Fluoride ingestion from toothpaste: background to European Union-funded multicentre project

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.

Does flavoured dentifrice increase fluoride intake compared with regular toothpaste in children? A systematic review and meta-analysis

BACKGROUND

Toothpaste manufacturers encourage through aggressive marketing strategies the overconsumption of fluoridated dentifrices. There are conflicting results regarding fluoride intake from toothpastes in children.

AIM

The aim of this systematic review and meta-analysis was to determine whether dentifrice flavour increases fluoride ingestion by children.

DESIGN

We included clinical trials on children that evaluated the use of flavoured dentifrice - FD vs regular dentifrice - RD to identify the fluoride intake. An electronic search was performed in PubMed, Web of Science, Scopus, The Cochrane Library, LILACS/BBO, and grey literature followed by manual search. The methodological quality of the studies was assessed using the Cochrane Collaboration common scheme for bias and ROBINS-I tool. Data were analysed in subgroups such as low (G1) and ordinary (G2) fluoride concentrations of dentifrices. We carried out heterogeneity and sensitive analyses.

RESULTS

For G1, the fluoride intake from RD was significantly higher than from FD [standardised mean difference = -2.57 (-3.26, -1.89), P < 0.00001]. For G2, the fluoride ingestion from RD was significantly higher than from FD [mean difference = -0.00 (-0.00, -0.00), P = 0.02].

CONCLUSIONS

There is evidence to support the null hypothesis that flavouring from dentifrice does not increase fluoride intake in young children.

Agreement in the diagnosis of dental fluorosis in central incisors performed by a standardized photographic method and clinical examination

The aim of this study was to assess agreement in the diagnosis of dental fluorosis performed by a standardized digital photographic method and a clinical examination (gold standard). 49 children (aged 7-9 years) were clinically evaluated by a trained examiner for the assessment of dental fluorosis. Central incisors were evaluated for the presence or absence of dental fluorosis and were photographed with a digital camera. Photographs were presented to three pediatric dentists, who examined the images. Data were analyzed using Cohen's kappa and validity values. Agreement in the diagnosis performed by the photographic method and clinical examination was good (0.67) and accuracy was 83.7%. The prevalence of dental fluorosis was reported to be higher in the clinical examination (49%) compared with the photographic method (36.7%). The photographic method presented higher specificity (96%) than sensitivity (70.8%), a positive predictive value (PPV) of 94.4% and a negative predictive value (NPV) of 77.4%. The diagnosis of dental fluorosis performed using the photographic method presented high specificity and PPV, which indicates that the method is reproducible and reliable for recording dental fluorosis.

Prospective study of the association between fluoride intake and dental fluorosis in permanent teeth

OBJECTIVE

To evaluate the relationship between fluoride intake and dental fluorosis in permanent central incisors and first molars.

METHODS

Fluoride intake (mg F/kg body weight/day) from diet, dentifrice and both combined was determined on a single occasion in 1998 among children aged 19-39 months living in two fluoridated Brazilian communities (0.6-0.8 ppm F). Six years later, when the permanent teeth of these children had erupted (central incisors and first molars), 49 children aged 7-9 years [20 girls (40.8%) and 29 boys (58.2%)] were evaluated for dental fluorosis. To test the association between fluorosis and fluoride intake, children were dichotomized into two groups, cases (children with dental fluorosis on at least two teeth, TFI > or =1) and noncases (children without dental fluorosis, TFI = 0).

RESULTS

Among the case group (n = 29), median fluoride doses from diet, dentifrice and combined were 0.031, 0.050 and 0.083 mg F/kg/day, respectively. Among the noncase group (n = 20), median fluoride doses were 0.029, 0.049, 0.084 mg F/kg/day, respectively. There was no association between dental fluorosis in permanent teeth and fluoride intake from diet, dentifrice and combined (p > 0.05).

CONCLUSIONS

There was no difference between children with and without fluorosis in the permanent central incisors and first molars regarding fluoride intake. However, this study has limitations that must be recognized: fluoride intake was only measured once, and there were no children in the sample with severe degrees of dental fluorosis.

Fluoride ingestion from toothpaste: conclusions of European Union-funded multicentre project

An important challenge encountered in this multicentred project was the need to take account of the different cultural and legal differences between the seven sites when agreeing the protocol. Examples such as access to registers of births and subject consent dictated that there were some differences in the methods used in the different sites. The data presented showed that it was possible to train and calibrate a number of examiners in a standardized photographic method for recording enamel fluorosis. This method has a number of important advantages for the objective monitoring of enamel fluorosis over time. There were considerable differences between the seven sites in the formulations of the toothpaste used and in the pattern of their use. The results indicate that it is possible to agree and adopt a standardized method for measuring fluoride ingestion from toothpaste. The aesthetic impact of enamel fluorosis seemed low in the populations included in this project, but further work is required on this issue.

Parental perception of fluorosis among 8-year-old children living in three communities in Iceland, Ireland and England

OBJECTIVES

To assess the impact of enamel fluorosis in three of the communities examined in 'Project FLINT', it was decided to conduct a structured telephone interview with the parents of some of the children who took part in the study.

METHODS

Three communities involved in this project were able to conduct this investigation: Reykjavik (Iceland), Cork (Ireland) and Knowsley (England). The aim was to interview the parents of children with a range of Thylstrup and Fejerskov (TF) index grades selected from each participating centre with respect to the appearance of their child's permanent maxillary central incisors. Interviewers were blinded as to the TF grade of the subject.

RESULTS

Interviews were conducted with parents of 215 children: 69 with TF grade 0; 70 with TF grade 1; 60 with TF grade 2 and 16 with TF grade 3 or greater. There was a trend towards more parents being unhappy with the appearance of their child's teeth with increasing TF grade. However, the main reasons given by parents for being unhappy with the appearance of their child's teeth was tooth alignment followed by the more yellow colour of permanent compared with primary teeth. Only with a TF grade of 3 was any appreciable concern expressed about fluorosis.

CONCLUSION

It would appear that there is a public awareness of both developmental defects and enamel fluorosis although this is not always expressed as dissatisfaction. Further research is required into the clinical impact of both fluorosis and other developmental defects of enamel.

A standardized photographic method for evaluating enamel opacities including fluorosis

OBJECTIVES

The objective of this study was to demonstrate the reproducibility of a standardized photographic technique for recording fluorosis when used by a group of epidemiologists as part of a large multicentred European study.

METHODS

Studies were first carried out to develop the equipment specification and photographic method. The author (JAC) was then trained and calibrated in this method. She was then responsible for the training and calibration of examiners from a further six European study sites. The method involved taking two transparencies of the permanent maxillary central incisors of 8-year-old children, the first after 8 s while the teeth were still wet and the second after 105 s when the teeth had been allowed to dry out naturally. Data were collected at a central location during a training/calibration exercise and subsequently, during the conduct of a large study to measure fluorosis prevalence, at the seven sites. Intra- and interexaminer reproducibility of the photographic method were measured by grading the transparencies produced by all the examiners according to the DDE and TF indices.

RESULTS

The time period in which the transparencies were taken was to within 4 s among the examiners. Transparencies scored according to the TF index gave a range of Kappa values of 0.45-0.66 for intraexaminer reliability and 0.32-0.55 for interexaminer reliability. When using the DDE index Kappa values ranged from 0.43 to 0.70 for intraexaminer reliability and from 0.34 to 0.69 for interexaminer reliability.

CONCLUSION

The photographic method was mostly robust and reproducible when used by epidemiologists from seven European study sites.

Fluoride ingestion from toothpaste: fluoride recovered from the toothbrush, the expectorate and the after-brush rinses

OBJECTIVES

The aim of this study was to determine the effects of rinsing and spitting on fluoride ingestion from toothpaste during normal oral-hygiene procedures of younger children, and hence to make recommendations on rinsing during toothbrushing.

METHODS

The brushing habits of 166 Dutch and 185 Irish children between 1.5 and 3.5 years were observed during home visits. The weight of the toothpaste tube was determined before and after use. After brushing, the toothbrush and any associated expectorate and rinses, combined with any toothpaste spilled during the brushing procedures, were collected. The amounts of fluoride retained on the toothbrush and in the associated expectorate and rinses were measured.

RESULTS

Over 90% of the Dutch children used a special toddlers' toothpaste with < or =500 ppm F. Eleven per cent of the younger (<2.5 years) Dutch children and 22% of the older children rinsed after brushing. Of the Irish children approximately 52% used a children's toothpaste containing around 500 ppm F. Of the younger Irish children 31% spat without rinsing, while another 31% rinsed during or after brushing. For the older Irish children, these percentages were 14 and 70%, respectively. On average, 22% of the fluoride dispensed on the toothbrush was retained on the brush after brushing irrespective of the rinsing and spitting behaviour of the children. The maximum ingestible amount of fluoride from toothpaste assuming no rinsing or spitting was calculated.

CONCLUSIONS

Fluoride ingestion from toothpaste is significantly reduced by rinsing and/or spitting during toothbrushing. Recommendations that younger children use small amounts of toothpaste (< 0.5 g) and that children using toothpaste with > or = 1000 ppm F rinse their mouths after brushing continue to be valid.

A European perspective on fluoride use in seven countries

OBJECTIVES

The aim of this study was to collate data on national policies for the use of fluoride in the seven European countries participating in the FLINT project.

METHODS

Policies on the use of fluoride were obtained for each of the study areas. Data collected included the presence of water fluoridation and regulations governing fluoride toothpaste and fluoride supplements.

RESULTS

In Ireland 74% of the population had a fluoridated water supply but in all the other countries fluoride toothpaste was the principal form of delivering fluoride, usually recommended as a dose of a pea-sized amount. Fluoride supplement use varied considerably between countries. The Netherlands had the clearest regulations covering the use of fluoride supplements and definition of at-risk individuals. Most countries, even if they recognized particular caries-risk did not define the term clearly. In Iceland all children were regarded as being at high risk of developing caries.

CONCLUSION

Considerable variation exists between European countries in their policies for fluoride use and no clear definitions of high-caries-risk individuals were found. The results show that there is even a lack of coherent thought and planning within the different countries, let alone between them.

Urinary fluoride excretion by preschool children in six European countries

OBJECTIVE

To measure and compare 24-h urinary fluoride excretion in children aged 1.5-3.5 years from European study sites and to use these data to estimate the 24-h fluoride intake.

METHOD

Twenty-four-hour urine samples were collected from 3-year-old children (n = 86) who were already participating in a European multicentre study. Samples were collected from Cork, Ireland (n = 19) where the water is fluoridated to a concentration between 0.8 and 1.0 ppm and from five sites with a water fluoride concentration <0.15 ppm: Knowsley, England (n = 18); Oulu, Finland (n = 18); Reykjavik, Iceland (n = 4); Haarlem, the Netherlands (n = 6); Almada/Setubal, Portugal (n = 21). The volume of the samples was measured; they were analysed for fluoride concentration and the 24-h urinary fluoride excretion was calculated. From this an estimate of the daily fluoride intake was made.

RESULTS

It was found that the mean fluoride excretion in response to the usual conditions of fluoride intake in the children in the nonfluoridated areas ranged from 0.16 mg (+/-0.08) in Oulu to 0.33 mg (+/-0.27) in Almada/Setubal with an overall mean of 0.23 mg (+/-0.19). The mean 24-h fluoride excretion in fluoridated Cork was 0.37 mg (+/-0.11). There was a significant difference between the fluoride excretion in the nonfluoridated areas and that in the fluoridated areas, and the data were broadly in agreement with WHO standards.

CONCLUSIONS

The daily urinary fluoride excretion and estimated fluoride intake in these children appeared to be within acceptable limits.

A comparison of the prevalence of fluorosis in 8-year-old children from seven European study sites using a standardized methodology

OBJECTIVES

The objectives of this study were to report on the prevalence of enamel opacities from seven European study sites using a standardized photographic method, and to investigate the importance of variables responsible for enamel fluorosis.

METHODS

The sample comprised a randomly selected group of 300 8-year-old children in each of the study areas. One examiner from each area was trained and calibrated in the use of a standardized photographic technique. Two transparencies were taken of each child's permanent maxillary central incisor teeth; one to represent the teeth 'wet' and one when the teeth had been allowed to dry out naturally for 105 s. The transparencies were viewed 'blind' by the author (JAC) and scored using the DDE and TF indices. Data relating to variables considered to be associated with enamel fluorosis were also collected.

RESULTS

The prevalence of diffuse opacities ranged from 61% in fluoridated Cork (Ireland) to 28% in Athens (Greece). The percentage of subjects with a TF score of three or more ranged from 4% in Cork and nonfluoridated Haarlem (the Netherlands) to zero in Oulu (Finland) and Athens. Fluoridated water and the prolonged use of fluoride tablets were found to be significant contributory factors to fluorosis.

CONCLUSIONS

The prevalence of fluorosis was found to be highest in fluoridated Cork. The prolonged use of fluoride supplements was also found to be a significant risk indicator associated with fluorosis.

Development of a standardized method for comparing fluoride ingested from toothpaste by 1.5-3.5-year-old children in seven European countries. Part 1: Field work

OBJECTIVES

To develop a standardized method for measuring the variables affecting fluoride ingestion from toothpaste in young children between the ages of 1.5 and 3.5 years, and to use the method at seven European sites.

METHODS

Random samples of children were invited to take part in the study. Parents who gave consent were visited at home. The children brushed their teeth using the toothpaste brand and toothbrush type currently in use. Variables measured were: type of toothpaste used, fluoride concentration of toothpaste used, weight of toothpaste used, frequency of brushing and body weight of the child.

RESULTS

It was not possible to follow the agreed protocol in all seven countries and in three countries appropriate alternative methods were employed. There was considerable variation between countries in the variables investigated. Use of children's toothpaste ranged from 69% in Ireland to 98% in Portugal. In the Netherlands up to 60% of the children were using toothpaste containing <400 ppm F and in Finland up to 27% of children were using toothpaste containing >1200 ppm F. Over half of the children used <0.25 g of toothpaste per brushing and the majority of children brushed once or twice per day.

CONCLUSION

Although adherence to the agreed protocol was not possible at all study sites there was a clear picture of considerable variation in the oral hygiene practices of young children throughout Europe.

Development of a standardized method for comparing fluoride ingested from toothpaste by 1.5-3.5-year-old children in seven European countries. Part 2: Ingestion results

OBJECTIVES

To develop a standardized method for measuring the variables affecting fluoride ingestion from toothpaste in young children between the ages of 1.5 and 3.5 years, and to use the method at seven European sites.

METHODS

Random samples of children were invited to take part in the study. Parents who gave consent were visited at home. The children brushed their teeth using the toothpaste brand and toothbrush type currently in use. The difference between the fluoride dispensed onto the toothbrush and the fluoride recovered after accounting for losses was deemed to be the fluoride ingested. Details of other oral health-care habits were collected by questionnaire. For each child, the fluoride concentration of the toothpaste used was measured in the laboratory, from which an estimate of total daily fluoride ingestion was made.

RESULTS

There was considerable variation between countries in the types of toothpaste used and in the amounts of toothpaste applied and ingested. The amount of fluoride ingested ranged from 0.01 to 0.04 mg fluoride per kg of body weight per day.

CONCLUSION

The amount of fluoride ingested that is likely to be a risk factor for the development of dental fluorosis during tooth formation is equivocal and was found to vary widely between European countries. There appears to be a need for clearer health messages regarding the use of fluoridated toothpaste by young children.