L.M.A. Tenuta, J.A. Cury, N. Dame-Teixeira, D. Heller, G. McKenna, B.H. Oliveira, C. Fox, and M.K.S. Charles-Ayinde
Various methods of fluoride use have been available since the discovery of the anticaries properties of this ion. This position statement deals with those which are applied to erupted teeth. Historically, those methods have been classified as "topical" (to be differentiated from the methods of fluoride use resulting in intentional systemic exposure, such as water fluoridation), which has been the cause of confusion considering that the predominant effect of fluoride in caries control, irrespective of the method of use, is local (topical) (see the IADR statement on community water fluoridation). Therefore, in this statement these methods will be separated according to their delivery approach, as fluoride used at the individual or professional level.
Irrespective of the mode of use and specific intraoral reactions, all the products discussed here work primarily through the delivery of fluoride ions to the oral fluids (saliva, biofilm fluid), where they can interfere with the equilibrium between the tooth minerals and the oral environment. Fluoride reduces the rate of mineral loss when available in a fermenting (low pH) biofilm (effect on the inhibition of demineralization), as well as enhances mineral deposition when available in a neutral biofilm or in saliva (effect on the enhancement of remineralization). This physicochemical effect has been demonstrated in a number of studies5,9,10,32 and translates into a number of systematic reviews of clinical studies investigating the anticaries effectiveness of different methods of fluoride use.
Fluoride used at the individual level
Rationale, mechanism of action and evidence
The most common, and perhaps the most important, way of fluoride use is through fluoride toothpastes. The addition of fluoride to toothpastes came as a consequence of the discovery of its anticaries properties, and after some years of product development, effective formulations became available to the public14. This happened during the 1970s and 1980s, which coincides with significant reductions in caries rates around the globe6, 27. Currently, fluoride toothpastes are the predominant type of toothpaste formulation, available worldwide and making part of daily oral hygiene. However, high quality toothpastes are not always available to populations in middle and low-income countries. Given its indisputable benefits to oral health, all efforts should be taken to make toothpaste with adequate fluoride concentration universally affordable and accessible35, 36.
Because dental caries is caused by an interplay between dental biofilm and its frequent exposure to sugar15, using fluoride as part of the oral hygiene routine is a very rational approach. When used to brush teeth, fluoride toothpaste helps remove the dental biofilm, and at the same time increases fluoride concentration in the oral fluids (in whole saliva, to bathe cleaned surfaces and help bring back minerals that were potentially lost under a fermenting biofilm, and in the fluid of biofilm remnants that were not removed by brushing, where it will help reduce mineral loss under a new sugar exposure). It is important to note that fluoride should be chemically soluble in the formulation (e.g. fluoride ion, monofluorophosphate ion)21, so that it will be bioavailable to affect the demineralization/remineralization process33.
The effectiveness of fluoride toothpastes to reduce caries has been demonstrated in randomized clinical trials (RCTs) and systematic reviews of RCTs which shows that: 1. Standard concentration toothpastes (1,000-1,500 ppm F (μg F/g)) increase the number of caries-free children and significantly reduce caries increment in children and adults, with a dose-response effect17,34; 2. Brushing two or more times daily provides greater protection than brushing once a day or less16; 3. High-fluoride toothpastes (e.g. 5,000 ppm F) prevent new root caries lesions and increase the likelihood of existing lesions becoming arrested in older adults13,23.
With a similar mode of action, fluoride mouth rinses are also part of oral hygiene regimes and their effectiveness has been tested mainly in school programs16. The recommendation to use fluoride mouth rinses, in addition to fluoride toothpastes, is usually determined based on the patient's caries risk; dental caries can be effectively controlled by proper oral hygiene with fluoride toothpaste, but in certain occasions when caries risk is increased (e.g. gingival recession in older people, exposing root surfaces; salivary gland hypofunction (dry mouth); high sugar consumption), increased oral fluoride levels can be sustained for longer by a fluoride mouth rinse used after toothbrushing.
In summary, fluoride toothpastes should be recommended to everyone as an effective method of fluoride use, as part of their daily oral hygiene regime. Brushing two or more times daily with a fluoride toothpaste provides superior caries protection to only once a day or less. An additional exposure to fluoride (via high fluoride concentration toothpastes, mouth rinses, or professionally applied products (see next section)) may be recommended for individuals at increased risk for caries.
Safety
Fluoride toothpastes and mouth rinses are generally considered to be safe methods of fluoride delivery. Available over-the-counter (except for high concentration toothpastes/mouth rinses, which often require a prescription), these products involve minimal safety concerns when properly used. However, fluoride toxicity should be considered. Acute fluoride toxicity involves the ingestion of a high fluoride dose, at once. The probable toxic dose for acute fluoride toxicity is 5 mg F/kg body weight; above this exposure, measures should be taken to reduce fluoride absorption or systemic effects. This level of exposure can be reached only if a very young child (ex. weighing around 10 kg) ingests more than half of an over the counter toothpaste tube (usually 1,100 ug F/g, tube weight approximately 100 g), or more than half a bottle of an over the counter mouth rinse (usually 226 ug F/mL, 300-500 mL bottle). Accidents with the ingestion of these products are very rare31, and can be prevented by keeping these products out of reach of children. It is recommended that fluoride mouth rinses and high fluoride toothpastes (5,000 ppm F) are not used by children under 6 years of age, because they may not be properly trained on spitting. For dependent older adults, high fluoride toothpastes should be considered safe, but care must be taken to minimize ingestion, which may cause gastric symptoms.
Aside from the safety of over the counter fluoride products in terms of acute toxicity, dental fluorosis may develop as a result of the inadvertent ingestion of fluoride toothpaste during the time teeth are mineralizing. Dental fluorosis associated with fluoride toothpaste use, even when it is combined with exposure to fluoridated water, has been shown to be mild to very mild37; mild and very mild fluorosis do not negatively affect the quality of life of the affected3,26. Considering the anticaries benefits of fluoride, the impact of early childhood caries on children's health and well-being, and the degree of dental fluorosis associated with its use, fluoride toothpastes should be recommended to children of all ages. To minimize the dose of exposure to fluoride, reduced amounts of toothpaste have been recommended by professional organizations for brushing teeth of young children considering their reduce body weight (e.g. approximately 0.1 g, or a grain of rice for children younger than 3, approximately 0.3 g, or a pea-sized amount for children between 3 and 6 years of age)1,2,29.
Professionally applied fluoride
Rationale, mechanism of action and evidence
roducts containing high fluoride concentrations (usually above 9,000 ppm F) at 3-6 month intervals, guided by an assessment of caries risk/activity. These products are formulated usually as gels or foams (which can be delivered using trays or applied to teeth using cotton swabs) or varnishes (which are applied with a brush and are supposed to adhere to the teeth). At these higher concentrations, the amount of fluoride reaction with the tooth structure is high, forming fluoride-releasing reservoirs on the surface of teeth or within early caries lesions. Therefore, in between the long interval for their re-application, these reservoirs will release fluoride ions to interfere with the caries process. Another type of professional fluoride product is silver diamine fluoride (SDF), which contains fluoride at very high concentration (e.g. 45,200 ppm F) and is used to arrest cavitated coronal and root caries lesions. Although the mechanism of action of SDF on the arrestment of dentin lesions is not clear, a combination of effects of the silver (254,000 ppm) and fluoride components at alkaline pH (8.0-10.0) seems to be important for the anticaries effect22.
Fluoride gels and varnishes have been shown to be effective to reduce caries increment19,20. They confer a small additional anticaries benefit in individuals already using fluoride toothpastes8,18. Therefore, they are recommended for individuals at an increased risk for caries, or as part of preventive programs targeting at-risk populations, including older adults12. Fluoride gels usually contain free, ionic fluoride, in acidic or neutral formulations, and their reaction with the tooth structure forming fluoride reservoirs takes place within minutes. Fluoride varnishes are intended to adhere to the tooth structure for a long-reaction time. Most of the fluoride in this formulation is insoluble, and their clinical effectiveness may rely on their ability to be retained for long periods of time (hours) on the tooth structure7.
Regarding SDF, there is evidence of its effectiveness in reducing the progression and development of dentin caries in primary teeth, and also for controlling root caries4,11,224,30.
Safety
Fluoride gels, varnishes and SDF are considered safe. Because of their high concentration, they should be manipulated with care by oral health professionals. Application of fluoride gels in trays is not recommended for children younger than 6 years of age due to the risk in ingestion of a significant amount of the product. Varnishes are considered safer because of their ability to adhere on teeth, and the ingestion of fluoride from the product occurs over a longer period of time. Nevertheless, all high fluoride concentration formulations should be used with care by oral health professionals to avoid unnecessary ingestion.
Summary
The International Association for Dental, Oral, and Craniofacial Research (IADR), recognizing that dental caries (tooth decay) ranks among the most prevalent chronic diseases worldwide, supports the individual and professional application of fluoride as a safe and effective, evidence-based intervention for the prevention of dental caries. Based on the available scientific evidence, the IADR supports that:
1. Fluoride toothpastes (1,000-1,500 ppm fluoride concentration) should be used twice per day by all individuals as an effective way to control caries in conjunction with daily oral hygiene; all efforts should be taken to make toothpaste with an adequate fluoride concentration universally affordable and accessible.
2. Fluoride toothpastes are used by children starting with the eruption of their first teeth, in reduced amounts until the age 6 to minimize the risk for dental fluorosis;
3. Additional methods of fluoride use or higher strength products, either at the individual level (mouthrinses, high fluoride toothpastes), or professional level (fluoride gels, varnishes, solutions), should be recommended to individuals or populations at higher risk for caries.
Author Contributions
L.M.A. Tenuta contributed to design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript, all members of the IADR Science Information Subcommittee, contributed to conception and design, critically revised the manuscript. M.K.S. Charles-Ayinde contributed to conception, design, and interpretation of the manuscript; C. Fox contributed to the conception and critically revised the manuscript. All authors gave final approval and agreed to be accountable for all aspects of the work.
Acknowledgements
The members of the 2022 IADR Science Information Subcommittee were J.A. Cury, N. Dame-Teixeira, D. Heller, G. McKenna, and B.H. Oliveira. The IADR Science Information Committee thanks all members of the Subcommittee for providing subject matter expertise during the drafting of the policy statement.
The authors received no financial support and declare no potential conflicts of interest with respect to the authorship and/or publication of this article.
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(Adopted June 2022)