Working with the University of Michigan and others, Grand Rapids was the first city to add fluoride to its public water supply in a study that showed dramatic improvements in dental health and led to an important public health initiative that has been adopted nation-wide.
The controlled addition of a fluoride compound to public water supply and raising the fluoride concentration to a predetermined level is an effective way to share the beneficial effects of fluoride among a large population and prevent dental caries
Community water fluoridation is the controlled adjustment of fluoride concentration in a community water supply.
Requirements
For successful implementation of community water fluoridation, the following condition needs to be fulfilled,
- Fair level of economic development.
- Availability of a central water supply.
- Reliable fluoride chemicals.
- Availability of trained workers.
- Sufficient funds for initial installation of the required equipments and treatment plant..
- Population at the risk of dental caries.
- Permissive laws.
Recommended levels of fluoride in water (WHO 1971)
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Optimum concentration : 0.7 to 1.2 ppm (0.5 - 1ppm).
- Cold climate : 1.2 ppm
- Summer or temperate climate : 0.7 ppm.
- In hot climatic conditions, water consumption is higher and hence, fluoride concentration is kept slightly below 1 ppm. On the other hand, during winters (cold climate), the fluoride concentration needs to be increased for compensation of lesser water consumption.
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Empiric formula for estimation of daily fluoride intake : Developed by Galagan and Vermillion (1957), based on body weight and climatic conditions and using the mean annual maximum daily air temperature.
- ppm fluoride = 0.34/E, where E (Estimated water intake) = 0.038 + 0.0062 x Temp(in oF).
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The fluoride concentration of water should be calculated after taking all other fluoride sources into account.
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Diffusion or Halo effect : Ingestion of various types of fluoride from sources other than water such as beverages, snacks, etc. prepared in fluoridated areas. The optimum level of fluoride has been reduced to 0.7 ppm from the earlier 1 ppm level due to diffusion effect.
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Dilution effect : Results from increased availability of fluoride from multiple sources, diluting the impact of any one source of fluoride including water.
Materials and Methods
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Fluorspar : It is a mineral containing calcium fluoride.
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Sodium fluoride (most expensive, powder, dry feeders) :
- First compound to be used in controlled water fluoridation.
- Widely used in smaller community water system fewer than 5,000 people.
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Sodium silicofluoride (cheapest form, powder, dry feeders)
- Most commonly used, as it is less expensive and requires simpler technical handling.
- It can be used for population more than 50,000.
- Solutions of this compound are corrosive, hence materials for piping etc should be chosen accordingly.
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Hydrofluorosilicic acid (solution feeders).
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Ammonium silicofluoride
Saturator system
In this system a 4% saturated solution of sodium fluoride is produced and injected at desired concentration at the water distribution source with the aid of a pump.
- Upflow saturator : Generally used in smaller community water systems (10,000 or less).
- Downflow saturator : Not used nowadays.
- Venturi saturator : Generally used in extremely small community water systems such as villages, or individual school buildings, although not used widely.
Dry-feeder
In this system, sodium fluoride or silicofluoride powder is introduced into a dissolving basin automatically, thus, maintaining desired amount of fluoride in the water supply.
- Gravimetric feeders (belt-type).
- Volumetric feeders (roll-type or screw-type).
Solution feeder
It involves a volumetric pump that permits addition of a given quantity of hydrofluorosilicic acid in proportion to the amount of water treated.
- Diaphragm solution feeder : Generally used in larger community water systems (25,000 or more).
Monitoring of fluoride levels
- It is necessary to monitor the level of fluoride in the community water supply.
- Ion specific electrode can be used as an effective method to achieve this objective.
Effects of water fluoridation
- Systemic effect : During tooth formation, makes enamel more resistant to dental decay.
- Topical effect : The release of fluoride in saliva after ingestion maintains an elevated fluoride level in the mouth for an extended period. This helps in protection against demineralisation and facilitates remineralisation.
- Pre-eruptive and post-eruptive effects : Changes the morphology of occlusal surfaces by making pit and fissures more shallow and self cleansing.
Advantages or Benefits of water fluoridation
- People can receive continuous benefit without any conscious effort.
- Does not require assembling of people at one central location.
- No costly services and recurring costs as involved in professionally applied.
- Consumer is hassle free and need not to worry about dosages.
- Available to everyone, irrespective of social class or discriminations.
Limitations
- Can be implemented only in areas that have a central water supply system.
- Interferes with personal choice or preferences.
- People may think of overprotection.
- Initial cost for installing fluoridation plant is more.
References
- C. M. Marya - A Textbook of Public Health Dentistry, Jaypee Brothers Medical Publishers (P) Ltd (2011). https://amzn.to/3SHP36G
- S. S. Hiremath - Textbook of Public Health Dentistry, Elsevier India (2016). https://amzn.to/49mh2jw
- The image used is licensed under Creative Commons Attribution-Share Alike 4.0 International license. (Author : Staircase1)
*This article is an excerpt from the above mentioned books and Medical Sutras does not make any ownership and affiliation claims.