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Changing water fluoridation levels
COMMENTARY Changing water fluoridation levels Background The United States Department of Health and Human Services (US HHS) has issued a recommendation for using an optimal concentration of 0.7 mg fluoride per liter (mg F/l) in water supplies, with the basis being a belief that this concentration permits the best balance of protection from dental caries and limitation of dental fluorosis risk. The recommendation changes the previous guideline that fluoride levels should be between 0.7 and 1.2 mg F/l based on the ambient air temperature of the geographic area. The rationale for this action should be questioned because considerable uncertainty is seen in the data used, the panel’s approach, and the lack of consideration of the consequences of the recommendation.
Risk/Protection Balance Dental fluorosis is essentially a disorder affecting children age birth to 8 years, whereas dental caries is a disorder that occurs across the lifetime and in all dentitions. Therefore protection against fluorosis should be focused on young children, whereas caries protection requires an ongoing effort throughout the lifespan. These differences make the balance of risk/protection difficult to conceptualize. Dental fluorosis and dental caries also differ in impact. Caries has well-established consequences and is the reason for most restorative or exodontic treatment to repair or replace damaged teeth. It has a significant impact both on the individual’s oral health and dental expenditures and on the societal investment in oral health and dental care. Dental fluorosis can range from barely discernable to severe, and individual reaction to its esthetic effect varies considerably. Recently, with an emergence of community expectations about ‘‘white teeth,’’ patients have had muted or even positive reactions to fluorosis, believing it has no serious impact on oral health. Low-severity dental fluorosis is seen as representing better oral health than no fluorosis. Severe fluorosis is rare in the United States and comparable countries, with low impact on communities and treatment costs.
284
Dental Abstracts
The natural history of dental fluorosis is also little understood. Most research is done in mixed dentitions or early permanent dentition, not throughout the process of development or after permanent dentition is in place. About two thirds of adolescents and/or young adults have fluorosis that is less severe after 5 to 6 years. Few develop more severe fluorosis after this age, so the impact actually diminishes with age. The impact of dental caries continues as a major influence throughout one’s lifetime.
Components Considered The key research components evaluated in formulating the recommendation were water consumption and ambient air temperature, prevalence of dental fluorosis, and protection against dental caries. Several analyses have documented the relationship between water intake and temperature. Often research has indicated seasonal and regional differences in water intake, but some studies show no relationship. These differences may reflect the type of data collected and the analytic approach adopted. In addition, some research focuses on individual-level analysis whereas others look across populations and temperature zones. As a result, shifting fluoride levels based on outside air temperature may be an erroneous practice. A further complication is the fact that a decreasing proportion of water intake is contributed by tap water. Both soft drinks and bottled waters are increasing in use, and these often use distilled water that has a low fluoride content. Reducing tap water intake would justify an increase in the fluoride concentration considered optimal rather than a reduction. This introduces uncertainty into deciding the correct approach to achieve low fluorosis but protect against caries. Dental fluorosis increased in prevalence in many countries during the 1980s and 1990s, when more fluoride vehicles were available for both home use and professional application. Many countries developed more conservative guidelines for the use of fluoride vehicles as a result. Research on what fluoride vehicle to target to reduce fluorosis is limited, but currently indicates that fluoride
supplements and tooth brushing practice are the major contributing factors in nonfluoridated water areas. Among children in fluoridated areas, most cases are attributed to the use of a larger than pea-sized amount of toothpaste for children during their first year of life. Overall, research implicates toothpaste use or misuse in fluorosis rather than water intake. In developing the guidelines for fluoride concentrations in water, the panel should have considered this.
Other Factors There is a curvilinear relationship between fluoride concentration and protection against caries in the United States and other countries. The dose-response relationship between fluoride concentration and caries experience measured as either decayed-missing-filled surfaces in permanent teeth (DFMS) or decayed-missing-filled teeth (DFMT) consists of a decrease in caries experience through fluoride levels of about 3 mg F/l, but a leveling off or increase subsequently. This finding did not appear to influence the panel’s interpretation of fluoride concentration and protection against caries. Lowering of the fluoride level as recommended instead appears to rest on a doseresponse for primary decayed and filled surfaces (dfs) in 5- to 10-year-olds and DMFS in 5- to 17-year-olds in at least four categories up to 1.2 mg F/l. Few data address fluoride concentrations over this level. In addition, no adjustments were made for socioeconomic factors. The data were drawn from the 1986-1987 National Survey of Oral Health of US Schoolchildren, which gathered data from the entire United States. About half of the children lived in areas with fluoride levels between 0.7 and 1.2 mg/l in the water supply. No more recent data were analyzed. More current analyses should be undertaken. In addition, a wider search of relevant literature should be performed to document toothpaste swallowing in very young children and the effects of lower water fluoride concentrations on caries.
Monitoring Along with the recommendations, the panel has called for enhanced surveillance of caries and fluorosis. Data collections will need to be carefully planned and analyzed to ensure changes are properly evaluated. In addition, there will need to be more data on both individual and population impacts related to caries and fluorosis, water intake patterns in various climate zones, and the curvilinear relationship of fluoride concentration in naturally fluoridated water supplies and the effect on caries. All of these investigations and monitoring activities would provide a better basis for making recommendations.
Clinical Significance.—Public health organizations are responsible for monitoring fluoride programs so that dental caries is prevented and unacceptable levels of dental fluorosis are avoided. Recommendations by the US Public Health Service panel appear to be a rush to judgment based on the criticisms offered. Rather than implementing them without further review, a careful analysis of all the factors should be undertaken to ensure that they are based on the most recent data that have been purposefully collected, sufficiently analyzed, and carefully interpreted.
Spencer AJ, Do LG: Caution needed in altering the ‘optimum’ fluoride concentration in drinking water. Community Dent Oral Epidemiol 44:101-108, 2016 Reprints available from AJ Spencer, Australian Research Ctr for Population Oral Health, The Univ of Adelaide, Adelaide, SA, Australia; fax: þ61 8313 3070; e-mail: [email protected]
Volume 61
Issue 6
2016
285
Risk/Protection Balance Dental fluorosis is essentially a disorder affecting children age birth to 8 years, whereas dental caries is a disorder that occurs across the lifetime and in all dentitions. Therefore protection against fluorosis should be focused on young children, whereas caries protection requires an ongoing effort throughout the lifespan. These differences make the balance of risk/protection difficult to conceptualize. Dental fluorosis and dental caries also differ in impact. Caries has well-established consequences and is the reason for most restorative or exodontic treatment to repair or replace damaged teeth. It has a significant impact both on the individual’s oral health and dental expenditures and on the societal investment in oral health and dental care. Dental fluorosis can range from barely discernable to severe, and individual reaction to its esthetic effect varies considerably. Recently, with an emergence of community expectations about ‘‘white teeth,’’ patients have had muted or even positive reactions to fluorosis, believing it has no serious impact on oral health. Low-severity dental fluorosis is seen as representing better oral health than no fluorosis. Severe fluorosis is rare in the United States and comparable countries, with low impact on communities and treatment costs.
284
Dental Abstracts
The natural history of dental fluorosis is also little understood. Most research is done in mixed dentitions or early permanent dentition, not throughout the process of development or after permanent dentition is in place. About two thirds of adolescents and/or young adults have fluorosis that is less severe after 5 to 6 years. Few develop more severe fluorosis after this age, so the impact actually diminishes with age. The impact of dental caries continues as a major influence throughout one’s lifetime.
Components Considered The key research components evaluated in formulating the recommendation were water consumption and ambient air temperature, prevalence of dental fluorosis, and protection against dental caries. Several analyses have documented the relationship between water intake and temperature. Often research has indicated seasonal and regional differences in water intake, but some studies show no relationship. These differences may reflect the type of data collected and the analytic approach adopted. In addition, some research focuses on individual-level analysis whereas others look across populations and temperature zones. As a result, shifting fluoride levels based on outside air temperature may be an erroneous practice. A further complication is the fact that a decreasing proportion of water intake is contributed by tap water. Both soft drinks and bottled waters are increasing in use, and these often use distilled water that has a low fluoride content. Reducing tap water intake would justify an increase in the fluoride concentration considered optimal rather than a reduction. This introduces uncertainty into deciding the correct approach to achieve low fluorosis but protect against caries. Dental fluorosis increased in prevalence in many countries during the 1980s and 1990s, when more fluoride vehicles were available for both home use and professional application. Many countries developed more conservative guidelines for the use of fluoride vehicles as a result. Research on what fluoride vehicle to target to reduce fluorosis is limited, but currently indicates that fluoride
supplements and tooth brushing practice are the major contributing factors in nonfluoridated water areas. Among children in fluoridated areas, most cases are attributed to the use of a larger than pea-sized amount of toothpaste for children during their first year of life. Overall, research implicates toothpaste use or misuse in fluorosis rather than water intake. In developing the guidelines for fluoride concentrations in water, the panel should have considered this.
Other Factors There is a curvilinear relationship between fluoride concentration and protection against caries in the United States and other countries. The dose-response relationship between fluoride concentration and caries experience measured as either decayed-missing-filled surfaces in permanent teeth (DFMS) or decayed-missing-filled teeth (DFMT) consists of a decrease in caries experience through fluoride levels of about 3 mg F/l, but a leveling off or increase subsequently. This finding did not appear to influence the panel’s interpretation of fluoride concentration and protection against caries. Lowering of the fluoride level as recommended instead appears to rest on a doseresponse for primary decayed and filled surfaces (dfs) in 5- to 10-year-olds and DMFS in 5- to 17-year-olds in at least four categories up to 1.2 mg F/l. Few data address fluoride concentrations over this level. In addition, no adjustments were made for socioeconomic factors. The data were drawn from the 1986-1987 National Survey of Oral Health of US Schoolchildren, which gathered data from the entire United States. About half of the children lived in areas with fluoride levels between 0.7 and 1.2 mg/l in the water supply. No more recent data were analyzed. More current analyses should be undertaken. In addition, a wider search of relevant literature should be performed to document toothpaste swallowing in very young children and the effects of lower water fluoride concentrations on caries.
Monitoring Along with the recommendations, the panel has called for enhanced surveillance of caries and fluorosis. Data collections will need to be carefully planned and analyzed to ensure changes are properly evaluated. In addition, there will need to be more data on both individual and population impacts related to caries and fluorosis, water intake patterns in various climate zones, and the curvilinear relationship of fluoride concentration in naturally fluoridated water supplies and the effect on caries. All of these investigations and monitoring activities would provide a better basis for making recommendations.
Clinical Significance.—Public health organizations are responsible for monitoring fluoride programs so that dental caries is prevented and unacceptable levels of dental fluorosis are avoided. Recommendations by the US Public Health Service panel appear to be a rush to judgment based on the criticisms offered. Rather than implementing them without further review, a careful analysis of all the factors should be undertaken to ensure that they are based on the most recent data that have been purposefully collected, sufficiently analyzed, and carefully interpreted.
Spencer AJ, Do LG: Caution needed in altering the ‘optimum’ fluoride concentration in drinking water. Community Dent Oral Epidemiol 44:101-108, 2016 Reprints available from AJ Spencer, Australian Research Ctr for Population Oral Health, The Univ of Adelaide, Adelaide, SA, Australia; fax: þ61 8313 3070; e-mail: [email protected]
Volume 61
Issue 6
2016
285