Fluoride and Dental Health

Fluoride in Dentistry

• Fluoride's role in dentistry is multifaceted, impacting caries and dental fluorosis.
• Early observations (1892, UK) linked fluoride to caries.
• 1901, Dr. F. McKay noted "mottled enamel"
• 1930s, early American studies linked low caries incidence with high fluoride.
• H. Trendley Dean (1930-40, South Dakota, USA) demonstrated fluoride concentration affected enamel mottling, correlating mild fluorosis with low caries. A near maximum caries reduction was seen with 1 ppm fluoride.
• 1945, sodium fluoride addition to the drinking water of Grand Rapids, MI, resulted in a 50% reduction in caries incidence.
• 1955, UK studies, like Kilmarnock, Watford, and Anglesey, also showed 50% reduced caries incidence upon 1 ppm fluoride in water, which ceased and reverted back to high rates of caries.
• 1969, the Committee on Fluoridation of Public Water Supplies (West Malaysia) studied the feasibility of fluoridation.
• 1972, the Federal Cabinet of Malaysia approved the addition of fluoride to public water supplies to prevent dental caries.
• Early optimum level (Malaysia) was 0.7 ppm. This was revised to 0.5 ppm in 2005 after Malaysian studies explored the effects of fluoride exposure and fluorosis on schoolchildren, considering alternative fluoride sources.
• Optimal fluoride concentration in water is approximately between 0.4 to 0.6 ppm.
• Water fluoridation in 2022, in most Malaysian states, had percentages above 90%, excluding Pahang, Sabah, Kelantan, and Sarawak which displayed coverage rates of 0.0%, 4.9% and 13.6%, respectively.
• Fluoridation programs were ceased in certain states, but were later reinstated.

History of Fluoride

• Sir James Crichton Browne (1892, UK) is credited with noticing the possible relationship between fluoride and caries.
• Dr. F. McKay (1901, Colorado Springs) observed mottled enamel and associated it with fluoride and fluorosis.
• Dr. McKay and GV Black (1930s, USA) coupled enamel mottling with low caries incidences, attributing them to high levels of fluoride in drinking water—or fluorosis.

Dental Fluorosis

• Dental fluorosis results from excessive fluoride exposure during tooth development.
• Fluorosis is dose and time-dependent; increased exposure correlated to more pronounced fluorosis.
• Fluorosis appears in a variety of forms depending on duration and degree of exposure; such manifestations include "thin, white opaque lines", "snowcapping of incisal edges and cusp tips", "cloudy areas of opacity", "chalky white appearance", "opacity with small pits," merging "pits to bands", "irregular and extensive enamel loss", and "anatomical changes."

Fluoride & Caries

• Fluoride lowers the critical pH needed for tooth enamel dissolution.
• Fluoride enhances remineralization and lowers the energy required to reform calcium fluoride.
• Fluoride inhibits the formation of acids by microorganisms which contribute to tooth decay.
• Pre-eruptive Mechanism: Fluoride is incorporated into enamel during tooth development. This builds stronger fluoroapatite crystals, more resistant to acid dissolution.
• Post-eruptive Mechanism: Fluoride works directly on the tooth surface, forming fluoroapatite and resisting acid. It also hinders microbial growth. Pre-eruptive mechanisms appear to be weaker than post-eruptive mechanisms in terms of caries prevention.

Physiology & Metabolism of Fluoride

• Absorption occurs via gastrointestinal tract (GIT) or lungs (inhalation).
• Excretion happens rapidly through the kidneys, or sweat and feces.
• Fluoride stores preferentially in bone and developing teeth. These storage levels vary.

Fluoride Toxicity

• Probable Toxic Dose (PTD): This low dose range can cause toxic effects that necessitate immediate intervention and hospitalization.
• The recommended safe dose is 5 mg of fluoride per kg of body weight.
• Symptoms include diffuse abdominal pain, diarrhea, vomiting, excessive salivation, perspiration, painful spasms and convulsions in the limbs, and headaches.

Long-Term Effects of Fluoride

• A 2000 York Review of studies concluded that there was no discernible association between fluoridated water and bone fractures or development problems. Nor was there any discernible association between fluoridation and bone, thyroid, and other cancers.