Fluoride and Oral Health.

The discovery during the first half of the 20th century of the link between natural fluoride, adjusted fluoride levels in drinking water and reduced dental caries prevalence proved to be a stimulus for worldwide on-going research into the role of fluoride in improving oral health. Epidemiological studies of fluoridation programmes have confirmed their safety and their effectiveness in controlling dental caries. Major advances in our knowledge of how fluoride impacts the caries process have led to the development, assessment of effectiveness and promotion of other fluoride vehicles including salt, milk, tablets, toothpaste, gels and varnishes. In 1993, the World Health Organization convened an Expert Committee to provide authoritative information on the role of fluorides in the promotion of oral health throughout the world (WHO TRS 846, 1994). This present publication is a revision of the original 1994 document, again using the expertise of researchers from the extensive fields of knowledge required to successfully implement complex interventions such as the use of fluorides to improve dental and oral health. Financial support for research into the development of these new fluoride strategies has come from many sources including government health departments as well as international and national grant agencies. In addition, the unique role which industry has played in the development, formulation, assessment of effectiveness and promotion of the various fluoride vehicles and strategies is noteworthy. This updated version of 'Fluoride and Oral Health' has adopted an evidence-based approach to its commentary on the different fluoride vehicles and strategies and also to its recommendations. In this regard, full account is taken of the many recent systematic reviews published in peer reviewed literature.

Scoping Review of Oral Health-Related Birth Cohort Studies: Toward a Global Consortium.

The multidisciplinary nature and long duration of birth cohort studies allow investigation of the relationship between general and oral health and indicate the most appropriate stages in life to intervene. To date, the worldwide distribution of oral health-related birth cohort studies (OHRBCSs) has not been mapped, and a synthesis of information on methodological characteristics and outcomes is not available. We mapped published literature on OHRBCSs, describing their oral health-related data and methodological aspects. A 3-step search strategy was adopted to identify published studies using PubMed, Embase, Web of Science, and OVID databases. Studies with baseline data collection during pregnancy or within the first year of life or linked future oral health data to exposures during either of these 2 life stages were included. Studies examining only mothers' oral health and specific populations were excluded. In total, 1,721 articles were suitable for initial screening of titles and abstracts, and 528 articles were included in the review, identifying 120 unique OHRBCSs from 34 countries in all continents. The review comprised literature from the mid-1940s to the 21st century. Fifty-four percent of the OHRBCSs started from 2000 onward, and 75% of the cohorts were from high-income and only 2 from low-income countries. The participation rate between the baseline and the last oral health follow-up varied between 7% and 93%. Ten cohorts that included interventions were mostly from 2000 and with fewer than 1,000 participants. Seven data-linkage cohorts focused mostly on upstream characteristics and biological aspects. The most frequent clinical assessment was dental caries, widely presented as decayed, missing, and filled teeth (DMFT/dmft). Periodontal conditions were primarily applied as isolated outcomes or as part of a classification system. Socioeconomic classification, ethnicity, and country- or language-specific assessment tools varied across countries. Harmonizing definitions will allow combining data from different studies, adding considerable strength to data analyses; this will be facilitated by forming a global consortium.

Relationships between fluoride intake, urinary fluoride excretion and fluoride retention in children and adults: an analysis of available data.

The aim of this study was to examine the relationship between total daily fluoride intake (TDFI), daily urinary fluoride excretion (DUFE) and fractional fluoride retention (FFR) using available data, in order to clarify the ability of DUFE to predict TDFI and, therefore, the risk of fluorosis development. Examination of published reports of simultaneous measurement of TDFI and DUFE, together with data from two unpublished Chilean studies, yielded data for 212 children aged less than 7 years and for 283 adults aged 18-75 years, providing a total of 212 and 269 data points, respectively. The relationship between DUFE and TDFI was studied for children and adults, separately. Daily fluoride retention (DFR) was estimated as a function of TDFI in children and adults assuming an average 90% fluoride absorption, and the numerical relationships between the estimated FFR and the TDFI were explored. Limiting FFR values of 0.55 and 0.36 were found for children and adults, respectively, above a threshold of TDFI of 0.5 and 2 mg, respectively. Neutral fluoride balances were predicted when the TDFI was equal to approximately 0.07 mg F/day for children and 0.8 mg F/day for adults. For children and adults, it is possible to obtain reasonably good estimations of community-based TDFI and DFR, using DUFE data. The advantages and limitations of these relationships, together with the need for future studies, are discussed.

Oral Health Birth Cohort Studies: Achievements, Challenges, and Potential.

Birth cohorts are those among observational studies that provide understanding of the natural history and causality of diseases since early in life. Discussions during an International Association for Dental Research symposium in London, United Kingdom, in 2018, followed by a workshop in Bangkok, Thailand, in 2019, concluded that there are few birth cohort studies that consider oral health and that a broader discussion on similarities and differences among those studies would be valuable. This article aims to 1) bring together available long-term data of oral health birth cohort studies from the low, middle, and high-income countries worldwide and 2) describe similarities and differences among these studies. This work comprises 15 studies from all 5 continents. The most studied dental conditions and exposures are identified; findings are summarized; and methodological differences and similarities among studies are presented. Methodological strengths and weaknesses are also highlighted. Findings are summarized in 1) the negative impact of detrimental socioeconomic status on oral health changes over time, 2) the role of unfavorable patterns of dental visiting on oral health, 3) associations between general and oral health, 4) nutritional and dietary effects on oral health, and 5) intergenerational influences on oral health. Dental caries and dental visiting patterns have been recorded in all studies. Sources of fluoride exposure have been documented in most of the more recent studies. Despite some methodological differences in the way that the exposures and outcomes were measured, some findings are consistent. Predictive models have been used with caries risk tools, periodontitis occurrence, and permanent dentition orthodontic treatment need. The next steps of the group's work are as follows: 1) establishing a consortium of oral health birth cohort studies, 2) conducting a scoping review, 3) exploring opportunities for pooled data analyses to answer pressing research questions, and 4) promoting and enabling the development of the next generation of oral health researchers.

The fractional urinary fluoride excretion of adults consuming naturally and artificially fluoridated water and the influence of water hardness: a randomized trial.

AIMS: To assess whether there was any significant difference in the average fractional urinary fluoride excretion (FUFE) values among adults consuming (NaF) fluoridated Ca-free water (reference water), naturally fluoridated hard water and an artificially (H2SiF6) fluoridated soft water. DESIGN: Sixty adult females (N=20 for each treatment) participated in this randomized, double-blind trial. The experimental design of this study provided an indirect estimation of the fluoride absorption in different types of water through the assessment of the fractional urinary fluoride excretion of volunteers. RESULTS: Average daily FUFE values (daily amount of fluoride excreted in urine/daily total fluoride intake) were not significantly different between the three treatments (Kruskal-Wallis; p = 0.62). The average 24-hour FUFE value (n=60) was 0.69; 95% C.I. 0.65-0.73. CONCLUSIONS: The results of this study suggest that the absorption of fluoride is not affected by water hardness.

Fluoride Revolution and Dental Caries: Evolution of Policies for Global Use.

Epidemiological studies over 70 y ago provided the basis for the use of fluoride in caries prevention. They revealed the clear relation between water fluoride concentration, and therefore fluoride exposure, and prevalence and severity of dental fluorosis and dental caries. After successful trials, programs for water fluoridation were introduced, and industry developed effective fluoride-containing toothpastes and other fluoride vehicles. Reductions in caries experience were recorded in many countries, attributable to the widespread use of fluoride. This is a considerable success story; oral health for many was radically improved. While previously, water had been the only significant source of fluoride, now there are many, and this led to an increase in the occurrence of dental fluorosis. Risks identified for dental fluorosis were ingestion of fluoride-containing toothpaste, water fluoridation, fluoride tablets (which were sometimes ingested in areas with water fluoridation), and infant formula feeds. Policies were introduced to reduce excessive fluoride exposure during the period of tooth development, and these were successful in reducing dental fluorosis without compromising caries prevention. There is now a much better understanding of the public perception of dental fluorosis, with mild fluorosis being of no aesthetic concern. The advantages of water fluoridation are that it provides substantial lifelong caries prevention, is economic, and reduces health inequalities: it reaches a substantial number of people worldwide. Fluoride-containing toothpastes are by far the most important way of delivering the beneficial effect of fluoride worldwide. The preventive effects of conjoint exposure (e.g., use of fluoride toothpaste in a fluoridated area) are additive. The World Health Organization has informed member states of the benefits of the appropriate use of fluoride. Many countries have policies to maximize the benefits of fluoride, but many have yet to do so.

Fluoridated Water Modifies the Effect of Breastfeeding on Dental Caries.

Breastfeeding is important for health and development. Yet, the interaction between breastfeeding duration and usage of fluoridated water on caries experience has not been investigated. This study examined exposure to fluoridation as an effect modifier of the association between breastfeeding duration and caries. The 2012 to 2014 national population-based study of Australian children involved parental questionnaires and oral epidemiological assessment. Children were grouped by parent-reported breastfeeding duration into minimal (none or <1 mo), breastfed for 1 to <6 mo, breastfed for 6 to 24 mo, and sustained (>24 mo). Residential history and main water source used for the first 2 y of life were collected to group children into exposed (WF) and nonexposed (NF) to fluoridation. Socioeconomic status, infant formula feeding, and sugar-sweetened beverage (SSB) consumption data were collected. The prevalence and severity of caries in children aged 5 to 6 y were primary outcomes. Multivariable regression models with robust error estimation were generated to compute prevalence ratios (PRs) and mean ratios (MRs) for 3 breastfeeding groups against the reference (breastfed for 6-24 mo). Of the 5- to 6-y-old children, 2,721 were in the WF and 1,737 were in the NF groups. The groups had comparable distributions of socioeconomic factors, infant formula feeding, and SSB consumption. There were U-shape distributions of caries experience among breastfeeding groups, being more pronounced among NF children. Among NF children, the minimal and sustained breastfeeding groups had significantly higher PR (1.4 [1.1-1.9] and 1.8 [1.4-2.4]) and MR (2.1 [1.4-3.3] and 2.4 [1.4-4.1]) than the reference group. However, among the WF children, this association between breastfeeding duration and caries attenuated after adjustment for other factors. The study contributes evidence of a nonlinear (U-shape) association between breastfeeding duration and dental caries. Early life exposure to fluoridated drinking water attenuated the potential cariogenic effect of both lack of and sustained breastfeeding.

Fractional urinary fluoride excretion of young female adults during the diurnal and nocturnal periods.

OBJECTIVES: This study aimed to confirm a previously obtained value for the fractional urinary fluoride excretion (FUFE) over a 24-hour period in adults and to assess whether there are significant differences between FUFE measured during the diurnal (7 a.m. and 6 p.m.) and the subsequent nocturnal (6 p.m. until 7 a.m. of the following day) periods. METHODS: Urine was collected over 24 h from 60 healthy female volunteers residing in Santiago, Chile. The individuals' fluoride intakes over the diurnal and nocturnal periods were calculated from their corresponding F ingestion, measured by dietary analysis. Separate urine collections during both periods were obtained from each volunteer. The fluoride concentrations were measured with a fluoride-ion-selective electrode either directly (urine, water and beverages) or after sample treatment with the microdiffusion technique (food). RESULTS: The average 24-hour FUFE value was 0.69, with a 95% CI of 0.65-0.72, while the average FUFE for the diurnal period was 0.46 (95% CI: 0.42-0.50), and the corresponding result for the nocturnal period showed a significantly higher (paired t test, p < 0.0001) amount of 1.09 (95% CI: 0.97-1.22). CONCLUSIONS: A recently published result for the daily FUFE value (0.71) in adults was confirmed. The diurnal average FUFE value is significantly lower than the average nocturnal one. Accepting that approximately 10% of the fluoride intake is not absorbed, the daily fluoride retention can be preliminarily estimated as 20% of the ingested fluoride.

Breastfeeding and Oral Health: Evidence and Methodological Challenges.

Breastfeeding is a powerful health-promoting behavior. A 2016 Lancet global collaboration to review the health implications of breastfeeding was among the first to consider oral health outcomes. While a role was suggested for breastfeeding in preventing malocclusion, caries was the only included disease condition unfavorably associated with breastfeeding. The present critical review examines the evidence connecting breastfeeding practices to these outcomes and discusses the methodological challenges inherent in reaching causal conclusions. Published systematic reviews show some evidence of a protective effect of breastfeeding against primary dentition malocclusion but no supportive evidence for mixed dentition and permanent dentition malocclusions. Regarding caries, well-conducted studies report a benefit with breastfeeding up to 12 mo but a positive association between caries and breastfeeding of longer duration, at times that vary between 12 and 24 mo, as well as nocturnal feeding. Future studies would be methodologically stronger if focused on specific malocclusion traits that are plausibly associated with sucking movements rather than using general malocclusion indices. Studies should use detailed and consistent terminology for breastfeeding definition, including frequency, intensity, and timing. Analytical studies should be carried out to distinguish between confounders (e.g., prematurity) and mediators (e.g., use of pacifier). Regarding a link to caries, standard terminology for exposures (e.g., nocturnal feeding) is recommended. Statistical analyses must account for known confounding factors (e.g., socioeconomic conditions) but avoid inappropriate adjustment for variables on a causal path between exposure and outcome or for variables not associated with breastfeeding (e.g., tooth brushing), as can be guided using tools such as direct acyclic graphs. For dental practice, the potential caries risk of long-duration breastfeeding should be part of individual patient counseling that incorporates patient values and circumstances. Given the unquestioned overall health benefits of breastfeeding, the dental community should support World Health Organization guidelines that encourage and promote breastfeeding.

Critique of the review of 'Water fluoridation for the prevention of dental caries' published by the Cochrane Collaboration in 2015.

The Cochrane Review on water fluoridation for the prevention of dental caries was published in 2015 and attracted considerable interest and comment, especially in countries with extensive water fluoridation programmes. The Review had two objectives: (i) to evaluate the effects of water fluoridation (artificial or natural) on the prevention of dental caries, and (ii) to evaluate the effects of water fluoridation (artificial or natural) on dental fluorosis. The authors concluded, inter alia, that there was very little contemporary evidence, meeting the Review's inclusion criteria, that evaluated the effectiveness of water fluoridation for the prevention of dental caries. The purpose of this critique is to examine the conduct of the above Review, and to put it into context in the wider body of evidence regarding the effectiveness of water fluoridation. While the overall conclusion that water fluoridation is effective in caries prevention agrees with previous reviews, many important public health questions could not be answered by the Review because of the restrictive criteria used to judge adequacy of study design and risk of bias. The potential benefits of using wider criteria in order to achieve a fuller understanding of the effectiveness of water fluoridation are discussed.

Interpreting the correlation coefficient when one of the variables is discrete.

The effect on the correlation coefficient of discretizing data was investigated in two ways. First, the theoretical effect of dichotomizing data was calculated, and it was shown that the resulting correlation coefficient is considerably less than that between the underlying bivariate normally distributed variables. Second, computer simulations were performed of a model in which a continuous variable (measured with some error) gives rise to a counting variable through a mechanism in which the count is zero below a certain threshold value for the continuous variable and then increases linearly as the continuous variable increases. It was shown that the correlation coefficient between the observed values of the continuous and counting variables decreased as (a) the measurement error increased, (b) the slope of the relationship decreased, and (c) the number of counts decreased. It is concluded that caution is required when interpreting correlation coefficients when one or both of the variables consist of a few (say only four or five) discrete scores.

The effect of altering the position of a sugary food in a meal upon plaque pH in human subjects.

Plaque pH in six adult subjects was monitored while they consumed a meal containing three foods. The marked fall in plaque pH caused by drinking sugared coffee was considerably reduced by eating the two non-sugary foods (egg and crisp-bread) before, during, or after the sugared coffee. This favorable action was negated by a pause between the sugary and non-sugary courses.

Associations between dietary intake, dental caries experience and salivary bacterial levels in 12-year-old English schoolchildren.

A population of 328 12-yr-old English schoolchildren, consuming their normal diets, was investigated in a cross-sectional study to determine the interactions between caries experience, oral hygiene status as gingival index (GI), dietary intake (as number of eating events per day and the number of eating events per day at which sugar-containing foodstuffs, confectionery or starch-containing foods were consumed) and salivary levels of caries-associated micro-organisms (mutants streptococci, lactobacilli and yeasts). The mean (+/- SD) decayed, missing and filled surfaces (DMFS) (excluding precavitation lesions) score was 3.05 +/- 3.85 and 5.72 +/- 5.00 (including precavitation lesions). The DMFS scores were significantly related to the salivary levels of caries-associated micro-organisms and to the number of eating events per day for total number of eating events and the number of eating events at which sugar-containing foods or confectionery were consumed. These associations were apparent in both bivariate and partial correlation coefficients with the caries-associated micro-organisms and GI controlled. The total daily intakes of food types, except for starch, were not associated with caries experience. No significant correlations were found between intake of food types and salivary levels of caries-associated micro-organisms except that the mean number of confectionery-eating events was correlated with lactobacillus levels (r = 0.136, p < 0.01). The salivary levels of mutans streptococci, lactobacilli and yeasts were significantly correlated with GI scores. These data do not indicate simple associations between dietary intake, caries and levels of caries-associated micro-organisms. Poor oral hygiene, in children consuming unrestricted diets, may influence the salivary levels of mutans streptococci, lactobacilli and yeasts irrespective of the frequency or amount of sugar consumed. Multiple regression analyses revealed that three variables--GI (probably an indicator of toothbrushing behaviour with a fluoride-containing toothpaste), salivary concentration of lactobacilli and frequency of ingestion of confectionery/sugary foods--were independently and positively related to caries experience.

Acid-etch patterns on the buccal surface of human permanent teeth.

Since the introduction of acid etching to aid adhesion to enamel, there has been much research into dental materials to improve bond strength, but little into the surface topography of etched enamel, particularly regarding possible variations between tooth types. This study was a systematic investigation into the quality and quantity of etch patterns found on the buccal surfaces of different human permanent teeth. Twenty-nine orthodontic patients had high-resolution silicone impressions taken of the buccal surface of incisor, canine, premolar and molar, upper and lower teeth, following etching for 30s with 37% phosphoric acid. Impressions (n=266) were replicated in epoxy resin and examined under high magnification in a scanning electron microscope. A modification of the classification of Galil and Wright was used, with histometric techniques, to quantify the quality of etch patterns on enamel surfaces where orthodontic brackets are typically bonded. There was no difference between right and left or between upper and lower teeth of the same type (P>0.05). There was a general trend toward the increasing occurrence of no etch (type D) from anterior to posterior teeth, and a trend toward fewer good-quality etches (types A and B) in the same direction. Etch types A and B were found to occupy the smallest area on the etched buccal surface enamel. The greatest amount of type A etch 'ideal' was found on the lower incisors, yet it occupied less than 5% of the etched buccal surface enamel. The greatest area of etched enamel surface was occupied by type C (etched, but enamel prisms not evident). It was concluded that there is a significant difference in the acid-etch patterns achieved on different tooth types, which suggests that bond-strength studies should be performed with a single tooth type or that an equal number of different tooth types be included.

Relationship between dietary habits and caries increment assessed over two years in 405 English adolescent school children.

The study was conducted in seven schools on children initially aged 11.5 years. They recorded their diet on five occasions, each of three days, and received an annual dental examination, including radiography. Caries increments were low, mostly (58 per cent) in fissure surfaces. Correlations between caries increment and dietary factors were low due to the low caries increments observed and the large error associated with dietary data where analyses attempt to discriminate between individuals. The highest correlation was between caries increment and weight of daily intake of sugars (+0.143, p less than 0.01). Multivariate analyses revealed that this relationship could not be explained by differences in sex, social class, tooth-brushing habits or level of plaque as measured by gingival inflammation. Weight of sugar intake appeared to be more strongly correlated to caries than frequency of intake; concentration of sugars in foods was positively related, and sugars in snacks were more strongly related to caries than total dietary sugars. The 31 children who consumed most sugar (greater than 163 g/day) developed 5.0 DMFS during the 2 years, 0.9 DMFS per year more than the 31 children (3.2 DMFS during 2 years) who had the lowest sugar intake (less than 78 g/day).

Combination of low parental educational attainment and high parental income related to high caries experience in pre-school children in Abu Dhabi.

Children aged 2, 4 and 5 years were examined for dental caries using WHO criteria, in the Emirate of Abu Dhabi, UAE, in 1996. The children were from the three administrative regions of Abu Dhabi, Al Ain and Western Region. Sampling of health centres and kindergartens was stratified by urban or rural location. Parents completed a questionnaire, and children were classified into high, middle or low groups on the basis of their parents' education and income. All 20 kindergartens and 22 health centres sampled agreed to participate. The participation rate of sampled children was high and complete data were available for 640 children--217 aged 2 years, 204 aged 4 years, and 219 aged 5 years. Similar numbers of boys and girls were included. The prevalence of dental caries was very high--36% to 47% at age 2 years, 71% to 86% at age 4 years and 82% to 94% at age 5 years. The mean dmft at age 5 years was 8.4 in Abu Dhabi, 8.6 in Al Ain and 5.7 in Western Region. Few teeth had been filled. Apart from age, the parents' education and income were found to be statistically significantly related to caries experience (P<0.05), while gender, ethnicity (UAE or non-UAE), region, and urban or rural living, were not related to dental caries experience (P>0.3). While high parental educational attainment was related to lower caries experience, conversely, high parental income was related to higher caries experience. Caries experience was higher than that recorded approximately 6 years previously and is a cause of concern.

Effect of filming on toothbrushing performance in uninstructed adults in north-east England.

Video recordings were obtained of 90 adults aged 18-22 yr brushing their teeth. Thirty subjects were unaware they were being filmed and 60 subjects had been informed that they would be filmed while they brushed their teeth. From repeated viewing of the tapes the areas of the mouth that were brushed, the total brushing time and the proportion of time spent brushing each of 16 areas of the mouth were obtained for each subject. Subjects who knew they were being filmed brushed significantly more mandibular occlusal surfaces, and lingual areas in both arches than subjects who were unaware they were being filmed. There was no significant difference in the mean toothbrushing time between the two groups. The informed group spent proportionally less time brushing posterior buccal areas and more time on occlusal and lingual areas than the group who were unaware they were being filmed, the difference being statistically significant for the mandibular arch areas. It was concluded that knowledge of filming alters toothbrushing behaviour to a small extent so that care should be taken when interpreting behavioural changes in future intervention studies.

Evaluation of a calibration trial to increase interexaminer reliability of radiographic diagnosis of approximal carious lesions.

Eighteen dentists working in the same School Dental Service participated in a calibration trial with the purpose of reducing interexaminer disagreement on radiographic diagnosis of approximal caries. The calibration program was in two stages: firstly, discussion in small groups and, secondly, the use of a reference standard. The effect of the training programs on interexaminer disagreement was limited, but a statistically significant decrease in the number of D-surfaces recorded per child was observed. The finding that the major part of the error variance was due to random error, rather than systematic error, may explain why the calibration program was unsuccessful at reducing error.