3. Preventing bacteria from producing sufficient organic acid to demineralize tooth surface.

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1 FACT SHEET - Dental Health : Vol. 1 No. 4 January 1998 Fluoride Used for Dental Caries Prevention Piyada Prasertsom. DDS. MSc. Dental Health Division, Department of Health, Ministry of Public Health, Tel: How does fluoride control dental caries? Basically, we are dealing with fluoride's direct and indirect effects on two different structures, teeth and plaque. In simple terms, one can view fluoride as having an effect on caries by: 1. Reducing the dissolution of teeth 2. Accelerating the remineralization of initial lesion and inhibiting the demineralization of the teeth 3. Preventing bacteria from producing sufficient organic acid to demineralize tooth surface. Because of the cariostatic effect of fluoride was first discovered in relation to natural fluoride content of drinking water. It was logically interpreted as meaning that fluoride's cariostatic effect was due to systemic, preeruptive incorporation of fluoride into tooth. This would make the enamel more crystals more perfect which result to more resist to acid produced by the bacteria in dental plaque. To date, when the understanding of the caries process is clearer, the effect of fluoride on dental caries has changed to focus on the demineralization and remineralization of tooth tissue. Many studies in recent yeras revealed the role of fluoride in enhancing the remineralization of the initial lesion of the tooth and the regression of the lesion to be sound enamel. Therefore, the effect of fluoride on dental caries is not only prevention but also therapeutic effect on tooth lesion. Moreover the antiseptic property of fluoride also interrupts the metabolism of bacteria which will make less acidicity in the mouth and less demineralization.

2 To date, when the understanding of the caries process is clearer, the effect of fluoride on dental caries has changed to focus on the demineralization and remineralization of tooth tissue. Dental caries is common in people of all ages. It's an infectious disease which related to many factors. The major components of the disease are susceptible teeth, dental plaque (the accumulation of bacteria) and diet (mainly sugar). For our knowledge now, the caries process is well explained as the process of demineralization (loss of mineral tissue from tooth) and remineralization (resuming mineral into the tooth) which is dynamic in the oral environment. Fluoride was found to have properties in caries prevention and control. It was introduced to be caries preventive agent for at least 50 years. At present fluoride is used in many forms which are familiar to our lives as dentifrice, mouth rinsing and fluoride tablets or drops. Fluoride level in natural water The human organism is exposed to fluoride in number of ways. Water is the predominent source of natural fluoride. Data from over country survey of natural drinking water sources showed that people in Northern and Western area of Thailand have more chance to expose to high fluoride (above optimal level) than other parts of the country. There are 429 sources of natural drinking water which contain fluoride level higher than 0.6 ppm.(mgf/l) and about 1% of the natural sources contain more than 2 ppm of fluoride. Most of them are artesian well water. (Fig 1)

3 Fluoride has both positive and negative effect on physical health. At one level, which we call optimal level, fluoride can treat initial lesion and prevent the progression of decay. Apart from its positive cariostaic properties, fluoride is a hazardous substance. An acute intake of large or chronic ingestion of lower doses of fluoride can result in a variety of side effects such as acute gastic and kidney disturbance, dental and skelatal fluorosis or even death. This comes the question of optimal level of fluoride for human. The optimal level in drinking water recommended by WHO is ppm. which the comment that this level may vary depend on the daily maximum temparature in each country. The study in Thailand by Prateep et al. (1984) showed that the optimal level of fluoride in drinking water for Thais is 0.5 ppm. Fluoride in bottle-drinking water Bottle-drinking water is a commercial product under the regulation of FDA. The use of this kind of water becomes substaintially high nowsaday because of the safety and convenience. Actually there are at least two regislations dealing with this product, the regislation of drinking water quality and the regislation of the label on the bottle. For the quality, fluoride has mentioned as one of control element in the drinking water at the level of not above 1.5 ppm. Although this level is already threefold higher than the optimal level for Thais there are still 12 samples out of 937 samples of bottle-drinking water contain fluoride higher than 1.5 ppm. and 85 samples above the optimal level in the survey of bottle drinking water done by Dental Health Division. The children under 7 years old who consume these water will be high risk to dental fluorosis or even skeletal fluorosis. (Fig.2)

4 Fluoride in dentifrice Most of the dentifrice sold in the market now (more than 80%) contain 800-1,000 ppm. fluoride as sodium fluoride (NaF) or sodium-monofluorophosphate (MFP). The regislation of FDA (1985) has control the level of fluoride ion in dentifrice at the maximum level 1,100 ppm. or 0.110% of active fluoride ion. The products have to label on the packge as "Children under 7 years should use a little amount of dentifrice and should not eat or swallow." Table 1 reveals the distribution of active fluoride ion in 39 dentifrices from the market shelves. Recommendation of fluoride using in Thailand The epidemiological data in many countries in recent years have showed the declining of dental caries but the prevalence of dental fluorosis is increasing. Though most of the fluorosis still in the very mild and mild level which is not significant aesthetic problem, there are numberous studies tried to explain the event. The explaination of increasing fluorosis is focused on the widely spread of fluoride dentifrice. Many countries have revised the recommendation for dose schedule of fluoride supplementation. In 1994 the American Dental Association has proposed the revised dose schedule, since then plenty of the countries have followed this new schedule. Thailand also has reviewed the epidemiological data of dental caries dental fluorosis and fluoride level in the environment periodically. Recently there is a consensus of fluoride experts in Thailand in 1997 on recommendation of fluoride using in Thailand as follow: 1. Promoting the use of fluoride dentifrice 2. Establishing public water fluoridatio in high caries area 3. Using the dose schedule of fluoride supplementation proposed by ADA 1994 (table2)

5 R E F E R E N C E 1. Fejerskov O., Ekstrand J., Burt BA. Fluoride in Dentistry 2 nd edition. Copenhagen: Munksgard, World Health Organization. Fluoride and Oral Health. Geneva : Pantumvanich P., Songpaisan Y., Hansawat S., Leksawat P. & R.G. Schamschula : The Relationship Between Fluoride Level in Drinking Water and Dental Fluorosis in Chiangmai, Program and Abstracts of Science and Technology in Thailand 10th, Chiangmai University 1984, p : 456. (in Thai) 4. Dental Health Division, Department of Health, Ministry of Public Health. Report of The Forth Thailand National Oral Health Survey The Veterans Press,Bangkok, 1995.(in Thai) 5. Government Gazette. The Regislation of Ministry of Public Health No. 61 (1981) : Bottle Drinking Water. Vol. 98, Sec. 157, 24 November (in Thai) 6. Government Gazette. The Regislation of Ministry of Public Health No. 68 (1982) : Label. Vol.99, Sec. 61, 29 April (in Thai) 7. Thailand Dental Public Health Society. Fluoride Use in Thailand: The situation and Trend. In: "The Conference of Fluoride : Dental public health Point of View." Central Plaza Hotel 17 December 1996, p: 5. (in Thai)