FLUORIDE: HUMAN HEALTH & CARIES PREVENTION CHAPTER 24 FLUORIDE: HUMAN HEALTH & CARIES PREVENTION

HISTORY OF DENTAL FLUOROSIS 1900’s - Dr. Frederick McKay - practice in Colorado Springs - Noticed “blotching” of enamel in many of his clients - “Colorado brown stain” - Mckay believed it was caused by an environmental agent that was active during period of enamel formation - Mckay found mottled enamel was “endemic” 1920’s - Mottled enamel was associated with community water supply 1930’s - H. Trendley Dean: a) researched prevalence of mottled enamel b) developed 6(7) point ordinal scale of fluorosis c) concluded that caries declined as fluoride rose toward 1.0 ppm and then plateaued

ENVIRONMENTAL FLUORIDE Fluoride occurs universally in soils and waters All plants and animals contain fluoride to some extent Eg: seawater: 1.2 - 1.4 ppm Eg: deep well waters in Arizona: 29.5 ppm

SOURCES & AMOUNTS OF FLUORIDE INTAKE Humans absosrb fluoride from air, food, and water Estimates from “market basket” surveys: eg: infant 0.21-0.54 mg F/day eg: toddler 0.41-0.61 mg F/day eg: adult 1 - 3 F/day Water and other beverages provide 75% of fluoride intake regardless of whether drinking water is fluoridated HOW? Fluoride concentration of various beverages available in nonfluoridated and fluoridated communities

FLUORIDE INTAKE Recommended Daily Intake 0.05 - 0.07 mg/kg/day Probable Toxic Dose 5mg/kg fluoride Certain Lethal Dose 32 - 64 mg/kg fluoride

DIETARY FLUORIDE SOURCES Constituent ppm / fluoride fruit, milk, eggs 0.2 - 0.4 grains, vegetables 0.2 - 1.2 meat, poultry, fish fillet 0.8 - 1.4 canned fish (in oil w/bones) 4.0 - 12.0 tea (brewed) 1.0 - 3.0

SELF APPLIED FLUORIDE Recommended for clients who are moderate to high risk for dental caries Used for patients under active orthodontic treatment to prevent caries and decalcification around brackets and bands that cause permanent white spots and lines on the enamel Recommended on elderly patients on medications that reduce salivary flow (xerostomia) and thus are prone to root caries

SELF APPLIED FLUORIDE Self applied gels are available by Rx: 1.1% neutral sodium fluoride (5000 ppm fluoride) of 0.4% stannous fluoride (900 ppm fluoride) Stannous fluoride may cause some staining; it delivers less fluoride ion to the teeth Delivery of fluoride gels is either by using a toothbrush or custom tray 4 minutes of use in a custom tray is more effective than 1 minute of brushing with the gel since saliva quickly dilutes the gel removing contact with the teeth

FLUORIDE SAFETY follow manufactures instruction judicious use of fluoride products careful monitoring during treatment maximize use of suction never leave a patient unattended while receiving treatment

ACUTE POISONING must be initiated immediately induce vomiting - often occurs spontaneously protect stomach - milk, milk & raw eggs, lime water maintain blood calcium - calcium chloride or calcium gluconate administered both intravenously and orally

OTC FLUORIDE RINSES reduce caries by 28% when used in a daily rinse program 0.5% (225 ppm) rinse for 30 to 60 seconds ; spit out the excess; not eat, drink, or smoke for at least 30 minutes recommended before bedtime so that a residue of fluoride can remain in the saliva during sleep Prescription rinses contain 0.2% sodium fluoride or 0.63% stannous fluoride

FLUORIDE ABSORPTION, RETENTION & EXCRETION Ingested fluoride is absorbed primarily from upper gastrointestinal tract 80% of fluoride in food is absorbed 85-97% of fluoride in water is absorbed Absorbed fluoride is transported in the plasma Most absorbed fluoride is excreted in the urine (5.0 mg F absorbed and cleared from blood in 8 hours) Fluoride that is not excreted is deposited in bone and developing teeth A greater proportion of ingested fluoride is excreted in older population than younger population

FLUORIDE ABSORPTION, RETENTION & EXCRETION Fluoride ingested on an empty stomach produces peak plasma level within 30 minutes Level of peak is reduced if fluoride is taken with food WHY? Kidneys are important in maintaining fluoride balance Individuals with severe renal impairment can consume fluoridated water without ill effects provided they receive regular dialysis treatment Water used for renal dialysis treated by reverse osmosis Aluminum, iron, and other minerals create greater technical problems for renal dialysis process than does fluoride

FLUORIDE BALANCE Refers to the net result from: a) accumulated effects of fluoride ingestion b) degree of fluoride deposition in bones and teeth c) mobilization rate of fluoride from bone d) efficiency of kidneys in clearing absorbed fluoride

OPTIMUM FLUORIDE INTAKE Frank McClure (biochemist with Public Health Service) estimated 0.05 to 0.07 mg F/kg body weight/day “optimum” of fluoride intake in 1980 eg: infant 22lbs (0.45 to 0.64 mg F/day) eg: adult 154lbs ( 3.5 to 4.9 mg F/day) National Research Council: a) establishes recommended dietary allowances b) considers fluoride to be a beneficial element for individuals It DOES NOT consider it to be an “essential” nutrient since it could not be confirmed as a contribution to human growth because the physiologic mechanisms by which fluoride influences growth is undetermined

FLUORIDE & HUMAN HEALTH: EARLY STUDIES McClure demonstrates close relationships between urinary fluoride and fluoride levels of domestic water 4 to 5 mg fluoride limit that could be ingested without hazard of excessive storage in the body

CANCER Study 1977 Burk and Yiamouyiannis proved that fluoridation led to an increase in cancer deaths in fluoridated American cities regardless of age, sex, or race Study - Britain and United States - more detailed age-sex race adjustments - proved that there was no link between cancer incidence and consumption of fluoridated water National Toxicology Program (NTP): 2 year study on several animal species using 4 levels of fluoride concentration (0,11,45,79 ppm) Conclusions: a) optimal fluoridation of drinking water does not pose a detectable cancer risk to humans b) increase osteosarcoma in males under 20

OSTEOPOROSIS High doses of fluoride (80 mg/day) is no longer recommended and does not prevent fractures resulting from osteoporosis No relationship between bone fracture experience and water with 1.0 ppm F

FLUORIDE TOXICITY Fluoride is beneficial in small amounts and toxic in higher amounts There is a big difference between single intake of 5.0 g F and constant intake of 1 to 3 mg F daily Toxic effects observed in workers in aluminum plants 5 to 10 g of single dose of sodium fluoride by an adult can result in death in 2 to 4 hours 10 - 20 mg F ingested or inhaled daily 10 to 20 years by an adult can cause crippling skeletal fluorosis DEGREES OF POTENTIALLY TOXIC INGESTION OF FLUORIDE

FLUORIDE & CARIES 3 MECHANISMS BY WHICH FLUORIDE INHIBITS DENTAL CARIES: 1) promote remineralization and inhibit demineralization of early carious lesions 2) inhibit glycolysis 3) reduce enamel solubility in acid NOTE: There is a stronger posteruptive fluoride action on caries inhibition Greater proportional caries reductions on _____________ surfaces than on pit and fissure surfaces When DMFS scores are declining in a population, the proportion of all decayed surfaces that are pit and fissure surfaces will increase even as the absolute number diminishes

FLUORIDE & PLAQUE Fluoride introduced in the oral cavity is partly taken up by plaque (95% bound form) Fluoride is absorbed more readily by demineralized enamel than by sound enamel Dental plaque contains approx. 10 mg F/kg weight in low fluoride regions and approx. 20 mg F/kg in fluoridated communities Fluoride in plaque inhibits glycolysis Fluoride from drinking water and dentifrices is higher in concentration than fluoride in saliva Higher concentrations of fluoride gels aid in the destruction of cariogenic bacteria in dental plaque

FLUORIDE & ENAMEL Higher concentration of enamel fluoride does not necessarily mean that a client will be caries-free There is a relatively ______ concentration of fluoride in enamel Eg: depth of 2 microns - enamel fluoride concentration 1700 ppm in non fluoridated community 2200- 3200 ppm in fluoridated community Fewer enamel lesions progress to dentinal caries in a fluoridated area compared to a nonfluoridated region Fluoride does not prevent the initial carious attack Fluoride in the mouth inhibits further ____________________ of the carious lesion and promotes ________________________

FLUORIDE & SALIVA Salivary fluoride concentrations are 3x higher in fluoridated than nonfluoridated communities Eg: fluoridated area: salivary fluoride levels: 0.016 Eg: nonfluoridated area: salivary fluoride levels: 0.006 ppm After brushing with fluoridated toothpaste or rinsing with fluorided solution, salivary fluoride levels can escalate 100 to 1000-fold and then return to normal The fluctuating salivary flow level is normal The average adult will produce approx. 0.5-1 liter of saliva/day When salivary and plaque pH drops below 5.5, demineralization of the enamel is likely to occur