/d or 0·028 (sd 0·008) mg/kg body weight per d. Fluoride ingestion from diet was higher in summer and higher in rural areas. The mean ingestion of fluoride from all sources was 0·426 (sd 0·126) mg/d and the mean fluoride urinary excretion was 0·339 (sd 0·100) mg/d. The difference between ingestion and urinary excretion was +0·087 (sd 0·143) mg, equivalent to 80 % excretion. Faecal excretion was not estimated. The results indicate fluoride retention at 4 years to be much lower than previously assumed.

Intra-oral distribution of dental fluorosis in Newburgh and Kingston, New York

Previous studies of intra-oral distribution of dental fluorosis in low-fluoride areas reported that teeth that formed later in life were more frequently affected compared with the early-forming teeth. The steady increase of plasma fluoride with age, even under constant fluoride exposure, has been suggested as a possible mechanism for this clinical manifestation. To determine the intra-oral distribution of Dean's Index scores and the effect of fluoride exposure on early- and late-forming teeth, we analyzed data collected on 2193 seven- to 14-year-old lifelong residents of fluoridated or non-fluoridated areas. Logistic regression procedures were used to determine the effects of fluoridation, early brushing, daily supplements, and other socio-demographic variables on early- and late-forming teeth. The results show that the occurrence of very mild or greater levels of fluorosis in the upper anterior teeth was 7 to 10% in the fluoridated area and 5 to 9% in the nonfluoridated area. In the fluoridated area, the occurrence of fluorosis increased from anterior to posterior teeth. Both early- and late-forming teeth were affected by exposure to fluoridation, daily fluoride supplement use, or brushing before the age of two years. This analysis showed that the esthetic consequence of exposure to multiple sources of fluoride was less dramatic, as evidenced by the lower frequency in upper anterior teeth compared with posterior teeth. The longer maturation process of the posterior teeth and the thicker enamel appear to be the likely explanation for the higher occurrence of dental fluorosis in posterior teeth.

Fluoride supplements and fluorosis: a meta-analysis

This paper presents a systematic review of the dental literature that was carried out to investigate whether the regular use of fluoride supplements in non-fluoridated communities during the period of tooth development increases the risk of dental fluorosis. A MEDLINE search was organized for all documents published, in English, between January 1966 and September 1997 using the following key words: fluorosis, dental, fluoride, fluoride supplement or supplements, drop or drops, and tablet or tablets. Twenty-four studies that assessed the development of dental fluorosis in children who had used fluoride supplements earlier in their life were included in this review. Of the 24 studies, 10 were cross-sectional/case control studies and four were follow-up studies. These studies had data that allowed a quantitative estimation of the risk of developing dental fluorosis in users of fluoride supplements. The other 10 studies were excluded because they either did not present enough data or had other methodological problems. A qualitative review of the studies found a consistent and strong association between the use of fluoride supplements and dental fluorosis. The meta-analyses of the cross-sectional/case-control studies estimated that the odds ratio of dental fluorosis in users of fluoride supplements compared with non-users ranged between 2.4 and 2.6. The meta-analyses of the follow-up studies estimated that the relative risk in long-term users was between 5.5 and 12.2. This review confirmed that in non-fluoridated communities the use of fluoride supplements during the first 6 years of life is associated with a significant increase in the risk of developing dental fluorosis.

Dental fluorosis: its use as a biomarker

Several epidemiological studies, beginning with those of Dean and co-workers in the 1940's, clearly demonstrate the relationship between dental fluorosis in humans and the level of fluoride in water supplies. These studies and others have shown that, in a population, there is a direct relationship among the degree of enamel fluorosis, plasma and bone fluoride levels, and the concentration of fluoride in drinking water. However, dental fluorosis is a reflection of fluoride exposure only during the time of enamel formation, somewhat limiting its use as a biomarker. In addition, the degree of fluorosis is dependent not only on the total fluoride dose, but also on the timing and duration of fluoride exposure. At the level of an individual response to fluoride exposure, factors such as body weight, activity level, nutritional factors, and the rate of skeletal growth and remodeling are also important. These variables, along with an individual variability in response to similar doses of fluoride, indicate that enamel fluorosis cannot be used as a biological marker of the level of fluoride exposure for an individual.

Epidemiologic indices for measuring the clinical manifestations of dental fluorosis: overview and critique

Several indices have been used to describe the clinical appearance of dental fluorosis. The purpose of this paper is to describe and compare the three principal ones in use today: those developed by Dean (1934, 1942), Thylstrup and Fejerskov (1978), and Horowitz et al. (1984). A recent index (Fluorosis Risk Index) developed by Pendrys (1990) is also included in this review. The continued use of Dean's classification system and derived index (CFI) for more than a half century is testimony to its simplicity and utility. The index has been criticized because the unit of analysis is the person, because criteria are unclear for some categories, or that they lack sensitivity, particularly for severe fluorosis, and because of the way in which data are summarized and reported. The Thylstrup and Fejerskov Index is appealing to clinicians and epidemiologists alike in that it corresponds closely to histological changes that occur in dental fluorosis and to enamel fluoride concentrations, thereby having biological validity. The TSIF described by Horowitz et al. makes a useful contribution because it provides clearer diagnostic criteria and provides for an analysis based on esthetic concerns. The Fluorosis Risk Index appears to be particularly useful for analytical epidemiologic studies, because it is designed to permit a more accurate identification of associations between age-specific exposures to fluoride and the development of dental fluorosis. All three indices in common use today provide useful indices for the study of dental fluorosis. The utility of the Fluorosis Risk Index will be determined as it receives wider use. The selection of one of these indices for use in an epidemiologic study depends in large measure on the purpose of the study. Research needs to continue on the validity of these indices, particularly for mild fluorosis, and on the public's perception of the cosmetic appearance of teeth with different severity levels of fluorosis.

Factors associated with the use of fluoride supplements and fluoride dentifrice by infants and toddlers

Dental fluorosis may be associated with the inappropriate use of fluoride dentifrices and/or dietary fluoride supplements by young children, especially for those who consume optimally fluoridated water. Studies to date have used retrospective designs that rely on anamnestic responses of adults to determine fluoride exposures in their children. The 1986 National Health Interview Survey (NHIS) collected information on current use of fluoride-containing dental products (dentifrices, drops, tablets, and mouthrinses) by all household members during home interviews. This report contains information obtained from adults for 1,996 children younger than two years of age. Nearly half of the children used fluoride dentifrices or dietary fluoride supplements. Eleven percent of the children younger than one year of age and nearly 60 percent of children between one and two years of age reportedly used a fluoride toothpaste. Dietary fluoride supplements were used about equally in these age groups (about 16%). The use of a fluoride dentifrice was similar across racial-ethnic groups, but the use of dietary fluoride supplements was less among blacks and Hispanics. A significantly higher proportion of children whose respondent knew the purpose of water fluoridation used some type of fluoride product. Because young children tend to swallow dentifrices, the findings of this study suggest the need for educational programs targeted to parents and health care providers regarding the appropriate use of fluorides and the risk of fluorosis when they are used inappropriately.

Fluoride supplements in caries prevention: a literature review and proposal for a new dosage schedule

Fluoride supplements have contributed significantly to caries prevention; however, better information about the dynamic nature of fluoride's effect on caries has made a reappraisal desirable. It seems, from a review of the literature, that the benefit from supplement use that can be expected today in populations in low-fluoride areas is small. Possible reasons include the low caries incidence in children of recent years. Few people are willing to use supplements with sufficient regularity to achieve an effect. The principal mode of action of fluoride in supplements, topical exposure of teeth to fluoride, can be achieved with toothpastes and other means. Supplement use has been associated with dental fluorosis in children. This is displeasing to look at and may put at risk the undoubted benefits of water fluoridation if the public associates fluoride with negative cosmetic effects. This reason alone should be sufficient to compel a reconsideration of existing recommendations. An appropriate new dosage schedule for fluoride supplements should be aimed only at identifiable high caries-risk individuals, not at groups defined by age or residence and should result in much lower fluoride intake in the age span birth-eight years than many current recommendations. It should start at six months or later, expressly recommend lozenges rather than tablets for swallowing to maximize the topical effect, stipulate that the maximum fluoride ion content of a tablet be 0.50 mg to reduce the chances of fluorosis and overconsumption, and have no upper age limit, as caries risk may occur at any age. A dosage schedule meeting these requirements is proposed.

Tensile strength of orthodontic brackets bonded directly to fluorotic and nonfluorotic teeth: an in vitro comparative study

Information related to bonding of orthodontic brackets to fluorotic teeth is scanty. The purpose of this study was to compare, in vitro, the tensile bond strength and the bond failure site of brackets bonded directly to fluorotic and nonfluorotic teeth. The etching patterns were also evaluated. The study involved 26 teeth classified as score 3 and 4, and 26 as score 0 with the Thylstrup and Fejerskov's (TF) fluorosis index. In addition to the clinical classification, difference in the concentration of fluoride in the teeth was verified by acid etching. Brackets were bonded with a composite resin after etching the enamel surface with 40% phosphoric acid for 60 seconds. Tensile bond strength was determined with an Instron testing machine. The bond failure site was assessed by the percentage of residue cement on the tooth surface after debonding and the etching pattern by SEM. The mean concentration of fluoride was 2888.5 ppm (SD 1081.7) in the fluorotic teeth and 1227.1 ppm (SD 526.3) in the nonfluorotic teeth. The mean bond strength was 7.8 N/mm2 (SD 1.47) for the fluorotic teeth and 8.6 N/mm2 (SD 2.19) for the nonfluorotic teeth. The difference between the means for bond strength was not statistically significant (p greater than 0.05). Bond failure site was primarily at the bracket-adhesive interface. The mean percentage of adhesive on the enamel surface after debonding was 70% (SD 25.90) for the fluorotic teeth and 75% (SD 24.66) for nonfluorotic teeth. The difference in the means was not statistically significant (p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Fluoride intake from beverage consumption in a sample of North Carolina children

Since the 1940's, the prevalence of dental fluorosis has increased in the US, concomitant with a reduction in dental decay. These changes have been attributed in part to the widespread use of systemic and topical fluorides. Various sources of increased systemic fluoride exposure have been investigated. However, little is known regarding fluoride intake from beverages in a sample of children of ages susceptible to dental fluorosis. The purpose of this study was to estimate the amount of fluoride ingested from beverages by a sample of North Carolina (NC) children of ages 2-10 years. Data on beverage consumption were collected by means of a diary format. A questionnaire was included so that demographic information and self-assessment on the accuracy of the diaries could be obtained. Beverages reported in the diaries were purchased, and their fluoride content was assayed. Daily total fluid intake ranged from 970 to 1240 mL, and daily beverage consumption ranged from 585 to 756 mL. The estimated mean daily fluoride intakes from beverages for children 2-3, 4-6, and 7-10 years of age were 0.36, 0.54, and 0.60 mg, respectively.

Evaluation of appropriate use of dietary fluoride supplements in the US

Recent epidemiologic and related evidence suggests the following trends: 1. the prevalence of caries continues to decline in children of the US and several other developed countries; 2. the prevalence of mild dental fluorosis is increasing; 3. the majority of the cariostatic effects of fluoride are topical; and 4. dietary fluoride supplements are a risk factor for dental fluorosis. These trends, and the scientific evidence on fluoride and fluorosis, suggest that it is time to re-evaluate the use of dietary fluoride supplements. This paper examines the evidence for each of the four trends and the use of fluoride supplements in caries prevention today.

Factors affecting the ingestion of fluoride dentifrice by children

Several factors affecting the amount of fluoride ingested during toothbrushing by 2- to 7-year-old children were investigated. The specific purpose of this study was to determine the contribution of age, the amount of dentifrice used, and rinsing after brushing to the variation in the ingestion of fluoride dentifrice. Four hundred and five children brushed their teeth in front of a portable sink. The tubes of dentifrice in gel (0.24% NaF) were weighed before and after use to determine the amount of toothpaste used. The fluoride content of the collected liquids was determined with a fluoride-ion-specific electrode. The amount of fluoride ingested was derived by determining the difference between the amounts used and recovered. The amount of dentifrice used, the age, and the rinsing habits, entered in a multiple regression model, explained up to 66 percent of the total variation in the amount of fluoride ingested. The amount of dentifrice used accounted by itself for 60 percent of the total variation. Therefore, these results indicate that the quantity of dentifrice used was the most important factor affecting the ingestion of fluoride through toothbrushing by young children.

The changing patterns of systemic fluoride intake

Fluorosis prevalence has increased in North America since the 1930's-1940's. It may also have increased since 1970, though the evidence for that is less clear. Continued monitoring will help determine whether increased fluorosis prevalence in children in the United States is a cohort effect from the 1970's. This review considers the evidence for an increase in fluoride ingestion from all sources since the 1970's. If an increase has occurred, the most likely sources are fluoride dietary supplements, inadvertent swallowing of fluoride toothpastes, and increased fluoride in food and beverages. For adults, there is no evidence from dietary surveys to show that fluoride intake has increased over the last generation. Dietary surveys for children aged six months to two years are similarly inconclusive, though the great variation in fluoride content of various infant foods might be obscuring real effects. The data on fluoride intake by children from food and beverages, infant foods included, are not strong enough to conclude that an increase in fluoride ingestion has occurred since the 1970's. However, the suggested upper limit of fluoride intake is substantially being reached in many children by ingestion of fluoride from food and drink (0.2-0.3 mg per day) and from fluoride toothpaste (0.2-0.3 mg per day). Two public health issues that arise from this review are: (a) the need for a downward revision in the schedule for fluoride supplementation, and (b) education on the potential for high fluoride concentration of soft drinks and processed fruit juices.

Dental fluorosis and fluoride exposure in Western Australia

Dental fluorosis in children is reported from many locations, and its prevalence may be increasing. This study aimed to measure fluorosis in 12-year-olds in fluoridated and non-fluoridated areas of Western Australia and to relate this to exposure. School dental clinics in Perth (F- 0.8 mg/L) and the Bunbury area (F- less than 0.2 mg/L) were the sampling units. Parents provided data on residence in fluoridated areas and on use of supplements and toothpaste. Exposure to water and supplemental fluoride between birth and four years was calculated. Clinical examinations (upper left central incisor) based on the TF classifications of fluorosis (which requires teeth to be dried) were conducted for 338 children in Perth and 321 in the Bunbury region. Re-examinations (n = 50) gave a weighted kappa of 0.78. Contingency analysis estimated bivariate relationships, and multiple logistic regression estimated odds ratios (OR) for risk factors. Fluorosis prevalence in the Perth region was 0.40, and in the Bunbury region 0.33 (chi 2 = 3.69, df = 1, p = 0.055). Prevalence was 0.44 in children with fluoride exposure equivalent to optimal water fluoridation and 0.20 among those with the lowest exposure (chi 2 = 35.99, df = 1, p = 0.0001). Increasing exposure was associated with higher fluorosis prevalence and higher TF scores, but overall, 27.3% of participants had TF score 1 (barely discernible), and only 9.4% had TF score greater than or equal to 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental caries and fluoride exposure in Western Australia

Most water supplies in Western Australia (WA) have been fluoridated since about 1968, but one region has persistently resisted. Supplement use has been encouraged there, and fluoride toothpaste is widely used. Caries prevalence and caries experience in children in Perth (F- 0.8 mg/L) have declined steadily since fluoridation, but in the Bunbury region (F- less than 0.2 mg/L), caries measures remain higher than in Perth. The purpose of this study was to correlate the magnitude and timing of fluoride exposure with caries experience. Altogether, 592 randomly selected children born in 1978 (mean age, 11.8 years) in Perth and the Bunbury region provided residence and fluoride exposure information for the periods from birth to four and from four to 12 years of age. Caries experience was recorded clinically in accordance with DMFT and WHO criteria. Sixty-one percent had been continuous residents of fluoridated areas from birth to four years, and 51% between the ages of four and 12 years. Fluoride supplement use was low. By the age of 1.5 years, 42% had used toothpaste. The prevalence of caries was 0.38 in Perth and 0.61 in the Bunbury region, and mean DMFT scores were 0.89 (SD, 1.39) and 1.57 (SD, 1.60), respectively. Bivariate analysis revealed all fluoride exposure to be associated with reduced caries experience, but there were large correlations between some variables. When unconditional logistic regression analysis was used, the most important (p less than 0.05) odds ratios associated with no caries experience were for residence in a fluoridated area from four to 12 years of age and early use of toothpaste.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of total fluoride intake to beneficial effects and enamel fluorosis

Recent studies indicate that the prevalence of very mild to moderate dental fluorosis, as classified by Dean, has increased relative to that found in earlier investigations. To date, fluoridated water, fluoride supplements, the diet, fluoride dentifrices, and other topical fluoride applications have been identified as sources of systemic fluoride. Recent evidence suggests that there is a strong association between mild to moderate enamel fluorosis and the use of fluoride supplements during early childhood, and that the presently recommended supplementation schedule for U.S. children above the age of 2 years may be too high. Evidence also suggests that there is a strong association between fluoride dentifrice use during early childhood and enamel fluorosis in fluoridated populations. These findings support the need for a careful review of existing supplementation schedules and early oral hygiene practices. There is a pressing need for additional analytical epidemiological studies to confirm existing findings and to determine whether other fluoride sources may be associated with enamel fluorosis. Further, since exposure to combinations of individual risk factors has been shown to carry more than merely an additive increase in the risk of fluorosis, these studies must be multifactorial in design. There is also a need for more fluorosis prevalence and severity data to be gathered, so that the development of enamel fluorosis as a public health problem can be assessed, and so that the success of measures implemented to maximize efficacy while minimizing unwanted side-effects can be monitored.