This course was published in the August 2018 issue and expires August 2021. The authors have no commercial conflicts of interest to disclose. This 2 credit hour self-study activity is electronically mediated.
After reading this course, the participant should be able to:
- Identify the optimal level of fluoride in community water fluoridation programs.
- Describe fluoride’s mechanism of action.
- Discuss the history of community water fluoridation.
- Explain the role of oral health professionals in caries risk prevention.
Water fluoridation is the adjustment of naturally occurring fluoride levels in water to a level that is known to prevent tooth decay.1 Exposure to small amounts of fluoride over time reduces the incidence of tooth decay by enhancing remineralization and inhibiting demineralization of tooth enamel.2–4 Fluoride’s action in preventing caries lesions results in fewer dental restorations and extractions, as well as in reduced pain associated with tooth decay.
Many public health agencies and professional health organizations have advocated for the addition of fluoride to drinking water to prevent dental caries. Although the practice of adjusting the level of fluoride in the water has been controversial, the U.S. Centers for Disease Control and Prevention (CDC), American Medical Association, American Dental Association, American Academy of Pediatrics and many others have recommended water fluoridation as an effective means of promoting oral health.2
While unproven allegations that water fluoridation is unsafe — including claims that it lowers IQ and increases the risk for cancer, bone fractures and Alzheimer’s disease — continue to be made, the approaches to generating controversy have varied.2 These include the distribution of fluoride misinformation via the internet, newspapers or other means, including health food stores, chiropractic offices and places of worship. Systematic reviews of the literature, however, support the use of optimally fluoridated water at 1 ppm as safe, with no adverse health effects.1–5 The totality of the scientific evidence gathered thus far does not support a direct link between the currently recommended levels of fluoride intake and any of the health concerns listed above. Further research is recommended, and is likely to focus on fluoride metabolism, fluoride as it relates to human genetics, and refinement of the optimal range of total fluoride intake.4 Therefore, oral health professionals should continue to monitor dental research regarding fluoride and water fluoridation as it relates to caries management.
HOW FLUORIDE WORKS
Drinking fluoridated water provides both a systemic and topical application of fluoride.5,6 After drinking fluoridated water, most of the fluoride is absorbed by the stomach and small intestine into the blood.2 Fluoride blood levels reach a peak concentration within 20 to 60 minutes, and decline over the next three to six hours, as fluoride is absorbed in calcified tissues and removed from the body by the kidneys.2
Research indicates that caries prevention from fluoridated water primarily results from topical contact of fluoride with the dentition.4 Fluoridated water surrounds teeth with a constant supply of low levels of fluoride and provides a reservoir of fluoride available for remineralization. Individuals consuming 1 L of fluoridated water at 0.7 mg/L receive 0.7 mg of fluoride.2 Drinking optimally fluoridated water reduces tooth decay by approximately 25%.2–4,6–8
Currently, more than 211 million Americans are served by water systems that provide optimally fluoridated water.1,3 In 2014, approximately 74% of the U.S. population was served by fluoridated community water supplies (Figure 1). Hawaii (11.3%), New Jersey (14.6%), and Oregon (22.6%) have the lowest percentage of residents receiving optimally fluoridated water,3 while the regions with the highest percentage (75% or more) are primarily located in the Southeast, Mid-Atlantic and Upper Midwest.
The first community in the world to fluoridate its public water system was Grand Rapids, Michigan, in 1945.1,3 The study of the Grand Rapids fluoridation experience analyzed the rate of dental caries among 30,000 schoolchildren. Results showed that children born after fluoride was added to the water experienced a 60% reduction in tooth decay.9 This breakthrough in caries prevention was viewed as a watershed moment for dentistry because, for the first time, caries was viewed as a preventable disease.
In the ensuing years, community water fluoridation has been recognized as one of the top 10 public health achievements of the 20th century because of its contribution to disease prevention.3 Research demonstrates that adults have benefited from community water fluoridation. The average number of caries-infected teeth has decreased from 18 per person in the 1960s to 10 per person in 1999 to 2004.1 Water fluoridation also benefits children, as evidenced by the decrease of caries in at least one permanent tooth per child from 90% of those age 12 to 17 in the 1960s to 60% of those age 12 to 17 in 1999 to 2004.1 Nevertheless, dental caries remains a significant concern, especially for underserved and low-income populations. Approximately 25% of children age 5 to 19 from low-income families have untreated caries.10 Untreated tooth decay continues to increase in adulthood, with 47% of low-income adults age 20 to 44 having untreated caries.10 Moreover, approximately 2 million people in the U.S. annually turn to the hospital emergency department for their dental needs.11 The primary diagnosis for 42% of all dental-related emergency department visits in the U.S. is untreated caries.12
ORAL HEALTH PROFESSIONALS’ ROLE
Dental teams can strengthen their caries prevention protocols simply by determining if patients are drinking fluoridated water and educating patients about the role it plays in caries management. Research indicates the percentage of dental patients who receive information from their oral health professional regarding water fluoridation is only 20%.13 This lack of promotion of such an important disease prevention measure is often due to a lack of awareness.13 Many oral health professionals note that patients do not ask about water fluoridation, so they do not discuss it. Others suggest they are not knowledgeable enough about fluoridation or comfortable in responding to patients who may present anti-fluoride arguments.13 The drinking water flow chart (Figure 2) provides a framework to determine the primary source of a patient’s drinking water. Once the source is determined, additional dialogue regarding appropriate fluoride exposure and caries management can take place.
In addition, research indicates that most oral health professionals focus their preventive efforts on the importance of oral hygiene. While oral hygiene is vital, the effect of fluoride on reducing dental decay is at least as impactful, if not more so, than simply brushing.13 Using fluoride toothpaste can reduce caries by approximately 20% to 25%.3 Drinking optimally fluoridated water also reduces dental decay by 25%.3,14 Patients with a low risk of developing caries may not need additional fluoride interventions beyond drinking optimally fluoridated water and brushing with a fluoride toothpaste. As opposed to conversations with the dental team, most patients learn about water fluoridation from the media.13 The quality of information in the media, on the internet, and in blogs varies considerably, and in some instances may be misleading or false.2 Oral health professionals should assist patients in identifying valid, peer-reviewed, scientific information regarding water fluoridation, using sources such as thecommunityguide.org/findings/dental-caries-cavities-community-water-fluoridation.15
Although three out of four Americans are served by fluoridated water systems, research indicates that individuals are generally unaware of their community water status.13 The U.S. Environmental Protection Agency is the agency responsible for monitoring water quality.2 The national Water Fluoridation Reporting System (WFRS) tracks the fluoride status of 54,000 community water systems.3 Approximately 40 states provide public access to WFRS data (Figure 3) at nccd.cdc.gov/doh_mwf/reports/default.aspx; the WFRS monitors the communities served, type of water system, and water fluoride concentrations.3 It also provides information regarding defluoridation; if the naturally occurring fluoride in the water happens to be above the recommended level, for example, local water system operators will defluoridate the water to the recommended level of 0.7 ppm.
BOTTLED WATER SOURCES
In 2016, Americans began drinking more bottled water than soda, according to Beverage Marketing Corp.16 This shift has been attributed to widespread concerns regarding the negative health effects of drinking sugary beverages. Bottled water is a healthy, but expensive, alternative, as bottled water is 2000 times more expensive than drinking tap water.16 The estimated annual per capita cost of providing fluoridated tap water ranges from $0.11 to $4.92 for communities with at least 1000 residents.10
The U.S. is the largest consumer of bottled water, with 13 billion gallons of bottled water sold annually. This works out to each individual in the U.S. consuming 39 gallons of bottled water annually.17 While some brands obtain their water from municipal water sources,17 bottled water generally contains less than optimal levels of fluoride. (A list of companies that provide fluoridated bottled water is available at bottledwater.org/health/fluoride.) Bottled water is regulated by the U.S. Food and Drug Administration as a packaged food product,2 and standards exist for labeling with regard to fluoride content — but only if fluoride is added during processing. Oral health professionals should ask patients about their source of drinking water and discuss the level of fluoride exposure most appropriate for caries management. Patients who primarily drink bottled water may be missing the caries prevention benefits provided by optimally fluoridated water. Bottled water is often purified by reverse osmosis, distillation, microfiltration or carbon filtration processes that can remove fluoride.17 In addition, if patients are using a point-of-use water treatment system at home, it is best to check with the manufacturer to determine if it removes fluoride.2
Dental fluorosis — the appearance of faint white lines, pitting or chalky streaks on the teeth of young children who consume too much fluoride — is generally caused by a variety of sources, including toothpastes, gels and mouthrinses.4–8 Ideally, fluoride intake should maximize the prevention of caries while minimizing the occurrence of fluorosis. This condition only occurs during tooth formation when fluoride intake is excessive.2,4 Most fluorosis is mild, presenting in faint white lines or streaks visible only to oral health professionals under good lighting in the clinic. More noticeable fluorosis, such as rarely occurring mottling, may lead to concerns about the appearance of the teeth. Dental fluorosis depends on the timing, amount and duration of excessive fluoride exposure during early childhood.4 Beyond the products mentioned, sources of fluoride exposure include fluoride supplements, infant formulas and fluoridated drinking water.4,5,7 Therefore, monitoring a child’s total fluoride intake, especially during the first 6 to 8 years (when the permanent maxillary central incisors are forming as tooth buds), is important to minimize the risk of fluorosis.2,18,19 Drinking optimally fluoridated water is a minor risk factor for developing fluorosis.20
While the methods of fluoride delivery may be intended to have a topical effect, the reality is that fluoride is inadvertently swallowed during brushing. The effect is systemic, as well as topical. Children younger than age 6 have yet to fully develop their swallowing reflex and are more likely to swallow excess toothpaste than expectorate it.20 Fluoride ingestion during toothbrushing and the use of fluoride supplements are significant factors in a child’s risk of developing dental fluorosis.2,4,20 Fluoride supplements, in the form of tablets, drops or fluoride vitamins, have been prescribed for decades in communities with unfluoridated water to prevent tooth decay. Supplemental fluoride prescriptions are contraindicated for children who reside in communities with optimally fluoridated water.2,20
Approximately 65% of dental fluorosis cases in unfluoridated communities is due to supplemental fluoride prescriptions.2,10 For children raised in fluoridated communities, 68% of fluorosis cases can be attributed to the use of toothpaste during the first year of life.10 Therefore, oral health professionals are advised to consult with patients to document their primary source of drinking water and assess total fluoride intake. In addition, parents and caregivers should be advised to supervise young children when brushing.
During pregnancy, fluoride in low concentrations crosses the placenta.20 This exposure is considered minimal and is not a reason to avoid fluoridated water. The recommendation of the Oral Health Care During Pregnancy Expert Workgroup is for pregnant women to drink fluoridated water (via fluoridated community water supplies or fluoridated bottled water).21 Once the child is born, breastfeeding may provide a small amount of fluoride to the infant from the mother’s milk via her plasma fluoride levels. This exposure is negligible, however.22 Likewise, most infant formulas that are mixed with water contain low levels of fluoride.20 Thus, in order to reduce the risk of fluorosis, parents and caregivers may choose unfluoridated water or low-level fluoridated water to mix with infant formula.10,20 Caretakers who prefer soy-based formulas should be advised these products may contain higher fluoride concentrations than milk-based formula.20 Hence, parents and caregivers may prefer to use unfluoridated water when mixing soy-based formula. Additional information regarding infant formula and water fluoridation is available at cdc.gov/fluoridation/faqs/infant-formula.html.
Once children are 6 months of age, they can be introduced to food and drink other than breast milk and infant formula.23 Healthy eating and drinking patterns begin early in life. Toddlers need approximately 2 cups of water daily to cover their fluid needs.23
Patients’ exposure to fluoride, fluoridated water and fluoridated dental products has evolved over the past century and will continue to evolve. Because fluoride exposure results from a variety sources, patients may be exposed to higher levels than originally anticipated. Consequently, questions have emerged about whether current water fluoridation practices provide the expected benefits while avoiding adverse effects, such as fluorosis. Drinking optimally fluoridated water reduces dental caries in children and adults primarily due to the topical effect of fluoride, which enhances remineralization.
Clinicians should assess a patient’s caries risk status, exposure to water fluoridation, and total fluoride intake to determine the appropriate level of fluoride needed for optimal caries management. Research indicates water fluoridation is safe and effective — and, in fact, should serve as a cornerstone of most individual caries management plans. For patients at low risk of caries, drinking fluoridated water and brushing with fluoride toothpaste are sufficient for effective caries prevention.
- U.S. Department of Health and Human Services Federal Panel on Community Water Fluoridation. US Public Health Service Recommendation for Fluoride Concentration in Drinking Water for the Prevention of Dental Caries. Available at: ada.org/~/media/EBD/Files/PHS_2015_Fluoride_Guidelines.pdf?la=en. Accessed June 20, 2018.
- American Dental Association. Fluoridation Facts. Available at: ada.org/en/public-programs/advocating-for-the-public/fluoride-and-fluoridation/fluoridation-facts. Accessed June 20, 2018.
- U.S. Centers for Disease Control and Prevention. Community Water Fluoridation. Available at: cdc.gov/fluoridation/statistics/index. htm. Accessed June 20, 2018.
- Buzalaf MAR. Review of fluoride intake and appropriateness of current guidelines. Adv Dent Res. 2018;29:157–166.
- Walls AWG. Guidelines for fluoride intake: second discussant. Adv Dent Res. 2018;29:179–182.
- Griffin SO, Regnier E, Griffin PM, Huntley V. Effectiveness of fluoride in preventing caries in adults. J Dent Res. 2007;86:410–415.
- Featherstone JD. Prevention and reversal of dental caries: Role of low level fluoride. Community Dent Oral Epidemiol. 1999;27 (1):31–40.
- Peckham S, Awofeso N. Water fluoridation: a critical review of the physiological effects of ingested fluoride as a public health intervention. Scientific World J. 2014;293019.
- National Institute of Dental and Craniofacial Research. The Story of Fluoridation. Available at: nidcr.nih.gov/health-info/fluoride/the-story-of-fluoridation. Accessed June 20, 2018.
- National Center for Health Statistics. Health, United States, 2016: With Chartbook on Long-term Trends in Health. Available at: cdc.gov/nchs/data/hus/hus16.pdf. Accessed June 20, 2018.
- National Center for Health Statistics. Health, United States, 2012: With Special Feature on Emergency Care. Available at: cdc.gov/nchs/data/hus/hus12.pdf. Accessed June 20, 2018.
- Wall T, Nasseh K. Dental-related emergency department visits on the increase in the United States. Available at: ada.org/~/media/ADA/Science%20and%20Research/HPI/Files/HPIBrief_0513_1.pdf. Accessed June 20, 2018.
- Melbye MLR, Armfield JM. The dentist’s role in promoting community water fluoridation: A call to action for dentists and educators. J Am Dent Assoc. 2013;144:65–75.
- Young DA, Featherstone JD, Roth JR. Curing the silent epidemic: Caries management in the 21st Century and beyond. J Calif Dent Assoc. 2007;35:681–685.
- Community Preventive Services Task Force. Guide to Community Preventive Services: Preventing Dental Caries. Available at: thecommunityguide.org/oral/fluoridation.html. Accessed June 20, 2018.
- Taylor K. Americans drink more bottled water than soda. Business Insider. March 9, 2017.
- Hirst RR. Drinking Water Research Foundation. Bottled Water and Tap Water: Just the Facts. Available at: https://www.bottledwater.org/files/BW%20PWS%20Just%20the%20Facts%202011%20Final.pdf. Accessed June 20, 2018.
- Bhagavatula P, Curtis A, Broffitt B, et al. The relationships between fluoride intake levels and fluorosis of late‐erupting permanent teeth. J Public Health Dent. December 29, 2017.
- Petersen PE, Lennon MA. Effective use of fluorides for the prevention of dental caries in the 21st century: the WHO approach. Community Dent Oral Epidem. 2004;32:319–321.
- Burt BA, Eklund SA. Dentistry, Dental Practice and the Community. 6th ed. Philadelphia: Elsevier Saunders Co; 2005.
- Oral Health Care During Pregnancy Expert Workgroup. 2012. Oral Health Care During Pregnancy: A National Consensus Statement. Available at: mchoralhealth.org/PDFs/OralHealthPregnancyConsensus.pdf. Accessed June 20, 2018.
- Sener Y, Tosun G, Kahvecioglu F, Gökalp A, Koç H. Fluoride levels in human plasma and breast milk. Eur J Dent. 2007;1:21–24.
- Pérez-Escamilla R, Segura-Pérez S, Lott M. Feeding Guidelines for Infants and Young Toddlers: A Responsive Parenting Approach: Guidelines for Health Professionals. Available at: http://healthyeatingresearch.org/wp-content/uploads/2017/02/her_feeding_guidelines_report_021416-1.pdf. Accessed June 20, 2018.
Featured image by WAVEBREAKMEDIA/ISTOCK/GETTY IMAGES PLUS
From Decisions in Dentistry. August 2018;4(8):36–39.